4>EPA
EPA/600/R-14/244 August 2014 www.epa.gov/research
United States
Environmental Protection
Agency
and Characterization
of Engineered Nanomaterials
in the Environment:
Current State-of-the-Art
and Future Directions
Report, Annotated Bibliography, and Image Library
RESEARCH AND DEVELOPMENT
-------
This page intentionally left blank.
-------
Detection and Characterization of
Engineered Nanomaterials in the
Environment: Current State-of-the-Art
and Future Directions
Report, Annotated Bibliography, and Image Library
Final Report Prepared by:
Manuel D. Montano and James Ranville
Colorado School of Mines, Department of Chemistry
Gregory V. Lowry
Carnegie Mellon University, Department of Civil and Environmental Engineering
Julie Blue, Nupur Hiremath, Sandie Koenig, and Mary Ellen Tuccillo
The Cadmus Group,Inc.
Scientific, Technical, Research, Engineering, and Modeling Support II (STREAMSII)
The Cadmus Group,Inc.
Contract No. EP-C-11-039
Task Order 5
for
Task Order Manager
Steven P. Gardner
Characterization and Monitoring Branch
U.S. Environmental Protection Agency
Office of Research and Development
National Exposure Research Laboratory
Environmental Sciences Division
Las Vegas, NV 89119
Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect
official Agency policy. Mention of trade names and commercial products does not constitute
endorsement or recommendation for use.
U.S. Environmental Protection Agency
Office of Research and Development
Washington, DC 20460
-------
This page intentionally left blank.
-------
Disclaimer
The United States Environmental Protection Agency through its Office of Research and
Development funded and managed the research described here. It has been peer reviewed by the
EPA and approved for publication.
-------
This page intentionally left blank.
-------
1. INTRODUCTION 1
Definition and properties of nanoparticles 2
2. NATURAL COLLOIDS AND NANOPARTICLES 5
Classification and origin of biogenic and geogenic materials 6
Composition and interferences of some common natural nanoscale minerals 6
Estimates of ENP behavior and fate 8
NM-facilitated contaminant transport in the subsurface 8
3. REACTIVITY AND PERSISTENCE 9
Alterations in Organic Coatings 10
Loss of coatings 11
Overcoating or Alteration of Coatings 11
Impact of coating loss or gain on the ability to detect NPs 12
Dissolution and Ligation 13
Oxidation and Reduction (Redox) Reactions 13
Aggregation 14
Biological Transformations 14
4. NANOMETROLOGY 15
A. Review of available analytical methodologies 19
Methods based on separation by size 19
Ensemble particle detection and characterization methods 22
Spectroscopy techniques 24
Particle counting and characterization methods 25
Optical and biological sensors 27
B. ENP Characterization in Complex Laboratory Matrices 28
Size, morphology, and aggregation state 28
Surface charge/surface groups 29
Dissolved ions vs. nanoparticulates 30
C. ENP Detection and Characterization in Environmental Samples 30
Expected low ENP concentrations 31
Elevated natural NP / colloid background 31
Preserving sample representativeness 34
5. NEW APPROACHES 34
-------
Mass spectrometry-based methods 35
Element Ratios 35
Isotope methods 36
MALDI-TOF-MS and LDI-TOF-MS 36
6. SITE-SPECIFIC ENM RELEASE SCENARIOS 37
ENP production site 37
Site of ENP use 37
Transport accident 37
Non-point sources 38
7. SUMMARY 38
8. REFERENCES 39
Tables
Table 1. Common engineered nanomaterials and typical applications 2
Table 2. Common methods of synthesis 3
Table 3. Common naturally occurring nanomaterials[5, 6, 42, 44] 7
Table 4. Analytical approaches: Limitations and needs for ENP analysis 18
-------
Acronyms
AF4
ATR
CCD
CFUF
CNT
CPE
DCS
DLS
EDS
ENM
ENP
ESEM
FFF
Fl-FFF
FTIR
HOC
HS
ICP-MS
IR
LCA
LffiD
MALS or MALLS
MAS
MS
NIR
NIRF
NM
NMR
NOM
NP
NTA
PCS
PECs
PEG
ppq
ppt
ROS
SdFFF
SEC
SEM
SEIRA
SLS
SPE
SP-ICP-MS
Asymmetric Flow Field Flow Fractionation
Attenuated total reflectance
Charge-coupled device
Cross-flow ultra-filtration
Carbon nanotube
Cloud point extraction
Differential centripetal sedimentation
Dynamic light scattering
Energy dispersive spectroscopy
Engineered nanomaterial
Engineered nanoparticle
Environmental SEM
Field flow fractionation
Flow FFF
Fourier-transform infrared spectroscopy
Hydrodynamic chromatography
Humic substances
Inductively coupled plasma mass spectrometry
Infrared
Life cycle assessment
Laser-induced breakdown detection
Multi-angle light scattering
Magic angle spinning
Mass spectrometry
Near infrared
Near-infrared fluorescence spectroscopy
Nanomaterial
Nuclear magnetic resonance spectroscopy
Natural organic matter
Nanoparticle
Nanoparticle tracking analysis
Photon correlation spectroscopy
Predicted environmental concentrations
Polyethylene glycol
Parts per quadrillion
Parts per trillion
Reactive oxygen species
Sedimentation FFF
Size exclusion chromatography
Scanning electron microscopy
Surface enhanced infrared absorbance
Static light scattering
Solid-phase extraction
Single particle ICP-MS
in
-------
SPM Suspended particulate matter
SWCNT Single-walled carbon nanotube
TEM Transmission electron microscopy
UV Ultraviolet
UV-Vis UV-visible spectroscopy
XAS X-ray absorption spectroscopy
IV
-------
1. INTRODUCTION
Nanotechnology has become a prominent industrial and scientific field. Its global market value is
estimated to exceed $1.5 trillion by the year 2015[l-3]. With increasing production and wider
applications, engineered nanoparticles (ENPs) are expected to become routinely present in
natural ecosystems. Although ENPs will certainly enter the environment through unintentional
releases, the possible development and application of nanomaterial-based agrochemicals could
lead to widespread intentional environmental dispersion [3, 4, 5].
Risk assessment models are being used to address the implications of ENPs for human health
and the environment. Development of accurate ENP risk assessment models will require robust
and efficient detection, characterization, and quantification of these materials in the environment
[2-4].
Nanomaterials (NMs) in the environment pose unique detection and quantification problems
because of their small size and low concentration and because of the high background level of
incidental and naturally occurring nanoparticulate matter, often with similar elemental
composition. Distinguishing between engineered and naturally occurring nanoparticles requires
improvement in the selectivity of nanometrology (the science of measurement at the nanoscale
level) rather than improvements in method sensitivity. It also requires understanding how a
nanoparticle may be altered in specific environmental conditions.
This paper provides an overview of the challenges to nanoparticle detection and focuses on
analytical methods applicable to dispersed nanoparticles. It provides details on possible methods
for detecting, quantifying, and characterizing engineered NMs in complex environmental
matrices (e.g., water and soil/sediment), particularly against high background levels of ambient
ENPs and naturally occurring nanoparticles. Nanoparticle characteristics that may facilitate
discrimination between engineered and natural NMs are emphasized. Future directions in
nanometrology development are identified. Estimates of ENP releases in life cycle assessments
(LCAs) suggest that the aqueous and soil/sediment environments will be the ultimate reservoir of
engineered NMs [5, 6]. Despite being significant sources of ambient NMs in the environment,
incidental nanoparticles (those created unintentionally), particularly atmospheric incidental
nanoparticles, have been excluded from this study. Methods for the detection and
characterization of atmospheric NMs have been reviewed elsewhere [7].
In this paper we first introduce the characteristics of ENPs and the major synthesis routes, which
through well-controlled conditions can lead to relatively monodispersed and chemically well-
defined ENPs. The identity and characteristics of natural nanoparticulate matter is then
discussed, particularly with respect to the difficulty their presence causes in the detection and
quantification of ENPs. After that section we introduce the transformation processes to which
ENPs are subject and discuss how these processes affect ENP detection. The existing
nanometrology tool kit is then described, followed by a discussion of possible new measurement
approaches that may overcome some of our current limitations for ENP analysis in complex
matrices.
-------
Definition and properties of nanoparticles
A commonly accepted definition of an NM is a material with at least one dimension between 1
and 100 nanometers (nm) long [3]. This definition allows for the inclusion of thin plate-like (one
nano dimension) and long fibrous (two nano dimensions) microscopic materials. NMs occupy
the smallest size range of colloidal materials, generally defined as sub-micron-size particulate
matter. The choice of 100 nm as the upper limit for the definition of NMs is somewhat arbitrary,
and it may be more accurate to define NMs by the size at which their chemical and physical
properties start to differ significantly from their bulk counterparts [12]. For example, NMs have
high specific surface area and a high fraction of surface atoms, leading to increased reactivity
and in some cases a size dependent change in their optical, electrical, and magnetic properties
(i.e., a "nano-effect"). Nano-effects for metal and metal oxide particles tend to be most
pronounced below about 10-20 nm.
Any material having the appropriate dimensions can be classified as an NM, but only certain
nanoscale materials exhibit the properties (e.g., solubility, reactivity, conductivity, optical
properties) desired for engineering applications. Common engineered NMs and some typical
applications are listed in Table 1. NM composition may be simple (e.g., nano-Ag) or quite
complex (e.g., CdSe/ZnS/polymer core shell materials) and is generally well defined and free of
major impurities. Natural NMs, on the other hand, tend to be chemically impure. Such
differences in chemical purity might suggest new analytical approaches for ENP detection.
However, chemical transformations in the environment may significantly alter ENPs' chemical
compositions (see Section 3), thereby reducing the potential for using composition as a
distinguishing characteristic.
Table 1. Common engineered nanomaterials and typical applications
ENP
Classification
Zerovalent metals
Metal oxides
Semiconductors
Carbonaceous
materials
Dendrimers
Elemental Composition
Examples
Au, Ag, Fe
SiO2, TiO2, ZnO, CeO2
CdSe, CdTe
Carbon nanotubes, fullerenes
Multi-functional polymers
Typical Applications
Catalysts, bactericides, groundwater
remediation
Photocatalysts, pigments, sunscreens,
cosmetics, polishing agents
Electronics, drug delivery, bio-
imaging
Super capacitors, hydrogen storage,
ultra-high-strength materials
Chemical sensors, drug delivery
Refs
[8],[9],[10]
[11],[12],[13]
[14]
[15],[16]
[17]
Size distribution is an important property routinely assessed when characterizing nanoparticles.
Size distributions can be number-based or mass-based (see Section 4). Metrics may also be based
on instrument measurements such as intensity or on physicochemical properties such as surface
area. Minimum characterization of size distribution can include the mean size, the mode size,
and the polydispersity index.
Nanotechnology relies on properties that scale with size, and thus ENPs are designed and
synthesized to be physically uniform (in addition to chemically pure) because they best exhibit
their nanoscale properties (e.g., photonic, catalytic) when the particles have a narrow size
-------
distribution (i.e., are monodisperse). Several approaches to the synthesis of NMs and the
resulting properties are provided in Table 2. Although synthesis often aims to produce
monodisperse particles, it should be noted that production of nanomaterials intended for large
scale use (e.g., nanoscale zerovalent iron for in situ remediation [13]) often results in
heterogeneous polydisperse materials as well because it can be challenging to carefully control
ENP properties when producing ENPs on a large scale.
Natural nanoparticles generally display a broader range of sizes (polydispersity), although there
can be notable exceptions (e.g., biogenic nanoparticles). This difference in particle polydispersity
between ENPs and naturally occurring nanoparticles may be useful for distinguishing between
engineered and natural particles. In environmental samples, however, transformation processes
(see Section 3) will tend to alter the size distribution of engineered nanoparticles, likely
eliminating narrow size distributions as a possible distinguishing property.
Table 2. Common methods of synthesis
Process
Chemical reduction
Sol-gel
Solvosynthesis
Vapor-phase
Organic synthesis
Elemental Composition
Examples
Zerovalent metals
Au, Ag, Fe
Metal oxides
SiO2, TiO2, ZnO, CeO2
Semiconductors
CdSe/ZnS, CdTe
Carbonaceous materials, metal
oxides
Carbon nanotubes, Mlerenes
Multi-functional polymers
Characteristics
Mono-elemental in composition, (Au,
Ag) monodisperse and often as spheres
or wires
Single metal, moderate polydispersity, 2-
D and 3-D nanoscale dimension
Multi-metal composition, low
polydispersity
Polydisperse, 2-D nanoscale dimension
Carbon-based, monodisperse,
3-D nanoscale dimensions
Refs
[18],[19]
[20],[21]
[22]
[23],[24]
[25]
Highly engineered surface coatings are a key component of engineered nanoparticles and help to
control properties such as solubility and reactivity. Common coatings range from organic
proteins (i.e. protein coronas) and polymers (e.g. polyvinyl pyrrolidine) to inorganic ligands and
surfactants (e.g., cysteine, citrate, carbonate) [26-28]. These coatings generally serve to limit
aggregation of the NMs and can act via electrostatic and/or steric stabilization. Electrostatic
stabilizers use charge repulsion to prevent particle aggregation, while steric stabilizers, because
of their large size, physically prevent aggregation [2, 3, 29, 30]. These highly specialized
coatings can be unique macromolecules and may provide a means for detecting ENPs (through
mass-spectrometry) and perhaps differentiating them from ambient nanoparticles with natural
organic macromolecular coatings. Upon entry into the environment, however, surface coatings
may be altered, over-coated, or replaced by natural organic matter such as organic acids and
humic substances [28, 31, 32]. Changes in coatings and the associated surface properties of NMs
are an ongoing area of study with implications for the effects, fate, and transport of NMs in the
environment and, for this discussion, ENP identification.
-------
Due to the ubiquity of natural nanoparticles and their role in several important geochemical and
biological chemical processes [5, 6], it is thought that organisms have adapted to their potential
toxic effects. However, the release of ENPs into the environment introduces a new class of
potentially toxic contaminants with a vast range of physiochemical properties, the impacts of
which are not yet fully understood [33]. Furthermore, differentiation and comparison between
natural and engineered nanoparticles may help in understanding the environmental behavior of
ENPs because the natural and engineered particles share some stability and transport properties.
For example, in addition to their own potential toxicity, ENPs may have the potential to serve as
vectors for the transport of other contaminants, much as natural colloids are known to do (see
Section 3). These concerns provide motivation to develop nanometrology that can both
differentiate ENPs from the natural nanoparticle background and quantify ENP concentrations.
Engineered nanomaterials (ENMs) can undergo changes throughout their manufacture, use, and
subsequent entry into and passage through the environment, and the resulting changes may affect
their chemical and physical forms, reactivity, potential mobility, detectability, and toxicity [34].
Physicochemical properties (e.g., size, charge, elemental composition, shape, coating) need to be
examined. For these properties, robust characterization and quantification metrologies do exist,
but their application outside the laboratory, and for other than simple ENMs, remains
underdeveloped. The aspects of ENM use, and subsequent release, most relevant to
nanometrology relate to analysis of ENPs in natural systems. ENPs are incorporated into nano-
enabled products, and pristine ENPs may be modified for incorporation into these products.
Furthermore, ENPs can be altered during normal product use. To enter the environment, ENMs
and ENPs must be released from the product through weathering, after which further
transformations can occur. Therefore, the ENM in an environmental sample may bear little
resemblance to the pristine ENP that was incorporated into the product.
Advances in the life cycle assessment of NMs provide predictions of where these materials will
flow during their production, use, disposal, and eventual introduction into the environment. For
example, LCA has demonstrated that wastewater treatment, in particular the production of
treatment residuals (i.e., biosolids), is a major pathway to the environment for ENMs released
from consumer products[34]. Predicted environmental concentrations (PECs) are important as
they relate to nanometrology sensitivity requirements. Most assessments suggest very low ENM
mass concentrations (< |ig/L) are likely. However, current data on the prevalence of ENP use and
the release of ENPs into the environment is limited. This lack of data poses a significant hurdle
to accurate risk assessment for NMs [35-38].
To illustrate some of the analytical challenges unique to ENPs, it is useful to compare the case of
other trace contaminants in wastewater. Although ENMs and pharmaceuticals are both released
into the environment via wastewater treatment residuals, pharmaceuticals are much more easily
detected and characterized due to the use of established, highly sensitive, and selective analytical
techniques.They also have a defined molecular structure, making them amenable to treatment as
chemicals, not materials. Methods such as liquid chromatography-tandem mass spectrometry
(LC-MS/MS) and gas chromatography- mass spectrometry (GC-MS) respond directly to the
compound of concern, so pharmaceuticals analysis has much less interference from background
constituents. Furthermore, these techniques are highly sensitive and such compounds can be
-------
detected and quantified at environmentally relevant and extremely low (parts per quadrillion
[ppq] or parts per trillion [ppt]) levels in environmental samples.
2. NATURAL COLLOIDS AND NANOPARTICLES
The detection and characterization of engineered nanoparticles in the environment is complicated
by ubiquitous naturally occurring colloids and NMs that are present in much larger
concentrations than the engineered particles. This section provides background information on
naturally occurring NMs and discusses some common interferences they create for ENP
detection.
The feasibility of differentiating ENPs from natural nanoparticles may depend in part on particle
size. In natural waters, number-based particle size distributions for natural particles have been
found to follow Pareto's power law, the differential form of which is:
dN p
= Zx-P
dx
Where:
N = the number of particles with sizes smaller than x.
Z = an empirical constant that describes the total amount of suspended particles.
P is an empirical constant generally found to be approximately 3 for natural waters [39],
although very little data exists for particles smaller than 100 nm. This relationship implies that
there are 1,000 times more 10-nm particles than there are 100-nm particles. Such a size
distribution means that interference from an abundance of naturally occurring nanoparticles will
be more problematic as nanoparticle size decreases. However, although there are fewer particles
at the upper end of the nanoscale size range, these larger particles will pose a problem for light
scattering methods, which exhibit strong size dependence in their capabilities. Nonetheless,
given that many ENPs are designed to be monodisperse, with clear upper and lower size limits,
the addition of ENPs into waters of low particle concentrations might be detectable as a
perturbation in the size distribution expected for naturally occurring particles.
These natural materials, which are included in what has classically been considered the dissolved
fraction in aqueous systems (can pass through a 0.45|im filter), vary in size, shape, elemental
composition, and properties. These materials also exist at relatively high mass concentrations in
the environment, ranging from 1 ppb to 1 ppm in groundwater, 1-1,000 ppm in surface waters,
and 0.01-80 ppm in marine environments [40]. The comparatively high concentrations of
naturally occurring NMs interfere with the detection and characterization of ENPs and thus
complicate accurate assessment of environmental exposure to ENPs.
Natural NMs will interfere with non-specific sizing techniques such as dynamic light scattering;
such methods do not analyze the composition of particles, and natural and engineered particles
cannot be differentiated.
-------
Some natural materials are similar in elemental composition to their engineered analogs and can
complicate X-ray-based methods or element-specific methods such as inductively coupled
plasma-mass spectrometry (ICP-MS). Examples of chemically similar particle types include:
Metal oxide minerals and engineered oxides.
Natural metal sulfides and some quantum dots.
Natural organic matter and carbon nanotubes (CNTs).
Despite similarities between natural and engineered nanoparticles, specific morphological or
chemical differences (e.g., elemental ratios) may provide a means of differentiation.
Classification and origin ofbiogenic andgeogenic materials
Nearly all minerals found in the environment undergo a nano-phase transformation at some point
in their life cycle, either during their initial formation (crystallization) or during weathering.
Nanoscale minerals have important implications for soil stability, contaminant transport in
groundwater, and (bio)geochemical reactions that play a role in the overall ecosystem [5, 41-43].
It has been proposed that nanoscale minerals be divided into two classes: nanominerals and
mineral nanoparticles [5, 6].
Nanominerals are materials that do not possess a bulk-phase equivalent and only exist at
the nanoscale (1 to 100 nm). An example of a nanomineral is ferrihydrite, a common iron
hydroxide. Nanominerals are formed by precipitation from supersaturated solutions due
to changes in redox conditions or solution composition, sometimes mediated by
biological processes.
Mineral nanoparticles can exist at nano and larger scales. They form either through
weathering of larger minerals or through precipitation and crystal growth.
Chemical weathering of silicates, oxides, and phosphates under environmental conditions is an
important mechanism for the formation of authigenic (formed where they are found) nanoscale
minerals. Nanoscale minerals can also be formed via biological pathways in which bacteria
sequester metal ions for use in metabolic redox reactions during which nanoparticles form within
the cytoplasm and excrete them [6, 42, 43].
Composition and interferences of some common natural nanoscale minerals
Nanoscale minerals may be composed of inorganic materials such as aluminosilicates (e.g., clay
minerals) and metal oxides (e.g., iron and manganese oxyhydroxides) and of organic materials
such as complex organic acids (humic substances) and biopolymers. Common natural NMs and
some of their key characteristics are presented in Table 3.
-------
Table 3. Common naturally occurring nanomaterials[5, 6, 42, 44]
Material
Composition
Characteristics
Clay fraction
Variable Al, Si, O with other
metallic cations
Provide ubiquitous surface for
particles to bind to. Possible to have
different charges on basal planes
(positive) and edges (negative)
Iron and aluminum oxides
Fe2O3 (Hematite)
FeOOH(-OCl) (Akaganeite)
Fe5HO8*4H2O (Ferrihydrite)
A1OH3 (Gibbsite)
High specific surface area, strong
binding affinity for metallic
contaminants
Metal sulfides
Ag2S, ZnS, CdS, FeS
Size-dependent morphology,
frequently present in anoxic
environments associated with
microbial processes
Humic substances
Variable C, H, O, N, abundance of
carboxylic acid and phenolic groups
Can impart stability to particle
suspensions due to abundance of
carboxyl and phenolic groups; might
be more appropriately described as
dissolved species
Although all the materials listed in Table 3 may interfere with detecting engineered NMs, three
examples are particularly relevant and are discussed in more detail below.
Example #1 Iron Oxides. There are an estimated 100,000 teragrams by mass of iron oxides in
soils (one teragram equals 1 million metric tons)[45]. Given that amorphous iron oxides are
largely nanoparticulates and a significant fraction of other iron oxides are nanoscale, iron oxide
nanoparticles may account for at least 1 percent of all inorganic nanoparticles globally [6]. Iron
oxides are highly effective at scavenging several potent contaminants such as arsenic and
uranium, significantly affecting their fate and transport[46-48]. Iron oxide particles are readily
formed in the environment, generally as part of the redox cycling of iron between the relatively
soluble Fe2+ and insoluble Fe3+ forms. Several types of iron oxides are present in the
environment, including ferrihydrite, hematite, magnetite, goethite, and akaganeite. The formation
of these various iron oxides is a function of numerous environmental factors such as temperature,
pH, and aqueous chemical composition. These materials can form through abiotic and biological
pathways, which determine the morphology of the iron oxide formed. Several nanoscale iron
oxides can be formed from pre-existing iron oxides that undergo phase transformations under
certain environmental conditions. For example, ferrihydrite (approximately FesHOg^FbO) is an
exclusively nanoscale iron oxide that commonly occurs as aggregates of primary particles having
a narrow size distribution of 2-7 nm. The aggregation, rearrangement, and dehydration of
ferrihydrate can lead to the formation of more thermodynamically stable colloidal phases of iron
oxides such as goethite and hematite [42, 43, 45, 49].
Example #2 Clay Minerals. Clay minerals are the most prevalent natural nanomaterials,
particularly in the soil environment. The clay-sized fraction of soils is defined as particles
smaller than 2 jim, encompassing both the colloidal fraction (1-1,000 nm) and the nano fraction
(<100 nm). Nanoscale clay minerals (phyllosilicates) and clay-sized particles are formed via one
of three abiotic pathways: 1) erosion of a pre-existing bulk material, 2) transformation of the
outer layer of a mineral to form two distinct mineral regions, and 3) neoformation, which is a
-------
result of precipitation or crystallization from cation complexes in solution[5]. Some minerals,
such as mica, can form via all three pathways, while others can only form through one process
(e.g., neoformation in the case of kaolinite). Clay-sized nanoparticles can also be formed
biologically as the negative surfaces of bacterial cells collect positively charged cations, which
can then complex with numerous anions present in solution to precipitate out as a nano-sized
material[5]. Clay minerals may be effective at destabilizing nanoparticle suspensions due to the
electrostatic charge on their surface, which can make the detection and characterization of
individual, dispersed ENPs problematic [42, 43].
Example #3 Metal Sulfides. Metal sulfides are abundant in anoxic environments that may have
high metal content (i.e., acid mine drainage waste sites). Abiotic sulfide formation is generally
not favored thermodynamically, but ubiquitous sulfate-reducing bacteria (often
Desulphobacteriaceae) can catalyze processes that result in the formation of a variety of metal
sulfides (i.e., HgS, As2, 83, ZnS, etc.). Using a carbon source as an electron donor, these bacteria
reduce sulfate to sulfide, which then complexes with the metals present, forming insoluble metal
sulfides. These metals sulfides, such as zinc sulfide (ZnS), are in the nanoscale range, typically
forming particles between 2 and 10 nm in size and forming aggregates between 500 nm and 1
jam. Because metal sulfides are frequently found in reduced waters and sediments, they can
potentially interfere with the detection of metallic and semi-conductor ENPs. This is particularly
true for ENPs made from class B and related soft metal cations, including silver nanoparticles
because silver sulfide (Ag2S) is easily formed under environmental conditions [43, 50-52].
Estimates ofENP behavior and fate
Although the examination of nanoscale processes on mineral surfaces is a relatively new field,
there is considerable understanding of the colloidal behavior of mineral nanoparticles. The
processes of surface charge development, flocculation behavior, solubility, and ion adsorption
are well understood, at least for materials in the submicrometer size range. Although unique
reactivity arises for some metal and metal oxide NMs less than 10-20 nm in size, their
environmental stability has been successfully described by much of classical colloid theory. This
includes filtration theory for transport in porous media and flocculation and sedimentation
behavior in surface waters. Only when the ENPs are extremely small and under very low ionic
strength conditions do the underlying assumptions of Derjaguin, Landau, Verwey and Overbeek
(DLVO) theory break down [36]. Thus, the large body of work examining environmental
colloids has direct application to predicting the fate and behavior of engineered nanoparticles.
NM-facilitated contaminant transport in the subsurface
The colloidal nature of nanominerals and mineral nanoparticles is of concern when considering
contaminant transport in groundwater systems. It has long been understood that colloids are
important components in the fate and transport of contaminants dissolved in groundwater. The
ability of colloids and nanoparticlesand by inference ENPsto serve as vectors for
contaminant transport through the subsurface depends on several factors[53]:
Contaminant association with the particle surface.
The concentration of dissolved organic carbon.
The hydrogeologic properties (e.g., hydraulic conductivity) of the aquifer.
-------
Research at one of the most contaminated nuclear waste sites in the world, near Mayak, Russia,
revealed that colloids are responsible for the long-distance transport of plutonium and other
actinides. As much as 70-90 mole percent plutonium was associated with colloids. It was
determined that amorphous iron (hydr)oxide colloids are responsible for the adsorption of Pu
(IV) hydroxides and carbonates as well as uranium carbonates, which can then be transported
through groundwater by way of this nano-vector [46, 47].
Similar behavior was seen at the Nevada Field Site, where actinides and rare earth elements were
also found to bind to iron oxides, manganese oxides, and clay minerals, which can facilitate
transport as far as 4 km from the source of the contamination [54, 55]. Up to 100 percent of the
manganese, cobalt, cerium, and europeum detected was associated with colloids [55]. These
observations lead to concerns that ENPs, under favorable conditions, might be significantly
transported in groundwater either as individual ENPs, as ENP aggregates, or as ENP-colloid
heteroaggregates.
3. REACTIVITY AND PERSISTENCE
The very high reactivity of NMs suggests that these materials will readily transform in the
environment. High reactivity has been observed for many NMs [41] and is a result of their large
surface-to-volume ratio or novel nanoscale properties. Predicting environment-specific ENM
transformations is not yet possible, making it difficult to forecast the fate, transport, reactivity,
and toxicity of NMs in environmental systems. Furthermore, because transformations can greatly
affect the particles' properties (e.g., chemical composition, size, charge, coating), they also affect
the ability to detect and quantify ENMs in environmental and biological matrices.
Transformations of ENMs in biological and environmental matrices will affect the properties of
the core and shell of the NMs and the ability to extract, detect, and quantify them in complex
biological and environmental matrices. Methods developed for the detection of NMs in real
matrices will have to consider the composition of the transformed NMs in that matrix in order to
be applied successfully. Additionally, their physicochemical state may have also been altered as
a result of environmental transformation, which may also affect the efficacy of the analytical
technique applied.
ENMs can be made from a single material (e.g., silver or gold), but often have a core-shell
configuration (Figure 1). Transformations of NMs in the environment can affect the core, shell,
or polymeric organic coating. The "shell" can be an organic molecule or macromolecule, or it
can be a coherent or incoherent metal oxide or metal sulfide.
-------
Ag2S, AgCl, Ag20
O OH O
PVP Citrate
* M^ Shell ZnS
Core
>re w
10 f
ZnO
Figure 1. Typical core/shell structures of Ag, ZnO NPs and CdSe/ZnS quantum dot
Several important transformations can occur in biological and environmental media and may
affect the chemical composition of nanomaterials as well as their properties (including reactivity
and persistence). These changes can affect natural and engineered materials and include:
1. Alterations in the organic coating of the particle.
2. Dissolution and ligation.
3. Oxidation and reduction (redox) reactions.
4. Aggregation.
These transformations greatly affect the potential toxicity of the NM [56, 57] and can inhibit the
ability to isolate, detect, or characterize the materials in environmental and biological media.
These transformations are discussed in the subsections below.
Alterations in Organic Coatings
The surface coatings on nanoparticles (e.g., surfactants or polymers [Figure 1]) strongly affect
how nanoparticles interact with other nanoparticles, via homoaggregation, and with mineral
surfaces (e.g., iron oxides) and organisms (e.g., bacteria or plant roots), via heteroaggregation.
This in turn can influence reactivity, transport, and fate in the environment. Surface coatings can
also affect properties of the nanoparticles that are often used for characterization such as
hydrodynamic radius, effective density, and charge. Changes in surface coatings therefore alter
the ability to detect and quantify nanoparticles in environmental and biological matrices.
Alteration of surface coatings can result from:
Loss of engineered surface coating.
Overcoating by adsorption of natural organic macromolecules.
Replacement of the engineered coating by natural organic macromolecules.
10
-------
Loss of coatings
Nearly all ENPs are designed with an organic coating to control aggregation, enable mixing into
polymeric matrices, or to provide specific functionality to the material. In all cases, there is the
potential for the release of these organic coatings. However, the degree to which release is
expected to occur depends on the nature of the interaction of the coating with the ENP. Coatings
can be strongly or weakly adsorbed to nanoparticles, or they can be covalently bound with
suitable chemistry (e.g., thiol linkages or silane linkages). Desorption is likely for ENP coatings
that are surfactants (e.g., cetrimonium bromide or sodium dodecylbenzenesulfonate). These
coatings typically are bound weakly to the ENPs through van der Waals interactions or
electrostatic attraction. Desorption of higher molecular weight polymeric coatings or proteins is
possible, but because they are strongly bound to the nanoparticle surfaces at multiple points, the
loss of such coatings is much slower [43, 44]. Hence, these coatings are often considered
irreversibly bound [58].
The loss of surfactant and polymeric coatings can change ENP charge and hydrodynamic radius
and therefore can affect interactions with other particles and surfaces (e.g., electrostatic
repulsion, steric repulsion, and electrosteric repulsion). This has significant consequences for the
behavior of nanoparticles in the environment and can also affect detection and characterization
techniques that leverage these properties for separation. These effects are discussed in detail at
the end of this section.
Overcoating or Alteration of Coatings
Overcoating or the alteration of an existing coating is more likely than the loss of strongly bound
coatings [41]. Biomacromolecules (e.g., proteins) are ubiquitous in living cells and in the
environment (e.g., natural organic matter [NOM], albumin, polysaccharides), and their
adsorption is expected to occur in all environments. Once discharged into the environment,
uncoated or coated NMs interact with naturally occurring biomacromolecules or
geomacromolecules including proteins, polysaccharides and humic substances (HS). The
adsorption of biomacromolecules on NM surfaces or within the organic macromolecular coating
of the particle can significantly alter surface chemistry and resulting behavior in biological and
environmental systems [59, 60].
Most work on NM-NOM interactions has used extracted HS. This organic material is a mixture
of macromolecules having different functional groups and range of molecular weight
distributions [28, 31]. Adsorbed NOM can form relatively "flat" monolayers or more extended
(thicker) monolayers or multilayers. The coherence and thickness of the layer depends on the
particle properties and the conditions (e.g., pH and ionic strength) during interaction. The
adsorbed NOM provides both charge and steric stabilization of NMs [31, 61], although it may
also result in bridging flocculation [62] or disaggregation [32].The effects of adsorbed NOM
layers are complex and can be difficult to predict. Inability to predict the effects of NOM on
nanoparticle behavior largely stems from poor characterization of the macromolecules in the
NOM mixture. For example, while it is known that the higher molecular weight fraction (-700
kDa) of NOM provides significantly better steric stabilization of gold nanoparticles compared to
the low molecular weight fraction (-13 kDa) [63], NOM derived from different sources and at
different times of the year will have varying molecular weight distributions. This makes it
difficult to predict how NOM will affect nanoparticle behavior. For larger molecular weight
11
-------
polymeric coatings that are strongly bound, mixed polymer-NOM layers may form on NMs.
However, in some cases, interactions with NOM may be minimal [64]. The conditions under
which mixed layers form and the influence of those layers on NM behavior has yet to be
explored.
Adsorption of lower molecular weight organic ligands, such as those containing thiol groups
(e.g., cysteine), is another interaction that may change NM dissolution, charge, and stability
against aggregation. Organics present in the atmosphere can also condense onto airborne NMs,
altering their surface chemistry [65]. Adsorbed protein coatings form in biological fluids for
several classes of NMs [66]. Adsorbed proteins are dynamic in nature, with the proteins
continuously exchanging between free and bound forms. Similar transformations may occur in
environmental media as well.
Adsorption of metal cations or oxo-anions can also occur, and this affects the NM's properties
[28, 31]. Understanding the effects of organic ligands and adsorbed co-contaminants onNM
properties and the ability to detect them in complex matrices are necessary to advance research
on the environmental behavior and health and safety implications of nanomaterials.
Interactions of colloids with NOM (a common biomacromolecule in the environment) are well-
studied phenomena, and much is known about how these interactions affect the behavior of
natural colloids in the environment. The observed interactions of ENPs with NOM are analogous
to those known for environmental colloids [34, 67]. They are also analogous to the interactions
with proteins in biological systems, which have been the subject of more intensive research
reaching similar conclusions; the behavior of ENPs depends highly on the types and amounts of
biological and environmental constituents associated with particle surfaces.
Impact of coating loss or gain on the ability to detect NPs
Many proteins and other macromolecules are irreversibly adsorbed by nanoparticles over
relevant time scales [58, 68]. Therefore, they partly determine the properties of the NMs (e.g.,
size, electrophoretic mobility, and surface composition) and subsequent environmental behavior
and biological response. Methods used to characterize NMs in environmental and biological
matrices often must consider these coatings as part of the nanomaterial. Otherwise, the coatings
can be obstacles to NM detection and characterization, especially if the methods used were
developed for pristine NMs.
For example, the use of field flow fractionation (FFF) for nanoparticle separation relies on
differences in the diffusion coefficients of materials. Because the loss or gain of a
macromolecular coating influences the diffusion coefficient of a particle, such alterations would
change the effectiveness of this method for separating ENPs. In addition, FFF presumes no
interaction between the nanoparticles and the membrane used in the device. The loss or gain of
coating may increase or decrease such interactions. Similar influences of surface charge on
hydrodynamic chromatography (HDC) separations have been observed [69]. Adsorption of
NOM has also been known to alter surface chemistry, for example, changing the oxidation state
of cerium oxide (ceria) NMs [62]. Changing the oxidation state of the NM affects properties such
as charge, density, and chemical composition. These changes alter the sensitivity of methods
used to quantify NMs and, in some cases, can make a method useless. For example, oxidation of
12
-------
metallic iron (Fe°) or magnetite particles to hematite can make them non-magnetic and decrease
their reactivity with water. Magnetic measurements for the presence of Fe° or tri-iron tetroxide
would thus be rendered useless.
Dissolution andLigation
Many metal and metal oxide nanomaterials made from soft metal cations (e.g. silver, zinc, and
copper) may undergo dissolution or complex with strong ligands, complicating detection and
other analyses. For example, in the absence of sulfide and in oxic environments, silver
nanoparticles will oxidize and readily react with chloride ions to form a silver chloride (AgCl[s])
shell around the silver (Ag°) particle core [70].
Dissolution and strong ligation may greatly affect the properties of NMs (size, charge, chemical
composition), making their detection in biological and environmental media difficult. This can
increase or decrease the difficulty of separating these ENPs from the environmental matrix.
Formation of a relatively insoluble metal-sulfide shell on the particle surface can also induce
aggregation [71], which can affect the ability to detect the number and size of ENPs in a sample.
Partial dissolution and strong ligation of the metal may form a shell on the particles. This change
in chemical composition may alter particle properties used for detection, including ultraviolet
absorbance, resonance, florescence, or reduction in ion release (e.g., dissolved cadmium,
selenium, tellurium, etc. could be an indicator for the presence of quantum dots).
Oxidation and Reduction (Redox) Reactions
Oxidation and reduction (i.e., redox reactions) are coupled processes in natural systems and
involve the transfer of electrons to and from chemical moieties (i.e., NM surfaces, functional
groups). NMs made from elements that can achieve multiple oxidation states (e.g., cerium,
silver, iron, and manganese) are potentially redox active. The occurrence of redox reactions
involving NMs depends on the standard potential for the redox transformation and the
availability of a suitable oxidant or reductant.
Dynamic redox environments (e.g., tidal zones, wetting/drying soils) create great potential for
the cycling of NMs between oxidation states. Many NMs undergo reduction, oxidation, or both
in aquatic and terrestrial environments. For example, NMs made from metals such as silver [72,
73] and iron [74] are readily oxidized in natural waters. Nanoscale zero-valent iron particles are
specifically engineered to be readily oxidized by environmental contaminants such as chromium
or chlorinated solvents [75]. Ceria nanoparticles are redox-labile under environmental conditions
and in biological media [76]. Sorption of macromolecules has been shown to alter the ratio of
Ce(III) to Ce(IV) on the nanoparticle surface [62]. Non-metallic elements in NMs may also be
susceptible to oxidation. For example, the sulfur and selenium in some metal sulfide and selenide
NMs (such as quantum dots) are susceptible to oxidation [77, 78]. The oxidation of reduced
sulfur to elemental sulfur, sulfite, or sulfate in these materials results in the release of soluble,
9-1-
toxic metal ions such as cadmium (Cd ) [79].
Sunlight-catalyzed redox reactions (e.g., photooxidation, photoreduction) may affect NM
coatings, oxidation states, generation of reactive oxygen species (ROS), and persistence in the
environment. This may be particularly important for titanium dioxide nanoparticles and
carbonaceous NMs such as fullerene and fullerene-like NMs [80, 81]. Exposure of aqueous
fullerene suspensions to sunlight can result in the oxidation of the carbon structure,
13
-------
functionalizing the surfaces with hydroxyl and carboxyl groups. Sunlight exposure can also
degrade the polymeric coatings on the NM. In one study, exposure to natural light caused the
degradation of gum arable coatings on silver nanoparticles and induced aggregation and
sedimentation of the silver nanoparticles from solution [82].
A variety of outcomes from redox transformations can affect the ability to isolate, separate, and
detect NMs in environmental and biological matrices. Redox transformations can change the size
and morphology of the particles. Oxidation of metal NMs can result in the formation of an oxide
shell, enhance dissolution, alter the surface charge of the particle, or change the crystal phase of
the material (e.g., oxidation of magnetite to maghemite) [83]. These alterations can also lead to
the loss of the organic coating from the particle, which may significantly impact their fate,
transport, behavior, and consequently their ability to be detected with current analytical
techniques.
Aggregation
Aggregation of ENMs reduces surface-area-to-volume effects on ENM reactivity. Increases in
aggregate size change ENMs' transport in porous media, sedimentation, reactivity, uptake by
organisms, and toxicity. Aggregation includes homoaggregation of particles of the same NMs
and heteroaggregation of an NM and another particle in the environment (e.g., clay, ferrihydrite
or soft biogenic matter). Both aggregation processes can affect the ability to detect these
materials in biological and environmental matrices. When aggregation occurs, the count of NMs
in the suspension decreases with a concomitant increase in their effective (aggregate) size (i.e.,
hydrodynamic diameter). Aggregation can also decrease the available surface area of the
materials, thereby decreasing reactivity. However, the decrease in surface area will depend on
particle number and size distribution and on the fractal dimensions of the aggregate [84].
Aggregation can therefore affect detection methods that may rely on reactivity (e.g., fluorescence
[85, 86] or ability to produce ROS) with the nanomaterial surface. Aggregation may also
decrease the rate of dissolution or degradation, which may affect detection as described in the
previous section on dissolution and ligation.
In most cases, a higher concentration of environmental solids than NMs will result in
heteroaggregation. Heteroaggregation of NMs and comparatively larger particles (e.g., clay) will
change the overall size of the nanoparticles, their charges, and their associated organic coatings.
If the NM-clay heteroaggregates have properties similar to clay particles, separation becomes
difficult, especially if the matrix has a large background of clay particles [87]. In addition, if the
NM of interest is made from elements that are common in the environment (e.g., aluminum, Si,
Fe), detection by chemical methods (e.g., single particle ICP-MS [SP-ICP-MS]) can be difficult
once NM heteroaggregates form.
Biological Transformations
Biological transformations of NMs are inevitable in living tissues and environmental media (e.g.,
soils). These transformations are predominantly redox reactions that occur intracellularly in the
cytoplasm, cell wall, and cell membrane and extracellularly via redox-labile enzymes and
cytochromes[57]. Ancillary intracellular ROS production, such as hydroxyl radical or hydrogen
peroxide (H2O2) production, can also cause biological transformations of nanoparticles. For
example, Geobacter and Shewanella spp. bacteria can respire naturally occurring nanoscale iron
14
-------
oxides, effectively reducing an Fe(III) oxide to a mixed Fe(II)/Fe(III) oxide [88]. The oxidation
and carboxylation of carbon nanotubes (CNTs) by hydroxide (OH) radicals produced from the
horseradish peroxidase enzyme has been demonstrated [89]. This oxidation increases the surface
charge of the CNTs and their stability against aggregation while decreasing hydrophobicity. This
can affect the ability to extract the CNTs from environmental matrices [90] and the ability to
detect single-walled CNTs (SWCNTs) in environmental media, because the oxidation of the
tubes changes their near-infrared (NIR) absorption [91].
Biotransformation of polymer coatings used on many NMs for biomedical applications is also
feasible. For example, bound polyethylene glycol (PEG) coatings on ENMs were shown to be
bioavailable to microorganisms isolated from an urban stream [92]. Moreover, the
biotransformation of the PEG coating caused the NMs to aggregate. These transformations, if
they occur in the natural environment at fast enough rates, will change the properties of the
particles and affect detection methods that rely on detecting the particles' organic coating.
Another characteristic behavior of NMs is persistence in the given media. Even NMs that can
dissolve or transform can persist continuously in a single location provided the appropriate
environmental conditions. Some studies have shown that silver nanoparticle dissolution for
instance will dissolve according to known particle dissolution kinetics [93]. However, when
these materials are applied to wetland soils in low concentrations via biosolid application, they
result in unique nanoparticle-specific effects on microbial populations and nitrogen cycling in the
soil . This is believed to result from their distinctive spatial distribution and long-term slow
release of silver ions in the vicinity of the nanoparticles compared to the Ag+ ion (added as silver
nitrate [AgNO3]) [94].
4. NANOMETROLOGY
Assessing ENP fate, transport, and toxicity in the environment depends on the ability to analyze
ENPs in complex matrices. Many options exist for analyzing pristine ENPs in simple matrices.
Validation and application of the these tools to environmental nanometrology, however, is
relatively underdeveloped. Several authors have reviewed the status of nanometrology [56, 95].
Therefore, this paper focuses on the broader issues of environmental nanometrology and
provides an update on recent literature.
Nanometrology methods can be classified as detection, quantification, or characterization
methods.
Detection determines ENP presence or absence. The detection of ENPs alone has limited
use, but may be helpful for specific studies such as rapidly screening nano-containing
products for NM weathering.
Quantification of ENPs is required for some questions such as: What is the degree of
ENP uptake by exposed organisms?
Characterization methods provide additional details on the physical properties (e.g., size
or shape) and chemical composition of the NMs and facilitate analyses of ENP fate and
transformation. Although relatively straightforward in pristine samples, measurement of
properties such as size, shape, and reactivity becomes increasingly complex in
environmental samples.
15
-------
Processes such as aggregation, dispersion, and dissolution may affect the environmental state of
ENPs. In addition, the ubiquity of naturally occurring colloidal material may further complicate
detection, quantification, and characterization. It is therefore important to determine the most
appropriate metrics for detection, quantification, and characterization of NMs in environmental
and biological media. Multiple metrics may be used to quantify ENPs.
The method for expressing concentration of ENPs is influenced by the research question at hand
and by the anticipated analytical methods. Mass concentrations (mass/vol, molarity) are
generally used for non-particulate contaminants and may also be appropriate metrics for some
ENPs. For readily soluble ENPs such as zinc oxide (ZnO), mass concentration may be the most
important metric, because organism exposure is often via the soluble metal, and organism uptake
is expressed on a mass basis. Particle number concentration has also long been recognized as an
important metric for particulate contaminants, including contaminants in surface waters [39, 96].
Some analytical methods, such as transmission electron microscopy (TEM) and nanotracking
analysis (NTA), rely on detecting and quantifying individual particles. Other methods such as
FFF-ICP-MS determine the mass-to-size-ratio using the integrated signal of the many thousands
of particles present in any given elution volume. Information on ENP size, shape, and density
allows conversion between mass- and number-based concentrations, at least for simple ENPs.
Homo- and heteroaggregation, however, may increase the difficulty of accurately determining
number concentration. Aggregates can be difficult to quantify and by their very nature have
constantly changing number concentrations.
Given the importance of surface-mediated reactions, a measurement of total ENP surface area
per volume could provide a highly relevant concentration metric. However, no available
methodology provides this measurement in aqueous media at environmentally relevant
nanoparticle concentrations. Traditional measurements of surface area (e.g., Brunauer-Emmett-
Teller nitrogen and ethylene glycol monoethyl ether adsorption) cannot be performed because
these measurements must be conducted in non-aqueous environments. Nuclear magnetic
resonance spectroscopy (NMR) techniques can provide surface area information in aqueous
media, but the required concentration range (on the order of a few weight percent) makes it
impractical for application to natural samples. Rather, surface area must generally be inferred
indirectly from both geometric characterization (size, shape, porosity) and mass or number
concentration.
Characterization of ENPs provides data on properties such as bulk chemical composition,
particle size and shape, and mineralogy. Particle size and distribution are often valuable
measurements because of their importance in fate, transport, and possible ecotoxicity [96].
However, particle size, although simple in concept, is a somewhat ambiguous property. Defining
size by a single metric, such as radius or diameter, ignores non-spherical particle geometry,
which is clearly an important characteristic of CNTs. In addition, different nanoparticle sizes are
obtained depending on the methodology employed. Examples of sizing methodology are:
The particle diameter of electron-dense material as determined by electron microscopy.
A hydrodynamic diameter obtained by dynamic light scattering.
A radius of gyration given by static light scattering.
16
-------
Furthermore, particle size distribution can be described in different ways, particularly for
polydisperse materials. Methods for determining size distribution respond differently to various
components of the size distribution depending on how the concentration of materials across the
size range is expressed. Size distribution can be defined as:
A number-weighted distribution, which is applied primarily when using particle-counting
techniques.
A volume- or mass-weighted distribution, obtained using methods that determine the
amount of material in given size or mass ranges.
For metallic ENPs, dissolved metal content is a very important parameter to determine in
environmental samples, although this property is often not considered a component of particle
size distribution. Intensity-weighted distributions, although not ecologically relevant, are
common for light-scattering-based methods. These distributions are skewed to larger sizes due to
the strong dependence of light scattering on particle size.
Engineered surface coatings might allow for selective ENP detection and characterization in the
presence of ambient natural nanoparticulate matter. Physical and chemical properties of the
particle surface are key NM characteristics. Many engineered NMs are highly functionalized
with surface coatings to enhance their stability and reactivity. Coating material composition can
be highly varied, and many materials can be used to impart a desired chemical function (e.g.,
chemical reactivity, electrostatic or steric stabilization). Adsorbed mass and surface
conformation of adsorbed molecules are also key NM characteristics, but the latter is difficult to
measure directly on ENPs in suspension [82].
Because several parameters need to be determined for full characterization of ENMs, multiple
analytical techniques should be used to accurately assess ENPs in environmental samples. The
following sections discuss several analytical techniques and some available instrumentation in
the nanometrology tool kit. Table 4 reviews current analytical approaches for characterizing
ENMs in environmental samples as a framework for determining potential future directions,
namely element-specific methods (i.e. spICPMS and FFF-ICPMS), for the detection,
quantification, and characterization of ENMs in the environment. Established methods to
facilitate ENP characterization in complex media are also re-evaluated [97].
17
-------
Table 4. Analytical approaches: Limitations and needs for ENP analysis
in environmental media
Measured
Property
Particle size
Surface
groups
Particle
number
concentration
Elemental
composition
Current
Analytical
Approaches
TEM, SEM, sP-
ICP-MS, UV-vis,
DLS, Fl-FFF, Sed-
FFF, HOC, NTA
NMR, FTIR, Zeta
potential
spICP-MS, NTA
SEM/EDX, sP-
ICP-MS, ICP-MS,
ICP-OES
Obstacles to Accurate
Detection/Characterization
- Introduction of artifacts from sample drying
(TEM/SEM)
- No elemental specificity (DLS)
- Inability to differentiate between ENMs and
NNPs of similar elemental composition (sP -ICP-
MS, TEM, SEM)
- Obstructed by high background of natural
particles (sP-ICP-MS, TEM, SEM, DLS, FFF)
- Original coating may have been replaced or
overcoated in the environment (NMR, FTIR,
Zeta potential)
- Ensemble techniques unable to characterize
individual particle populations without prior
fractionation steps (FTIR, NMR, zeta potential)
- Unable to determine aggregates from single
particle without parallel imaging/sizing
technique
- NTA is nonspecific for particle type
- Unable to discern particles of natural or
engineered origins
- May require acidification, eliminating particle
integrity (ICP-MS, ICP-OES)
- Sample preparation may alter sample
representativeness
Potential Need
- Analysis of samples in
situ with minimal sample
preparation
- Elemental specificity to
differentiate between
dissimilar nanomaterials
- Requires another
measured property to
differentiate between
particles of similar
elemental composition
- Ability to differentiate
between different particle
populations in situ
- Knowledge of how
surface groups are
attached may help
determine if original
coating persists
- Require knowledge
pertaining to aggregation
state of ENMs
- Determination of
elemental composition in
situ with additional
sample preparation (i.e.
acidification)
General Considerations
Mass detection limit
Size detection limit
Aggregation state
Naturally occurring
nanomaterials
- ENMs are expected to enter into the environment at very low concentrations
(PPt)
- Most nanomaterials are between 1-lOOnm (many smaller than 20 nm)
- Some nanomaterials are not expected to preserve monodisperse state in the
environment
- Degree of dispersion/aggregation is not static and will likely vary in time
- Need ability to discern aggregated from single particle material.
- Concentration of NNPs in the environment are several orders of magnitude
above that of ENMs (ppm vs. ppt)
- Some NNPs have similar elemental composition and morphologies to
ENMs.
- Natural nanoparticles tend to be very polydisperse and can interact with
ENMs in the environment.
18
-------
A. Review of available analytical methodologies
Methods based on separation by size
A very useful, and perhaps necessary, step in the analysis of nanoparticles in the environment is
the separation of particles by size. Separation by size can provide important information on
mass-based size distributions, determine compositional variations with size, and possibly
distinguish ENMs from natural nanoparticles and naturally occurring colloids. The operationally
simplest methods are filtration and centrifugation, but they have been shown to be susceptible to
artifacts and to suffer from low size resolution, particularly for low-density ENMs. As a result,
analytical techniques such as FFF and size exclusion chromatography (SEC)/hydrodynamic
chromatography (HDC) have been developed into very powerful methods for high-resolution
separation and sizing of particles over a wide size distribution. Their characterization power is
enhanced when coupled with other techniques for characterization and chemical analysis of the
size fractions. Disc centrifugation, while lacking the capability of fraction collection or online
coupling to other instruments, provides extremely high-resolution information.
a. Filtration and centrifugation
One of the most common methods used for the pre-fractionation of nanoparticles prior to
characterization is filtration, specifically membrane filtration and cross-flow ultra-filtration
(CFUF). Filtration is limited, however, to only two size distributions: those larger and those
smaller than the membrane pore size. Greater resolution in size fractionation can be achieved
through multi-stage filtration, and its simplicity makes this technique highly attractive for
determining size distributions obtained by chemical analysis of size fractions. However, the
incomplete passage of small particles through membranes can create significant artifacts. But it
is possible that filtration can be used to separate nanoparticles from dissolved constituents if the
membrane size is on the order of a few nanometers [98].
Membrane filtrationparticularly "dead-end" filtration, which uses pore sizes typically greater
than 100 nmis a common method of fractionation, but it is prone to several issues and artifacts.
Concentration polarization, the collection of particles on the membrane surface due to collisions
and electrostatic attraction, can lead to the aggregation of nanoparticles on the membrane
surface, which biases the particle size distribution. This is particularly problematic for particles
that have no surface-attached stabilizing groups, which enables aggregation to occur readily.
Physical clogging of the pores and the buildup of a filter cake are other issues that affect the
passage of nanoparticles smaller than the filter pore size. CFUF partially overcomes these
artifacts by constantly recirculating the sample tangentially across the top of the membrane. The
resulting shear forces limit the amount of sample that accumulates at the membrane surface. As a
result, only small fractions of the filtered particles pass through the membrane at each cycle.
Although promising for some applications (e.g., for the large-scale separation of nanoparticles),
CFUF also has the potential to alter the aggregation state that arises from the increase in colloid
concentration [99].
Centrifugation can also be used to separate particles while minimizing sample perturbation. The
separation of particles is contingent upon the settling velocity overcoming the Brownian motion
of the particles. The settling velocity is controlled by a number of factors such as particle size
and shape, the g-force applied, and the density difference between the particle and the medium.
19
-------
As such, centrifugation is more effective at removing dense inorganic particles as opposed to
almost neutrally buoyant organic material. One of the most pertinent problems with this
technique is that settling particles may scavenge smaller particles due to different settling
velocities, thereby altering the particle size distribution [98].
A hybrid of these methods, centrifugal filtration, is becoming increasingly common for defining
the dissolved fraction of a sample. Several configurations are commercially available. While
centrifugal forces are employed in this method, centrifugation is used to force the sample
through the membrane and is not used to determine particle size.
b. Field flow fractionation
FFF is a very powerful and versatile technique for continuous separation of particles over a
broad size range according to their hydrodynamic diameter (Stokes diameter) [96]. The particles
are separated by the combination of an applied field and a longitudinal channel flow; the
separation all occurs in the mobile phase (as the fluid moves along the channel). The extent to
which the particles act against the applied field (back diffusion) is responsible for the
fractionation of the particle sizes.
The two most applicable types of FFF for the fractionation of nanoparticles are flow FFF (Fl-
FFF) and sedimentation FFF (Sd-FFF) [98]. Both techniques have enhanced characterization
power through online coupling of various detection methods, such as ICP-MS and light
scattering. This allows the sequential analysis of sample fractions that have narrow size
distributions. The linkage of the method to ICP-MS in particular may lead to the elemental
specificity needed to chemically identify particles and perhaps distinguish nanoparticle types
(e.g., ENPs and natural nanoparticles) in complex mixtures.
Generating particle size distributions relies on converting retention times into sizes and detector
response into a concentration metric. While uncertainty in sizing can arise in FFF, determining
the concentration metric depends greatly on the detector type. ICP-MS gives a direct measure of
the mass concentration of nanoparticles eluting at any given size. The responses of absorbance
and light scattering detectors are influenced by the optical properties of the nanoparticles, which
are both material and size dependent. Depending on the extent of the size range under
investigation, analysis times can be longon the order of 20 minutes to more than one hour.
Consequently, FFF does not readily lend itself to high throughput analyses, although advances in
automated analysis can allow continuous operation of FFF.
In Asymmetric Flow Field Flow Fractionation (AF4), particles are injected into a ribbon like-channel
(75-250 |im thick) where a fluid cross-flow acts on the particles, causing the nanoparticles to move
towards an accumulation wall covered by an ultrafiltration membrane that retains particles in the
channel [67, 100]. The concentration of particles forms an equilibrium cloud, where the thickness of
the cloud depends on the velocity of the cross-flow field and on the diffusion coefficient of the particles.
According to the Stokes-Einstein equation, the diffusion coefficient depends on both the viscosity of the
medium and the hydrodynamic radius of the particle. As a result, smaller particles will migrate
away from the accumulation wall and towards the middle of the channel. The geometry of the
channel creates a parabolic flow profile, carrying particles in the middle along streamlines of
higher velocity than those closer towards the accumulation wall [67, 98, 100, 101]. Sufficiently
20
-------
high fields can be generated so that nanoparticles as small as about 2 nm can be analyzed. Some
drawbacks of AF4 include possible membrane interactions, as well as laborious method
optimization [67, 95].
Sedimentation FFF (SdFFF) uses centrifugal force, rather than fluid flow, as the applied field.
This causes particles to separate according to their effective mass, which is the difference
between the particle's true mass and the mass of the liquid displaced by the particle. Currently
available instruments provide g-forces sufficient to analyze gold particles as small as 5-10 nm,
with materials of lower density having consequently larger size detection limits. Resolution in
SdFFF is considerably higher than in Fl-FFF. Buoyant mass is determined and particle
hydrodynamic diameter is a secondary property that can only be determined if particle density is
known [32, 100, 102, 103]. For unknown samples, compositional data obtained by SdFFF-ICP-
MS may allow for an estimate of particle density, and thus allow sizing. In addition, by
combining the buoyant mass obtained by SdFFF and the hydrodynamic diameter from Fl-FFF
the density can be directly computed. Another advantage of SdFFF over Fl-FFF may be the
reduced degree of non-ideal interactions with the stainless steel channel, contrary to polymeric
membranes of the Fl-FFF, making method optimization simpler. The tradeoff is that SdFFF
works best for larger, denser particles.
c. Size exclusion and hydrodynamic chromatography
Column chromatography, both SEC and HDC, also has application in the fractionation and
sizing of nanoparticles for detection and characterization. Analysis times for SEC and HDC are
generally faster than for FFF, and automation may lead to high throughput applications. For
these techniques, size measurement relies on the analysis of known standards, which
(presumably) behave in a manner similar to the analytes of interest during separation. As in FFF,
direct coupling to ICP-MS may give the specificity necessary to differentiate nanoparticle types.
Interpretation of the size distribution depends on the detector used.
In SEC, the particle mixture passes through a column that contains porous packing material
whose pore sizes are in the range of the particles to be fractionated. Separation of the
nanoparticles depends on the length of the flow paths of the analyte. Larger particles will have
access to fewer of the pores than smaller particles. Therefore, the particles are separated by
hydrodynamic volume (both shape and size). The effectiveness of SEC depends mainly on the
pore size of the packing material being within the range of the particles being fractionated [26,
98]. Several problems are associated with SEC, including:
Irreversible adsorption to the packing material is common among ENMs due to the high
surface area of the stationary phase (pore volume) and the high surface activity of the
nanoparticles [104].
Electrostatic interactions may degrade the purely size-dependent transport of particles
through the column. The high ionic strength carriers commonly employed to minimize
this problem, however, may result in aggregation.
SEC has been shown to have low resolution when distinguishing particles of similar
hydrodynamic volume. One possible solution is to recycle the analyte through the
column, thereby increasing the resolution ratio with the square root of the cycle number,
according to both theory and experimental data. Performing this recycling step not only
increases resolution, it also reduces the problems associated with a longer column, such
21
-------
as an increase in back pressure [105]. However, this approach greatly increases analysis
time.
HDC is another column chromatography method that can be used to separate nanoparticles
according to hydrodynamic diameter. Unlike SEC, HDC uses a column packed with nonporous
beads. Flow channels are built up near the surface of the packing material, where the flow
velocity approaches zero near the surface of the bead and reaches its maximum velocity at a
certain distance away from the surface of the stationary phase. Accordingly, larger particles will
elute sooner than smaller particles, as the smaller particles will approach the packing material
closer and interact with the lower velocity areas. Because the separation of the analyte is based
solely on the hydrodynamic size of the particles, the dynamic range of the packed column runs
from molecular sizes up to micron-sized particles [106-108].
Compared to SEC and FFF, HDC has poor peak resolution. But, unlike SEC, this technique
largely avoids phase interactions and has a very large operating range [109]. Several factors can
affect the rate of transport of nanoparticles through the HDC column. At lower ionic strength,
particles are repelled from the stationary phase due to electrostatic repulsion. Conversely, higher
ionic strength compresses the electrical double layer, allowing for van der Waals interactions
between the stationary phase and the particles, which can reduce the transport rate. If the
particles are sufficiently large, van der Waals interactions may also result from the greater area
over which these attractive forces may interact with one another [108].
d. Differential Centripetal Sedimentation
Recent advances in instrumentation have made differential centripetal sedimentation (DCS) an
attractive means of obtaining high-resolution size information, provided the density of the
particles is known. In DCS, a sample is injected into a transparent spinning disc that contains a
fluid in which a density gradient has been created. The sample particles are accelerated towards
the outside of the disc and pass through a beam of visible light. The resulting data (absorbance
versus time) are converted into a particle size distribution using Stokes law, assuming a spherical
geometry. Depending on the particle density and degree of polydispersity, analysis times can be
on the order of a few minutes [68]. This short analysis time would make DCS amenable to high
throughput analysis. However, only a limited number of samples, on the order of a few dozen,
can be injected before the analysis must be stopped, the disc drained, and the fluid replaced.
Ensemble particle detection and characterization methods
Several techniques collect data from a large number (i.e., an ensemble of particles) of
nanoparticles simultaneously, in contrast to the single-particle techniques described below. These
ensemble techniques (e.g., light-scattering, light adsorption) can be useful for characterizing
samples with or without prior fractionation. Information such as particle size, surface
characterization, and particle size distribution can be obtained. Some of these techniques exploit
quantum confinement effects that are unique to NMs, while others rely solely on the particles'
physical characteristics. Although the data obtained from these measurements are complicated by
the inherent polydispersity of the sample, they can be helpful in providing general information
about the sample as a whole.
a. Dynamic Light Scattering
Dynamic light scattering (DLS), also known as photon correlation spectroscopy (PCS) or
22
-------
quasi-elastic light scattering, is the most commonly used method for sizing nanoparticles in
aqueous media. The advantages to DLS include its simple operation, its non-destructive nature,
and its short analysis time. (Results are often available in less than a minute.) DLS is a very
powerful method for monodisperse particles with a narrow size distribution.
DLS measures the rate of fluctuations in light scattered from the nanoparticles. These
fluctuations arise when neighboring particles in solution either constructively or destructively
interfere with the scattered light. The rate of these intensity fluctuations in the scattered light is
analyzed as an autocorrelation function. Due to Brownian motion, smaller particles diffuse light
more rapidly than larger particles and the autocorrelation function decays more quickly. The
diffusion coefficient of the particle can be calculated using this decay rate, the refractive index of
the solvent, the scattering angle, and the wavelength of incident light. The diffusion coefficient
can then be used to determine the hydrodynamic radius of the materials based on the Stokes-
Einstein relationship [98].
DLS has several compounding factors when analyzing polydisperse samples:
Light scattering depends greatly on particle size; smaller particles exhibit scattering
intensity according to the Rayleigh approximation (for Dh < A/20, scattering intensity: I ~
Dh6) and large particles exhibit light scattering according to the Debye approximation
(A/20 < Dh < -A,, scattering intensity: I ~ Dh2). Large particles can mask the scattering
intensity of smaller particles in the autocorrelation function and bias the measurement to
larger particle sizes.
DLS measurements can be very sensitive to dust contamination and have a low size
resolution.
DLS provides no chemical specificity and cannot distinguish ENP types.
DLS assumes spherical particles and cannot provide information about the particle
morphology.
Despite these problems, DLS is still useful for quickly determining the size distribution of
nanoparticles in simple media without pretreatment of the sample [96, 98, 110]. Used alone it is
not suitable for analysis of environmental samples. However, DLS has been used as an online
detector for FFF and SEC, because introducing fractionated nanoparticles into the scattering cell
reduces the issue of polydispersity and dust contamination.
b. Static light scattering
Static light scattering (SLS)also known as multi-angle light scattering (MALS or
MALLS), classical light scattering, or Rayleigh scatteringis a technique that also uses the light
scattering properties of nanoparticles to determine the size of the analyte of interest. Unlike DLS,
which uses the relative motion of the particles to determine particle size, SLS relies on the
angular dependency of the scattered light derived from particle size. This is based on the
principle that particles of different sizes will generate constructive and destructive interference at
certain angles. As a result, the scattered intensity of light is measured at different angles over
time and averaged. This information can then be used to obtain particle properties such as size
and the root mean squared of the radius of gyration. Unlike DLS, SLS can also be used to obtain
information about particle structure and morphology, which can be used in conjunction with data
from DLS to determine particle shape. Like DLS, SLS depends on the Rayleigh-Gans-Debye
23
-------
approximation, which requires the refractive index difference between solvent and particle to be
negligible and for light absorption to approach zero as particle concentration decreases [96, 98,
110]. One of the most successful applications of SLS is the use of MALLS as an online detector
for FFF and SEC. By providing particle fraction prior to MALLS analysis, the problem of
sample polydispersity is reduced. The disadvantage of online coupling is that dilution occurring
during separation creates a need to work at high nanoparticle concentrations, on the order of
milligrams per liter.
Spectroscopy techniques
Various spectroscopy techniques can also be used for nanoparticle detection and
characterization. At the nanometer scale, some particles can experience quantum confinement
effects that result in unique absorbance and fluorescence effects, which depend on particle
composition, shape, and size. Measurement techniques such as infrared (IR) spectroscopy and
NMR spectroscopy can be used to study the surface of these particles, giving information about
surface functionality.
a. Absorption and photo-luminescent spectroscopy
A common method for characterizing nanoparticle size is UV-visible spectroscopy (UV-Vis),
which uses UV radiation to excite the sample and measure its absorbance as a function of the
intensity of light initially transmitted through the sample. Due to their size, several nanoparticles
have the capacity to exhibit unique optical-electrical properties caused by quantum confinement
effects. These effects are responsible for both size-dependent band gaps within ENMs (band gaps
increase with decreasing particle size) and size-dependent absorption extinction coefficients
(absorptivity increases as particle size increases) [111]. Some ENMs also exhibit a surface
plasmon resonance band, which is caused by the oscillation of electrons at the metal-dielectric
interface, leading to a characteristic absorption band that is dependent on size. These properties
can be used to characterize the size, shape, and surface functionality [98, 112] of a given
nanoparticle. UV-Vis has been used to study the aggregation state of functionalized and bare
gold nanoparticles. When the gold nanoparticles aggregated, the surface plasmon degenerated
into two bands: a transverse resonance band that absorbed shorter wavelengths of light and a
longitudinal resonance band that absorbed longer wavelengths of light. Both bands were
detectable by UV-Vis, demonstrating the ability to monitor stability and surface functionality of
the gold particles [31, 113]. The surface plasmon resonance is also affected by the shape of the
ENM because the interface between the surface of the ENM and the dielectric medium depends
on the shape and size of the nanoparticle [114]. Application of UV-Vis to complex multi-
component systems requires pre-fractionation by methods such as FFF or HDC.
b. Infrared spectroscopy
Fourier-transform infrared spectroscopy (FTIR), which can determine functional groups based
on their vibrational stretching modes and molecular symmetry, has the capability to characterize
not only the NM but also the surface groups attached to the surface of the nanoparticle. In
particular, near-infrared fluorescence spectroscopy (NIRF) has been used to characterize
carbonaceous NMs such as CNTs and both Ceo and C?o fullerenes [115]. Although the number of
IR active vibrational modes in the analysis of CNTs is diameter-independent, the location of the
peaks is highly dependent on tube diameter. Smaller diameter tubes have been shown to exhibit
greater absorption intensity at shorter wave-numbers, which may be useful in distinguishing
24
-------
single-walled and multi-walled CNTs from one another [116]. The use of NIRF for the analysis
of CNTs is very promising due to its high sensitivity, ease-of-use, and low background signal
due to the fact that biological and naturally occurring molecules rarely fluoresce in the near-
infrared region [56].
FTIR is also commonly used to characterize fullerenes because four strong vibrational modes are
present in Ceo fullerenes due to their truncated icosahedral symmetry [117]. This can distinguish
Ceo fullerenes from C?o fullerenes, which exhibit six vibrational modes due to their relatively
lower symmetry [118]. By using a rough metal surface, the FTIR signal can be enhanced in both
reflected and attenuated total reflectance (ATR) modes. This is accomplished by exploiting
surface plasmon effects of the substrate, increasing measurement sensitivity. This technique is
known as surface enhanced infrared absorbance (SEIRA) and has been used to characterize Ceo
NMs[119].
IR spectroscopy has also been useful in characterizing the functional groups attached to the
surfaces of NMs because the technique is specifically attuned to the vibrational stretching of the
bond between one element and another. It has been used to characterize the surface groups on a
wide range of NMs, from mesoporous silica such as mobile crystalline material-41 to gold
nanoparticles and iron oxide nanoparticles [120-122]. Application to natural samples, where
nanoparticle concentrations are low and possible interferences are present, may limit this
technique's applicability.
c. Nuclear magnetic resonance
NMR can be used to study the local arrangement of atoms in a nanomaterial. In particular, solid-
state magic angle spinning (MAS) NMR has been used to characterize a wide array of ENMs,
ranging from the structural arrangement of amorphous zinc phosphate nanoparticles to the
characterization of zeolites used in the dehydrogenation of benzene [115, 123, 124]. In addition
to studying the local arrangement of atoms in a material, NMR can be employed to study the
binding of surface groups to nanoparticles [125]. NMR has been used to investigate water
adsorption to CNTs, specifically by using hydrogen (1H) MAS NMR to increase spatial
resolution [126]. In addition, phosphorous (31P) NMR was used to investigate the binding of
phosphoric acid to tin dioxide (SnC^) nanoparticles [125]. Despite its high sensitivity and ability
to characterize a material at the atomic level, this technique has a number of drawbacks. They
include difficulty in selecting an appropriate isotope for analysis and interference from naturally
occurring magnetic materials such as iron oxides.
Particle counting and characterization methods
In contrast to the previously discussed methods, the following methods determine the
characteristics of NMs one particle at a time:
Electron microscopy.
Nanoparticle tracking analysis.
Single particle ICP-MS.
Laser-induced breakdown detection.
The particle-number-based methods give information on the physical characteristics of the NMs
and in some cases can provide number concentration data.
25
-------
a. Electron microscopy
Several electron microscopy techniques can give direct size and characterization information
about a single particle in a sample:
In TEM, the electron beam passes through the sample, interacting with the electron
density of the sample to produce an image. This gives a physical image of the particle
shape and size and can be used on particle sizes ranging from micron to sub-nanometer
materials.
SEM also uses an electron beam, but instead of passing through the sample, the beam is
reflected back at an angle towards a detector that gives a surface image of the particle. In
doing so, a better picture of the shape and morphology of the particle can be obtained.
Cryogenic SEM has been used in some studies to obtain a snapshot of the sample that
preserves the state of the ENM in an environmental sample [30, 96, 98, 127].
Most transmission and scanning electron microscopes come equipped with energy dispersive X-
ray capability, which allows the user to determine the chemical composition of the material
being imaged. Though the size information obtained from electron microscopy is very precise, it
would require many images of the sample to obtain a statistically significant particle number
concentration. In addition, these techniques require high vacuum, which alters the natural state of
the ENM in an environmental sample.
b. Nanoparticle tracking analysis
Like previously discussed light scattering techniques, nanoparticle tracking analysis (NTA) uses
Brownian motion and diffusion coefficients to determine the size of a nanoparticle. Unlike DLS
and MALS, however, a single nanoparticle is tracked by a charge-coupled device (CCD) camera.
The particle first is detected by light scattering, then tracked from its initial position as a function
of the distance moved in a given time interval determined by the camera's frame speed. The
distance traveled is then related back to the hydrodynamic radius using a modified Stokes-
Einstein relationship. An obstacle to the use of NTA is the need to choose a travel distance long
enough for a statistically relevant number of particles to be sized so that a particle size
distribution can be determined while still maintaining accuracy in the measurement [128-130].
Some information on particle aggregation can be obtained by comparing the intensity of light
scattered by particles of the same size.
c. Single particle ICP-MS
ICP-MS has been a mainstay in determining the elemental content of aqueous and environmental
samples. Typically, this technique has only been used to determine total elemental concentration
in a sample, but recent advances have made it possible to determine the elemental composition of
single particles in the sample. This technique has been used for a wide range of applications
including the detection of CNTs, the analysis of silver nanoparticles in wastewater, and the
release of nanoparticles from consumer products [131-133]. In single particle ICP-MS (SP-ICP-
MS) an undigested sample is first nebulized into an argon plasma, which decomposes the sample
and ionizes the constituent atoms. The ions then pass through a mass selector (e.g., quadrapole,
magnetic sector) and are detected. Determining the elemental composition of single particles is
achieved by reducing the dwell time (the duration for which the instrument takes a reading) to a
microsecond value. This allows a nanoparticle to be detected as a pulse of intensity above a
26
-------
background of ambient ion signal. The assumption is that each pulse correlates to one
nanoparticle event, which allows a particle number concentration to be calculated as the number
of pulses obtained during a reading divided by the volume of sample analyzed. Size information
can also be obtained by generating a calibration curve of intensity for a given mass of dissolved
analyte and using a standard particle to determine the efficiency of the mass flux for a given
intensity. The signal intensity produced by a given particle event can then be used to calculate
the equivalent mass of the particle, which can be converted into a size if the density of the
material is known. Samples often need to be diluted for this technique so that the concentration
will be sufficiently low (low parts per trillion to parts per billion, depending on particle size) to
ensure that only one particle enters the plasma at a time [128, 131, 133-135]. Because only
particles containing the element of interest are detected by the ICP-MS, other background
particles do not interfere with the method.
d. Laser-induced breakdown detection.
A highly sensitive single particle characterization technique is laser-induced breakdown
detection (LIBD), which uses a pulsed laser to form a plasma when a particle passes within the
focal volume of the optical cell. This technique is based on the principle that the energy required
to breakdown the dielectric properties of water surrounding a nanoparticle will be less than that
of pure water. As such, breakdown should only occur when the particle passes through the path
of the laser. Either a piezo-electro crystal attached to the cuvette or a CCD camera captures the
breakdown event. LIBD measures the breakdown probability, which depends on particle size and
concentration. The main drawback of this technique is its extreme sensitivity to small particle
sizes and low concentration (less than parts per trillion). However, this technique is not able to
distinguish between particle types, and variation in particle composition may cause problems in
relating the information obtained during the measurement back to the calibration curve [67, 98,
136].
Optical and biological sensors
A relatively new method for the direct detection and characterization of NMs is the application
of sensors. Two types of sensors typically are employed. The first type is nano-enabled sensors
that incorporate nanoscale materials. Chemical sensors, such as fluorophores, can be used to
detect NMs at very low concentrations. For instance, a rhodamine-derivative fluorophore can be
transformed into oxazoline in the presence of Ag+ (resulting from the oxidation of a silver
nanoparticle), which elicits a strong fluorescent response. This enables detection of the presence
of silver nanoparticles down ug L"1 concentration levels, although this particular technique's
effectiveness can be reduced by ambient silver ions in the environment as well as other ions that
may interfere with sensors that are less-ion specific [26, 96, 137]. Biological sensors are the
second type of sensor used to detect ENPs. Antibody-antigen recognition can be a highly
selective mechanism for the identification of nanoparticles. For example, oligonucleotides with
repeating cytosine bases combined with a fluorophore can be used to detect silver nanoparticles.
Coordination between surface-associated silver ions and cytosine leads to a conformational shift
in the oligonucleotide from a random coil to a hairpin structure, which greatly enhances the
fluorescence signal [26].
Biological sensors are used more commonly to detect the toxicological response to ENPs in
biological systems. In particular, several techniques measure the generation of reactive oxygen
27
-------
species as a result of ENM cytotoxicity. Dissolved oxygen sensors also can be used to monitor a
cell's respiration, giving insight into ENP toxicity. Last, more complex biological systems, such
as the Langerndorff heart, can be used to monitor the toxicity of ENPs [138]. Though these
sensor techniques have the potential to be tailored to ENMs, several possible interferences, such
as dissolved constituents, may bias the measurements [96].
B. ENP Characterization in Complex Laboratory Matrices
Although nanotechnology is a fast-growing commercial enterprise, and some of its materials
incorporate ENMs, its widespread integration into commercial products is relatively recent (i.e.,
occurring over the past 15 years). While a goal of many government agencies is to determine the
extent of the risks nanotechnology may pose to the environment, very little is known about how
ENMs behave in environmental matrices. The appropriate application of nanometrology for the
detection and characterization of NMs in complex systems is still in its early stages. As a result,
a great deal of effort has been spent studying nanoparticles in a controlled laboratory setting,
where researchers can precisely control variables that may mimic environmental matrices. Some
key characteristics that need to be identified in the environment are:
Size.
Surface charge.
Aggregation or dispersion state.
The extent of dissolution.
This section reviews research that has been performed to characterize and identify these metrics
under controlled conditions that mimic those that may be found in environmental systems.
Size, morphology, and aggregation state
Information about the size of NMs may be key in determining the extent of potential
bioaccumulation and transport of these materials in the environment. Some ENP dispersions may
have narrower size distributions than their naturally occurring counterparts as nanomaterials
produced anthropogenically are tailored for specific, size-dependent properties; whereas,
naturally occurring nanomaterials generally will not have such restrictions.
Most electron microscopy measurements can be performed in conjunction with elemental
analysis via energy dispersive spectroscopy (EDS), which can give particle-specific information
about composition. This technique has been used to characterize a wide variety of NMs in
different matrices, including silver nanoparticles that had been synthesized in the presence of
natural organic matter and metallic NMs found in various food and commercial products [110,
130, 139]. Despite its utility, there are some disadvantages to this technique. Many images are
required to generate an appropriate size distribution, because the technique determines the size of
individual particles one at a time, and, because NMs are found in very low concentrations in the
environment, it may be necessary to evaporate the sample in order to concentrate it enough for a
TEM measurement [134]. Due to the high background level of naturally occurring nanoparticles
in the environment, it may also be difficult to find ENPs in a TEM sample image. Last, TEM
requires the samples be dried for analysis, which may disturb the state in which the NMs are
found in the environment.
28
-------
In addition to microscopy, DLS is one of the most frequently used methods for determining the
size of nanoparticles in aqueous media [98, 110]. Many studies have recorded DLS
measurements in short time intervals, in what is known as time-resolved DLS. Using DLS to
measure hydrodynamic size rapidly allows the growth of aggregates to be monitored over time.
This capability has been used to understand the effect of humic and fulvic acid interactions with
particles, particle homoaggregation, and particle heteroaggregation with clay minerals in an
aqueous environment [28, 31, 32, 140]. Unlike some other measurements, there is no need to
generate a calibration curve or pretreat a sample in order to record a DLS measurement. Despite
its many uses, the information available through DLS measurements is limited, because the light
scattering mechanics cannot account for the shape or chemical composition of the particle. In
addition, larger particles may mask the signal from smaller particles, making the analysis of
polydisperse samples (the norm for environmental samples) intractable.
The size of some NMs may be indirectly determined using UV-Vis spectroscopy and exploiting
the surface plasmon resonance of the nanoparticle. This technique has been used frequently to
monitor the size and aggregation kinetics of gold nanoparticles [141-143]. Studies have shown
that the intensity of the surface plasmon resonance maxima may decrease with aggregation, or
red-shift from the transverse plasmon band to the longitudinal band upon aggregation [31]. UV-
Vis has also been used to study the shape-dependent properties of silver nanoparticles, which
may be useful in characterizing the shape of NMs in aqueous samples [114].
FFF can also be used to size nanoparticles. With a standard calibration curve, one can separate
and size a poly-dispersed sample of NMs. When coupled with the appropriate detector, other
important properties such as surface charge and composition can be ascertained. Both flow and
sedimentation FFF have been used in a variety of complex biological and environmental
matrices. Although FFF cannot distinguish between natural and engineered nanoparticles on its
own, element-specific information can be obtained when it is coupled with ICP-MS. This
coupling can aid in differentiating ENPs from high background levels of naturally occurring
NMs [101, 144]. This technique has also been applied to silica nanoparticles extracted via acid
digestion from rat tissue homogenate and human endothelial cell lysate [102]. FFF can also be
used to monitor aggregate growth, as was shown in solutions of silver nanoparticles in
wastewater [144].
One other technique capable of sizing nanoparticles is SP-ICP-MS, which can provide element-
specific information about individual particles that are ablated in the plasma. This technique has
been used to size a variety of NMs such as silver, gold, and metal oxide particles in various
complex media (e.g., wastewater, bovine serum albumin). Although this technique requires
information regarding particle shape and is currently limited by the size of the nanoparticle, it
can be a powerful technique for characterizing NMs at environmentally relevant concentrations
and does not require any prior fractionation [128, 131, 135, 145].
Surface charge/surface groups
The surface groups attached to ENMs may help in distinguishing them from naturally occurring
NMs. Surface groups serve many purposes, such as stabilizing the particles to prevent
aggregation or imparting binding specificity to the nanoparticle for a specific use. As such,
characterizing these surface groups is important to the characterization of ENPs. Different
29
-------
methods can be employed to study nanoparticle-surface group interactions. These methods
include NMR and IR spectroscopy. FTIR spectroscopy has been used to study humic acid
sorption onto silica and magnetite ENPs, which may be an important mechanism upon release
into the environment [146-148].
Similarly, zeta potential is an important property to measure and has implications for the
transport and retention of NMs in the environment. Although most ENPs are coated with specific
surface groups, these groups may be replaced or overcoated in aqueous environments by
ubiquitous organic acids. Many studies have shown that ENPs in the presence of humic acid
exhibit a strong negative charge, a result of the many carboxylic acid and phenolic groups
present on the molecule [28, 31]. Surface charge is important because strong charges (both
positive and negative) tend to lead to more stable particle dispersions. In contrast, as surface
charge approaches zero, particles are less electrostatically stabilized, leading to a higher
incidence of aggregation [140]. Measuring the surface charge of ENPs in environmental matrices
(e.g., soil and sediment pore water) is not possible without isolating the specific ENPs of interest
from other charged particles in the matrix.
Dissolved ions vs. nanoparticulates
In addition to high background levels of incidental and naturally occurring NMs, many
environmental samples will contain a high concentration of dissolved ions that, when using
chemical analysis-based methods, may overestimate the amount of material present in
nanoparticle form. One way of distinguishing between nanoparticles and dissolved forms of the
material is through filtration methods, whereby particles can be size-fractionated, with the
remaining fraction composed of dissolved ions. Similarly, centrifugation can also be employed to
where particles may settle out under the centrifugal force, and the supernatant that is decanted
should contain the dissolved forms of the material [147, 149].
SP-ICP-MS can also distinguish between dissolved and nanoparticulate forms of the material, as
NMs will be represented as pulses above the background levels and dissolved forms are present
as an elevated background signal. Although still under development, this technique has already
shown promise in its ability to distinguish between nanoparticles and dissolved forms of the
nanoparticle [128, 131, 135, 145].
C. ENP Detection and Characterization in Environmental Samples
Despite efforts to recreate the conditions ENPs are exposed to in the environment, the primary
goal of most research is to develop sufficient techniques to detect and characterize these
materials in environmental samples. Several challenges impede the ability to effectively
characterize ENPs, including their expected low aqueous exposure concentrations (measured in
ng/L), the high background levels of naturally occurring suspended colloidal material, and the
inability of current techniques to isolate the ENPs from the matrix without introducing artifacts
or perturbing the sample. These challenges are compounded for soil and sediment systems by the
even higher concentrations of background particles ranging from nanometer to micron size.
Although few reports on detecting ENPs in environmental samples exist, their number can only
be expected to grow as a greater number of manufactured NMs are increasingly released into the
environment. The following section is a brief summary of research into the detection and
30
-------
characterization of ENPs in environmental media. The section also discusses general
considerations for the analysis of these materials in complex environmental matrices.
Expected low ENP concentrations
Current risk assessment models and projections have determined that ENPs will enter the
environment at parts-per-trillion (ng/L) concentrations [26, 150]. As such, the ability to detect
and characterize these materials may be limited by the detection limits of the chosen
instrumentation. Various sizing techniques for the characterization of ENPs in simulated lake
water were reviewed[151]. They determined only electron microscopy techniques could operate
at the appropriate concentration levels for the study (1-100 mg/L). Some techniques, such as
NTA, could not generate a sufficient light-scattering signal to analyze the sample properly. Many
of these sizing techniques require higher concentrations of analyte to operate than are found in
the environment [151].
To characterize ENPs in environmental samples, it may be necessary to pre-concentrate the
sample. Occasionally, concentrating ENPs in a sample can be simple, such as evaporation or
centrifugation [26, 152]. Other techniques, such as cloud point extraction (CPE) and solid-phase
extraction (SPE), have been used to separate nanoparticles from their environmental media in
order to concentrate and characterize them [153, 154]. Many of these pre-concentration steps
may introduce artifacts into the sample, which obscure the sample's environmental state. It is
therefore important to either choose the appropriate technique to analyze the sample at the
expected concentrations, or be aware of the many artifacts that can develop when concentrating
the sample. A higher concentration of particles can also result in agglomeration of the smaller
colloids, distorting the representativeness of the sample [151, 152].
Elevated natural NP / colloid background
The many analytical challenges resulting from the low concentrations of ENPs in environmental
samples are further compounded by the relatively high concentration of naturally occurring
nanoparticles and incidental nanoparticles that are ubiquitous in the environment. These natural
nanoparticles arise from various biological and abiotic processes in the environment that produce
particles of similar sizes, shapes, and in some cases composition, to the ENPs expected to enter
the environment [5, 6]. ENPs are likely to constitute a very small fraction of the total colloidal
population in environmental systems. Sample prefractionation methods that separate ENP from
natural background materials may facilitate detection and characterization.
The most widely used fractionation techniques are centrifugation and filtration [152, 155]. These
techniques have been applied to soil leachates and wastewaters to fractionate particle size
distributions with mixed results. Although filtration is the preferred method due to its relative
ease of use and cost, artifacts can be introduced as a result of particle adhesion and aggregation
at the membrane surface [152, 156]. Similarly, centrifugation can induce aggregation as the
differential settling velocities during the centrifugation process can result in a higher number of
particle collisions [98, 152].
To limit the generation of fractionation artifacts, many researchers use FFF as a suitable
alternative for the separation of nanoparticles. AF4 has been used in the analysis of organic
macromolecules and inorganic colloids in different environmental media such as lakes, oceans,
31
-------
and soils [98, 101]. SdFFF has also been applied to the fractionation of colloids from soil
leachate and is both a complement and an alternative to centrifugation and filtration fractionation
methods [152]. The ability to characterize the separated fractions, however, will be reliant on the
detector coupled to the FFF. Whereas light-scattering detectors require relatively high
concentrations (< 1 mg/L) to achieve sufficient scattering (DLS, MALLS or absorption [UV-
Vis]), FFF may be coupled to ICP-MS to produce detection limits as low as ng/L for some
elements, approximately the concentration expected for ENPs in the environment [131, 144,
151].
The surface properties imparted by engineered coatings may allow for selective extraction of
these colloids from environmental samples. This is most often the case with carbonaceous
materials such as fullerenes. Their hydrophobic nature is exploited via extraction with a non-
polar solvent (i.e., toluene) and subsequently analyzed. For functionalized water-soluble
nanoparticles, extraction by toluene may be insufficient and salt addition, evaporation, or solid-
phase extraction may be necessary [154]. In addition to extraction, sensors may be developed to
interact specifically with nanoparticle coatings and selectively detect the NMs in a complex
matrix. The greatest obstacle in using this technique is either the degradation or over-coating of
the surface coating in the environment as a result of natural processes [26, 96].
Selective detection and characterization of SWCNTs in the environment has been achieved using
NIRF. SWCNTs can be classified as metallic or semi-conducting based on their chiral-wrapping
index, with the semi-conducting type accounting for nearly two-thirds of the distribution of
chiralities. These semi-conducting CNTs fluoresce in the NIR range when excited by visible/NIR
light at wavelengths between 600 and 800 nm. Such emission allows for specific detection of
SWCNTs even against the high background levels of other organic and carbonaceous materials
that are abundant in environmental samples. The emission wavelength is also directly related to
the diameter of the CNT, making this a useful characterization technique as well. This technique
has been used to detect different diameters of SWCNTs in estuarine, sediment, and biological
matrices[91]. The extraction and pre-treatment of these samples will be extremely important.
Yet, the selective identification and characterization of SWCNTs shows that NIRF spectroscopy
is a promising and powerful tool for the detection of semi-conducting CNTs in the environment
[90, 91].
X-ray Absorption Spectroscopy
Many nanomaterials are crystalline metal or metal-oxide materials, or they are made from semi-
or highly ordered arrays of atoms. One technique for determining the speciation of metal
nanoparticles in environmental and biological samples is X-ray absorption spectroscopy (XAS).
This technique has been used to speciate metals in environmental samples for several decades
[157]. One advantage of XAS over other techniques is that absorption spectra can be collected
directly from wet samples, including soil, sediment, and tissue. This non-destructive, in situ
analysis eliminates the need to isolate the NMs from the sample prior to measurement provided
that the NMs are present in sufficient concentrations. Another advantage of the technique is that
it is element specific, i.e., information can be collected on only a specific element in the sample
such as cerium, silver, or titanium. While detection limits are energy dependent and element
specific, the speciation of metal and metal oxide nanoparticles can be determined in samples
with concentrations of metal as low 10 to 100 mg/kg [56]. With fairly simple sample
32
-------
concentration techniques (e.g., collection of fines from specific samples), the lower end of the
detection limit may be extended.
Disadvantages of XAS include:
The spectra provide an "average" speciation of the specific element in the samples and
therefore cannot provide particle-specific information.
XAS must be performed at a synchrotron facility, which is highly specialized and
expensive to operate.
ENMs made from very common environmental elements such as iron or aluminum could
be difficult to characterize using XAS due to the presence of high background
concentrations of that element.
Despite these limitations, XAS is perhaps the only technique that can provide in situ
determinations of the speciation of metal ENPs directly in environmental samples and so is a
critical tool to advancing research in the environmental health and safety of ENMs.
XAS can provide two principal types of information:
The first type is the average oxidation state of the metal in the sample being investigated.
This information comes from the X-ray Absorption Near Edge Region known as XANES
(X-ray Absorption Near Edge Structure) or Near Edge X-ray Absorption Fine Structure
(NEXAFS). Simply stated, the ability to eject a core electron from the metal atom with
X-ray photons is easier for less oxidized materials, so the energy at which a sample
begins to absorb X-ray photons indicates the oxidation state of the metal in that material.
For example, the oxidation state (or ratio of oxidation state) of cerium in cerium dioxide
nanoparticles was evaluated using XANES [158]. XANES can also be used to indicate
the degree to which redox transformation of the ENM may have occurred.
Second, XAS provides information about the local bonding environment surrounding the
metal being probed. This information is garnered from the X-ray Absorption Fine
Structure (XAFS) or Extended X-ray Absorption Fine Structure (EXAFS) region of the
XAS spectra, or it can be determined from the XANES region if different species have
distinct XANES features. Simply stated, this allows the determination of what elements
the metal is bonded to. For example, silver will have all silver nearest neighbors in a
Ag(0) ENP, but will have oxygen or sulfur nearest neighbors in silver oxide (Ag2O) and
silver sulfide (Ag2S), respectively. This gives rise to unique spectra that can be used to
determine the average speciation of the ENP in the samples. The shape of the spectra and
bonding distances can also be used to obtain structural order information about the metal
in the sample.
Both XANES and EXAFS have been used to monitor the transformation of ENPs in
environmental samples such as biosolids, soils, sediments, plants, and other biological tissues.
For example, the speciation of silver was monitored using EXAFS during an 18-month,
simulated wetland mesocosm experiment[159] and using XANES in biosolids [160]. Speciation
of ZnO and CuO NPs were determined using XANES in the shoots of wheat plants exposed to
these nanomaterials [161]. The transformation of the speciation of titanium dioxide nanoparticles
(anatase vs. rutile ratio) inside plant tissues was identified using XANES [162].
33
-------
Preserving sample representativeness
Arguably the greatest challenge in characterizing of ENPs in the environment is the ability to
analyze these materials in situ with minimal perturbation. Currently, no field instrumentation
exists that can detect ENPs in environmental samples. Therefore, great care must be taken when
sampling these materials to minimize any perturbation that would diminish the sample's
representativeness.
The imaging of ENPs is a particular challenge, because the mainstay of nanoparticle imaging,
TEM, requires a vacuum that can introduce artifacts such as aggregation from the concentration
of particles, the formation of a meniscus that can obstruct particle imaging, the precipitation of
salts and other dissolved species that obscure particle imaging, and the introduction of several
interferences into the EDS spectrum. To this end, some researchers have used environmental
SEM, which operates above vacuum pressure. However, the residual water layer obstructs some
of the particle imaging and reduces the resolution due to interactions of the electrons with the
water vapor [98]. A relatively new imaging technique, WetSEM, uses electron-transparent
capsules, which allow for imaging of the ENPs under fully liquid conditions. Tiede et al. [146]
used this technique to image metal oxide nanoparticles under fully liquid conditions and
investigated various capsule membrane coatings to adhere the particles of interest to the
membrane wall to improve imaging. Although more work is required to fully develop this
technique, it has several advantages over conventional SEM, as the various drying artifacts are
avoided and an accurate EDS spectrum can be obtained [163].
Another rapidly developing technique that could allow for the characterization of ENPs is SP-
ICP-MS. By detecting individual particles and aggregates as pulses of intensity during a given
dwell time, the signal intensity generated can be converted to mass and, assuming a particular
morphology, determine particle size. This technique has been applied to various metal oxides,
gold and silver nanoparticles, and CNTs, demonstrating the technique's utility for characterizing
these materials under environmentally relevant conditions [128, 131, 133, 135, 144, 145, 164].
Although data on its application to environmental samples are limited, this technique has been
used to detect silver nanoparticles in wastewater effluent, confirming that current wastewater
treatment methods are insufficient at removing ENPs from waste streams [131].
5. NEW APPROACHES
The need for the development of sensitive and selective techniques for the detection and
characterization of ENMs stems from their unknown ecological risk. The current paradigm is
that risk is a combination of exposure and hazard. Hazard will be a result of the inherent
ecotoxicity of the ENM. It can be assumed that most exposure will come from NMs used (and
released) from consumer products or product manufacture. If either of these components is
considered "high," then risk is possible. Exposure can be conceptually related to a number of life
cycle components in the following equation:
E = I (S xf) x D
34
-------
Where
E is the exposure potential that varies as a function of S.
S is the sum of the NM source mass in various commercial products.
/is the fraction of NMs released from the various products.
D is the distribution of NMs within environmental compartments.
Whereas current studies are ongoing in assessing the hazard of these nanomatierals, the
instrumentation and methodology necessary to quantitatively assess the exposure is still
underdeveloped. Though many of the previous analytical techniques discussed can be employed
to nanomaterials in pristine conditions, and in some cases complex environmental matrices, there
is still a need for instrumentation that is sufficiently selective, sensitive, and robust to overcome
the significant challenges to ENM detection in the environment. This section details potential
future directions for nanometrology and its ability to overcome: the challenges of environmental
transformations of ENMs; low expected release concentraitons; and the ubiquity of naturally
occurring nanomatierials that obstruct the detection of ENMs in the environment.
Mass spectrometry-based methods
MS has become the workhorse for both inorganic and organic environmental analysis. Organic
contaminant analysis by MS, generally coupled with some form of chromatography, allows
evaluation of exposure concentrations and the study of contaminant transformations at
exceedingly small concentrations (e.g., parts per quadrillion). Similarly, inorganic analysis,
generally by ICP-MS, can give information on elemental concentrations at parts-per-trillion
levels. The addition of chromatography allows the form of the metal and its speciation to be
determined. This can be essential to risk assessments of metals, because not all metal species are
equally bioavailable. Although powerful, MS is challenged by NMs. In general, NMs do not
display molecular structures that MS can identify and distinguish from background components
as readily as MS can for organic contaminants. Furthermore, physical characteristics and
chemical composition must be determined to fully characterize NMs. Despite these limitations, a
number of applications of MS may serve to detect and quantify NMs in environmental and
biological media.
Element Ratios
A number of important ENMs contain relatively common elements such as silicon, iron,
titanium, and cerium. These are manufactured as pure oxides and thus contain only oxygen in
addition to the metallic element. In contrast, in natural background particles, these elements
generally either exist largely in more complex, multi-element-containing minerals, or contain
trace element impurities. Thus, in environmental samples containing only natural particles, water
samples in particular, a specific ratio of these elements to other background elements will exist.
The element ratios should be a fingerprint of the natural particle population and reflect the source
materials (i.e., watershed soils or aquifer materials). The introduction of elementally pure
materials should perturb the natural ratio. The ability to detect ENPs through perturbations in the
natural ratio depends on the amount of ENPs introduced, the concentration of background
elements, and the accuracy of the MS in quantifying the ratios.
In general, high-resolution ICP-MS instruments can measure element ratios to 0.1 percent (one
part per thousand) accuracy. For example, a bulk sample analysis of element ratios, in order for
35
-------
an engineered titanium dioxide particle to be detected, it must contribute at least 1/1,000 of the
total titanium mass in the sample. If background particulate matter is in the mg/L range, with
titanium present as a few percent of the particle mass, then titanium from ENPs must be present
in the range of a few hundred micrograms per liter (|ig/L). Although certainly possible, for most
elements associated with ENPs, these levels are not expected in most environments. Methods to
separate ENPs from the larger particles in the matrix and concentrate them will further improve
the sensitivity of this method.
Both FFF-ICP-MS and SP-ICP-MS may provide a partial solution. With FFF-ICP-MS, the
element ratio within a narrower size range can be determined. If the ENP is somewhat
monodisperse, the isotopic ratio across this size range would be more highly perturbed than
across the entire size spectrum, which is what is examined by bulk analysis. Thus, by using FFF-
ICP-MS, the effective detection limit for ENPs could be substantially reduced. Recent
developments in "fast scan" SP-ICP-MS may allow for the simultaneous detection of multiple
elements in a nanoparticle-generated elemental pulse. Whereas bulk isotope ratio measurements
rely on the ratio of masses of elements in background particles and ENPs, SP-ICP-MS relies on
detecting a certain number of ENPs in the presence of a much larger number of natural particles.
To make an analogy to the previous discussion, the question arises "Can one ENP be robustly
detected in the presence of 999 natural particles?" If the background particles are considerably
larger than the ENPs, then there are fewer of them and the mass-based detection limit is reduced
when using SP-ICP-MS. The "fast scan" approach also allows for higher particle number
concentrations to be examined, which provides better counting statistics for short data
acquisition times.
Isotope methods
Somewhat analogous to the element ratio approach, stable isotopes of the elements making up
ENPs and background particles might be used. Discrimination might be possible if the source of
the materials used in making the ENP has a very different isotopic signature than the background
particles present in the environment into which the ENPs are released. Furthermore, detection
would be facilitated if isotopic fractionation occurred during ENP manufacture. These natural
differences are likely small and would probably result in a detection limit higher than the
element-ratio-based approach. A more likely scenario would be to purposely introduce a unique
isotopic composition into the ENP. This has been done for a number of research studies,
particularly those examining zinc oxide bioavailability [165-167]. However, it is rather unlikely
that manufacturers will take on the financial burden of creating isotopically labeled ENPs for use
in nano-enabled products.
MALDI-TOF-MS and LDI-TOF-MS
The accurate size determination of ultrasmall (>lnm) ENMs by conventional electron
microscopy is challenging as a result of drying artifacts introduced by the vacuum in TEM which
may incorrectly represent the size of the nanocluster. To this end, matrix-assisted laser
desorption ionization-time-of-flight mass spectrometry (MALDI-TOF-MS) has been used to
determine the mass of these ultrasmall particles, which can then be converted to a volume
assuming a spherical geometry. This technique has so far been applied to titanium dioxide
nanoparticles in a dithranol matrix (as dithranol lacks an acidic proton allowing for accurate
determination of peaks). The maximum of the broad, normal distribution obtained was then used
36
-------
to calculate the diameter of the particles assuming a spherical geometry. Laser desorption
ionization time-of-flight mass spectrometry (LDI-TOF-MS) was also used to characterize the
particles showing a maxima at m/z = 167, which corresponds to titanium(III) oxide (T^Cb) with
a sodium ion, a frequent contaminant. With more development, this technique may be a valuable
tool in the characterization of sub-nanometer particles [168].
6. SITE-SPECIFIC ENM RELEASE SCENARIOS
Due to the many challenges involved in detecting and characterizing ENMs in environmental
samples, it may be beneficial to narrow the analysis to focus on only certain NMs. Knowing the
source of the ENP release could aid in the analysis of the environmental sample and increase the
efficacy of the techniques used. ENPs may be released from a variety of sources in forms
different from their initial, pristine morphologies. In addition to unintentional environmental
exposure through the use of nano-containing products, the intentional application of NMs to soils
(i.e., remediation via zero-valent iron, nanopesticides) could be a source of ENPs in
environmental samples. NMs could enter the environment from a variety of potential point and
non-point sources, as discussed below.
ENP production site
The most likely exposure to pristine, unaltered NMs will occur at the site of manufacturing.
Several studies have investigated the effects of workplace exposure to NMs, particularly airborne
exposure. In particular, CNTs have been investigated due to their similarities to other known
toxic high-aspect-ratio materials (e.g., asbestos). In addition to inhaling NMs, it is possible those
working in the production and synthesis of these materials may come into dermal contact with
these ENPs [169-171].
Site of ENP use
A common exposure route of nanomaterials will occur at the site where the nanomaterial product
is employed. Studies have attempted to model the expected environmental exposure to silver
nanoparticles. All of the current models used to predict nanomaterial environmental exposure
rely on extrapolation from limited production-quantity data, which makes predicting
environmental concentrations of these materials difficult. Understanding the potential use of
nanomaterials may aid in determining which ENPs can be expected to be used at a particular
area. For instance, as titanium dioxide and zinc oxide ENPs are common components of
sunscreens and lotions, their concentrations might be higher near coastal areas and beaches.
Some nanomaterials, such as zero-valent iron, are directly applied to the environment in order to
remediate other contaminants such as trichloroethylene (TCE) [83]. Information on where the
ENPs are most likely applied may help narrow the search for them in the environment [3, 34-36,
172, 173].
Transport accident
Nanomaterials may be accidentally released into the environment during transport. In these
situations, detailed knowledge of the composition and quantity of the ENPs may assist in an
accurate assessment of the risk posed by the environmental exposure to them. The detection and
characterization of these materials would also be assisted by this knowledge, leading to a quicker
response to and remediation of these potential contaminants [36].
37
-------
Non-point sources
Lastly, there are several non-point sources that are likely to contain ENPs. Exposure to these
sources will most likely occur through the treatment of the waste in which these materials may
be contained. For instance, many of the waters containing ENPs will likely be treated at a
wastewater treatment plant. The biosolids collected at these treatment facilities may then contain
certain ENPs that can be applied to soils and enter the environment [94]. In some countries,
waste incineration is a common practice. Although this process may destroy carbon-containing
nanomaterials, inorganic and metallic nanoparticles may persist and be released into the
atmosphere. Locational information on these waste processes and waste disposal areas may aid
in the detection of ENPs that enter the environment [34, 36, 174, 175].
7. SUMMARY
Responsible development of nanotechnology requires an understanding of potential ENP releases
throughout the life cycle. Some points of the life cycle (e.g., manufacturing) may not offer
substantial challenges to existing nanometrology. Whereas other points, such as end-of-life may
be more challenging. Detecting, quantifying, and characterizing ENMs in environmental and
biological samples continues to be difficult. Current research is focused on developing new
methods and procedures for applying existing methods that will likely become more accessible
to a broader user base in the next few years. Quantitative measurements of inorganic ENMs are
already being advanced by developments in spICP-MS and FFF-ICP-MS, as well as by
improvements in sample preparation for automated electron microscopy. For carbon nanotbues,
strides have been made through the use of near-infrared fluorescence spectroscopy. While many
of these methods are already sufficiently developed for laboratory and microcosm experiments
on ENP reactivity and behavior, they are not ready for application to environmental monitoring.
For example, environmental transformations of nanomaterials may reduce the efficacy of these
analytical techniques that insofar have been developed for laboratory measurements under
pristine or minimally complex scenarios.
Although improvements in methodology are expected, low predicted environmental
concentrations for ENMs and background particles will remain a challenge to any given set of
techniques. Methods that can separate ENPs from the environmental matrix and concentrate
them (e.g., cloud point extraction) without altering their chemistry would improve our ability to
detect and quantify them. However, it will be necessary to preserve the repesentativeness of the
ENMs' environmental state, as this will likely affect how the they interact with the ecosystem
[153]. In addition to the separation of ENMs from environmental constituents, such as DOC and
mineral colloids, the high concentration of naturally occurring NMs will require new,
sophisticated analytical techniques that can distinguish between these two particle types. The
advent of microsecond spICP-MS and ICP-TOF-MS may allow for the differentiation of
engineered and natural nanoparticles by virtue of their elemental ratios [176-178]. For
nanomaterials with naturally occurring analogues, this detection of ENMs in the environment
will require the exploitation of ENM properties that are rarely encountered in environmental
samples. Other techniques may be developed to take advantage of ENP-specific properties such
as their size distribution and highly engineered surface coatings, but will require further study
into how the environment affects these properties.
38
-------
A critical capability of future nanometrologies will be quick, highly automated methods to allow
analysis of the large number of samples needed for quantitative ENP risk assessment. The
dynamic nature of nanomaterials ensures that their physicochemical states can change within
short time frames, and as such, it will be necessary to develop appropriate methodologies to
rapidly characterize these nanomaterials in their altered, environmental state. As previously
established, various potential artifacts that can be introduced in the sampling and measurement of
ENMs will require multiple orthogonal techniques to confirm the presence and characteristics of
these materials found in the environment.
As additional research is performed to assess the ecotoxicity of these materials, it is important to
also consider the exposure and its contribution to environmental risk analysis. Although much
work still needs to be done, the continued development of nanometrology, specific to the
detection and characterization of ENMs in the environment, is a step towards assessing the
environmental risk and impact these materials may pose.
8. REFERENCES
1. Roco, M.C., International perspective on government nanotechnology funding in 2005.
Journal of Nanoparticle Research, 2005. 7(6): p. 707-712.
2. Klaine, S.J., et al., Nanomaterials in the environment: Behavior, fate, bioavailability, and
effects. Environmental Toxicology and Chemistry, 2008. 27(9): p. 1825-1851.
3. Nowack, B. and T.D. Bucheli, Occurrence, behavior and effects of nanoparticles in the
environment. Environmental Pollution, 2007. 150(1): p. 5-22.
4. Moore, M.N., Do nanoparticles present ecotoxicological risks for the health of the
aquatic environment? Environment International, 2006. 32(8): p. 967-976.
5. Hochella, M.F., Nanogeoscience: From Origins to Cutting-Edge Applications. Elements,
2008. 4(6): p. 373-379.
6. Hochella, M.F., et al., Nanominerals, Mineral Nanoparticles, and Earth Systems.
Science, 2008. 319(5870): p. 1631-1635.
7. Majestic, B.J., et al., A Review of Selected Engineered Nanoparticles in the Atmosphere:
Sources, Transformations, and Techniques for Sampling and Analysis. International
Journal of Occupational and Environmental Health, 2010. 16(4): p. 488-507.
8. Daniel, M.-C. and D. Astruc, Gold nanoparticles: assembly, supramolecular chemistry,
quantum-size-related properties, and applications toward biology, catalysis, and
nanotechnology. Chemical reviews, 2004. 104(1): p. 293-346.
9. Marambio-Jones, C. and E.M. Hoek, A review of the antibacterial effects of silver
nanomaterials and potential implications for human health and the environment. Journal
of Nanoparticle Research, 2010. 12(5): p. 1531-1551.
10. Li, X.-q., D.W. Elliott, and W.-x. Zhang, Zero-Valent Iron Nanoparticles for Abatement
of Environmental Pollutants: Materials and Engineering Aspects. Critical Reviews in
Solid State and Materials Sciences, 2006. 31(4): p. Ill - 122.
11. Mahulikar, D., B. Mravic, and A.M. Pasqualoni, Slurry compositions and method for the
chemical-mechanical polishing of copper and copper alloys. 2000, Google Patents.
39
-------
12. Smijs, T.G. and S. Pavel, Titanium dioxide and zinc oxide nanoparticles in sunscreens:
focus on their safety and effectiveness. Nanotechnology, science and applications, 2011.
4: p. 95.
13. Sajith, V., C. Sobhan, and G. Peterson, Experimental investigations on the effects of
cerium oxide nanoparticle fuel additives on biodiesel. Advances in Mechanical
Engineering, 2010. 2010.
14. Chan, W.C.W., et al., Luminescent quantum dots for multiplexed biological detection and
imaging. Current Opinion in Biotechnology, 2002. 13(1): p. 40-46.
15. Baughman, R.H., A.A. Zakhidov, and W.A. de Heer, Carbon nanotubesthe route
toward applications. Science, 2002. 297(5582): p. 787-792.
16. Niemann, M.U., et al., Nanomaterials for hydrogen storage applications: a review.
Journal of Nanomaterials, 2008. 2008.
17. Gajbhiye, V., et al., Dendrimers as therapeutic agents: a systematic review. Journal of
Pharmacy and Pharmacology, 2009. 61(8): p. 989-1003.
18. Kimling, J., et al., Turkevich method for gold nanoparticle synthesis revisited. The
Journal of Physical Chemistry B, 2006. 110(32): p. 15700-15707.
19. Brust, M. and C.J. Kiely, Some recent advances in nanostructure preparation from gold
and silver particles: a short topical review. Colloids and Surfaces A: Physicochemical
and Engineering Aspects, 2002. 202(2-3): p. 175-186.
20. Lakshmi, B.B., P.K. Dorhout, and C.R. Martin, Sol-gel template synthesis of
semiconductor nanostructures. Chemistry of materials, 1997. 9(3): p. 857-862.
21. Macwan, D., P.N. Dave, and S. Chaturvedi, A review on nano-TiO2 sol-gel type
syntheses and its applications. Journal of Materials Science, 2011. 46(11): p. 3669-3686.
22. Dabbousi, B.O., et al., (CdSe)ZnS Core-Shell Quantum Dots: Synthesis and
Characterization of a Size Series of Highly Luminescent Nanocrystallites. The Journal of
Physical Chemistry B, 1997. 101(46): p. 9463-9475.
23. Dai, H., Carbon nanotubes: synthesis, integration, and properties. Accounts of chemical
research, 2002. 35(12): p. 1035-1044.
24. Swihart, M.T., Vapor-phase synthesis of nanoparticles. Current Opinion in Colloid &
Interface Science, 2003. 8(1): p. 127-133.
25. Gopidas, K.R., J.K. Whitesell, and M.A. Fox, Nanoparticle-coreddendrimers: synthesis
and characterization. Journal of the American Chemical Society, 2003. 125(21): p. 6491-
6502.
26. Weinberg, H., A. Galyean, and M. Leopold, Evaluating engineered nanoparticles in
natural waters. TrAC Trends in Analytical Chemistry, 2011. 30(1): p. 72-83.
27. Cedervall, T., et al., Understanding the nanopartide-protein corona using methods to
quantify exchange rates and affinities of proteins for nanoparticles. Proceedings of the
National Academy of Sciences, 2007. 104(7): p. 2050-2055.
28. Stankus, D.P., et al., Interactions between Natural Organic Matter and Gold
Nanoparticles Stabilized with Different Organic Capping Agents. Environmental Science
& Technology, 2010. 45(8): p. 3238-3244.
29. Yates, P.D., et al., Heteroaggregation with nanoparticles: effect of particle size ratio on
optimum particle dose. Colloids and Surfaces A: Physicochemical and Engineering
Aspects, 2005. 255(1-3): p. 85-90.
40
-------
30. Yates, P.D., G.V. Franks, and GJ. Jameson, Orthokinetic heteroaggregation with
nanopartides: Effect of particle size ratio on aggregate properties. Colloids and Surfaces
A: Physicochemical and Engineering Aspects, 2008. 326(1-2): p. 83-91.
31. Diegoli, S., et al., Interaction between manufactured gold nanoparticles and naturally
occurring organic macromolecules. Science of the Total Environment, 2008. 402(1): p.
51-61.
32. Baalousha, M., et al., Aggregation and surface properties of iron oxide nanoparticles:
Influence ofph and natural organic matter. Environmental Toxicology and Chemistry,
2008. 27(9): p. 1875-1882.
33. Handy, R., R. Owen, and E. Valsami-Jones, The ecotoxicology of nanoparticles and
nanomaterials: current status, knowledge gaps, challenges, and future needs.
Ecotoxicology, 2008. 17(5): p. 315-325.
3 4. Nowack, B., et al., Potential scenarios for nanomaterial release and subsequent
alteration in the environment. Environmental Toxicology and Chemistry, 2012. 31(1): p.
50-59.
3 5. Gottschalk, F., et al., Modeled Environmental Concentrations of Engineered
Nanomaterials (TiO2, ZnO, Ag, CNT, Fullerenes) for Different Regions. Environmental
Science & Technology, 2009. 43(24): p. 9216-9222.
36. Mueller, N.C. and B. Nowack, Exposure Modeling of Engineered Nanoparticles in the
Environment. Environmental Science & Technology, 2008. 42(12): p. 4447-4453.
37. Hansen, S., et al., Categorization framework to aid exposure assessment of nanomaterials
in consumer products. Ecotoxicology, 2008. 17(5): p. 438-447.
38. Baun, A., et al., Setting the limits for engineered nanoparticles in European surface
waters - are current approaches appropriate? Journal of Environmental Monitoring,
2009. 11(10): p. 1774-1781.
39. Buffle, J. and G.G. Leppard, Characterization of Aquatic Colloids and Macromolecules.
1. Structure and Behavior of Colloidal Material. Environmental Science & Technology,
1995. 29(9): p. 2169-2175.
40. Buffle, J.v.L., H. P., ed. Environmental Particles. Environmental analytical and physical
chemistry series, ed. J.v.L. Buffle, H. P. Vol. 2. 1993, Lewis Publishers. 448.
41. Taha, M. and O. Taha, Influence ofnano-material on the expansive and shrinkage soil
behavior. Journal of Nanoparticle Research, 2012. 14(10): p. 1-13.
42. Theng, B.K.G. and G. Yuan, Nanoparticles in the Soil Environment. Elements, 2008.
4(6): p. 395-399.
43. Banfield, J.F. and H. Zhang, Nanoparticles in the Environment. Reviews in Mineralogy
and Geochemistry, 2001. 44(1): p. 1-58.
44. Deonarine, A., et al., Effects ofHumic Substances on Precipitation and Aggregation of
Zinc Sulfide Nanoparticles. Environmental Science & Technology, 2011. 45(8): p. 3217-
3223.
45. Guo, H. and A.S. Barnard, Naturally occurring iron oxide nanoparticles: morphology,
surface chemistry and environmental stability. Journal of Materials Chemistry A, 2013.
1(1): p. 27-42.
46. Kalmykov, S.N., et al., Plutonium and neptunium speciation bound to hydrous ferric
oxide colloids. Comptes Rendus Chimie, 2007. 10(10-11): p. 1060-1066.
47. Novikov, A.P., et al., Colloid Transport of Plutonium in the Far-Field of the Mayak
Production Association, Russia. Science, 2006. 314(5799): p. 638-641.
41
-------
48. Shipley, H., et al., A sorption kinetics model for arsenic adsorption to magnetite
nanoparticles. Environmental Science and Pollution Research, 2010. 17(5): p. 1053-
1062.
49. Wigginton, N.S., K.L. Haus, and M.F. Hochella Jr, Aquatic environmental nanoparticles.
Journal of Environmental Monitoring, 2007. 9(12): p. 1306-1316.
50. Druschel, G.K., et al., Geochemical Modeling ofZnS in Biofilms: An Example of Ore
DepositionalProcesses. Economic Geology, 2002. 97(6): p. 1319-1329.
51. Moreau, J.W., R.I. Webb, and J.F. Banfield, Ultrastructure, aggregation-state, and
crystal growth ofbiogenic nanocrystalline sphalerite andwurtzite. American
Mineralogist, 2004. 89(7): p. 950-960.
52. Posfai, M., et al., Reaction Sequence of Iron Sulfide Minerals in Bacteria and Their Use
asBiomarkers. Science, 1998. 280(5365): p. 880-883.
53. Hassellov, M. and F. von der Kammer, Iron Oxides as GeochemicalNanovectorsfor
Metal Transport in Soil-River Systems. Elements, 2008. 4(6): p. 401-406.
54. Utsunomiya, S., A.B. Kersting, and R.C. Ewing, Groundwater Nanoparticles in the Far-
Field at the Nevada Test Site: Mechanism for Radionuclide Transport. Environmental
Science & Technology, 2009. 43(5): p. 1293-1298.
55. Buddemeier, R.W. and J.R. Hunt, Transport of colloidal contaminants in groundwater:
radionuclide migration at the Nevada test site. Applied Geochemistry, 1988. 3(5): p. 535-
548.
56. von der Kammer, F., et al., Analysis of engineered nanomaterials in complex matrices
(environment and biota): General considerations and conceptual case studies.
Environmental Toxicology and Chemistry, 2012. 31(1): p. 32-49.
57. Lowry, G.V., et al., Transformations of nanomaterials in the environment. Environmental
science & technology, 2012. 46(13): p. 6893-6899.
5 8. Kim, H. -J., et al., FeO Nanoparticles Remain Mobile in Porous Media after Aging Due to
Slow Desorption of Polymeric Surface Modifiers. Environmental Science & Technology,
2009. 43(10): p. 3824-3830.
59. Phenrat, T., et al., Estimating Attachment ofNano- and Submicrometer-particles Coated
with Organic Macromolecules in Porous Media: Development of an Empirical Model.
Environ. Sci. Technol., 2010. 44(12): p. 4531-4538.
60. Nel, A.E., et al., Understanding biophysicochemical interactions at the nano-bio
interface. Nature Materials, 2009. 8(7): p. 543-557.
61. Cumberland, S.A. and J.R. Lead, Particle size distributions of silver nanoparticles at
environmentally relevant conditions. Journal of Chromatography A, 2009. 1216(52): p.
9099-9105.
62. Baalousha, M., et al., Characterisation of structural and surface speciation of
representative commercially available cerium oxide nanoparticles. Environmental
Chemistry, 2010. 7(4): p. 377-385.
63. Louie, S.M., et al., Parameter Identifiability in Application of Soft Particle Electrokinetic
Theory To Determine Polymer and Poly electrolyte Coating Thicknesses on Colloids.
Langmuir, 2012. 28(28): p. 10334-10347.
64. Hitchman, A., et al., The effect of environmentally relevant conditions on PVP stabilised
gold nanoparticles. Chemosphe, 2012. in press.
65. Lee, J. and N.M. Donahue, Secondary organic aerosol coating of synthetic metal-oxide
nanoparticles. Environ Sci. Technol., 2011. 45: p. 4689-4695.
42
-------
66. Shannahan, J.H., et al., Silver nanoparticleprotein corona composition in cell culture
media. PloS one, 2013. 8(9): p. e74001.
67. Baalousha, M., B. Stolpe, and J.R. Lead, Flow field-flow fractionation for the analysis
and characterization of natural colloids and manufactured nanoparticles in
environmental systems: A critical review. Journal of Chromatography A, 2011. 1218(27):
p. 4078-4103.
68. Walczyk, D., et al., What the Cell "Sees" in Bionanoscience. Journal of the American
Chemical Society, 2010. 132(16): p. 5761-5768.
69. Gray, E.P., et al., Analysis of gold nanoparticle mixtures: a comparison of hydrodynamic
chromatography (HDC) and asymmetrical flow field-flow fractionation (AF4) coupled to
ICP-MS. Journal of Analytical Atomic Spectrometry, 2012. 27(9): p. 1532-1539.
70. Levard, C., et al., Effect of Chloride on the Dissolution Rate of Silver Nanoparticles and
Toxicity toE. coli. Environmental Science & Technology, 2013. 47(11): p. 5738-5745.
71. Levard, C., et al., Sulfidation Processes of PVP-CoatedSilver Nanoparticles in Aqueous
Solution: Impact on Dissolution Rate. Environ. Sci. Technol., 2011. 45(12): p. 5260-
5266.
72. Henglein, A., Colloidal silver nanoparticles: Photochemical preparation and interaction
with O-2, CC14, and some metal ions. Chemistry of Materials, 1998. 10(1): p. 444-450.
73. Lok, C .N., et al., Silver nanoparticles: partial oxidation and antibacterial activities.
Journal of Biological Inorganic Chemistry, 2007. 12(4): p. 527-534.
74. Liu, Y.Q., et al., TCE dechlorination rates, pathways, and efficiency ofnanoscale iron
particles with different properties. Environ. Sci. Technol., 2005. 39(5): p. 1338-1345.
75. Liu, Y., et al., TCE Dechlorination Rates, Pathways, and Efficiency of Nanoscale Iron
Par tides with Different Properties. Environmental Science & Technology, 2005. 39(5):
p. 1338-1345.
76. Karakoti, A., et al., Redox-active radical scavenging nanomaterials. Chemical Society
Reviews, 2010. 39(11): p. 4422-4432.
77. Liu, J.C. and C.P. Huang, Electrokinetic characteristics of some metal sulfide-water
interfaces. Langmuir, 1992. 8(7): p. 1851-1856.
78. Park, S.W. and C.P. Huang, The surface acidity of hydrous CdS(s). Journal of Colloid
and Interface Science, 1987. 117(2): p. 431-441.
79. Derfus, A.M., W.C.W. Chan, and S.N. Bhatia, Probing the cytotoxicity of semiconductor
quantum dots. Nano Letters, 2004. 4(1): p. 11-18.
80. Hou, W.C. and C.T. Jafvert, Photochemical Transformation of Aqueous C(60) Clusters in
Sunlight. Environ. Sci. Technol., 2009. 43(2): p. 362-367.
81. Adams, L.K., D.Y. Lyon, and P.J. Alvarez, Comparative eco-toxicity ofnanoscale TiO<
sub> 2, SiO< sub> 2, and ZnO water suspensions. Water research, 2006.
40(19): p. 3527-3532.
82. Cheng, Y.W., et al., Toxicity reduction of polymer-stabilized silver nanoparticles by
sunlight. Journal of Physical Chemistry C, 2011. 115(11): p. 4425-4432.
83. Reinsch, B.C., et al., Chemical Transformations during Aging ofZerovalent Iron
Nanoparticles in the Presence of Common Groundwater Dissolved Constituents.
Environmental Science & Technology, 2010. 44(9): p. 3455-3461.
84. Hotze, E.M., J.Y. Bottero, and M.R. Wiesner, Theoretical Framework for Nanoparticle
Reactivity as a Function of Aggregation State. Langmuir, 2010. 26(13): p. 11170-11175.
43
-------
85. Jassby, D., J. Farner Budarz, and M. Wiesner, Impact of Aggregate Size and Structure on
the Photocatalytic Properties ofTiO2 andZnO Nanoparticles. Environmental Science &
Technology, 2012. 46(13): p. 6934-6941.
86. Jassby, D. and M. Wiesner, Characterization of ZnS Nanoparticle Aggregation using
Photoluminescence. Langmuir, 2011. 27(3): p. 902-908.
87. Hotze, E.M., T. Phenrat, and G. V. Lowry, Nanoparticle Aggregation: Challenges to
Understanding Transport and Reactivity in the Environment. Journal of Environmental
Quality, 2010. 39(6): p. 1909-1924.
88. Richter, K., M. Schicklberger, and J. Gescher, Dissimilatory Reduction of Extracellular
Electron Acceptors in Anaerobic Respiration Appl. Environ. Microbiol., 2012. 78(4): p.
913-921.
89. Allen, B.L., et al., Biodegradation of single-walled carbon nanotubes through enzymatic
catalysis. Nano Letters, 2008. 8(11): p. 3899-3903.
90. Plata, D.L., P.L. Ferguson, and P. Westerhoff, Express It in Numbers: Efforts to Quantify
Engineered Nanoparticles in Environmental Matrices Advance. Environmental Science
& Technology, 2012. 46(22): p. 12243-12245.
91. Schierz, A., et al., Characterization and Quantitative Analysis of Single-Walled Carbon
Nanotubes in the Aquatic Environment Using Near-Infrared Fluorescence Spectroscopy.
Environmental Science & Technology, 2012. 46(22): p. 12262-12271.
92. Kirschling, T.L., et al., Microbial Bioavailability ofCovalently Bound Polymer Coatings
on Model EngineeredNanomaterials. Environ. Sci. Technol., 2011. 45(12): p. 5253-
5259.
93. Ma, R., et al., Size-controlled dissolution of organic-coated silver nanoparticles.
Environmental science & technology, 2011. 46(2): p. 752-759.
94. Colman, B.P., et al., Low Concentrations of Silver Nanoparticles in Biosolids Cause
Adverse Ecosystem Responses under Realistic Field Scenario. PLoS ONE, 2013. 8(2): p.
e57189.
95. Hassellov, M., et al., Nanoparticle analysis and characterization methodologies in
environmental risk assessment of engineered nanoparticles. Ecotoxicology, 2008. 17(5):
p. 344-361.
96. Zanker, H. and A. Schierz, Engineered Nanoparticles and Their Identification Among
Natural Nanoparticles. Annual Review of Analytical Chemistry, 2012. 5(1): p. 107-132.
97. von der Kammer, F., et al., Analysis of engineered nanomterials in complex matrices
(environment and biota): General considerations and conceptual case studies.
Environmental Toxicology and Chemistry, 2012. 31(1): p. 32-49.
98. Hassellov, M., et al., Nanoparticle analysis and characterization methodologies in
environmental risk assessment of engineered nanoparticles. Ecotoxicology, 2008. 17(5):
p. 344-361.
99. Liu, R. and J.R. Lead, Partial Validation of Cross Flow Ultrafiltration by Atomic Force
Microscopy. Analytical Chemistry, 2006. 78(23): p. 8105-8112.
100. Giddings, J.C., Measuring colloidal and macromolecular properties by FFF. Analytical
Chemistry, 1995. 67(19): p. 592A-598A.
101. Baalousha, M., et al., Size fractionation and characterization of natural colloids by flow-
field flow fractionation coupled to multi-angle laser light scattering. Journal of
Chromatography A, 2006. 1104(1-2): p. 272-281.
44
-------
102. Tadjik!, S., et al., Detection, separation, and quantification of unlabeled silica
nanoparticles in biological media using sedimentation field-flow fractionation. Journal of
Nanoparticle Research, 2009. 11(4): p. 981-988.
103. Ratanathanawongs Williams, S.K., et al., Separation of protein inclusion bodies from
Escherichia coli lysates using sedimentation field-flow fractionation. Journal of
Microcolumn Separations, 1997. 9(3): p. 233-239.
104. Wei, G.-T., F.-K. Liu, and C.R.C. Wang, Shape Separation of Nanometer Gold Particles
by Size-Exclusion Chromatography. Analytical Chemistry, 1999. 71(11): p. 2085-2091.
105. Al-Somali, A.M., et al., Recycling Size Exclusion Chromatography for the Analysis and
Separation of Nanocrystalline Gold. Analytical Chemistry, 2004. 76(19): p. 5903-5910.
106. Williams, A., et al., Characterisation ofnanoparticulate systems by hydrodynamic
Chromatography. International Journal of Pharmaceutics, 2002. 242(1-2): p. 295-299.
107. Jimenez, M.S., et al., An approach to the natural and engineered nanoparticles analysis
in the environment by inductively coupled plasma mass spectrometry. International
Journal of Mass Spectrometry, 2011. 307(1-3): p. 99-104.
108. Small, H., F.L. Saunders, and J. Sole, Hydrodynamic Chromatography A new approach to
particle size analysis. Advances in Colloid and Interface Science, 1976. 6(4): p. 237-266.
109. Tiede, K., et al., Considerations for environmental fate and ecotoxicity testing to support
environmental risk assessments for engineered nanoparticles. Journal of
Chromatography A, 2009. 1216(3): p. 503-509.
110. Brar, S.K. and M. Verma, Measurement of nanoparticles by light-scattering techniques.
TrAC Trends in Analytical Chemistry, 2011. 30(1): p. 4-17.
111. Yu, W.W., et al., Experimental Determination of the Extinction Coefficient ofCdTe,
CdSe, and CdS Nanocrystals. Chemistry of Materials, 2003. 15(14): p. 2854-2860.
112. Homola, J., S.S. Yee, and G. Gauglitz, Surfaceplasmon resonance sensors: review.
Sensors and Actuators B: Chemical, 1999. 54(1-2): p. 3-15.
113. Pallem, V.L., H.A. Stretz, and M.J.M. Wells, Evaluating Aggregation of Gold
Nanoparticles andHumic Substances Using Fluorescence Spectroscopy. Environmental
Science & Technology, 2009. 43(19): p. 7531-7535.
114. Mock, J. J., et al., Shape effects in plasmon resonance of individual colloidal silver
nanoparticles. The Journal of Chemical Physics, 2002. 116(15): p. 6755-6759.
115. Rao, C.N.R. and K. Biswas, Characterization of Nanomaterials by Physical Methods, in
Annual Review of Analytical Chemistry. 2009, Annual Reviews: Palo Alto. p. 435-462.
116. Branca, C., et al., Characterization of Carbon Nanotubes by TEM and Infrared
Spectroscopy. The Journal of Physical Chemistry B, 2004. 108(11): p. 3469-3473.
117. Kratschmer, W.L., L. D.; Fostriopoulos, K.; Huffman, D. R., Solid C60: a new form of
carbon. Nature, 1990. 347(6291): p. 354-358.
118. Treubig Jr, J.M. and P.R. Brown, Analysis ofC60 and C70fullerenes using high-
performance liquid chromatography-Fourier transform infrared Spectroscopy. Journal of
Chromatography A, 2002. 960(1-2): p. 135-142.
119. Andrievsky, G. V., et al., Comparative analysis of two aqueous-colloidal solutions ofC60
fullerene with help ofFTIR reflectance and UV-Vis Spectroscopy. Chemical Physics
Letters, 2002. 364(1-2): p. 8-17.
120. Zhao, X.S., et al., Comprehensive Study of Surface Chemistry ofMCM-41 Using 29 Si
CP/MASNMR, FTIR, Pyridine-TPD, and TGA. The Journal of Physical Chemistry B,
1997. 101(33): p. 6525-6531.
45
-------
121. Sylvestre, J.-P., et al., Surface Chemistry of Gold Nanoparticles Produced by Laser
Ablation in Aqueous Media. The Journal of Physical Chemistry B, 2004. 108(43): p.
16864-16869.
122. Ma, M., et al., Preparation and characterization of magnetite nanoparticles coated by
amino silane. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2003.
212(2-3): p. 219-226.
123. Rocha, A.S., et al., Characterization by 27Al NMR, X-ray Absorption Spectroscopy, and
Density Functional Theory Techniques of the Species Responsible for Benzene
Hydrogenation in Y Zeolite-Supported CarburizedMolybdenum Catalysts. The Journal of
Physical Chemistry B, 2006. 110(32): p. 15803-15811.
124. Roming, M., et al., Characterization of Noncrystalline Nanomaterials: NMR of Zinc
Phosphate as a Case Study. Chemistry of Materials, 2008. 20(18): p. 5787-5795.
125. Holland, G.P., et al., NMR Characterization of Phosphonic Acid CappedSnO2
Nanoparticles. Chemistry of Materials, 2007. 19(10): p. 2519-2526.
126. Sekhaneh, W., et al., High resolution NMR of water absorbed in single-wall carbon
nanotubes. Chemical Physics Letters, 2006. 428(1-3): p. 143-147.
127. Mavrocordatos, D., W. Pronk, and M. Boiler, Analysis of environmental particles by
atomic force microscopy, scanning and transmission electron microscopy. Water science
and technology : a journal of the International Association on Water Pollution Research,
2004. 50(12): p. 9-18.
128. Pace, H.E., et al., Single Particle Inductively Coupled Plasma-Mass Spectrometry: A
Performance Evaluation and Method Comparison in the Determination of Nanoparticle
Size. Environmental Science & Technology, 2012.
129. Boyd, R.D., S.K. Pichaimuthu, and A. Cuenat, New approach to inter-technique
comparisons for nanoparticle size measurements; using atomic force microscopy,
nanoparticle tracking analysis and dynamic light scattering. Colloids and Surfaces A:
Physicochemical and Engineering Aspects, 2011. 387(1-3): p. 35-42.
130. Farkas, J., et al., Characterization of the effluent from a nanosilver producing washing
machine. Environment international, 2011. 37(6): p. 1057-1062.
131. Mitrano, D.M., et al., Detecting nanoparticulate silver using single-particle inductively
coupled plasma-mass spectrometry. Environmental Toxicology and Chemistry, 2012.
31(1): p. 115-121.
132. Mitrano, D.M., et al., Presence of Nanoparticles in Wash Water from Conventional Silver
andNano-Silver Textiles. ACS nano, 2014.
133. Reed, R.B., et al., Detection of single walled carbon nanotubes by monitoring embedded
metals. Environmental Science: Processes & Impacts, 2013. 15(1): p. 204-213.
134. Benn, T.M. and P. Westerhoff, Nanoparticle Silver Released into Water from
Commercially Available Sock Fabrics. Environmental Science & Technology, 2008.
42(11): p. 4133-4139.
135. Pace, H.E., et al., Determining Transport Efficiency for the Purpose of Counting and
Sizing Nanoparticles via Single Particle Inductively Coupled Plasma Mass Spectrometry.
Analytical Chemistry, 2011. 83(24): p. 9361-9369.
136. Scherbaum, F.J., R. Knopp, and J.I. Kim, Counting of particles in aqueous solutions by
laser-inducedphotoacoustic breakdown detection. Applied Physics B, 1996. 63(3): p.
299-306.
46
-------
137. Sadik, O.A., et al., Sensors as tools for quantitation, nanotoxicity and nanomonitoring
assessment of engineered nanomaterials. Journal of Environmental Monitoring, 2009.
11(10): p. 1782-1800.
138. Stampfl, A., et al., Langendorff heart: a model system to study cardiovascular effects of
engineerednanoparticles. ACS nano, 2011. 5(7): p. 5345-5353.
139. Akaighe, N., et al., Humic Acid-Induced Silver Nanoparticle Formation Under
Environmentally Relevant Conditions. Environmental Science & Technology, 2011.
45(9): p. 3895-3901.
140. Zhou, D., A.I. Abdel-Fattah, and A. A. Keller, Clay Particles Destabilize Engineered
Nanoparticles in Aqueous Environments. Environmental Science & Technology, 2012.
46(14): p. 7520-7526.
141. Haiss, W., et al., Determination of Size and Concentration of Gold Nanoparticles from
UV-Vis Spectra. Analytical Chemistry, 2007. 79(11): p. 4215-4221.
142. Khlebtsov, N.G., Determination of Size and Concentration of Gold Nanoparticles from
Extinction Spectra. Analytical Chemistry, 2008. 80(17): p. 6620-6625.
143. Liu, X., et al., Extinction coefficient of gold nanoparticles with different sizes and
different capping ligands. Colloids and Surfaces B: Biointerfaces, 2007. 58(1): p. 3-7.
144. Poda, A.R., et al., Characterization of silver nanoparticles using flow-fieldflow
fractionation interfaced to inductively coupled plasma mass spectrometry. Journal of
Chromatography A, 2011. 1218(27): p. 4219-4225.
145. Reed, R.B., et al., Overcoming challenges in analysis of poly disperse metal-containing
nanoparticles by single particle inductively coupled plasma mass spectrometry. Journal
of Analytical Atomic Spectrometry, 2012. 27(7): p. 1093-1100.
146. Liu, J.-f, Z.-s. Zhao, and G.-b. Jiang, Coating Fe3O4 Magnetic Nanoparticles with
Humic Acid for High Efficient Removal of Heavy Metals in Water. Environmental
Science & Technology, 2008. 42(18): p. 6949-6954.
147. Chen, Q., et al., Adsorption of cadmium(II) on humic acid coated titanium dioxide.
Journal of Colloid and Interface Science, 2012. 367(1): p. 241-248.
148. Liang, L., L. Luo, and S. Zhang, Adsorption and desorption of humic andfulvic acids on
SiO'2 particles at nano- and micro-scales. Colloids and Surfaces A: Physicochemical and
Engineering Aspects, 2011. 384(1-3): p. 126-130.
149. Benn, T., et al., The Release of Nanosilver from Consumer Products Used in the Home
Supplemental data file available online for this article. All rights reserved. No part of this
periodical may be reproduced or transmitted in any form or by any means, electronic or
mechanical, including photocopying, recording, or any information storage and retrieval
system, without permission in writing from the publisher. J. Environ. Qual., 2010. 39(6):
p. 1875-1882.
150. Stone, V., et al., Nanomaterials for environmental studies: Classification, reference
material issues, and strategies for physico-chemical characterisation. Science of The
Total Environment, 2010. 408(7): p. 1745-1754.
151. Domingos, R.F., et al., Characterizing Manufactured Nanoparticles in the Environment:
Multimethod Determination of Particle Sizes. Environmental Science & Technology,
2009. 43(19): p. 7277-7284.
152. Gimbert, L.J., et al., Comparison of Centrifugation and Filtration Techniques for the Size
Fractionation of Colloidal Material in Soil Suspensions Using Sedimentation Field-Flow
Fractionation. Environmental Science & Technology, 2005. 39(6): p. 1731-1735.
47
-------
153. Liu, J.-f, et al., Cloud Point Extraction as an Advantageous Preconcentration Approach
for Analysis of Trace Silver Nanoparticles in Environmental Waters. Analytical
Chemistry, 2009. 81(15): p. 6496-6502.
154. Isaacson, C.W., M. Kleber, and J.A. Field, Quantitative Analysis ofFullerene
Nanomaterials in Environmental Systems: A Critical Review. Environmental Science &
Technology, 2009. 43(17): p. 6463-6474.
155. Simonet, B.M. and M. Valcarcel, Monitoring nanoparticles in the environment.
Analytical and Bioanalytical Chemistry, 2009. 393(1): p. 17-21.
156. Chen, Y.-W. and J. Buffle, Physicochemical andmicrobial preservation of colloid
characteristics of natural water samples. I: Experimental conditions. Water Research,
1996. 30(9): p. 2178-2184.
157. Papelis, C. and K.F. Hayes, Distinguishing between interlayer and external sorption sites
of clay minerals using X-ray absorption spectroscopy. Colloids and Surfaces A:
Physicochemical and Engineering Aspects, 1996. 107: p. 89-96.
158. Zhang, F., et al., Cerium oxidation state in ceria nanoparticles studied with X-ray
photoelectron spectroscopy and absorption near edge spectroscopy. Surface Science,
2004. 563(1-3): p. 74-82.
159. Lowry, G.V., et al., Long-Term Transformation and Fate of Manufactured Ag
Nanoparticles in a Simulated Large Scale Freshwater Emergent Wetland. Environmental
Science & Technology, 2012. 46(13): p. 7027-7036.
160. Ma, R., et al., Fate of zinc oxide and silver nanoparticles in a pilot wastewater treatment
plant and in processed biosolids. Environmental science & technology, 2013. 48(1): p.
104-112.
161. Dimkpa, C., et al., CuO andZnO nanoparticles:phytotoxicity, metal speciation, and
induction ofoxidative stress in sand-grown wheat. Journal of Nanoparticle Research,
2012. 14(9): p. 1-15.
162. Servin, A.D., et al., Synchrotron Micro-XRFandMicro-XANES Confirmation of the
Uptake and Translocation ofTiO2 Nanoparticles in Cucumber (Cucumis sativus) Plants.
Environmental Science & Technology, 2012. 46(14): p. 7637-7643.
163. Tiede, K., et al., Imaging of engineered nanoparticles and their aggregates under fully
liquid conditions in environmental matrices. Water Research, 2009. 43(13): p. 3335-
3343.
164. Laborda, F., et al., Selective identification, characterization and determination of
dissolved silver(i) and silver nanoparticles based on single particle detection by
inductively coupled plasma mass spectrometry. Journal of Analytical Atomic
Spectrometry, 2011. 26(7).
165. Dybowska, A.D., et al., Synthesis of isotopically modifiedZnO nanoparticles and their
potential as nanotoxicity tracers. Environmental Pollution, 2011. 159(1): p. 266-273.
166. Misra, S.K., et al., Isotopically Modified Nanoparticles for Enhanced Detection in
Bioaccumulation Studies. Environmental Science & Technology, 2011. 46(2): p. 1216-
1222.
167. Larner, F. and M. Rehkamper, Evaluation of Stable Isotope Tracing for ZnO
NanomaterialsNew Constraints from High Precision Isotope Analyses and Modeling.
Environmental Science & Technology, 2012. 46(7): p. 4149-4158.
48
-------
168. Guan, B., et al., Characterization of Synthesized Titanium Oxide Nanoclusters by
MALDI-TOFMass Spectrometry. Journal of the American Society for Mass
Spectrometry, 2007. 18(3): p. 517-524.
169. Walser, T., et al., Exposure to engineered nanopar tides: Model and measurements for
accident situations in laboratories. Science of The Total Environment, 2012. 420(0): p.
119-126.
170. Wu, J., et al., Toxicity and penetration ofTiO< sub> 2 nanoparticles in hairless
mice and porcine skin after subchronic dermal exposure. Toxicology letters, 2009.
191(1): p. 1-8.
171. Monteiro-Riviere, N.A., et al., Multi-walled carbon nanotube interactions with human
epidermal heratinocytes. Toxicology letters, 2005. 155(3): p. 377-384.
172. Blaser, S.A., et al., Estimation of cumulative aquatic exposure andriskdue to silver:
Contribution of nano-functionalizedplastics and textiles. Science of The Total
Environment, 2008. 390(2-3): p. 396-409.
173. Lorenz, C., et al., Characterization of silver release from commercially available
functional (nano)textiles. Chemosphere, 2012. 89(7): p. 817-824.
174. Schmid, K. and M. Riediker, Use of Nanoparticles in Swiss Industry: A Targeted Survey.
Environmental Science & Technology, 2008. 42(7): p. 2253-2260.
175. Kookana, R.S., et al., Nanopesticides: Guiding principles for regulatory evaluation of
environmental risks. Journal of agricultural and food chemistry, 2014.
176. Montafio, M.D., et al., Improvements in the detection and characterization of engineered
nanoparticles using spICP-MSwith microsecond dwell times. Environmental Science:
Nano, 2014.
177. Borovinskaya, O., et al., Simultaneous mass quantification of nanoparticles of different
composition in a mixture by microdroplet generator-ICPTOFMS. Analytical chemistry,
2014.
178. Borovinskaya, O., et al., A prototype of a new inductively coupled plasma time-of-flight
mass spectrometer providing temporally resolved, multi-element detection of short
signals generated by single particles and droplets. Journal of Analytical Atomic
Spectrometry, 2013. 28(2): p. 226-233.
49
-------
-S-EPA
United States EPA/600/R-14/244
Environmental Protection
Agency
Annotated bibliography in support of:
Detection and characterization of engineered nanomaterials in the
environment: current state-of-the-art and future directions
Report, annotated bibliography, and image library
RESEARCH AND DEVELOPMENT
-------
August 2014
www.epa.gov
Annotated bibliography in support of:
Detection and characterization of engineered nanomaterials in the
environment: current state-of-the-art and future directions
Report, annotated bibliography, and image library
EPA Contract EP-C-11-039
Task Order No. 5
Steven P. Gardner
U.S. Environmental Protection Agency
Office of Research and Development
National Environmental Research Laboratory
Environmental Sciences Division
Characterization and Monitoring Branch
944 E. Harmon Ave.
Las Vegas, NV89119
Julie Blue, Ph.D.1
Manuel Montano2
James F. Ranville, Ph.D.2
Gregory V. Lowry, Ph.D.3
Nupur Hiremath1
Clare Stankwitz1
Sandie Koenig1
1The Cadmus Group, Inc.
1005th Avenue, Suite 100
Waltham, MA 02451
2Colorado School of Mines
1500 Illinois Street
Golden, CO 80401
3Carnegie Mellon University
5000 Forbes Avenue
Pittsburgh, PA 15213
Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy. Mention of trade names and
commercial products does not constitute endorsement or recommendation for use.
U.S. Environmental Protection Agency
Office of Research and Development
Washington DC 20460
-------
Disclaimer
The United States Environmental Protection Agency through its Office of Research and Development funded
and managed the research described here. It has been peer reviewed by the EPA and approved for
publication.
-------
Doc ID
1
2
4
5
6
7
8
Title
Stability of
nanoparticles in
water
Nanoparticles in
aquatic systems
Silver Nanoparticles:
A Microbial
Perspective
Engineered
nanoparticles and
their identification
among natural
nanoparticles
Characterization of
surface
hydrophobicity of
engineered
nanoparticles
Clay particles
destabilize
engineered
nanoparticles in
aqueous
environments
Transport of
engineered
nanoparticles in
saturated porous
media
Authors
Brant, J. and
Labille, J.
Delay, M. and
Frimmel, F.H.
Sweet, M.J. and
Singleton, I.
Zanker, H.and
Schierz, A.
Xiao, Y. and
Wiesner, M.R.
Zhou, D., Abdel-
Fattah,A.I., and
Keller, A.A.
Tian,Y., Gao,
B., Silvera-
Batista, C., and
Ziegler, K.
Year
2010
2012
2011
2012
2012
2012
2009
Journal Title, Vol.
No., and Page No.
(or Year)
Nanomedicine, 5(6),
985-989
Analytical and
Bioanalytical
Chemistry, 402(2),
583-582
Advances in Applied
Microbiology, 77, 115-
133
Annual Review of
Analytical Chemistry,
5(1), 107-132
Journal of Hazardous
Materials, 215-216,
146-151
Environmental
Science and
Technology, 46(14),
7520-7526
Journal of
Nanoparticle
Research, 12(7), 2371
2380
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Labille and Brant (201 0) present a review of manufactured nanoparticles and their interactions in aqueous media. Three categories of nanoparticles are covered in this review: metal oxides, pure metals, and
fullerenes. The interactions of nanoparticles with surrounding media (e.g., water) are largely governed by the surface of the particle, which maybe oxidized, reduced, or dissolved. Due to their small radius of
curvature, nanoparticles have high surface tension, which serves as an attractive force causing agglomeration that can lead to greater thermodynamic stability in nanoparticles. High surface tension, which
leads to thermodynamically unstable nanoparticles, may result in unique properties such as increased dissolution, phase transformation, or crystallization. Nanoparticles may release chemical solutes during
dissolution, which may be more mobile and stable than the parent nanoparticles, and therefore may be a greater environmental concern than the nanoparticles themselves. Similarly, nanoparticle agglomerates
may interact differently with the environment than their constituent nanoparticles. The formation of agglomerates depends on acid-base interactions (attractive for hydrophobic or non-polar surfaces and
repulsive for hydrophilic or polar surfaces), electrostatic interactions (which occur when surfaces are charged), and van der Waals interactions (which change as the distance between particles increases).
Manufactured nanoparticles are surface-modified, functionalized, or coated to modify their surface properties for specific commercial and industrial applications. Most occurrences of manufactured
nanoparticles in the environment will be of degraded or transformed nanoparticles, whose surface properties, which dictate their fate and transport, may vary according to the environmental conditions and the
mode of degradation or transformation. This article suggests that future research efforts should focus on understanding the types and properties of nanomaterial degradation or transformation/conversion
products.
Delay and Frimmel summarize the interactions, fate, and transport of nanoparticles, both natural and engineered (ENPs), in natural aquatic systems. The most important properties of ENPs are: surface
chemistry (functionalization and charge), agglomeration (state, shape, and fractal dimensions), chemical composition and crystal structure, and solubility. Natural nanoparticles may enter aquatic systems
through formation by biotic or abiotic activity or by human activity, while ENPs may enter the aquatic environment through accidental or intentional anthropogenic release. Natural nanoparticles have a greater
variety of physical and chemical properties than ENPs. Isotope-labeling may help distinguish between natural nanoparticles and ENPs in the environment. Of the nanoparticles present in the natural
environment, only a small fraction are ENPs. The article lists the following 13 representative ENPs: gold, iron, silver, aluminum oxides, zinc oxides, cerium oxides, silicon dioxide, titanium dioxide, fullerenes,
single- and multi-walled carbon nanotubes, dendrimers, and nanoclays. Surface modifications made to these EN Ps for industrial or commercial applications may be lost or altered in the natural environment,
resulting in significant changes in their behavior and making it more challenging to detect them using known analytical methods. Challenges with detection include: low concentrations of nanoparticles;
difficulties in sample preparation; artifacts and sample stability; polydispersity; and lack of reference and standard materials for calibration and validation. Delay and Frimmel suggest that future research focus
on identifying reference nanoparticles as a baseline for comparison with ENPs.
Sweet and Singleton (2011) document the formation, microbial properties and application, and environmental implications of naturally-occurring nanosilver particles and engineered nanosilver particles (silver
EN Ps). The article summarizes key literature that documents the production of nanosilver in the natural environment by bacteria (e.g., Pseudomonas stutzeri, bacteria isolated from silver mines in Africa, which
produce spherical-, triangular-, and hexagonal-shaped nanosilver particles) and by fungi (e.g., Verticillium sp. and Fusarium oxysporum, which can reduce silver nitrate solution to 25-nm-sized silver particles).
Naturally-synthesized nanosilver particles demonstrate the same properties as commercially-synthesized nanosilver ENPs. ENPs are typically released into the natural environment as a part of a matrix rather
than as individual particles. Release may largely be associated with use and disposal of consumer products. Transformation or degradation due to light, microbes, oxidants, or other environmental factors may
result in the release of free ENPs from the matrix. Silver ENPs may have adverse effects on soil (e.g., they may reduce denitrification rates), but the authors note that additional research is needed to document
adverse effects and toxic potential.
Zanker and Schierz (201 2) present a summary of methodologies for identifying and characterizing engineered nanoparticles (EN Ps). Identifying risks posed by EN Ps is challenging due to interactions between
ENPs and natural nanoparticles, the presence of organic matter coatings on ENPs, surface modifications introduced during manufacturing of ENPs, subsequent surface changes due to interactions with the
natural environment, and the tendency of contaminants to adhere to ENPs. Parameters for nanoparticle characterization include size, size distribution, shape, concentration, dispersion or aggregation, structure
and chemical composition, surface properties (area, charge, functional groups, speciation), desorption or dissolution rates, and the nature and stability of coatings. Analytical methods for identification and
characterization of nanoparticles covered in this article include particle fractionation (e.g., microfiltration, field-flow fractionation, capillary electrophoresis), spectroscopy and related techniques (e.g., photon
correlation spectroscopy, laser-induced breakdown detection), visualization (e.g., scanning, transmission, and/or atomic force electronic microscopy), and deployment of sensors that can detect specific types
of nanoparticles (e.g., optical sensors, biosensors). Of these, Zanker and Schierz identify flow field-flow fractionation (FFF), sedimentation FFF, capillary electrophoresis, and liquid phase extraction as the most
reliable methods for nanoparticle identification and characterization. However, the authors note that knowledge of the type of nanoparticles present in a sample is key to selecting the best method for their
detection, as there are many challenges associated with detecting unknown particles in environmental media.
Xiao and Wiesner present an evaluation of the surface hydrophobicity of coated and uncoated carton- and metal-based engineered nanoparticles (ENPs). Hydrophobicity is important because it can affect the
fate, transport, and bioavailability of EN Ps. The seven EN Ps characterized in this study are: aqueous nC60, tetrahydrofuran-nC60, fullerol, nanogold coated with citrate, nanosilver coated with
polyvinylpyrrolidone (PVP), nanosilver coated with citrate, and nanosilver coated with gum arable. Three methods were used to evaluate surface hydrophobicity: surface adsorption (using organic dye and
naphthalene adsorption), affinity coefficient (using octanol and water phases), and contact angle measurement (using a thin film of EN Ps). The results of this study show that aqueous nC60 and tetrahydrofuran-
nC60 are the most hydrophobic, followed by nanosilver and nanogold with the citrate-functionalized surfaces, followed by nanosilver coated with PVP or gum arable, and lastly, fullerol.
Zhou et al. examine the interactions that two of the most commonly produced engineered nanoparticles (ENPs), nanosilver and nano-titania, have with clay, in order to determine how these interactions affect
particle stability. Montmorillonite, a clay mineral, has a sheet-like structure, with two layers of silicon tetrahedra that flank a layer of aluminum octahedra. At the typical pH of clay minerals, which ranges
between 5 and 8, negative charges develop on the planes while positive charges develop at the edges. A stock suspension of montmorillonite was mixed with nano-titania solution and with citrate-coated
nanosilver solution. The resultant mixtures were analyzed by dynamic light scattering to determine hydrodynamic data and by Laser DopplerVelocimetryto determine electrophoretic mobility. At a pH of 8,
there was no change in the stability of the montmorillonite system with either nanosilver or nano-titania. However, at pH 4, the critical coagulation concentration of the system shifts to a lower ionic strength,
causing montmorillonite/nanosilver or montmorillonite/nano-titania agglomerates, demonstrating the ability of the clay mineral to destabilize both positively charged (titania) and negatively charged (silver, which
is negatively charged due to the citrate coating) ENPs. The authors note under real-world conditions, clay-nanoparticle interactions maybe affected by varying clay/nanoparticle concentration ratios, the
presence of naturally-occurring oxides and hydroxides and organic matter, and other factors.
Tian et al. (201 0) examine the fate and transport of two engineered nanoparticles (EN Ps), nanosilver and single-walled carton nanotubes, in saturated porous media to simulate fate and transport in soil. Two
types of porous media were used: quartz sand washed sequentially with tap water and deionized water and baked at 550 deg C, and quartz sand washed sequentially with tap water and 10% nitric acid and
baked at 550 deg C. The sand was packed into columns 2.5 cm in diameter and 15 cm in height. Solutions of carton nanotubes and nanosilver in aqueous sodium dodecylbenzene sulfonate (orSDBS, an
anionic surfactant) were added to the columns. Solutions of montmorillonite (a clay mineral) in deionized water or in SDBS were also added to the columns. Bromide was used as a tracer. The
Derjaguin-Landau-Verwey-Overteek (DLVO) theory for estimating interactive forces between the nanoparticles and the sand grains was applied, and the colloid filtration theory was used to simulate
retention, transport, and re-mobilization of the ENPs. The results showed the transport of carbon nanotubes through the sand was similar to that of colloidal montmorillonite with 100% recovery at the bottom of
the column. Similarly, nanosilver also mimicked the transport of colloidal clay with a 75% recovery at the bottom of the column, demonstrating that ENPs may move fairly quickly through saturated porous
media. Some combinations (e.g., carton nanotubes and S DBS-dispersed montmorillonite), however, deviated from the DLVO and colloidal filtration theory. The authors assert that these deviations are due to
the presence of the surfactant.
Complete Citation
Brant, J. and Labille, J. 2010.
Stability of nanoparticles in water.
Nanomedicine, 5(6), 985-989.
Delay, M. and Frimmel, F.H.
2012. Nanoparticles in aquatic
systems. Analytical and
Bioanalytical Chemistry, 402(2),
583-582.
Sweet, M.J. and Singleton, I.
2011. Silver Nanoparticles: A
Microbial Perspective. Advances
in Applied Microbiology, 77, 1 1 5-
133.
Zanker, H . and Schierz, A. 201 2.
Engineered nanoparticles and
their identification among natural
nanoparticles. Annual Review of
Analytical Chemistry, 5(1), 107-
132.
Xiao, Y. and Wiesner, M.R. 2012.
Characterization of surface
hydrophobicity of engineered
nanoparticles. Journal of
Hazardous Materials, 215-216,
146-151.
Zhou, D., Abdel-Fattah, A.I., and
Keller, A.A. 201 2. Clay particles
destabilize engineered
nanoparticles in aqueous
environments. Environmental
Science and Technology, 46(14),
7520-7526.
Tian, Y., Gao, B., Silvera- Batista,
C., and Ziegler, K. 2009.
Transport of engineered
nanoparticles in saturated porous
media. Journal of Nanoparticle
Research, 12(7), 2371-2380.
Page 4
-------
Doc ID
g
10
11
12
13
Title
Environmental and
Colloidal Behavior of
Engineered
Nanoparticles
Occurrence,
behavior and effects
of nanoparticles in
the environment
Nanoparticles:
structure, properties,
preparation, and
behavior in
environmental media
An approach to the
natural and
engineered
nanoparticles
analysis in the
environment by
inductively coupled
plasma mass
spectrometry
Characterization of
nanoparticles
released during
construction of
photocatalytic
pavements using
engineered
nanoparticles
Authors
Xing, B.
Nowack, B. and
Bucheli,T.D.
Christian, P., von
der Kammer, F.,
Baalousha, M.,
and Hofmann, T.
Jimenez, M.S.,
Gomez, M.T.,
Bolea, E.,
Laborda, F., and
Castillo, J.
Dylla, H.and
Hassan, M.M.
Year
2010
2007
2008
2011
2012
Journal Title, Vol.
No., and Page No.
(or Year)
In Molecular
Environmental Soil
Science at the
Interface in the Earth's
Critical Zone, 246-248
Environmental
Pollution, 150(1), 5-22
Ecotoxicology, 17(5),
326-343
International Journal
of Mass
Spectrometry, 307(1-
3), 99-104
Journal of
Nanoparticle
Research, 14(4), 825
Document
Type
Book
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Xing (2010) examines the colloidal behavior of three types of engineered nanoparticles (ENPs) in the natural environment: carton nanotubes (single- and multi-walled), fullerenes, and oxides (aluminum oxide,
zinc oxide, and titanium dioxide). Suspensions of ENPs with humic acid were created. Colloidal stability, particle stability, and zeta potentials were examined with a Zetasizer, and pH, presence of cations, and
presence of organic matter were also assessed. Adsorption capacity of ENPs was examined with polyaromatic hydrocarbons (phenanthrene, naphthalene, pyrene) and endocrine disrupting compounds (17a-
ethinyl estradiol, bisphenol A) as adsortates. Adsorption isotherms were obtained by batch equilibration. Toxicity of these ENPs to plants, bacteria, and nematodes was also assessed. Of the ENPs, single-
walled carton nanotubes had the highest sorption capacity and fullerenes had the lowest sorption capacity. The sorption capacity of carbon nanotubes was particularly high for endocrine disrupting compounds.
Zinc oxide ENPs were taken up easily by roots and inhibited plant growth. All oxide ENPs showed highertoxicityto bacteria and nematodes than their bulk counterparts. Humic acid was found to increase the
dispersibility, and therefore the stability, of carton nanotubes and aluminum oxide in suspension.
Nowack and Bucheli (2007) present a review of engineered nanoparticles (EN Ps) and naturally-occurring nanoparticles, documenting: how they are produced; their characteristics and properties; methods for
analyzing them; release, occurrence, fate, and transport in the natural environment; and uptake by and toxicity for organisms. Natural nanoparticles can be geogenic orpyrogenic (e.g., carton nanotubes,
fullerenes), biogenic (e.g., magnetite), or atmospheric (e.g., sea salt). Anthropogenic nanoparticles are those produced inadvertently through human activities, such as combustion (e.g., soot), or deliberately
engineered (e.g., functionalized nanosilver or nanotitania). Types of nanoparticles featured in this study are: soot (natural and unintentionally produced), fullerenes and carbon nanotubes (natural, unintentionally
produced, engineered), and inorganic particles (natural, unintentionally produced, engineered). The article discusses specific processes for and sources of formation for each of these nanoparticles.
It also presents specific methods for analyzing each of these types of nanoparticles, including microscopic methods (e.g., electron microscopy, atomic force microscopy), size fractionation techniques (e.g.,
ultrafiltration, flow-field fractionation, centrifugation), and chromatography (e.g., size-exclusion, gel permeation). Behavior of natural nanoparticles and ENPs in various media, including water and porous media,
and in environments with different adsorbents (e.g., organic contaminants, metals), is documented. The uptake of these types of nanoparticles and their ecotoxicity in plant, animal, and microbial species is
discussed. Functionalization for industrial or commercial applications or coating of nanoparticles by natural compounds in the environment affects their fate and transport; this is an area that requires additional
research.
Christian et al. (2008) present a review of the surface chemistry of nanoparticles (both natural and engineered) and how it may influence fate and transport in the natural environment. Engineered nanoparticles
(ENPs) have three layers: the core material; shell material that maybe intentionally added (e.g., zinc sulfide on cadmium selenide nanoparticle cores) or may form from the particle itself (e.g., iron oxide, which
forms on the surface of iron nanoparticle cores); and outer surface with added functional groups (e.g., metal ions, small molecules, surfactants, or polymers) designed for a specific application. The morphology
of ENPs (e.g., rod, wire, tetrapod, teardrop, dumbbell, dendrite) maybe dependent on the phases of the components in the system surrounding the nanoparticle as well as on the properties of the
nanoparticles themselves. The authors provide a detailed discussion of additional properties of ENPs, including particle mobility, surface energy, and colloidal interactions (e.g., charge stabilization and steric
stabilization), optical properties, and potential for catalysis. Detailed top-down (breaking off EN Ps from larger pieces of material) and bottom-up (growing from simple molecules) approaches for the preparation
of engineered nanoparticles (ENPs), including metal oxides, polymers, nanowires, nanotubes, and others, are outlined. The behavior of ENPs in the aquatic environment, their interaction with pollutants, the
formation of nanoparticle coatings by natural organic matter, aggregation of nanoparticles (including the effect of humic acid and cations), and their behavior in porous media are further documented in this
article.
Jimenez et al. (2011) review analytical methods for detection of nanomaterials. They review a series of techniques using inductively coupled mass spectrometry (1C P-MS) to detect nanoparticles containing
metals. They begin with a discussion of a technique used to detect natural nanoparticles, using polyacrylamide gel electrophoresis laser ablation (PAGE-LA) as a separation technique and 1C P-MS for
detection. PAGE has commonly been used for characterization of dissolved organic matter but has recently found more use in detecting nanoparticles with metals. The article cites a study that used PAGE-LA-
ICP-MS to examine lead complexes. The paper reviewed several studies that examined metal complexes with humic and fulvic acids. The paper also discusses how PAGE-LA has been used to detect metals
bound in proteins. One problem encountered in use of PAGE-LA-ICP-MS is metal loss in complexes that are not strongly bound. The problem maybe reduced by using native PAGE instead of denaturing
PAGE. The paper then discusses analytical methods for engineered nanoparticles (ENPs). These methods use either chromatography or field-flow fractionation (FFF) as a separation technique for ICP-MS.
Size-exclusion chromatography (SEC), a common method for characterization of ENPs, involves passing the ENPs through a column with a stationary phase containing pores. The size range of ENPs that can
be detected depends on the pore size of the stationary phase. Hydrodynamic chromatography (HC), on the other hand, passes the ENPs through a column filled with packed beads. This separation technique
depends only on particle size and is independent of density and particle type. FFF uses an external field to separate particles and does not have a stationary phase. FFF is good for particles in the 300 Da to
100 nm range. A few studies have used FFF ICP-MS for ENP characterization. Single particle detection uses ICP-MS to detect single particles: on entering the plasma, a particle produces a flash of gaseous
ions. To use this method, concentrations must be low enough so that two particles do not enter the ICP at the same time (usually less than 109 particles per liter). The concentration must also be high enough
to allow a minimum number of counting events. The particle must also be large enough to produce enough gaseous ions. This method can provide information on: differentiation between dissolved metals and
nanoparticles, size distribution of nanoparticles, mass of dissolved and nanoparticle metal, and number and concentration of nanoparticles. Faster electronics, allowing faster dwell times, can improve the time
resolution. Increasing the transmission efficiency from the skimmer to the detector will improve size detection. Use of simultaneous double focusing sector field spectrometers will allow detection of more than
one metal at a time.
Dylla and Hassan (2012) studied release of titanium dioxide ENPs during construction of self-cleaning cements. They performed both lab and field experiments. A scanning mobility particle sizer(SMPS) was
used to determine particle concentrations emitted from construction activities. In the lab, application of a mortar overlay was studied; 5 percent (by weight) of titanium particles with diameters between 15 to 28
nm was added to the mortar overlay either as a powder or as a liquid. Both methods produced higher concentrations than the control. The mortar overlay application with nanoparticles in powdered form
released approximately 1 x 1 0A6 particles/cm3 compared to 4 x 1 0A5 particles/cm3 without the nanoparticles. The liquid application produced slightly more nanoparticles, but most of the release was during the
measurement of the powder and the mixing of the powder with the liquid. The size distribution of the released particles varied from 30 to 52 nm, with a surface area of between 1.9 and 5.4 x 10A9 nm2/cm3
and a mass concentration of between 3.9 and 1 0.8 |jg/m3. In the field, investigators studied the application of a spray coating with 2 percent titanium dioxide nanoparticles. Particle concentrations released
were higher than in the morter overlay experiments, at 2 x 1 0A8 particles/cm3. Particles were smaller than in the mortar overlay, at between 23 and 37 nm with a surface area of between 1 and 9 x 1 0A1 1
nm2/cm3. Released particles were examined for shape. They appeared spherical, whereas the applied particles were rod-shaped. The resolution, however, was not clear and the shape appeared to change
over time, possibly suggesting volatile particles. The authors suggest further study to better define particle morphology. Additional studies on release during wear and runoff events are also suggested.
Complete Citation
Xing, B. 2010. Environmental and
Colloidal Behavior of Engineered
Nanoparticles. In Molecular
Environmental Soil Science at the
Interface in the Earth's Critical
Zone, 246-248.
Nowack, B. and Bucheli, T.D.
2007. Occurrence, behavior and
effects of nanoparticles in the
environment. Environmental
Pollution, 150(1), 5-22.
Christian, P., von der Kammer,
F., Baalousha, M., and Hofmann,
T. 2008. Nanoparticles: structure,
properties, preparation, and
behavior in environmental media.
Ecotoxicology, 17(5), 326-343.
Jimenez, M.S., Gomez, M.T.,
Bolea, E., Laborda, F., and
Castillo, J. 201 1 . An approach to
the natural and engineered
nanoparticles analysis in the
environment by inductively
coupled plasma mass
spectrometry. International
Journal of Mass Spectrometry,
307(1-3), 99-104.
Dylla, H.and Hassan, M.M. 2012.
Characterization of nanoparticles
released during construction of
photocatalytic pavements using
engineered nanoparticles. Journal
of Nanoparticle Research, 14(4),
825.
Pages
-------
Doc ID
14
15
16
17
18
Title
The ecotoxicology of
nanoparticles and
nanomaterials:
current status,
knowledge gaps,
challenges and
future needs
Nanoparticle analysis
and characterization
methodologies in
environmental risk
assessment of
engineered
nanoparticles
Quantitative analysis
of fullerene
nanomaterials in
environmental
systems: a critical
review
Monitoring
nanoparticles in the
environment
Considerations for
environmental fate
and ecotoxicity
testing to support
environmental risk
assessment for
engineered
nanoparticles
Authors
Handy, R.D.,
Owen, R., and
Valsami-Jones,
E.
Hassellov, M.,
Readman, J.W.,
Ranville, J.F.,
andTiede, K.
Isaacson, C.W.,
Kleber, M., and
Field, J.A.
Simonet, B.M.
and Valcarcel,
M.
Tiede, K.,
Hassellov, M.,
Breitbarth, E.,
Chaudhry, Q.,
and Boxall, A.B.
Year
2008
2008
2009
2009
2009
Journal Title, Vol.
No., and Page No.
(or Year)
Ecotoxicology, 17(5),
315-325
Ecotoxicology, 17(5),
344-361
Environmental
Science and
Technology, 43(17),
6463-6474
Analytical and
Bioanalytical
Chemistry, 393(1), 17-
21
Journal of
ChromatographyA,
1216(3), 503-509
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Handy et al. (2008) present a review of the ecotoxicology and environmental chemistry of natural nanoparticles and engineered nanoparticles (ENPs). Natural nanoparticles can be produced by geologic
processes (e.g., weathering, authigenesis/neoformation, volcanic eruptions), which typically generate inorganic nanoparticles, and by biological processes (e.g., formation by microorganisms, degradation of
biological matter). Natural nanoparticles maybe less of a concern than ENPs as they may dissolve in aqueous media or become larger through aggregation. However, some natural nanoparticles (e.g.,
volcanic acid) have are known to be toxic or to bind to contaminants in the environment to become toxic. The article covers the physico-chemistry of nanoparticles (natural and engineered), summarizing
properties (particle shape, size, surface area, and surface charge), aggregation chemistry, adsorption of particles onto surfaces, and the effect of abiotic factors (e.g., pH, water hardness, and presence of
natural organic matter) on behavior. The authors also summarize literature on the ecotoxicity of nanoparticles in aquatic, marine, and terrestrial species, including microbes as well as more complex species.
The authors note that there are major research needs associated with nanoparticle ecotoxicity, including chemical characterization of the ecotoxicology test materials, reference nanomaterials for regulatory
ecotoxicology, modifications to methods to adapt them for testing regulatory ecotoxicity of nanoparticles, and additional testing methods.
Hassellov et al. (2008) provide a review of characterization techniques for nanoparticles. Important parameters include not only concentration but also size distribution, surface area, surface charge,
composition, and shape. Nanoparticle sampling needs to be conducted in such a way as to minimize disturbance of the particles, and traditional assumptions about adsorption to sampling apparatus need to be
reexamined. Prefractionation of samples before analysis is often necessary. This can include centrifugation, filtration, or settling. Centrifugation minimizes particle disturbance but can cause aggregation.
Filtration is the most common method but can cause aggregation as well. Cross-flow filtration can minimize particle aggregation. Dialysis can also be used as a separation technique but can result in particle
dissolution and ionic strength effects. Field-flow fractionation (FFF) separates samples based on diffusion coefficients in a thin channel. It depends only on particle size. It requires appropriate ionic strength and
use of surfactants to prevent aggregation. Size-exclusion chromatography passes the sample through a series of different sized pores. Hydrodynamic chromatography uses flow in narrow capillaries. It has
poor separation efficiency but an excellent size range. Light scattering is a technology for measuring particle size. Dynamic light scattering (DLS) is rapid, simple, and has low sample perturbation but can be
difficult to interpret. Larger particles can ruin the signal of nanoparticles, so small size ranges and lack of contamination are necessary. Static light scattering is used in conjunction with DLS to give information
on particle shape. Measurement of turbidity can give information for well-defined particles with a small size distribution. Laser induced breakdown detection (LIBD) tunes a laser so water passing through will
break down dielectrically when a particle is present. It is very sensitive and can detect concentrations down to parts per trillion, but is unable to distinguish types of particles and needs to be calibrated for each
different particle type. Fluorescence can be used for particle detection in combination with chromatography or FFF. It is more sensitive than light scattering. Microscopy techniques are single particle methods
that require sample preparation. Drying of particles may alter them. Scanning electron microscopes (SEM) can give 3-dimensional pictures. Environmental SEM allows variable pressure and humidity in the
sample but decreases resolution. Transmission electron microscopy (TEM) requires staining of light elements but can give atom-by-atom resolution. Atomic force microscopy can be used in liquids but can
overestimate lateral dimensions. X-ray diffraction can be used with microscopy to determine composition. The Brunauer, Emmett, and Teller (BET) method can be used to determine surface area. With all
nanoparticle techniques, careful attention must be paid to standards and quality control.
Isaacson et al. (2009) provide a critical review of analytical methods available to examine fullerene engineered nanoparticles (ENPs) both in their original form and their functionalized form. The authors note
that the greatest challenge in analyzing these nanoparticles is their dual nature, in that they can change from hydrophobic to hydrophilic upon exposure to aqueous media or other charged surroundings. The
authors review the various methods available for extraction (deriving fullerenes from solids), separation (separating fullerene forms), detection (differentiating fullerene forms), and quantitative analytical
methods for detection in geological, biological, and aqueous matrices. The authors note that there are no known natural occurrences of fullerenes in the environment, and they document processes for fate and
transport of these nanoparticles in the natural environment. Further, the authors note the lack of research conducted to date on quantitative assessments of biological exposure to fullerenes, and on defining the
properties of dissolved fullerenes and fullerene aggregates, which can affect their resultant toxicity.
Simonet and Valcarcel (2009) present a review of methodologies for effectively monitoring engineered nanoparticles (ENPs) in the environment. The article presents an overview of appropriate sample
preparation and handling techniques (noting the lack of in situ detection methods) and methods for separating nanoparticles in environmental samples (e.g., ultrafiltration, field-flow fractionation, inductively
coupled plasma mass spectrometry or ICP-MS, size-exclusion chromatography). It summarizes detection methods at three scales: nanoscale (e.g., transmission electron microscopy or TEM, atomic force
microscopy or AFM), microscale (e.g., scanning electron microscopy or SEM), and bulk-scale (e.g., atomic absorption spectroscopy, inductively coupled plasma atomic emission spectroscopy or ICP-AES, and
ICP-MS). The authors note that the accurate analysis of ENPs depends on the development of effective preconcentration methods, detection techniques with variable resolution, and more sensitive and
selective analytical methods.
Tiede et al. (2009) present a review of literature on the characteristics, methods of detection, fate, exposure, and effects of engineered nanoparticles (EN Ps) in the environment. The authors present detailed
information on the development of testing materials (noting that these should be well-characterized prior to any testing), selection of test concentrations that are environmentally relevant to allow determination
of aggregation behavior, and selection of test conditions (e.g., pH, organic carbon concentrations, humic substance content) that accurately reflect environmental conditions. The authors state that the selection
of the appropriate analytical method for ENP detection will depend on the question being asked and the environmental conditions being simulated. The authors provide an overview of existing analytical
techniques (e.g., scanning electron microscopy or SEM, transmission electron microscopy or TEM, energy-dispersive spectrometry or EDS, electron energy loss spectrometry or EELS, field-flow fractionation,
hydrodynamic chromatography and size-exclusion chromatography).
Complete Citation
Handy, R.D., Owen, R., and
Valsami-Jones, E. 2008. The
ecotoxicology of nanoparticles
and nanomaterials: current status,
knowledge gaps, challenges and
future needs. Ecotoxicology,
17(5), 315-325.
Hassellov, M., Readman, J.W.,
Ranville, J.F., and Tiede, K. 2008.
Nanoparticle analysis and
characterization methodologies in
environmental risk assessment of
engineered nanoparticles.
Ecotoxicology, 17(5), 344-361.
Isaacson, C.W., Kleber, M., and
Field, J.A. 2009. Quantitative
analysis of fullerene
nanomaterials in environmental
systems: a critical review.
Environmental Science and
Technology, 43(17), 6463-6474.
Simonet, B.M. and Valcarcel, M.
2009. Monitoring nanoparticles in
the environment. Analytical and
Bioanalytical Chemistry, 393(1),
17-21.
Tiede, K., Hassellov, M.,
Breitbarth, E., Chaudhry, Q., and
Boxall, A.B. 2009. Considerations
for environmental fate and
ecotoxicity testing to support
environmental risk assessment
for engineered nanoparticles.
Journal of Chromatography A,
1216(3), 503-509.
Page 6
-------
Doc ID
19
20
21
22
23
24
Title
Evaluating
engineered
nanoparticles in
natural waters
Fullerene
nanoparticles exhibit
greater retention in
freshwater sediment
than in model porous
media
Analysis of
engineered
nanomaterials in
complex matrices
(environment and
biota): general
considerations and
conceptual case
studies
State of the science
literature review:
nano titanium dioxide
environmental
matters
Nanomaterial case
studies: nanoscale
titanium dioxide in
water treatment and
in topical sunscreen
Electrochemical
detection of chloride
at the multilayer
nano-silver modified
indium-tin oxide thin
electrodes
Authors
Weinberg, H.,
Galyean, A., and
Leopold, M.
Zhang, W.,
Issacson, C.W.,
Rattanaudompol
, U.S., Powell,
T.B.,and
Bouchard, D.
von der
Kammer, F.,
Ferguson, P.L.,
Holden, P.A.,
Masion, A.,
Rogers, K.R.,
Klaine, S.J.,
Koelmans, A.A.,
Home, N., and
Unrine, J.M.
U.S.
Environmental
Protection
Agency
U.S.
Environmental
Protection
Agency
Chu, L. and
Zhang, X.
Year
2011
2012
2012
2010
2009
2012
Journal Title, Vol.
No., and Page No.
(or Year)
Trends in Analytical
Chemistry, 30(1), 72-
83
Water Research,
46(9), 2992-3004
Environmental
Toxicology and
Chemistry, 31(1), 32-
49
2010
2009
Journal of
Electroanalytical
Chemistry, 665, 26-32
Document
Type
Published
journal
Published
journal
Published
journal
Unreviewed
EPA
document
Peer reviewed
EPA
document
Published
journal
Article Summary
Weinberg et al. (2011) review characterization techniques for nanoparticles (NP) in the environment. Treatment processes are not optimized to remove engineered nanoparticles (ENPs), so therefore ENPs
are likely to find their way into water sources. Their fate will depend on particle properties such as size, composition, surface area and charge. During sampling aggregation, adsorption to sampling devices
needs to be minimized. To measure ENPs, concentration techniques are required. Stepwise centrifuging is one method for separation. Stepwise filtration has also been used but may experience aggregation or
precipitation of particles. Cross-flow filtration can minimize such problems. Fullerenes, a type of EN P, have been extracted using a destabilizing agent and solvent. Size-exclusion chromatography (SEC) is a
common extraction technique which depends on the pore size of the stationary phase. Columns may need to be modified to deal with electrostatic repulsion or steric hindrance by ligands. Environmental
samples will require pretreatment to prevent clogging of pores. Field-flow fractionation (FFF) does not require a stationary phase. FFF can reduce sample complexity while providing information on different size
groupings. It can experience significant agglomeration and may require preconcentration if concentrations are low. Asymmetric flow FFF allows for a wide range of size distributions. It does require selecting an
appropriate carrier fluid to prevent ENP alteration. Capillary electrophoresis (CE) can be used, although modification of the capillary surface to prevent retention maybe required. The detector used after CE
may be fluorescence or UV adsorption. Mass spectrometry (MS) could be used but has not been reported. After separation, ENPs must be characterized for a number of properties that will require a number
of techniques. Quantitative techniques such as mass spectrometry are often coupled with qualitative techniques such as microscopy to obtain a full set of information. Electron and scanning probe microscopy
can be used at the nanometer level. Near-field scanning optical microscopy may also be useful. Transmission electron microscopy , scanning electron microscopy (SEM), and atomic force microscopy are the
preferred microscopy methods and can give information on shape, size, aggregation, and sorption. Analytical electron microscopy and Auger electron spectroscopy can determine composition. Environmental
SEM can examine ENPs in their natural state. Dynamic light scattering can give in-situ particle size information. Laser-induced breakdown detection is a new method that can give concentration and number
weighted mean diameter. Visible spectroscopy has been used for noble metal ENPs to determine size distribution. X-ray spectroscopy can determine surfaces and coating of ENPs. Separation techniques
must be coupled with characterization techniques for appropriate analysis, for example FFF with MS or filtration with microscopy. The authors go on to state more work is needed on sensors specifically
designed to characterize ENPs. They give an example of fluorescence based detectors being designed to detect silver and gold ENPs.
Zhang et. al (201 2) investigated the retention of two fullerene types (aqu/C60 and water-soluble C60-TPA) in model porous media, taking into account various aquatic parameters such as pH and ionic
strength. The researchers also investigated retention time in lota quartz, Ottawa sand, and sediment. They found that surface heterogeneity plays a large role in the retention of fullerene particles. In addition,
higher pH systems may facilitate greater transport of the nanomaterial as there is stronger electrostatic repulsion between the surface and the fullerene nanomaterial. The implications of this study show that
various parameters play a role in the retention of nanomaterials, and that model porous media may not adequately reflect the conditions nanomaterials (NMs) may be exposed to. Due to these various
parameters, the vadose zone may also play a role in preventing N M transport.
Von der Kammer et al (2012) provided a critical review of several aspects of the analysis and characterization of nanoparticles in the environment. Specific attention was given to various aspects of sample
preparation, separation from environmental media, and distinguishing between engineered nanoparticles (ENPs) and naturally-occurring nanomaterials. Four case studies were presented. The use of near-
infrared spectroscopy (NIR) to detect and characterize nanomaterials was discussed at length. The challenges of characterizing nanomaterials (specifically CdSe quantum dots and TiO2 ENPs) in biological
media and cells was discussed. Difficulties encountered in detecting CeO2 and TiO2 in natural sediment samples were addressed, and possible solutions involving isotopic abundance, single-particle electron
microscopy, and mass spectrometry techniques were discussed. For silver nanoparticles in wastewater, with different separation methods reviewed, including field-flow fractionation (FFF) coupled with an
element-specific detector such as ICP-MS. In short, this paper provides a comprehensive review of the challenges that arise from the analysis of engineered nanoparticles in environmental media and proposes
theoretical solutions to begin to address these issues.
This EPA report summarizes available information pertaining to the manufacturing, processing, use, and end-of-life for nanoscale titanium dioxide (nano-TiO2). Primary data gaps identified in the report include:
domestic production volumes for nano-TiO2; identities of domestic manufacturers, processors, and industrial users (and corresponding throughput of nano-TiO2 at these facilities); standardized sampling and
analysis methods; a better understanding of the fate and transport of nano-TiO2 after release into the environment; and a thorough review of human health and toxicological data.
In this report EPA presents two case studies of nanotechnology applications. The goal was to apply life cycle analysis methodology to evaluate the ecological and human health risks from nanotechnologies.
The two case studies chosen were the known use of nano-TiO2 as a physical blocker in sunscreens, and the possible use of nano-TiO2 to remove arsenic from drinking water. The report summarizes available
information about routes of entry of coated and uncoated nano-TiO2 into environmental media (during manufacture, use, and disposal), fate and transport in environmental media, and analytical methods,
among other topics. The report summarizes data gaps and suggested research priorities, including an assessment of the appropriateness of standard health and ecological toxicity testing protocols for use with
nano-TiO2, and development of improved methods for physicochemical characterization of nanomaterials under controlled conditions, in environmental matrices, and in biological systems.
Zhang and Chu, 2012 used SEM to study the surface of an electrode containing silver nanoparticles. They were able to determine particle size, shape, and spacing.
Complete Citation
Weinberg, H., Galyean, A., and
Leopold, M. 2011. Evaluating
engineered nanoparticles in
natural waters. Trends in
Analytical Chemistry, 30(1), 72-
83.
Zhang, W., Issacson, C.W.,
Rattanaudompol, U.S., Powell,
T.B., and Bouchard, D. 2012.
Fullerene nanoparticles exhibit
greater retention in freshwater
sediment than in model porous
media. Water Research, 46(9),
2992-3004.
von der Kammer, F., Ferguson,
P. L., Holden, P.A., Masion, A.,
Rogers, K.R., Klaine, S.J.,
Koelmans, A.A., Home, N., and
Unrine, J.M. 2012. Analysis of
engineered nanomaterials in
complex matrices (environment
and biota): general considerations
and conceptual case studies.
Environmental Toxicology and
Chemistry, 31(1), 32-49.
U.S. Environmental Protection
Agency 2010. State of the
science literature review: nano
titanium dioxide environmental
matters. 2010.
U.S. Environmental Protection
Agency 2009. Nanomaterial case
studies: nanoscale titanium
dioxide in water treatment and in
topical sunscreen. 2009.
Chu, L. and Zhang, X. 2012.
Electrochemical detection of
chloride at the multilayer nano-
silver modified indium-tin oxide
thin electrodes. Journal of
Electroanalytical Chemistry, 665,
26-32.
Page?
-------
Doc ID
101
102
103
104
105
106
Title
Coating Fe3O4
magnetic
nanoparticles with
humic acid for high
efficient removal of
heavy metals in
water
Preparation and
characterization of
magnetite
nanoparticles coated
by amino silane
Synthesis and
magnetic properties
of CoO nanoparticles
Ion and pH sensing
with colloidal
nanoparticles:
influence of surface
charge on sensing
and colloidal
properties
Surface and related
bulk properties of
titania nanoparticles
recovered from
aramid-titania hybrid
films: A novel
attempt
Effect of surface
properties of silica
nanoparticles on
their cytotoxicity and
cellular distribution in
murine macrophages
Authors
Liu, J.,Zhao,Z.,
and Jiang, G.
Ma, M., Zhang,
Y.,Yu,W.,
Shen, H., Zhang,
H., andGu, N.
Ghosh, M.,
Sam path kumara
n, E., and Rao,
C.
Zhang, F., All,
Z., Amin,F.,
Feltz, F.,
Oheim, M., and
Parak,W.
Al-Omani, S.,
Bumajdad, A.,
Sagheer, F., and
Zaki, M.
Nabeshi, H.,
Yoshikawa, T.,
Arimori, A.,
Yoshida,!.,
Tochigi, S.,
Hirai,T.,Akase,
T., Nagano, K.,
Abe, Y.,
Kamada, H.,
Tsunoda, S.,
Itoh, N.,
Yoshioka,Y.,
andTsutsumi, Y.
Year
2008
2003
2005
2010
2012
2011
Journal Title, Vol.
No., and Page No.
(or Year)
Environmental
Science and
Technology, 42(1 8),
6949-6954
Colloids and Surfaces
A: Physicochemical
and Engineering
Aspects, 212(2-3),
219-226
Chemistry of
Materials, 17(9), 2348-
2352
Chemphyschem: A
European Journal of
Chemical Physics and
Physical Chemistry,
11(3), 730-735
Materials Research
Bulletin, 47(11), 3308-
3316
Nanoscale Research
Letters, 6(1), 93
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Liu et. al (2008) investigated the coprecipitation of Fe3O4 with humic acid to form magnetic nanoparticles with a humic acid coating. The nanoparticles synthesized were approximately 1 0nm in diameter. The
uncoated nanoparticles had a pHPZC~ 6.0, whereas those coated with humic acid saw a sharp decrease in the point of zero charge (~3.7). These particles were then studied to determine their efficacy in the
removal of heavy metals from groundwater via sorption onto the nanoparticles. In all conditions, the nanoparticles coated with humic acid showed a greater sorption and removal of heavy metals than the
uncoated particles. The results indicate a method for the development of a relatively inexpensive nanoparticle that can be used for the remediation of heavy metals in a variety of natural systems.
Ma et. al (2003) synthesized magnetic Fe3O4 particles with an average diameter of 7.5nm and coated with an amino silane. Preparation occurred through the co-precipitation of FeCI3 and FeSO4 The
particles were characterized using TEM, EDS and powder x-ray diffraction. The binding of the amino silane to the surface of the nanoparticle was confirmed through the use of fourier transform infrared
spectroscopy. An enzyme (horseradish peroxidase) assay was used to determine the absorbance efficacy of the coated nanoparticles; the coating was found to dramatically increase adsorption.
Ghosh et al. (2005) synthesized stable CoO nanoparticles using a solvothermal method involving the decomposition of a Cobalt (II) cupferronate in the presence of an organic solvent (i.e. Decalin). Obtaining
stable CoO nanoparticles presented a challenge due to the ready reducibility of CoOto Co metal as well as the presence of the more stable Co3O4. Nanoparticles were characterized using XRD, TEM, FT-IR,
and TGA. The addition of the organic coating provides stability and prevents the oxidation of the nanoparticles. In the larger nanoparticle sizes synthesized (16 and 18nm), an antiferromagnetic transition was
observed at temperatures around 300 deg K. This procedure demonstrates a method of synthesizing stable CoO nanoparticles that are resistant to oxidation.
Zhang et al. (2010) looked at the effect of pH on the ion-sensing capability of simple and modified colloidal nanoparticles (NPs). Counter-ions are expected to concentrate near the nanoparticle surface due to
electrostatic attraction, as explained by the Debye-Huckel model, and these may interfere with the ability of an ion-sensing fluorophore attached to the NP to determine ion concentrations in the medium. The
results of the study confirm this. The pKa can be modified by varying the distance between the NP surface and the fluorophore through modification of the length of the PEG (poly-ethylene glycol) polymer that
attaches the analyte-sensitive fluorophores to the particle.
Al-Omani et al. (201 2) synthesized anatase-T\O2 nanoparticles using an aramid-titania hybrid film as the parent precuror. The titani species were bonded to the polymer backbone using ICTOS (3-isocyanto-
propyltriethoxysilane), which helped prevent agglomeration of the nanoparticles. The film was then thermally degraded, yielding anatase-T\O2 nanoparticles. The material produced was thermally stable up to
high temperatures (800 deg C) and also exhibited a highly stable surface chemical composition. It was found that the higher the titanium loading on the precursor film, the more thermally stable the surface
texture but the less thermally stable the surface chemical composition.
Nebeshi et al. (2011) investigated the role surface groups and surface charge play in the cytotoxicity of silica nanoparticles to a murine macrophage cell (RAW264.7). Uncoated silica nanoparticles were found
to penetrate into the nucleus of the cell and deliver the greatest toxic effect (EC5D=121.5 (jg/L). The coated nanoparticles (an amine-coated nanoparticle and a cartoxylated nanoparticle) showed a significant
reduction in toxicity, with very little toxicity occurring even at concentrations of up to 1000 |jg/L. Confocal laser scanning microscopy also visualized the uptake of the uncoated silica particles into the nucleus,
whereas no uptake was observed for the treated particles. The surface processing of nanoparticles should be tuned in order to synthesize safer materials that are limited in their ability to produce a cytotoxic
effect.
Complete Citation
Liu, J., Zhao, Z., and Jiang, G.
2008. Coating Fe3O4 magnetic
nanoparticles with humic acid for
high efficient removal of heavy
metals in water. Environmental
Science and Technology, 42(18),
6949-6954.
Ma, M., Zhang, Y.,Yu,W., Shen,
H., Zhang, H., andGu, N. 2003.
Preparation and characterization
of magnetite nanoparticles coated
by amino silane. Colloids and
Surfaces A: Physicochemical and
Engineering Aspects, 212(2-3),
219-226.
Ghosh, M., Sampathkumaran, E.,
and Rao, C. 2005. Synthesis and
magnetic properties of CoO
nanoparticles. Chemistry of
Materials, 17(9), 2348-2352.
Zhang, F., All, Z., Amin, F., Feltz,
F., Oheim, M., and Parak, W.
2010. Ion and pH sensing with
colloidal nanoparticles: influence
of surface charge on sensing and
colloidal properties.
Chemphyschem: A European
Journal of Chemical Physics and
Physical Chemistry, 11(3), 730-
735.
Al-Omani, S., Bumajdad, A.,
Sagheer, F., and Zaki, M. 2012.
Surface and related bulk
properties of titania nanoparticles
recovered from aramid-titania
hybrid films: A novel attempt.
Materials Research Bulletin,
47(11), 3308-3316.
Nabeshi, H., Yoshikawa, T.,
Arimori, A., Yoshida, T., Tochigi,
S.,Hirai,T.,Akase,T., Nagano,
K.,Abe,Y., Kamada, H.,
Tsunoda, S., Itoh, N., Yoshioka,
Y., and Tsutsumi, Y. 201 1 . Effect
of surface properties of silica
nanoparticles on their cytotoxicity
and cellular distribution in murine
macrophages. Nanoscale
Research Letters, 6(1), 93.
Pages
-------
Doc ID
107
108
109
110
111
Title
Surface structural
characteristics and
tunable electronic
properties of wet-
chemically prepared
Pd nanoparticles
Surface properties
and dye loading
behavior of Zn2SnO4
nanoparticles
hydrothermally
synthesized using
different mineralizers
Tuning the properties
ofZnO, hematite,
and Ag nanoparticles
by adjusting the
surface charge
Physicochemical
properties and
cellulartoxicity of
nanocrystal quantum
dots depend on their
surface modification
Aggregation and
surface properties of
iron oxide
nanoparticles:
influence of pH and
natural organic
material
Authors
Cook, S.,
Padmos, J., and
Zhang, P.
Annamalai, A.,
Eo,Y., lm,C.,
and Lee, M.
Zhang, J., Dong,
G.,Thurber, A.,
Hou,Y., Gu, M.,
Tenne, D.,
Hanna, C., and
Punnoose, A.
Hoshino, A.,
Fujioka, K.,Oku,
T.,Suga, M.,
Sasaki, Y., Ohta,
T., Yasuhara,
M., Suzuki, K.,
and Yamamoto,
K.
Baalousha, M.,
Manciulea, A.,
Cumberland, S.,
Kendall, K., and
Lead, J.R.
Year
2008
2011
2012
2004
2008
Journal Title, Vol.
No., and Page No.
(or Year)
The Journal of
Chemical Physics,
128(15), 154705
Materials
Characterization,
62(10), 1007-1015
Advanced Materials,
24(9), 1232-1237
Nano Letters, 4(11),
2163-2169
Environmental
Toxicology and
Chemistry, 27(9),
1875-1882
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Cook et al. (2008) used X-ray techniques to study the surface of palladium nanoparticles. They used X-ray absorption fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS) to characterize the
surface. The XAFS examination used total electron yield primarily to analyze the surface, although fluorescence yield was measured as well. XAFS gave information on the chemical composition and bonding
of molecules on the particle surface. TEM was also used to determine particle size and counts.
Annamalai et al. (201 1 ) investigated the hydrothermal synthesis of ZnSnO4 nanoparticles for use in dye-sensitized solar cell (DSSC) applications. By manipulating the mineralizer component during synthesis,
they were able to tune the isoelectric point (IEP) of the material in order to achieve a greater extent of N719 dye loading. The isoelectric points of the different ZnSnO4 nanoparticles were 5.1, 7.4, and 8.1 for
Na2CO2, KOH and tert-butyl amine mineralizers, respectively. As the IEP of the ZnSnO4 nanoparticles synthesized with butyl amine was highest, it showed the greatest adsorption of dye due to the carboxylic
groups of the dye preferentially binding to the numerous positive sites on the ZnSnO4 surface. Such work has applications for improving the properties of DSSCs.
Zhang et al. (201 2) investigated the effect of surface on zinc oxide, hematite (iron oxide), and silver nanoparticle by coating the materials with varying concentrations of poly (acryl) acid (PAA), thereby
modifying the zeta potential and making it increasingly negative. By doing so, they found that properties such as saturation magnetization, surface plasmon resonance and cytotoxicity could be modified by
changing the surface charge. The cytotoxicity of the nanomaterials was enhanced the more positively charged they were, as this would increase the electrostatic attraction between the particles and the
negatively-charged cells. The silver nanoparticle surface plasmon resonance diminished with decreasing surface charge. The coercive force of the hematite N Ps dropped from 70 to 9 Oe as surface charge
was decreased. Overall, the case was made that several properties can be tuned with the introduction of variance into the surface charge of the material.
Hoshino et al. (2004) investigated the effect of surface modification on the cytotoxicity of quantum dots. The group used CdSe quantum dots coated with various surface groups ranging from cartoxylic groups
stemming from an MU A coating, and aminated quantum dots with a positive charge. Only slight cytotoxicity was observed with quantum dots coated with carboxylic acid groups, whereas no toxicity was
observed with the aminated QDs, though this maybe a result of the amines interacting with the MTT reagents. Using a comet assay, it was determined that the QD-COOH samples caused very slight DMA
damage that was repaired after a 1 2-hour exposure, whereas all other quantum dot types induced no DMA damage at the concentrations studied. The coatings themselves were found to induce some amount
of cytotoxicity by themselves. The toxicity of quantum dots may not be wholly dependent on the chemical composition of the core material, and may vary with the chemistry of the functionalized surface.
Baalousha et al. (2008) investigated the influence of humic acid and pH on the aggregation state of iron oxide nanoparticles. They found that the addition of humic acid shifted the point of zero charge of the
iron nanoparticles to lower pH, resulting in extensive aggregation. It was also found that at higher pH (pH >4), aggregation of iron oxide nanoparticles occurred more readily. Aggregation was confirmed through
flow field-flow fractionation (FI-FFF) and DLS and TEM measurements which showed increasing aggregation at higher pH and at greater concentrations of humic acid. Aggregation by humic acid results in
more compact aggregates than those formed at higher pH in the absence of humic acid. The results have implications for nanomaterial fate and transport in the environment as suspended particles will likely
travel further in aqueous media. Those nanoparticles that settle out in the water column will more likely impact benthic organisms.
Complete Citation
Cook, S., Padmos, J., and
Zhang, P. 2008. Surface
structural characteristics and
tunable electronic properties of
wet-chemically prepared Pd
nanoparticles. The Journal of
Chemical Physics, 128(15),
154705.
Annamalai, A., Eo,Y.,lm,C., and
Lee, M. 201 1 . Surface properties
and dye loading behavior of
Zn2SnO4 nanoparticles
hydrothermally synthesized using
different mineralizers. Materials
Characterization, 62(10), 1007-
1015.
Zhang, J., Dong, G., Thurber, A.,
Hou.Y., Gu, M., Tenne, D.,
Hanna, C., and Punnoose, A.
201 2. Tuning the properties of
ZnO, hematite, and Ag
nanoparticles by adjusting the
surface charge. Advanced
Materials, 24(9), 1232-1237.
Hoshino, A., Fujioka, K., Oku, T.,
Suga, M., Sasaki, Y., Ohta, T.,
Yasuhara, M., Suzuki, K., and
Yamamoto, K. 2004.
Physicochemical properties and
cellular toxicity of nanocrystal
quantum dots depend on their
surface modification. Nano
Letters, 4(11), 2163-2169.
Baalousha, M., Manciulea, A.,
Cumberland, S., Kendall, K., and
Lead, J.R. 2008. Aggregation and
surface properties of iron oxide
nanoparticles: influence of pH and
natural organic material.
Environmental Toxicology and
Chemistry, 27(9), 1875-1882.
Page 9
-------
Doc ID
112
115
116
117
119
Title
Methods of detection
and identification of
manufactured
nanoparticles
Characterization of
the effluent from a
nanosilver producing
washing machine
Nanoparticle silver
released into water
from commercially
available stock
fabrics
The release of
nanosilver from
consumer products
used in the home
Quantification of
fullerene aggregate
n C60 in wastewater
by high-performance
liquid
chromatography with
UV-vis
spectroscopic and
mass spectrometric
detection
Authors
Gendrickson,
O.D.,
Safenkova, I.V.,
Zherdev, A.V.,
Dzantiev, B.B.,
and Popov, V.O.
Farkas, J.,
Peter, H.,
Christian, P.,
Gallego Urrea,
J.A., Hassellov,
M., Tuoriniemi,
J., Gustafsson,
S., Olsson, E.,
Hylland, K., and
Thomas, K.V.
Benn,T.M. and
Westerhoff, P.
Benn, T.,
Cavanagh, B.,
Hristovski, K.,
Posner, J.D.,
and Westerhoff,
P.
Wang, C.,
Shang, C., and
Westerhoff, P.
Year
2011
2011
2006
2010
2010
Journal Title, Vol.
No., and Page No.
(or Year)
Biophysics, 56(6), 965
994
Environmental
International, 37(6),
1057-1062
Environmental
Science and
Technology, 42(11),
4133-4139
Journal of
Environmental Quality,
39(6), 1875-1882
Chemosphere, 80(3),
334-339
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Hendrickson et al., 201 1 reviewed methods for detection and identification of biologically active nanoparticles. Particles of interest included fullerenes, carbon nanotubes, and nanoparticles of various metals
including: gold, silver, alumina, zinc, cerium, titanium, and silicon. In order to assess risks posed by engineered nanoparticles (ENPs), measurement of the following characteristics must be known: particle size;
size distribution; shape; crystallinity; presence of agglomeration/aggregation; characteristics of surface properties surface area, porosity, charge, reactive ability; presence of defects; solubility; and thermal
and UV stability. After a discussion of effects of ENPs, the authors discuss methods of detection and identification. Items to consider in method selection include: detection limit, ability to quantitate particles,
preservation of original state, correctness in measuring dimensional parameters, ability to distinguish EN Ps from natural nanoparticles, availability of standard protocols, suitability for homogenous preparations,
and ability to identify composition. Microscopy is good at detecting particle size but loses sensitivity and requires difficult sample preparation. Near scale optical microscopy can detect particles to 50 nm. X-ray
microscopy can measure particle size and composition and can provide resolution to 30 nm. Confocal laser scanning microscopy determines the distribution of fluorescing nanoparticles. It has a larger depth of
field than most microscopy and can be used to measure particles throughout a volume. Transmission electron microscopy (TEM) provides sub-nanometer resolution. TEM passes through samples that are very
thin and can be enhanced by energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS). Scanning electron microscopy makes use of the scattering of electrons from the surface.
Microscopy requires attention to sample preparation to minimize aggregation and large particle size differences arising from the support structure. TEM has the advantage of being well established and being
able to measure the entire volume of the sample. Its drawbacks include difficult sample preparation, expensive equipment, and the fact that the structure of the particles depends of the orientation on the
matrix. TEM with EELS can spatially determine composition of particles. Atomic force microscopy (AFM) scans the surface of particles at a few angstroms' depth. One AFM technology, scanning transmission
electron microscopy, can measure biological components without contrasting metals, unlike TEM. Environmental scanning electron microscopy can measure components in natural environments. AFM
techniques can measure samples in natural atmospheres, do not require a vacuum, and are cheaper than electron microscopy. But these methods cannot detect nanoparticles below the surface, have a small
field of view, and can be distorted. Some new AFM techniques such as electron force microscopy (EFM) can distinguish between organic and metallic particles by using a second scan that measures electrical
properties. Scanning tunneling microscopy (STM) can determine composition of metallic elements. Different methods exist to separate EN Ps for analysis. Gel permeation chromatography uses movement of a
liquid front through pores of a stationary phase. It has good separation of particles but suffers from artifacts from interaction with the stationary phase. Field flow fractionation (FFF) is used for samples of
complicated composition. Capillary electrophoresis can also separate ENPs. Dynamic light scattering (DLS) is used to determine hydraulic radius and agglomeration of ENPs. Transmission gratings can
enhance the signal-to-noise ratio of DLS. DLS does not work well with large particle size distributions. Small-angle x-ray scattering (SAXS) uses x-ray scattering to determine size, shape, orientation, structure,
composition, and distribution of particles. Small angle neutron scattering (SANS) can detect non uniformities in colloids. Spectrometry is not well suited for samples with multiple components but can be with
proper extraction techniques. Infrared spectroscopy can be used to quantify some EN Ps such as fullerenes. Fluorescent spectroscopy can be used for fluorescing nanoparticles. Laser-induced breakdown
detection can detect ENPs regardless of the physical state of the sample but must be calibrated independently for quantification. Raman spectroscopy has been used to detect ENPs in-vivo. Nuclear magnetic
resonance has been used to detect some types of ENPs such as silicon dioxide. X-ray spectroscopy enables quantification of composition of ENPs. Mass spectrometry can identify ENPs after separation. ICP-
MS has been used with electrospray ionization matrix assisted laser desorption/ionization to measure ENPs. Other methods include single particle mass spectrometry, and aerosol time of flight spectroscopy.
Particle counters measure EN Ps by measuring the change in conductivity of an electrolyte containing nanoparticles.
Farkas et al. (201 1 ) examined the effluent from a "nanowashing" laundry machine that utilizes silver nanoparticles for its anti-bacterial properties. An average concentration of 1 1 ppb silver was found in the
effluent of the washing machine. The presence of silver nanoparticles were confirmed using single particle ICP-MS, nanotracking analysis, transmission electron microscopy, and ultrafiltration techniques. The
average size of the silver nanoparticles were found to be approximately 10 nm. The effluent from the washing machine was found to significantly reduce the viability of a bacterial community when compared
to the control. The results of this study show that washing machines such as this can be a major source of release of engineered nanoparticles into the environment.
Benn and Westertioff (2006) investigated the release of silver from sock fabrics. Five of the six sock samples were found to contain silver via an acid digestion analysis by ICP-OES. Three of the six sock
samples were found to contain nanoparticulate silver. The nanoparticulate silver was confirmed via SEM imaging; particle sizes ranged from 100 to 500 nm. Physical separation by both filtration and ion
selective electrode analysis suggest that both dissolved and nanoparticulate silver leach from the sock material. The sorption of silver to biomass suggests that wastewater treatment facilities have the potential
to treat high quantities of silver that may be released into the environment.
Benn et al. (201 0) investigated the release of silver nanomaterials from a wide range of products such as textiles, toothpastes, and detergents. Silver was found to be released in concentrations up to 45 |jg
Ag/g product. The presence of silver nanoparticles was confirmed by SEM and EDX analysis in addition to acid digestion analysis by ICP-OES. Toxicity characterization was carried out using the toxicity
characterization leaching procedure (USE PA, 1992). The likelihood of silver binding to biosolids in waste treatment plants was also investigated. The possibility of silver leaching from commercial products and
entering the environment is discussed as apparent and inevitable, with implications for environmental as well as human health.
Wang et al. (2010) compare liquid-liquid extraction (LLE) and solid phase extraction (SPE) for determination of fullerenes. They also compare UV-visible spectrometry to mass spectrometry for quantification of
the nanoparticles. LLE was applicable in several wastewater matrices, while SPE required filtration in more concentrated wastewaters. SPE also had poorer recoveries and smaller detection ranges. UV-visible
spectrometry and mass spectrometry performed similarly. Mass spectrometry had a smaller detection range but provided specificity from the mass/charge ratio.
Complete Citation
Gendrickson, O.D., Safenkova,
I.V., Zherdev, A.V., Dzantiev,
B.B., and Popov, V.O. 2011.
Methods of detection and
identification of manufactured
nanoparticles. Biophysics, 56(6),
965-994.
Farkas, J., Peter, H., Christian,
P., Gallego Urrea, J.A.,
Hassellov, M., Tuoriniemi, J.,
Gustafsson, S., Olsson, E.,
Hylland, K., and Thomas, K.V.
201 1 . Characterization of the
effluent from a nanosilver
producing washing machine.
Environmental International,
37(6), 1057-1062.
Benn, T.M. and Westertioff, P.
2006. Nanoparticle silver released
into water from commercially
available stock fabrics.
Environmental Science and
Technology, 42(1 1 ), 41 33-41 39.
Benn, T., Cavanagh, B.,
Hristovski, K., Posner, J.D., and
Westerhoff, P. 2010. The release
of nanosilver from consumer
products used in the home.
Journal of Environmental Quality,
39(6), 1875-1882.
Wang, C., Shang, C., and
Westerhoff, P. 2010.
Quantification of fullerene
aggregate nC60 in wastewater by
high-performance liquid
chromatography with UV-vis
spectroscopic and mass
spectrometric detection.
Chemosphere, 80(3), 334-339.
Page 10
-------
Doc ID
121
122
123
124
125
126
128
129
Title
Beyond nC60:
strategies for
identification of
transformation
products offullerene
oxidation in aquatic
and biological
samples
Synthesis and optical
properties of
naturally occurring
fluorescent mineral,
ferroan sphalerite,
inspired (Fe,Zn)S
nanoparticles.
A sorption kinetics
model for arsenic
adsorption to
magnetite
nanoparticles
Influence of nano-
material on the
expansive and
shrinkage of soil
behavior
Soil organic matter in
nano-scale
structures of a
cultivated Black
Chernozem
Lead coprecipitation
with iron
oxyhydroxide nano-
particles
The nano-
mechanical
morphology of shale
Interactions of humic
acid with nanosized
inorganic oxides
Authors
Pycke, B.F.,
Herckes, P.,
Westerhoff, P.,
and Halden,
R.U.
Boyle, T.J., Pratt
III, H.D.,
Hemadez-
Sanchez, B.A.,
Lambert, T.N.,
Headley,T.J.
Shipley, H.J.,
Yean, S., Kan,
AT., and
Tomson, M.B.
Taha, M.R. and
Taha, O.M.E
Monreal, C.M.,
Sultan, Y., and
Schnitzer, M.
Lu,P.,Nuhfer,
NT., Kelly, S.,
Li, Q., Konishi,
H., Elswick, E.,
andZhu, C.
Bobko, C. and
Ulm,F.J.
Yang, K., Lin, D.,
and Xing, B.
Year
2012
2007
2010
2012
2010
2011
2008
2009
No., and Page No.
(or Year)
Analytical and
Bioanalytical
Chemistry, 404(9),
2583-2585
Journal of Materials
Science, 42(8), 2792-
2795
Environmental
Science Pollution and
Research, 17(5), 1053
1062
Journal of
Nanoparticle
Research, 14, 1190
Geoderma, 159(1-2),
237-242
Geochemica et
Cosmochimica Acta,
75(1 6), 4547-4561
Mechanics of
Materials, 40(4-5),
318-337
Langmuir, 25(6), 3571
3576
Document
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Pycke et al. (2012) reviewed the occurrence of carbonaceous nano-materials in the environment and possible methods of detection and quantitation in environmental and biological samples. The most obvious
impediment to fullerene and CNT detection in the environment is the regular occurrence of naturally-occurring carbon-containing nanomaterials in the environment. Possible strategies for detection and
quantification involve either functionalization ordefunctionalization of these materials in order to manipulate their solubility and subsequent separation for detection. However, the ready transformation of these
materials once released into the environment may compromise accurate quantification in the environment.
Boyle et al. (2007) investigated alternatives to lead and cadmium chalcogenide semiconducting nanomaterials by synthesizing a naturally-occurring fluorescent material in ferroan sulfide. As lead and cadmium
are toxic materials, the goal was to find a relatively non-toxic material that still exhibited potential for narrow emission wavelengths based on quantum confinement principles. Using various solvothermal and
solution synthesis processes, [(Fe,Zn)S] was synthesized in particles of size 3 nm or less with an emission wavelength of 400 nm when excited by UV. It maybe possible to manipulate the bandgap of this
material with non-toxic doping techniques. This nanomaterial could serve as a non-toxic alternative to the current lead- and cadmium-based semi-conducting nanoparticles.
Shipley et al. (201 0) developed a model to study arsenic sorption onto iron oxide nanoparticles in the presence of various counter-ions in order to accurately predict the amount of arsenic removal in variable
water chemistry. Silicate, bicarbonate, fulvic acid, sulfate and ferrous/ferric ions were all introduced to study the competing sorption of arsenic onto the magnetite particles. As expected, the addition of negative
counter-ions such as bicartonate and phosphate impeded arsenic removal with increasing concentration. The addition of feme ions, on the other hand, created nucleation sites that allowed for greater removal
of arsenic from solution. The model created had very good agreement with experimental results, though it consistently over-predicted the amount of arsenic removal from the system.
Taha et al. (201 2) performed expansion and shrinkage tests on residual soils with different ratios of bentonite (0, 5, 1 0, 20% bentonite) when different nano-materials (i.e. nano-clay, nano-alumina, nano-
copper) were added. It was found that the addition of nano-clay does not necessarily improve these properties of the soil. However, it was found that the addition of nano-alumina and nano-copper can improve
soil properties such as compaction, shrinkage strain, and expansive strain, and can reduce the crack intensity factor (C IF). There is an upper limit to the improvement, however, as the addition of nanomaterials
may lead to significant aggregation which can increase pore size, leading to increased water content and greater shrinkage and swelling strain.
Monreal et al. (2010) studied a soil organic matter (SOM) collected from a cultivated Black Chernozem of Canada, specifically using TEM, pyrolysis field ionization mass spectrometry, and radiocarbon dating
to characterize both the nano-sized structure and the clay fraction of the SOM. Using TEM, they found that SOM in the nanosized fraction occurred both in organ o-m in eral complexes and within humic
substances that formed nano-scale carbonaceous networks. It was found that the humic substances dictated the arrangement of minerals within the SOM and were responsible for the physical and physio-
chemical stabilization of the SOM. Using Py-FIMS, it was found that the SOM found in the nano-structured fraction possessed greater thermal stabilization than those found in the clay fraction. Lastly, the nano-
sized fraction was primarily comprised of carbohydrates, peptides, and N-heterocyclics whereas the clay fraction was rich in fatty acids, phenols, and lipids.
Lu et al. (2001 ) investigated the removal of lead from solution by either coprecipitation with Fe2+ or by adsorption onto ferrihydrite particles. High resolution transmission and analytical electron microscopy was
utilized to analyze lead sorption to the iron materials. It was found that coprecipitation was a more efficient technique for removing lead from solution when compared to adsorption experiments. The
subsequent removal of lead from these iron complexes with addition of EDTA also led to differences in sorption behavior as removal from adsorbed iron ferrihydrite followed a parabolic relationship, whereas
the same behavior was linear in coprecipitation experiments. It is hypothesized that lead first adsorbs onto the initial nucleus of forming iron oxide particles in coprecipitation experiments and is subsequently
incorporated into the particle with further growth, lending itself to greater sequestration of lead in the iron oxyhydroxide complex.
Bobko et al. (2008) studied the nanomorphology of shale by validating a nanoindentation technique to investigate the properties of the clay particles that comprise shale materials. The results from this study led
to an improved model for the nano-mechanical behavior of shale, with a spherical particle as the elementary building block. These spherical building blocks exhibit a non-granular behavior and are responsible
for the packing density and subsequent compositive behavior of porous clay. The results of this study will aid in the development of more precise models of elasticity and strength for micromechanical
substances.
Yang et al. (2009) investigated the adsorption behavior of humic acid on various metal oxide nanoparticles (TiO2, SiO2, AI2O3, and ZnO) using zeta potentiometry, Fourier transform infrared spectroscopy, and
elemental analysis by a Perkin Elmer 2400 CHN Elemental Analyzer. As expected, the surface of these particles there was a strong affinity for humic acid on the surface of these particles through either
electrostatic attraction or ligand exchange (except for SiO2, which has a negative zeta potential across most pH, lending itself to electrostatic repulsion). Humic acid imparts a strong negative charge to the
nanoparticles, which could possibly stabilize them in environmental systems and allow for greater transport through the environment. As humic acid has a high potential to bind hydrophobic organic compounds
(HOCs), these nanoparticles could potentially serve as vectors to transport toxic materials through the environment.
Complete Citation
Pycke, B.F., Herckes, P.,
Westerhoff, P., and Halden, R.U.
201 2. Beyond nC60 : strategies
for identification of transformation
products offullerene oxidation in
aquatic and biological samples.
Analytical and Bioanalytical
Chemistry, 404(9), 2583-2585.
Boyle, T.J., Pratt III, H.D.,
Hemadez-Sanchez, B.A.,
Lambert, T.N., Headley, T.J.
2007. Synthesis and optical
properties of naturally occurring
fluorescent mineral, ferroan
sphalerite, inspired (Fe,Zn)S
nanoparticles.. Journal of
Materials Science, 42(8), 2792-
2795.
Shipley, H.J., Yean, S., Kan, AT.,
and Tomson, M.B. 2010. A
sorption kinetics model for arsenic
adsorption to magnetite
nanoparticles. Environmental
Science Pollution and Research,
17(5), 1053-1062.
Taha, M.R. and Taha, O.M.E
2012. Influence of nano-material
on the expansive and shrinkage
of soil behavior. Journal of
Nanoparticle Research, 14, 1190.
Monreal, C.M., Sultan, Y., and
Schnitzer, M. 2010. Soil organic
matter in nano-scale structures of
a cultivated Black Chernozem.
Geoderma, 159(1-2), 237-242.
Lu,P.,Nuhfer, NT., Kelly, S., Li,
Q., Konishi, H., Elswick, E., and
Zhu, C. 2011. Lead
coprecipitation with iron
oxyhydroxide nano-particles.
Geochemica et Cosmochimica
Acta, 75(1 6), 4547-4561.
Bobko, C. and Ulm, F.J. 2008.
The nano-mechanical morphology
of shale. Mechanics of Materials,
40(4-5), 318-337.
Yang, K., Lin, D., and Xing, B.
2009. Interactions of humic acid
with nanosized inorganic oxides.
Langmuir, 25(6), 3571-3576.
Page 11
-------
Doc ID
130
131
132
135
136
137
Title
Adsorption of
cadmium(ll) on
humic acid coated
titanium dioxide
Transport behavior
of humic acid-
modified nano-
hydroxyapatite in
saturated packed
column: Effects of
Cu, ionic strength,
and ionic
composition.
Adsorption and
desorption of humic
andfulvic acids on
SiO2 particles at
nano- and micro-
scales.
Transformations of
nanomaterials in the
environment
Natural nanoparticles
structure, properties
and reactivity from x-
ray studies.
The current state of
engineered
nanomaterials in
consumer goods and
waste streams: the
need to develop
nanoproperty-
quantifiable sensors
for monitoring
engineered
nanomaterials
Authors
Chen, Q.,Yin,
D.,Zhu, S., and
Hu,X.
Wang, D.,Chu,
L, Paradelo, M.,
Peijnenburg, W.,
Wang, Y., and
Zhou, D.
Liang, L., Luo,
L., and Zhang,
S.
Lowry, G.V.,
Gregory, K.B.,
Apte, S.C., and
Lead, J.R.
Waychunas,
G.A., Gilbert, B.,
Banfield, J.F.,
Zhang, H., Jun,
Y.S.,andKim,
C.S.
Wise, K. and
Brasuel, M.
Year
2012
2011
2011
2012
2009
2011
Journal Title, Vol.
No., and Page No.
(or Year)
Journal of Colloid and
Interface Science,
367(1), 241-248.
Journal of Colloid and
Interface Science,
360(2), 308-407
Colloids and Surfaces
A: Physicochemical
and Engineering
Aspects, 384(1-3),
126-130
Environmental
Science and
Technology, 46(13),
6893-6899
Powder Diffraction,
24(2), 89-93
Nanotechnology,
Science and
Applications, 4, 73-86
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Chen et al. (201 2) modeled the sorption of Cd(ll) onto nano-TiO2 with and without a humic acid coating in order to demonstrate the ability of the engineered nanoparticle to strongly sorb a toxic metal. As
expected, the nano-TiO2 coated with humic acid sorbed more cadmium in all cases when compared to bareTiO2. The sorption of Cd(ll) also increased with increasing pH. Sorption also increased slightly with
increasing salinity to a point, but then decreased due to electrostatic repulsion. These results show that the introduction of nanoparticles into the environment may alter the bioavailability of toxic metals as a
result of their association with humic substances.
Wang et al. (2011) investigated the efficacy of nano-hydroxyapatite (n-HAP)to remediate contaminated soils when coated with humic acid. Using column experiments, the transport of n-HAP was investigated
under various conditions where the ionic strength, ion composition and contaminant (Cu) concentration were variable. As predicted by DLVO theory, deposition of the nanoparticles increased at higher ionic
strength. In addition, divalent cations (viz., Ca2+) were more effective at the deposition of these nanoparticles due to cation bridging effects. Cupric ions (Cu2+) were even more effective due to their ability to
form complexes with the surface of n-HAP. The transport of these particles varied considerably depending on the ionic strength, ion composition, and contaminant concentration. Results such as these hold
significance for the efficacy of nano-hydroxyapatite in remediation of contaminated soils.
Liang, Luo, and Zhang (201 1 ) studied the adsorption/desorption behavior of fulvic and humic acid on silica nanoparticles of different sizes (20, 1 00, SOOnm) at different pH and electrolyte concentrations. Due to
the higher specific surface area, the 20nm SiO2 particles adsorbed humic and fulvic acid to a greater extent than the larger particles. The sorption of fulvic and humic acid decreased with increasing pH, most
likely due to electrostatic repulsion between the silica surface and the negatively-charged humic molecules. A lesser extent of adsorption occurred at higher ionic strengths, though this effect was less
pronounced with fulvic acid than it was with humic acid. These results will have obvious implications for transport of the particle through the environment.
Lowry et al. (201 2) summarize various transformations that may affect manufactured nano-materials upon release into the environment. These processes include chemical transformations, physical
transformation, and nanomaterial/macromolecule interactions. Among chemical transformations, dissolution, oxidation, and sulfidation are all important processes that may affect the toxicity and persistence of
nanomaterials in the environment. Physical processes such as aggregation (both homo- and heteroaggregation) may play a large role in the transport of these materials in the environment, as well as
influencing their reactivity as aggregated particles have a reduced surface area that is thereby less reactive. Interactions with macromolecules such as proteins and humic substances may influence the
aggregation state of nanomaterials as well as their reactivity. In short, once released into the environment, the nanomaterial will quickly transform from its "pristine" or manufactured state into a more complex
particle with possibly different properties from its original state. The authors state that research is needed on the chemical and physical properties of nanomaterials in their transformed states in the
environment.
Waychunas et al. (2009) studied synthetic analogues of naturally-occurring nanomaterials using X-ray techniques to gain an understanding of some of their physical and chemical properties in the environment.
Both ZnS and TiO2 nanoparticles exhibit a core-shell structure with a strained outer layer that is highly distorted. This strained layer can be manipulated and relaxed through the binding of ligands to the surface.
The distortions in TiO2 are so extensive that the crystal structure is almost amorphous, similar to that of silicate glass. The chemistry of iron oxyhydroxide appears to be size-dependent. Iron oxyhydroxide's
oriented aggregation may help contaminants caught up in the structure persist in the environment.
Wise and Brasuel (201 1 ) review the current medical applications and subsequent potential toxicity of common nanomaterials such as silver nanoparticles, carbon nanotubes, quantum dots, and gold
nanoparticles. They conclude that the same properties that make nanomaterials unique and beneficial could possibly be detrimental to human health. Current regulations for nanotechnology are minimal, and
many of these products are regarded as safe for use. Yet detection and characterization methods needed to assess the toxicity of these materials are lacking. The authors propose that new techniques are
necessary to fully understand the potential toxic effect of nanomaterials and properly regulate their use in the medical community.
Complete Citation
Chen, Q., Yin, D.,Zhu, S., and
Hu,X. 2012. Adsorption of
cadmium(ll) on humic acid coated
titanium dioxide. Journal of
Colloid and Interface Science,
367(1), 241-248.
Wang, D., Chu, L., Paradelo, M.,
Peijnenburg, W., Wang, Y., and
Zhou, D. 201 1 . Transport
behavior of humic acid-modified
nano-hydroxyapatite in saturated
packed column: Effects of Cu,
ionic strength, and ionic
composition.. Journal of Colloid
and Interface Science, 360(2),
308-407.
Liang, L., Luo, L., and Zhang, S.
201 1 . Adsorption and desorption
of humic and fulvic acids on SiO2
particles at nano- and micro-
scales.. Colloids and Surfaces A:
Physicochemical and Engineering
Aspects, 384(1-3), 126-130.
Lowry, G.V., Gregory, K.B., Apte,
S.C., and Lead, J.R. 2012.
Transformations of nanomaterials
in the environment. Environmental
Science and Technology, 46(13),
6893-6899.
Waychunas, G.A., Gilbert, B.,
Banfield, J.F., Zhang, H., Jun,
Y.S., and Kim, C.S. 2009. Natural
nanoparticles structure, properties
and reactivity from x-ray studies..
Powder Diffraction, 24(2), 89-93.
Wise, K. and Brasuel, M. 201 1 .
The current state of engineered
nanomaterials in consumer goods
and waste streams: the need to
develop nanoproperty-quantifiable
sensors for monitoring
engineered nanomaterials.
Nanotechnology, Science and
Applications, 4, 73-86.
Page 12
-------
Doc ID
201
202
203
204
205
207
208
Title
Challenges and
Opportunities of
Nanomaterials in
Drinking Water
Colloid transport of
plutonium in the far-
field of the Mayak
Production
Association, Russia
Competitive actinide
interactions in
colloidal humic acid-
mineral oxide
systems
Groundwater
nanoparticles in the
far-field at the
Nevada test side:
mechanism for
radionuclide
transport
Iron oxides as
geochemical
nanovectorsfor
metal transport in soil
river systems
Nanogeoscience:
from origins to
cutting edge
applications
Nanomaterials in the
environment:
behavior, fate,
bioavailability and
effects
Authors
Water Research
Foundation
Novikov, A.P.,
Kalmykov, S.N.,
Utsunomiya, S.,
Ewing, R.C.,
Horreard, F.,
Merkulov, A.,
Clark, S.B.,
Tkachev, V.V.,
and Myasoedov,
B.F.
Righetto, L,
Bidoglio, G.,
Azimonti, G.,
and Bellobono,
I.R.
Utsunomiya, S.,
Kersting, A.B.,
and Ewing, R.C.
Hassellov, M.
and von der
Kammer, F.
Hochella, M.F.
Klaine, S.J.,
Alvarez, P.J.,
Batley, G.E.,
Fernandes, T.F.,
Handy, R.D.,
Lyon, D.Y.,
Mahendra, S.,
Mclaughlin,
M.J., and Lead,
J.R.
Year
2011
2006
1991
2009
2008
2008
2008
Journal Title, Vol.
No., and Page No.
(or Year)
2011
Science, 314(5799),
638-641
Environmental
Science and
Technology, 25(11),
1913-1919
Environmental
Science and
Technology, 43(5),
1293-1298
Elements, 4(6), 401-
406
Elements, 4(6), 373-
379
Environmental
Toxicology and
Chemistry, 27(9),
1825-1891
Document
Type
Unreviewed
Water
Research
Foundation
document
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Tuccillo et al. (201 1 ) discuss the state of knowledge regarding nanomaterials in the environment and identify data gaps, with a particular focus on issues relevant to drinking water. The report includes
information on nanomaterials, human health effects, fate and transport in the environment, detection methods, the potential of drinking water treatment processes to remove nanomaterials, potential
applications of nanomaterials in drinking water treatment and water quality monitoring, and regulatory developments. The authors conclude by identifying the following data gaps: environmental occurrence data
for engineered nanomaterials; information on the effectiveness of drinking water treatment processes for removing both natural and engineered nanoparticles; research on analytical methods for
characterization and quantification of nanomaterials; research on the effects of water chemistry on the aggregation or disaggregation of different types of nanomaterials; research on the fate and transport of
nanomaterials; and research on human health effects.
Novikov et al. (2006) studied the migration of plutonium hydroxides and carbonates at the Far-Field of the Mayak Production Association, Russia. The study confirmed that the amorphous iron oxide colloids
were responsible for adsorbing and transporting plutonium long distances (4 kilometers in approximately 55 years) and noted that this was comparable to the rate seen at the Nevada Test Site. In addition, it
was observed that uranium under oxidizing conditions also adsorbed to the colloids. The authors conclude that site-specific investigations should be conducted for actinide colloids due to the differences in
physico-chemical conditions at potential nuclear waste repository sites.
Righetto et al. (1991) studied the adsorptive behavior of americium, thorium, neptunium, and plutonium in the presence of inorganic particles (y-alumina or amorphous silica) and humic acid colloids from a clay
formation rich in organics. The actinides' sorption selectivity was similar to that of other complex formations when reacting with hydrous mineral hydroxides. The actinides' adsorption when humic acid colloids
were added to the solution depended on the coordinating strengths of humic acid on the surface and in the solution. The pH of the water also played a role in adsorption of the actinides, with adsorption
improving in lower-pH waters. Righetto et al. conclude that the particle transport dynamics between actinides and humic acid be studied using packed beds and porous media.
Utsunomiya et al. (2008) studied colloidal nanoparticles and their ability to transport contaminants, specifically radionuclides, in groundwater. In the study, nanoparticles were sampled in the groundwater at the
far-field at the Nevada Test Site, using advanced electron microscopy techniques. The samples were found to contain colloidal nanoparticles associated with fission product elements, such as strontium and
cesium, and an actinide, uranium. The authors conclude that at this test site, the colloidal nanoparticles' ability to adsorb and transport fission-product elements and actinides must be considered in order to
accurately model the transport of these contaminants.
Hassellov and von der Kammer (2005) studied the effects natural nanoparticles have on soils contaminated with heavy metals. The authors measured natural nanoparticles and colloidal organic matter in soil
and river samples using a nanoparticle separation technique combined with elemental detection. In this study, it was determined through sampling that iron oxide colloidal nanoparticles, ubiquitous in nature,
efficiently transport heavy metals such as lead from soils through rivers to estuaries. In the estuary, the particles accumulate via flocculation and settle.
Hochella (2008) discusses natural nanomaterials and their presence in the environment. The article discusses the properties of natural nanomaterials and how they can differ from their bulk material
counterparts (or may not exist as a larger-sized material), as well as their global occurrence and distribution in the atmosphere, oceans, ground and surface water, soils ,and most living organisms. The author
also discusses the importance of nanomaterials: elemental distribution, biological-abiotic Earth interaction, heterogeneous catalysis, reaction pathways, and mineral growth, transformation, and weathering all
take place at the nano-scale. He also notes that what happens at this scale has no equivalent on smaller and larger scales. The author concludes that understanding natural nanoparticles will provide another
perspective for understanding Earth's chemical and physical properties.
Klaine et al. (2008) discuss the key aspects pertaining to nanomaterials in the environment, including where naturally-occurring nanoparticles exist (e.g., soil, water, air) and the classes of manufactured
nanoparticles, their commercial applications, and their potential to be released into the environment. The article discusses what is known of the fate, behavior, disposition, and toxicity of nanoparticles in the
environment through existing research, with a focus on manufactured nanoparticles. The authors state that immediate research is needed to develop quantitative measures of both exposure to and effects of
nanoparticles in the environment, so that the risks they pose to the environment and human health can be better understood and so that regulators may have the tools to adequately manage nanoparticles in
the environment. The authors note challenges in research regarding the variability of nanoparticles produced from different manufacturers, as well as the need for standard testing protocols, including
standardization of methods for creating test media and particle and particle suspension characterization requirements so that researchers can adequately interpret the results of their research. Klaine et al. also
discuss the need for research in freshwater, marine, and soil ecosystems. They state that the focus should be testing with organisms in sediment and soils since this will most likely be where nanoparticles are
deposited. They also point out that further research is needed regarding the interaction between nanoparticles and natural organic matter (NOM) in aquatic environments since NOM has been shown to stabilize
nanoparticles in the water column.
Complete Citation
Water Research Foundation
2011. Challenges and
Opportunities of Nanomaterials in
Drinking Water. 2011.
Novikov, A.P., Kalmykov, S.N.,
Utsunomiya, S., Ewing, R.C.,
Horreard, F., Merkulov, A., Clark,
S. B., Tkachev, V.V., and
Myasoedov, B.F. 2006. Colloid
transport of plutonium in the far-
field of the Mayak Production
Association, Russia. Science,
314(5799), 638-641.
Righetto, L., Bidoglio, G.,
Azimonti, G., and Bellobono, I.R.
1991. Competitive actinide
interactions in colloidal humic acid-
mineral oxide systems.
Environmental Science and
Technology, 25(11), 1913-1919.
Utsunomiya, S., Kersting, A.B.,
and Ewing, R.C. 2009.
Groundwater nanoparticles in the
far-field at the Nevada test side:
mechanism for radionuclide
transport. Environmental Science
and Technology, 43(5), 1293-
1298.
Hassellov, M. and von der
Kammer, F. 2008. Iron oxides as
geochemical nanovectors for
metal transport in soil river
systems. Elements, 4(6), 401-
406.
Hochella, M.F. 2008.
Nanogeoscience: from origins to
cutting edge applications.
Elements, 4(6), 373-379.
Klaine, S.J., Alvarez, P.J., Batley,
G.E., Fernandes, T.F., Handy,
R.D., Lyon, D.Y., Mahendra, S.,
McLaughlin, M.J., and Lead, J.R.
2008. Nanomaterials in the
environment: behavior, fate,
bioavailability and effects.
Environmental Toxicology and
Chemistry, 27(9), 1825-1891.
Page 13
-------
Doc ID
209
210
211
212
300
302
303
304
Title
Nanominerals,
mineral
nanoparticles, and
earth systems
Nanoparticles in the
atmosphere
Nanoparticles in the
soil environment
Structure, chemistry,
and properties of
mineral nanoparticles
Marine
sedimentation of
nano-quartz forming
flint in North Sea
Danian chalk
Biocompatibility
assessment of Si-
based nano- and
micro-particles
Bioavailable iron in
the Southern Ocean:
the significance of
the iceberg conveyor
belt
Naturally occurring
nanoparticles from
English ivy: an
alternative to metal-
based nanoparticles
forUV protection
Authors
Hochella, M.F.,
Lower, S.K.,
Maurice, P.A.,
Penn, L.R.,
Sahai, N.,
Sparks, D.L.,
and Twining,
B.S.
Buseck, P.R.
andAdachi, K.
Theng, B.K.G.
and Yuan, G.
Waychunas,
G.A. and Zhang,
H.
Lindgreen, H.
and Jakobsen,
F.
Jaganathan, H.
andGodin, B.
Raiswell, R.,
Benning, L.G.,
Tranter, M., and
Tulaczyk, S.
Xia, L,
Lenaghan, S.,
Zhang, M.,
Zhang, Z, and Li,
Q.
Year
2008
2008
2008
2008
2012
2012
2008
2010
Journal Title, Vol.
No., and Page No.
(or Year)
Science, 319(5870),
1631-1635
Elements, 4(6), 389-
394
Elements, 4(6), 395-
399
Elements, 4(6), 381-
387
Marine and Petroleum
Geology, 38(1), 73-82
Advanced Drug
Delivery Reviews,
64(15), 1800-1819
Geomedical
Transactions, 9(7)
Journal of
Nanobiotechnology,
8(12)
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Hochella et al. (2008) discuss the origin and occurrence of nanominerals and mineral nanoparticles, and their distribution in the atmosphere, oceans, groundwater and surface waters, soils, and in and/or on
most living organisms. The article also discusses the distinction between nanominerals and mineral nanoparticles (i.e., nanominerals only exist in the nano size range and mineral nanoparticles are minerals that
can also exist in larger sizes), and their characteristics, including changes that occur with mineral size, their reactivity and stability, and their influence on Earth's chemistry. The authors note that nanophase
minerals can influence the movement of heavy metals, and they cite an example of a newly discovered nanocrystalline vemadite-like mineral (a manganese oxyhydroxide), found at the Clark Fork River
Superfund Complex in western Montana, that has transported lead, arsenic, copper, and zinc over hundreds of kilometers within the Clark Fork River drainage basin. The authors acknowledge that more
research is necessary to understand nanominerals and mineral nanoparticles and their effects in the environment.
Buseck and Adachi (2008) discuss human exposure to nanoparticles in air, the nature of nanoparticles in the atmosphere (e.g., concentration and composition), and the mechanisms that introduce these
particles into the atmosphere, including vehicles, industries, vegetative and sea spray, and volcanoes. The authors state that since nanoparticles react rapidly in the atmosphere, they grow into larger particles
that can affect the earth's radiative balance and therefore affect climate. The authors note that due to recent improvements in analytical in stm mentation, both natural and anthropogenic nanoparticles can be
detected in the atmosphere. The authors suggest that it is necessary to conduct more research to evaluate the long-term effects of nanoparticles on the atmosphere and living organisms.
Theng and Yuan (2008) discuss naturally-occurring inorganic and organic nanoparticles that can be found in soils. The article focuses on clay minerals, metal oxides and hydroxides, humic substances, and
substances (e.g., allophane and imogolite) that are abundant in volcanic soils. The authors note that very few nanoparticles exist discreetly in soils (e.g., organic colloids are associated with their inorganic
counterparts), which makes it difficult to obtain adequate yields and conduct analyses. In addition, the sorptive properties of a discrete nanoparticle can be greatly altered if an interaction with another particle
occurs. While sophisticated methods are used to characterize soil nanoparticles, nanoparticles are also very reactive towards external solute molecules. To avoid these issues, laboratory-synthesized materials
have been used in research, but the authors note that even then the results are not easy to interpret. Theng and Yuan conclude that due to the intrinsic complexity of soil physicochemical processes, a
multidisciplinary approach and advanced instrumental techniques are necessary to improve our understanding of sorption phenomena and nanoparticle interactions. The authors acknowledge that soil is also a
repository for engineered nanoparticles and that there are concerns regarding their potential adverse effects on animal and human health, but state that detailed treatment of that topic was beyond the scope of
the paper.
Waychunas and Zhang (2008) provide a general discussion of the unique characteristics and properties of nanomaterials compared to their bulk counterparts. The authors emphasize that the size of the
particle directly affects chemical reactivity, molecular and electronic structure, and mechanical behavior and that major differences in properties can result from these variations. Surface properties of
nanoparticles can locally disrupt the organization of water molecules, which may create unusual aggregation, sorption, or other chemical effects. The article also specifically discusses some mineral-based
naturally-occurring nanoparticles (e.g., silica and silicates), but acknowledges that little research has been conducted on mineral-based nanoparticles. They conclude that more insight into naturally-occurring
nanoparticles can serve to help predict how manufactured nanomaterials will behave in the environment.
Lindgreen and Jakobsen (201 2) proposed a new theory for the formation of flint in the North Sea Danian Ekofisk chalk formation. The proposed theory involves the sedimentation of nano-sized a-quartz
particles that were crystallized from the dissolution of radiolarians. This theory was investigated by applying XRD, AFM, SEM and thermal analysis (DTA-EGA)to sedimentary features in the silicon-containing
chalk. The flint in the chalk was composed of 1 00-300 nm silica spheres, which had perfect 3-dimensional order but slightly larger cell dimension than standard a-quartz.
Jaganthan and Godin (2012) reviewed the toxicity of SiO2 nanoparticles and the methods used to test the toxicity of these materials. Though silica is generally not considered toxic, it has been shown that
crystalline SiO is more toxic than amorphous silica and elemental Si. It is apparent, however, that there is a lack of standardization among toxicity tests, making comparison between laboratories a difficult
challenge.
Raiswell et al. (2008) present the results of a study of iceberg samples. They demonstrate that bioavailable Fe is tied into ferrihydrite and goethite nanoclusters found in the glacial landmass. Due to their small
size and high reactivity, these iron nanoparticles are more soluble than crystalline iron oxyhydroxides. These nanoparticles are also transported from coastal regions to the ocean. Upon dissolution the iron
becomes bioavailable, leading to an increase in phytoplankton production. It is hypothesized that identifying icebergs as a significant source of bioavailable Fe may help explain and predict how oceans respond
to climate change.
Xia et al. (2010) synthesized organic nanoparticles from English Ivy and investigated them as an alternative to TiO2 and ZnO, which have previously shown to be cytotoxic. The UV absorption of the naturally
synthesized particles was better than TiO2 nanoparticles at the same concentration. Examination of toxicity to HeLa cell lines via flow cytometry demonstrated that the ivy nanoparticles were much less toxic
than TiO2 nanoparticles at the same concentration. The biodegradability of the ivy nanoparticles also help assuage concerns of environmental contamination. A mathematical model was applied to estimate
the penetration of the ivy nanoparticles into the stratum comeum (SC) layer of the skin. It was determined that ivy particles with a diameter of 65.3 nm will not reach the bottom of SC layer in normal conditions
for short periods of time after application. This investigation shows the possibility of utilizing naturally-derived nanoparticles as a safer alternative to the photoreactive engineered nanomaterials that are currently
used in cosmetics. The naturally-derived particles warrant further investigation.
Complete Citation
Hochella, M.F., Lower, S.K.,
Maurice, P.A., Penn, L.R., Sahai,
N., Sparks, D.L., andTwining,
B.S. 2008. Nanominerals, mineral
nanoparticles, and earth systems.
Science, 319(5870), 1631-1635.
Buseck, P.R. and Adachi, K.
2008. Nanoparticles in the
atmosphere. Elements, 4(6), 389-
394.
Theng, B.K.G. and Yuan, G.
2008. Nanoparticles in the soil
environment. Elements, 4(6), 395-
399.
Waychunas, G.A. and Zhang, H .
2008. Structure, chemistry, and
properties of mineral
nanoparticles. Elements, 4(6),
381-387.
Lindgreen, H. and Jakobsen, F.
2012. Marine sedimentation of
nano-quartz forming flint in North
Sea Danian chalk. Marine and
Petroleum Geology, 38(1), 73-82.
Jaganathan, H. and Godin, B.
2012. Biocompatibility
assessment of Si-based nano-
and micro-particles. Advanced
Drug Delivery Reviews, 64(15),
1800-1819.
Raiswell, R., Benning, L.G.,
Tranter, M., and Tulaczyk, S.
2008. Bioavailable iron in the
Southern Ocean: the significance
of the iceberg conveyor belt.
Geomedical Transactions, 9(7).
Xia, L., Lenaghan, S., Zhang, M.,
Zhang, Z, and Li, Q. 2010.
Naturally occurring nanoparticles
from English ivy: an alternative to
metal-based nanoparticles for UV
protection. Journal of
Nanobiotechnology, 8(12).
Page 14
-------
Doc ID
305
306
307
308
309
310
Title
Naturally occurring
iron oxide
nanoparticles:
morphology, surface
chemistry and
environmental
stability
Interaction between
manufactured gold
nanoparticles and
naturally occurring
organic
macromolecules
Extraction and
characterization of
natural soil
nanoparticles from
Chinese soils
Humic acid-induced
silver nanoparticle
formation under
environmentally
relevant conditions
Natural and
anthropogenic
environmental
nanoparticulates:
Their micros! ructural
characterization and
respiratory health
implications
Biodegradability of
organic nanoparticles
in the aqueous
environment
Authors
Quo, H. and
Barnard, A.
Diegoli, S.,
Maniciulea, A.,
Begum, S.,
Jones, I., Lead,
J., and Preece,
J.
Li, W.,He, Y.,
Wu, J., andXu,
J.
Akaighe, N.,
MacCuspie, R.,
Navarro, D.,
Aga, D.,
Banerjee, S.,
Sohn,M.,and
Sharma, V.
Murr, L. and
Garza, K.
Kummerer, K.,
Menz, J.,
Schubert, T.,
andThielemans,
W.
Year
2013
2008
2012
2011
2009
2011
Journal Title, Vol.
No., and Page No.
(or Year)
Journal of Material
Chemistry A, 1(1), 27-
42
Science of the Total
Environment, 402(1),
51-61
European Journal of
Soil Science, 63(5),
754-761
Environmental
Science and
Technology, 45(9),
3895-3901
Atmospheric
Environment, 43(7),
2683-2692
Chemosphere,
82(10), 1387-1392
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Quo and Barnard (201 3) reviewed various physical and chemical properties of nanostructured iron oxides and iron oxyhydroxides. Several phases of iron found in water, soil, and sediment were studied. It was
determined that increases in crystallinity of ferrihydrite or the formation of more crystalline phases (such as hematite and goethite) can cause a significant decrease in adsorbed arsenic and uranium. The
phases of iron oxide found in the environment can also supply detailed information about the conditions under which they were formed (i.e., acidity, water content, etc.). The nanostructures may also give insight
into the precursors that formed them.
Diegoli et al. (2008) investigated the influence of humic acid on the stability of gold nanoparticles. As expected, the addition of humic acid caused a significant decrease in the zeta potential of these particles,
enhancing their stability. At high ionic strength, particles tended to agglomerate even with the addition of humic acid. Agglomeration without humic acid was detected byTEM and also indicated by a shift in the
surface plasmon resonance from the transverse to the longitudinal plasmon band. Though agglomeration was still evident with the addition of humic acid at high ionic strength, there was no shift in the plasmon
band as the humic acid coating was thick enough to keep the particles far enough apart to preserve the surface plasmon resonance. It is still unknown whether humic acid overcoats the particle coating or
instead undergoes a ligand exchange with the existing surface groups; this remains an active area of research.
Li et al. (2012) collected several Chinese soil samples (one mollisol, three alfisols, six ultisols, and two entisols) and used ultrasonic centrifugation to disperse and extract nanoparticles. These nanoparticles
were then analyzed byXRD, TEM, FTIR, XRD and zeta potentiometry. The mollisols and alfisols released a significant quantity of nanoparticles (80-130 mg NP/g soil) with relatively small sizes (less than 25
nm) and were mainly comprised of muscovite and montmorillonite. These particles were generally round and could be dispersed in solution. The other soils, conversely, released much fewer nanoparticles that
were larger in size (~70nm) and were generally not as stable in aqueous suspension.
Akaighe et al. (201 1 ) investigated the formation of silver nanoparticles via reduction of dissolved silver (Ag+) by humic acid under environmentally relevant conditions. Aliphatically-rich humic substances such as
those found in aquatic and sedimentary humic acids were able to reduce silver ions to colloidal silver at temperatures ranging from room temperature (22 deg C) up to 90 deg C (a temperature relevant for hot
springs and other thermally active environments). Other humic acids derived from soils were found to only reduce silver ions at elevated temperatures. UV-vis, DLS, and a suite of microscopy techniques were
used to investigate the size distributions of the colloidal silver formed. Many samples were polydisperse, but could be made more mono-disperse with greater addition of humic acid. Results show that colloidal
and nan o-particu late silver found in the environment may not originate from exclusively anthropogenic sources and that the fate and transformation of silver nanoparticles in the aqueous environment may be
subject to changing redox conditions.
Murr and Garza (2009) studied various naturally-occurring nanomaterials found in both indoor and outdoor environments by collecting them through filtration, electrostatic precipitation, and thermophoretic
precipitation and analyzing them byTEM, SEM and EDS. Toxicity assays were also performed, investigating ROS production and cytokine release in human epithelial (lung model) cells. Approximately 42% of
all outdoor particulate matter is carbonaceous nanoparticulates. It was discovered that more than 80% of all nanoparticulate matter is agglomerated. Cytokine (IL-8) release was detected for Fe2O3, chrysotile
asbestos, black carbon, and multi-walled carton nanotube aggregate material. Reactive oxygen species were demonstrated with all these species as well as with various collections of soot material. Natural
soot material also produced extensive cell death. These results demonstrate that engineered nanomaterials may be capable of causing a variety of respiratory health problems.
The biodegradability of various organic nanoparticles was investigated by Kummerer et al. (2011) in response to concerns about environmental exposure to engineered nanoparticles. Fullerenes, single and
multi-walled CNTs (both functionalized and unfunctionalized), cellulose, and starch nanoparticles were all looked at for their biodegradability. Fullerenes and carbon nanotubes showed no degradation over the
experimental time frames. The starch and cellulose nanoparticles did show degradation, even at higher rates than their bulk counterparts, but none of the nanomaterials investigated qualified as "readily
biodegradation" per OECD standards (60% degraded by 28 days).
Complete Citation
Quo, H . and Barnard, A. 201 3.
Naturally occurring iron oxide
nanoparticles: morphology,
surface chemistry and
environmental stability. Journal of
Material Chemistry A, 1 (1 ), 27-42.
Diegoli, S., Maniciulea, A.,
Begum, S., Jones, I., Lead, J.,
and Preece, J. 2008. Interaction
between manufactured gold
nanoparticles and naturally
occurring organic
macromolecules. Science of the
Total Environment, 402(1), 51-61.
Li,W.,He,Y.,Wu, J.,andXu, J.
2012. Extraction and
characterization of natural soil
nanoparticles from Chinese soils.
European Journal of Soil Science,
63(5), 754-761.
Akaighe, N., MacCuspie, R.,
Navarro, D., Aga, D., Banerjee,
S., Sohn, M., and Sharnia, V.
201 1 . Humic acid-induced silver
nanoparticle formation under
environmentally relevant
conditions. Environmental
Science and Technology, 45(9),
3895-3901 .
Murr, L. and Garza, K. 2009.
Natural and anthropogenic
environmental nanoparticulates:
Their microstructural
characterization and respiratory
health implications. Atmospheric
Environment, 43(7), 2683-2692.
Kummerer, K., Menz, J.,
Schubert, T., and Thielemans, W.
201 1 . Biodegradability of organic
nanoparticles in the aqueous
environment. Chemosphere,
82(10), 1387-1392.
Page 15
-------
Doc ID
311
312
411
502
503
504
505
Title
Nanoparticles in the
environment
Inorganic nanotubes
andfullerene-like
nanoparticles
Research Priorities
to Advance Eco-
Responsible
Nanotechnology
Detecting
nanoparticulate silver
using single-particle
inductively coupled
plasma-mass
spectrometry
Determining
transport efficiency
for the purpose of
counting and sizing
nanoparticles via
single particle
inductively coupled
plasma mass
spectrometry
Single Particle
Inductively Coupled
Plasma Mass
Spectrometry: A
Performance
Evaluation and
Method Comparison
in the Determination
of Nanoparticle Size
Toxic potential of
materials at the
nanolevel
Authors
Banfield, J. and
Zhang, H.
Tenne, R.
Alvarez, P.J.J.,
Colvin, V., Lead,
J., and Stone, V.
Mitrano, D.M.,
Lesher, E.K.,
Bednar,A.,
Monsemd, J.,
Higgins,C. P.,
and Ranville,
J.F.
Pace, H.E.,
Rogers, N.J.,
Jarolimek, C.,
Coleman, V.A.,
Higgins, C.P.,
and Ranville,
J.F.
Pace, H.E.,
Rogers, N.J.,
Jarolimek, C.,
Coleman, V.A.,
Gray, E.P.,
Higgins, C.P.,
and Ranville,
J.F.
Nel,A.,Xia,T.,
Madler, L, and
Li, N.
Year
2001
2006
2009
2012
2011
2012
2006
Journal Title, Vol.
No., and Page No.
(or Year)
Reviews in Mineralogy
and Geochemistry,
44(1), 1-58
Nature
Nanotechnology, 1(2),
103-111
ACSNano, 3(7), 1616
1619
Environmental
Toxicology and
Chemistry, 31(1), 115-
121
Analytical Chemistry,
83(24), 9361-9369
Environmental
Science and
Technology, 46(22),
12272-12280
Science, 311(5761),
622-627
Document
Type
Published
journal
Published
journal
Published
Journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
This article introduces examples of the types of solids that are commonly encountered as nanoparticles in natural systems, describes some of the inorganic and biological processes that generate nanoparticles
in the environment, reviews the special properties (including stability and reactivity) of naturally occurring nanoparticles that make them significant in natural processes and geological systems, and identifies
research needs in this area. Natural nanoparticles may have geologic origins (e.g., clays) or biological origins (e.g., ferritins). Low-temperature environments, such as the earth's surface, are the most favorable
environments for formation of nanoparticles. All crystal formation passes through a nano size phase. Geochemical or biological processes that generate high degrees of supersaturation lead to production of
very many crystal nuclei, and therefore many nanoparticles. Geochemical examples include undersea hydrothermal vents, regions where streams of highly acidic solutions mix with neutral pH water, zones of
mixing between groundwater fluids, and sites of evaporation of soil water solutions. Biological examples include microorganisms that generate metabolic energy by pathways that involve inorganic ions that
participate in redox reactions. Challenges for future research include: synthesis of materials suitable for quantification of size-related phenomena; characterization of nanoparticles of varying sizes and the ways
they contrast with their bulk counterparts; study of the role of nanoparticles in complex organic-inorganic systems; understanding the self-organization of nanoparticles; characterization of early-growth crystals
that are smaller than nanoscale; and study of transport in aqueous media.
Tenne (2006) reviewed inorganic nanomaterials that were similar in structure to carbon nanotubes and fullerenes. Such material include inorganic nanotubes of WS2, MoS2, BN, and V2O5 that have unique
physical, mechanical, and tribological properties. The fullerene-like structures also have shown excellent lubrication behavior that could make them appropriate for many applications in kitchen appliances,
medical technology, and the aerospace industry. Though these materials have several interesting properties, the manipulation of their size, shape, and composition is still in its beginning stages and may
warrant further research.
Alvarez et al. (2009) introduced several topics for consideration in advancing the eco-responsible design and regulation of engineered nanomaterials. Research needs include: structu re-activity relationships to
predict functional stability of engineered nanoparticles (ENPs); protocols that assess ENP bioavailability, trophic transfer, and sublethal effects; and validated transport models. One of the areas that requires
the greatest amount of work is proper analytical techniques to detect and characterize engineered nanoparticles in environmental and biological samples. Proactive risk assessment is also necessary to guide
further research and determine the future of nanomaterial production.
Mitrano et al. (2012) utilized single-particle ICP-MS to detect and characterize silver nanoparticles in both wastewaterand a commercially-available colloidal silver product. Using this technique, one is able to
distinguish between nanoparticulate silver and dissolved silver in the sample, and to quantify particle number and size. Samples of wastewater showed that the wastewater treatment facility was able to remove
dissolved silver through the treatment process but was unable to remove the silver nanoparticles. The applicability of filters to the quantification of dissolved silver in a sample was also examined, but the binding
of silver to the filter membranes may reduce the accuracy in the quantification of silver in solution. With these results, the applicability of single particle ICP-MS to the detection of nanoparticles in environmental
samples was demonstrated, and further work is needed to validate this method.
Pace et al. (2011) presented a framework to count and size nanoparticles using ICP-MS run using single particle mode (i.e., short dwell times, dilute samples). Different strategies for evaluating the transport
efficiency (i.e., the nebulization efficiency) were discussed. Single particle ICP-MS (SP-ICP-MS) was shown to be an effective analytical technique for determining particle number concentration and particle
size for metal-containing nanoparticles.
Pace et al. (2012) compare various methods used in sizing metallic nanoparticles and demonstrate the performance of single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) in
comparison to other sizing techniques such as dynamic light scattering (DLS), nanotracking analysis (NTA), transmission electron microscopy (TEM), and differential centrifugal sedimentation (DCS). The
results show the ability of SP-ICP-MS to size and count nanoparticles with elemental specificity. One major drawback, however, is the inability of the techniques to distinguish between particles of the same
elemental composition (i.e., silver NP vs. silver chloride NP). Overall, with the continued development of this technique, it may one day be applied to the detection and characterization of nanoparticles in the
environment.
Nel et al. (2006) outline the potential mechanisms of toxicity resulting from nanomaterial exposure. In particular, special attention is paid to how nanomaterials may elicit a biological response either through
dissolution and/or generation of reactive oxygen species. Different pathophysiological effects that arise from different nanomaterials effects are outlined. Lastly, the challenges that are present in the in vivo and
in vitro characterization of nanomaterials are discussed.
Complete Citation
Banfield, J. and Zhang, H. 2001.
Nanoparticles in the environment.
Reviews in Mineralogy and
Geochemistry, 44(1), 1-58.
Tenne, R. 2006. Inorganic
nanotubes and fullerene-like
nanoparticles. Nature
Nanotechnology, 1(2), 103-111.
Alvarez, P.J.J., Colvin, V., Lead,
J., and Stone, V. 2009. Research
Priorities to Advance Eco-
Responsible Nanotechnology.
ACSNano, 3(7), 1616-1619.
Mitrano, D.M., Lesher, E.K.,
Bednar, A., Monserud, J.,
Higgins,C. P., and Ranville, J.F.
2012. Detecting nanoparticulate
silver using single-particle
inductively coupled plasma-mass
spectrometry. Environmental
Toxicology and Chemistry, 31 (1 ),
115-121.
Pace, H.E., Rogers, N.J.,
Jarolimek, C., Coleman, V.A.,
Higgins, C.P., and Ranville, J.F.
201 1 . Determining transport
efficiency for the purpose of
counting and sizing nanoparticles
via single particle inductively
coupled plasma mass
spectrometry. Analytical
Chemistry, 83(24), 9361-9369.
Pace, H.E., Rogers, N.J.,
Jarolimek, C., Coleman, V.A.,
Gray, E. P., Higgins, C. P., and
Ranville, J.F. 2012. Single
Particle Inductively Coupled
Plasma Mass Spectrometry: A
Performance Evaluation and
Method Comparison in the
Determination of Nanoparticle
Size. Environmental Science and
Technology, 46(22), 12272-
12280.
Nel, A., Xia, T., Madler, L., and Li,
N. 2006. Toxic potential of
materials at the nanolevel.
Science, 311(5761), 622-627.
Page 16
-------
Doc ID
506
507
508
509
510
511
Title
Economics and
governance of
nanomaterials:
potential and risks
Do nanoparticles
present
ecotoxicological risks
for the health ofthe
aquatic
environment?
A review of selected
engineered
nanoparticles in the
atmosphere:
sources,
transformations, and
techniques for
sampling and
analysis
Heteroaggregation
with nanoparticles:
effect of particle size
ratio on optimum
particle dose
Orthokinetic
heteroaggregation
with nanoparticles:
Effect of particle size
ratio on aggregate
properties
Interactions between
natural organic
matter and gold
nanoparticles
stabilized with
different organic
capping agents
Authors
Delgado, G.C.
Moore, M.N.
Majestic, B.J.,
Erdakos, G.B.,
Lewandowski,
M., Oliver K.D.,
Willis, R.D.,
Kleindienst.T.E.,
and Bhave, P.V.
Yates, P.O.,
Franks, G.V.,
Biggs, S., and
Jameson, G.J.
Yates, P.O.,
Franks, G.V.,
and Jameson,
G.J.
Stankus, D.P.,
Lohse, S.E.,
Hutchison, J.E.,
and Nason, J.A.
Year
2010
2006
2010
2005
2008
2010
Journal Title, Vol.
No., and Page No.
(or Year)
Technology in Society,
32(2), 137-144
Environment
International, 32(8),
967-976
International Journal
of Occupational and
Environmental Health,
16(4), 488-507
Colloids and Surfaces
A: Physicochemical
and Engineering
Aspects, 255(1-3), 85-
90
Colloids and Surfaces
A: Physicochemical
and Engineering
Aspects, 326(1-2), 83-
91
Environmental
Science and
Technology, 45(8),
3238-3244
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Delgado (201 0) discusses the economic potential of nanomaterials, and the need for standardization in assessing the toxicological and environmental impact of nanomaterials. Figures of note include plots
detailing the number of patents in the U.S. and Europe dedicated to nanomaterials, the distribution of nanomaterials in different industries, and estimated global production of nanomaterials for various
applications. The paper concludes that there is a pressing need to develop nanotechnology in a safe and responsible manner.
Moore (2006) reviews the potential toxicological impact, environmental entry, and biological uptake of nanomaterials. Some attention is paid to how nanomaterials enter into biological cells and result in in vivo
toxicity. How the environment may change nanomaterial fate, behavior, and toxicity are also discussed. It is postulated that the regulation and governance of nanomaterials may need to be performed on a
material-by-material basis, rather than treating all nanomaterials similarly.
Majestic et al. (201 0) review the various processes by which atmospheric nanoparticles are generated, the processes they are subject to in the environment, and the appropriate instrumentation and
methodology by which to study and characterize them in the environment.
Yates et al. (2005) investigated heteroaggregation between negatively charged silica nanoparticles and positively charged alumina colloids (31 0 nm). The addition of increasing sizes of silica and increasing
concentration of silica were investigated with respect to the optimum dose that produces the greatest extent of heteroaggregation. It was found that the size ratios and concentrations that produce a 50%
surface coverage ofthe alumina particles produce the greatest amount of heteroaggregation, as these conditions result in a zeta-potential close to zero (where electrostatic repulsive forces are neutralized).
Yates et al. (2008) investigated the strength of interaction between particles and consequently the strength of alumina aggregates by aggregating alumina colloids using polymer-alumina heteroaggregation,
alumina-silica particle heteroaggregation, and alumina homoaggregation provoked by neutralization of surface charge by raising the pH (pH =9). The strongest particle interactions were achieved with alumina
homoaggregation and alumina-silica heteroaggregation, with increasing particle-particle interactions at smaller sizes of silica nanoparticles. DLVO theory, which explains aggregation of aqueous materials, was
used to model the strength of interactions between particles.
Stankus et al. (201 0) studied the interaction and aggregation processes of different gold nanoparticles in the presence of humic acid. As expected, the addition of humic acid stabilizes nanoparticles by
imparting a strong negative charge, as a result ofthe ubiquity of carboxyl and phenolic groups present in the humic acid molecules. This resulted in a strong negative charge across the pH range that kept the
particles stabilized. However, in the presence of elevated concentrations of divalent cations (i.e. Ca2+, Mg2+, etc.), aggregation was enhanced with humic acid. This is possibly a result of cation bridging
between humic acid molecules.
Complete Citation
Delgado, G.C. 2010. Economics
and governance of
nanomaterials: potential and risks.
Technology in Society, 32(2), 137-
144.
Moore, M.N. 2006. Do
nanoparticles present
ecotoxicological risks for the
health ofthe aquatic
environment?. Environment
International, 32(8), 967-976.
Majestic, B.J., Erdakos, G.B.,
Lewandowski, M., Oliver K.D.,
Willis, R.D., Kleindienst, T.E., and
Bhave, P.V. 201 0. A review of
selected engineered
nanoparticles in the atmosphere:
sources, transformations, and
techniques for sampling and
analysis. International Journal of
Occupational and Environmental
Health, 16(4), 488-507.
Yates, P.O., Franks, G.V., Biggs,
S., and Jameson, G.J. 2005.
Heteroaggregation with
nanoparticles: effect of particle
size ratio on optimum particle
dose. Colloids and Surfaces A:
Physicochemical and Engineering
Aspects, 255(1-3), 85-90.
Yates, P.O., Franks, G.V., and
Jameson, G.J. 2008. Orthokinetic
heteroaggregation with
nanoparticles: Effect of particle
size ratio on aggregate
properties. Colloids and Surfaces
A: Physicochemical and
Engineering Aspects, 326(1-2),
83-91 .
Stankus, D.P., Lohse, S.E.,
Hutchison, J.E., and Nason, J.A.
2010. Interactions between
natural organic matter and gold
nanoparticles stabilized with
different organic capping agents.
Environmental Science and
Technology, 45(8), 3238-3244.
Page 17
-------
Doc ID
512
513
514
515
516
517
Title
Modeled
environmental
concentrations of
engineered
nanomaterials (TiO2,
ZnO,Ag, CNT,
fullerenes)for
different regions
Exposure modeling
of engineered
nanoparticles in the
environment
Categorization
framework to aid
exposure
assessment of
nanomaterials in
consumer products
Setting the limits for
engineered
nanoparticles in
European surface
waters - are current
approaches
appropriate?
Potential scenarios
fornanomaterial
release and
subsequent
alteration in the
environment
Environmental
Particles
(Environmental
Analytical and
Physical Chemistry
Series)
Authors
Gottschalk, F.,
Sonderer, T.,
Scholz, R.W.,
and Nowack, B.
Mueller, N.C.
and Nowack, B.
Hansen, S.,
Michelson, E.,
Kamper, A.,
Borling, P., Stuer
Lauridsen, F.,
and Baun, A.
Baun, A..
Hartmann, N..
Grieger, K., and
Hansen, S.
Nowack, B.,
Ranville, J.,
Diamond, S.,
Gallego-Urrea,
J., Metcalfe, C.,
Rose, J., Home,
N., Koelmans,
A., and Klaine,
S.
Buffle, J. and
van Leeuwen,
H.P.
Year
2009
2008
2008
2009
2012
1992
Journal Title, Vol.
No., and Page No.
(or Year)
Environmental
Science and
Technology, 43(24),
9216-9222
Environmental
Science and
Technology, 42(12),
4447-4453
Ecotoxicology, 17(5),
438-447
Journal of
Environmental
Monitoring, 11(10),
1774-1781
Environmental
Toxicology and
Chemistry, 31(1), 50-
59
Lewis Publishers,
International Union of
Pure and Applied
Chemistry (1992, 1st
ed.)
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
Journal
Published
Journal
Article Summary
Gottschalk et al. (2009) use a probabilistic materials flow analysis to determine predicted environmental concentrations (PECs) for various engineered nanomaterials. Many nanomaterials are expected to be
released in concentrations of ng L"1 or less. The majority of ecotoxicological impact may occur from nanomaterials such as nano-Ag and nano-TiO2 released from sewage treatment plant effluent, considered
to be a major sink for a variety of nanomaterials.
Mueller and Nowack (2008) modeled the amount of nanomaterials (nano-Ag, nano-TiO2, CNTs) released into the environment and compared the predicted environmental concentrations (PECs) to the
predicted no-effect concentrations (PN EC) to understand potential risk of these materials. Whereas the PEC/PNEC ratio was greater than 1 for TiO2, establishing possible risk, the PEC/PN EC ratios for nano-
Ag and CNTs were less than 1 . This quantitative approach may be used to understand environmental risk and establish life cycle assessments for engineered nanomaterials.
Hansen et al. (2008) provide a framework to assess potential risk of nanomaterials to the environment. This framework was used to quantify possible consumer exposure to these materials but was hampered
by the lack of information regarding EN P incorporation into commercial products and the lack of reliable sources containing the information needed to develop an accurate risk assessment.
Baun et al. (2009) review Europe's Water Framework Directive (WFD) and its relation to the eventual release of engineered nanomaterials into the environment. It was concluded that current information
regarding ENP behavior, concentrations, and environmental impact is insufficient to set appropriate limits for ENPs in the environment. More work is needed to assess the environmental impacts of
nanomaterials in order to accurately classify them as "priority substances" with regard to the WFD.
Nowack et al. (2012) discuss the release of engineered nanomaterials into the environment and the possible environmental processes that may alter the pristine state of the nanomaterial. Different case studies
are presented to demonstrate the numerous processes that can affect EN Ms in the environment and how these alterations may impact the chemistry, reactivity, and characterization of these materials in
environmental samples. Attention was paid to the current knowledge gaps that need to be overcome in order to accurately assess the risk of these EN Ms to environmental and human health, as well as the
implications these alterations have with regard to environmental health and safety.
Buffle and van Leeuwen (1992) compile various papers related to the sampling, monitoring, and reactivity of environmental colloids in both atmospheric and aqueous systems. Techniques such as filtration,
centrifugation, and electron microscopy are discussed in their ability to characterize these materials; in addition, properties such as surface charge and elemental ratios are discussed in relation to their
detection and characterization in environmental samples. Lastly, the role and processes these materials participate in in environmental samples are discussed.
Complete Citation
Gottschalk, F., Sonderer, T.,
Scholz, R.W., and Nowack, B.
2009. Modeled environmental
concentrations of engineered
nanomaterials (TiO2, ZnO, Ag,
CNT, fullerenes) for different
regions. Environmental Science
and Technology, 43(24), 921 6-
9222.
Mueller, N.C. and Nowack, B.
2008. Exposure modeling of
engineered nanoparticles in the
environment. Environmental
Science and Technology, 42(12),
4447-4453.
Hansen, S., Michelson, E.,
Kamper, A., Borling, P., Stuer-
Lauridsen, F., and Baun, A. 2008.
Categorization framework to aid
exposure assessment of
nanomaterials in consumer
products. Ecotoxicology, 17(5),
438-447.
Baun, A.. Hartmann, N.. Grieger,
K., and Hansen, S. 2009. Setting
the limits for engineered
nanoparticles in European
surface waters - are current
approaches appropriate?. Journal
of Environmental Monitoring,
11(10), 1774-1781.
Nowack, B., Ranville, J.,
Diamond, S., Gallego-Urrea, J.,
Metcalfe, C., Rose, J., Home, N.,
Koelmans, A., and Klaine, S.
2012. Potential scenarios for
nanomaterial release and
subsequent alteration in the
environment. Environmental
Toxicology and Chemistry, 31 (1 ),
50-59.
Buffle, J. and van Leeuwen, H.P.
1992. Environmental Particles
(Environmental Analytical and
Physical Chemistry Series). Lewis
Publishers, International Union of
Pure and Applied Chemistry
(1992, 1st ed.).
Page 18
-------
Doc ID
518
519
520
521
522
523
524
525
Title
Aquatic
environmental
nanoparticles
Geochemical
modeling of ZnS in
biofilms: An example
of ore depositional
processes
Ultra structure,
aggregation-state,
and crystal growth of
biogenic
nanocrystalline
sphalerite and
wurtzite
Reaction sequence
of iron sulfide
minerals in bacteria
and their use as
biomarkers
Characterization of
Aquatic Colloids and
Macromolecules
Subsurface transport
of contaminants
Plutonium and
neptunium speciation
bound to hydrous
ferric oxide colloids
Transport of colloidal
contaminants in
groundwater:
radionuclide
migration at the
Nevada Test Site
Authors
Wigginton, S.,
Haus, K., and
Hochella, Jr., M.
Druschel, G.,
Labrenz, M.,
Thomsen-Ebert,
T., Fowle, D.,
andBanfield, J.
Moreau, J.,
Webb, R., and
Banfield, J.
Posfai, M.,
Buseck, P.,
Bazylinski, D.,
and Frankel, R.
Buffle, J. and
Leppard, G.G.
McCarthy, J. and
Zachara, J.
Kalmykov, S.,
Kriventsov, V.,
Teterin, Y., and
Novikov, A.
Buddemeier, R.
and Hunt, J.
Year
2007
2002
2004
1998
1995
1989
2007
1988
No., and Page No.
(or Year)
Journal of
Environmental
Monitoring, 9(12),
1306-1316
Economic Geology,
97(6), 1319-1329
American
Mineralogist, 89(7),
950-960
Science, 280(5365),
880-883
Environmental
Science and
Technology, 29(9),
2169-2175
Environmental
Science and
Technology, 23(5),
496-502
Comptes Rendus
Chimie, 10(10-11),
1060-1066
Applied
Geochemistry, 3(5),
535-548
Document
Published
journal
Published
Journal
Published
Journal
Published
journal
Published
journal
Published
journal
Published
Journal
Published
Journal
Article Summary
Wigginton et al. (2007) discuss the formation of naturally occurring nanomaterials and give insight into their importance in environmental processes. In particular, the utility of iron oxide nanoparticles in the
remediation of environmental contaminants is discussed. Possible tools and analytical techniques for the detection and characterization of these materials in the environment are also reviewed along with a
case study showcasing the application of these techniques to the characterization of naturally occurring nanomaterials in an environmental sample.
Druschel et al. (2002) studied the formation of nanocrystalline ZnS (primarily sphalerite and wurtzite) within biofilms growing on mine timbers. The precipitation mechanism was driven by sulfate-reducing
bacteria of the family Desulfobacteriaceae. The model proposed details the reduction of sulfate, followed by cluster formation (1-3 nm in size), subsequently followed by aggregation of these clusters. By
identifying characteristics unique to these ZnS particles, nanocrystalline zinc sulfides of biogenic origin can be identified.
Moreau et al. (2004) investigated the formation of nanocrystalline ZnS in neutral waters flowing from an abandoned Pb-Zn mine. High resolution TEM revealed the formation of spherical nanoparticles 1-3 nm in
diameter that came together to form micron-sized aggregates. The crystal structure of the ZnS material was size-dependent, and the study shows some size-dependent phase stability in the biogenic formation
of these nanomaterials.
Posfai et al. (1 998) studied the formation of various nanocrystalline iron-containing minerals (greigite (Fe3S4), mackinawite (tetragonal FeS), and cubic FeS) formed intracellulariy in magnetotactic many-celled
prokaryotes (MMPs). The findings of this study may have implications for the presence of these iron sulfides in the Martian meteorite ALH8001.
Buffle and Leppard (1995) review important literature regarding the behavior, composition, and size distribution of naturally occurring colloids in environmental samples. In particular, the section on the size
distribution of these colloids in the environment shows that environmental colloids tend to follow Pareto's Law in environmental samples, with a B value of 3. In addition, aggregation, sedimentation, and
transport processes are also discussed.
McCarthy and Zachara (1 989) discuss naturally occurring colloids and their potential for the transport of groundwater contaminants. In particular, they postulate that colloids act as a third highly mobile phase
(aqueous (mobile) and sediment (immobile) being the other two). As a result of their mobility in aqueous systems and their high surface area for the adsorption of contaminants, these colloids play a major role
in the fate and transport of contaminants in aqueous systems.
Kalmykov et al. (2007) studied the Mayak production site, investigating the speciation of plutonium and neptunium bound to the hydrous ferric oxide colloids that transport these contaminants into the far-field. It
was discovered that near the source of contamination, intrinsic plutonium oxide colloids are formed that break down in the far-field to form pseudo-colloids through adsorption onto the iron oxide colloids.
Buddemeier and Hunt (1 988) collected groundwater samples within a nuclear detonation cavity and approximately 300 m away from the sampled cavity. It was discovered that all the transition metals of
interest (Mn, Co) and lanthanides (Ce, Eu) were associated with the colloidal fraction of the sample. The results indicate that the transport from the cavity is assisted through colloidal transport.
Complete Citation
Wigginton, S., Haus, K., and
Hochella, Jr., M. 2007. Aquatic
environmental nanoparticles.
Journal of Environmental
Monitoring, 9(12), 1306-1316.
Druschel, G., Labrenz, M.,
Thomsen-Ebert, T., Fowle, D.,
andBanfield, J. 2002.
Geochemical modeling of ZnS in
biofilms: An example of ore
depositional processes.
Economic Geology, 97(6), 1319-
1329.
Moreau, J., Webb, R., and
Banfield, J. 2004. Ultrastructure,
aggregation-state, and crystal
growth of biogenic nanocrystalline
sphalerite and wurtzite. American
Mineralogist, 89(7), 950-960.
Posfai, M., Buseck, P.,
Bazylinski, D., and Frankel, R.
1 998. Reaction sequence of iron
sulfide minerals in bacteria and
their use as biomarkers. Science,
280(5365), 880-883.
Buffle, J. and Leppard, G.G.
1995. Characterization of Aquatic
Colloids and Macromolecules.
Environmental Science and
Technology, 29(9), 2169-2175.
McCarthy, J. and Zachara, J.
1 989. Subsurface transport of
contaminants. Environmental
Science and Technology, 23(5),
496-502.
Kalmykov, S., Kriventsov, V.,
Teterin, Y., and Novikov, A. 2007.
Plutonium and neptunium
speciation bound to hydrous ferric
oxide colloids. Comptes Rendus
Chimie, 10(10-11), 1060-1066.
Buddemeier, R. and Hunt, J.
1 988. Transport of colloidal
contaminants in groundwater:
radionuclide migration at the
Nevada Test Site. Applied
Geochemistry, 3(5), 535-548.
Page 19
-------
Doc ID
526
527
528
529
530
Title
Stabilization of
aqueous nanoscale
zerovalent iron
dispersions by
anionic
polyelectrolytes:
adsorbed anionic
polyelectrolyte layer
properties and their
effect on
aggregation and
sedimentation
Nanomaterial
enabled biosensors
for pathogen
monitoring-A review
FeO nanoparticles
remain mobile in
porous media after
aging due to slow
desorption of
polymeric surface
modifiers
Estimating
attachment of nano-
and submicrometer-
particles coated with
organic
macromolecules in
porous media:
development of an
empirical model
Understanding
biophysicochemical
interactions at the
nano-bio interface
Authors
Phenrat, T.,
Saleh, N., Sink,
K., Kim,H-J.,
Tilton, R., and
Lowry, G.
Vikesland, P.
and Wigginton,
K.
Kim.H.J.,
Phenart,!.,
Tilton, R., and
Lowry, G.
Phenrat,!.,
Song, J.,
Cisneros, C.,
Schoenfelder,
D., Tilton, R.,
and Lowry, G.
Nel, A., Madler,
L.,Velegol, D.,
Xia.T., Hoek,
E.,
Somasundaran,
P., Klaessign, F.,
Castranova, V.,
and Thompson,
M.
Year
2008
2010
2009
2010
2009
Journal Title, Vol.
No., and Page No.
(or Year)
Journal of
Nanoparticle
Research, 10(5), 795-
814
Environmental
Science and
Technology, 44(10),
3656-3669
Environmental
Science and
Technology, 43(10),
3824-3830
Environmental
Science and
Technology, 44(12),
4531-4538
Nature Materials, 8(7),
543-557
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
Journal
Article Summary
Phenrat et al. (2008) prepared various dispersions of nanoscale zero-valent iron (NZVI) with different polystyrene sulfonate), carboxymethyl cellulose and polyaspartate polymeric coatings to stabilize the
particle and prevent aggregation. As these particles are used for groundwater remediation, the ability of these particles to remain dispersed will enhance their ability to remediate contaminants, as aggregation
and settling reduce the reactive surface area. It was found that all polymers were able to stabilize the particles to a degree, but there is a fraction of particles that nevertheless aggregate and settle out of
solution.
Vikesland and Wigginton (201 0) explore the current state-of-the-art in pathogen monitoring using nanomaterial-enabled biosensors. Different signal transduction methods can be exploited in nanomaterials,
such as electrochemical, fluorescence, surface-enhanced plasmon resonance and magnetic methods. By functionalizing a nanomaterial with the appropriate antibody or biomolecule, one can tailor it to be a
very sensitive and specific sensor for a variety of water-borne pathogens.
Kim et al. (2009) investigated the desorption of polymeric surface coatings that had modified zerovalent iron nanoparticles to prevent aggregation and subsequent sedimentation. It was found that many of the
coatings remained adsorbed to the particles and subsequently remained mobile in porous media even after extensive aging (4 months). High molecular weight polyelectrolyte had greater adsorbed mass and
slower desorption rates. It was concluded that the mobility of aged modified nanoparticles was similar to that of freshly modified particles, in contrast to the immobility of aged unmodified zero valent iron
nanoparticles.
Phenrat et al. (201 0) created an empirical correlation between nanoparticle properties and their sticking coefficients under a variety of electrolyte and flow conditions. It was discovered that semiempirical
correlations that had been used to predict the attachment efficiency of electrostatically stabilized (uncoated) nanoparticles overestimate the attachment efficiency of nanoparticles coated with natural organic
matter or polyelectrolytes. This is because these correlations fail to take into account the electrosteric repulsions and decreased friction afforded by these coatings. A dimensionless parameter (NLEK) is added
to represent these steric repulsion and decreased friction forces that arise as a result of the adsorption of these molecules.
Nel et al. (2009) review the current knowledge about the reactivity and interactions of nanomaterials at the biological interface. Different processes such as particle dissolution, intracellular uptake, and the
formation of protein coronas on the surface of a nanomaterial are all discussed. The interactions with proteins, membranes, and organelles as well as various colloidal and biophysiochemical interactions will
determine the extent of interaction between nanoparticles and biological systems. By understanding these interactions, one can develop predictive relationships that link nanoparticle properties such as size,
shape, and surface coatings to potential biological interactions.
Complete Citation
Phenrat, T., Saleh, N., Sirk, K.,
Kim, H-J., Tilton, R., and Lowry,
G. 2008. Stabilization of aqueous
nanoscale zerovalent iron
dispersions by anionic
polyelectrolytes: adsorbed anionic
polyelectrolyte layer properties
and their effect on aggregation
and sedimentation. Journal of
Nanoparticle Research, 10(5),
795-814.
Vikesland, P. and Wigginton, K.
2010. Nanomaterial enabled
biosensors for pathogen
monitoring-A review.
Environmental Science and
Technology, 44(10), 3656-3669.
Kim, H.J., Phenart,T., Tilton, R.,
and Lowry, G. 2009. FeO
nanoparticles remain mobile in
porous media after aging due to
slow desorption of polymeric
surface modifiers. Environmental
Science and Technology, 43(10),
3824-3830.
Phenrat, T., Song, J., Cisneros,
C., Schoenfelder, D., Tilton, R.,
and Lowry, G. 2010. Estimating
attachment of nano-and
submicrometer-particles coated
with organic macromolecules in
porous media: development of an
empirical model. Environmental
Science and Technology, 44(12),
4531-4538.
Nel, A., Madler, L, Velegol, D.,
Xia, T., Hoek, E., Somasundaran,
P., Klaessign, F., Castranova, V.,
and Thompson, M. 2009.
Understanding
biophysicochemical interactions at
the nano-bio interface. Nature
Materials, 8(7), 543-557.
Page 20
-------
Doc ID
531
532
533
534
535
536
Title
Effects of humic
substances on
precipitation and
aggregation of zinc
sulfide nanoparticles
Thiolation of
maghemite
nanoparticles by
dimercaptosuccinic
acid
Secondary Organic
Aerosol Coating of
Synthetic Metal-
Oxide Nanoparticles
Understanding the
nanoparticle-protein
corona using
methods to quantify
exchange rates and
affinities of proteins
for nanoparticles
Nanoparticle size
and surface
properties determine
the protein corona
with possible
implications for
biological impacts
Protein-nanoparticle
interactions
Authors
Deonarine, A.,
Lau, B., Aiken,
G., Ryan, J., and
Hsu-Kim, H.
Fauconnier, N.,
Rons, J., Roger,
J., and Bee, A.
Lee, J. and
Donahue, N.
Cedervall, T.,
Lynch, I.,
Lindman, S.,
Berggard,!.,
Thulin, E.,
Nilsson, H.,
Dawson, K., and
Linse, S.
Lundqvist, M.,
Sigler, J., Elia,
G., Lynch,!.,
Cedervall, T.,
and Dawson, K.
Lynch, I. and
Dawson, K.
Year
2011
1997
2011
2007
2008
2008
No., and Page No.
(or Year)
Environmental
Science and
Technology, 45(8),
3217-3223
Journal of Colloid and
Interface Science,
194(2), 427-433
Environmental
Science and
Technology, 45(11),
4689-4695
Proceedings of the
National Academy of
Sciences, 104(7),
2050-2055
Proceedings of the
National Academy of
Sciences, 105(38),
14265-14270
Nano Today, 3(1), 40-
47
Document
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
Journal
Article Summary
Deonarine et al. (2011) investigated how the composition of natural organic matter (NOM) affected the aggregation of nanoparticulate zinc sulfides. Characteristics such as molecular weight, type of carton,
and ligand density were all studied to determine how well they correlated to the growth and aggregation ofZn-S-NOM nanoparticles, as monitored by dynamic light scattering. It was found that the composition
of natural organic matter may contribute significantly to the stabilization of zinc sulfide nanoparticles in the environment.
Fauconnier et al. (1 997) investigated the adsorption of disulfide species onto maghemite nanoparticles in an effort to stabilize these particles for biological applications. It was found that the charge of the
particles is modified in the presence of a chelating agent, such that the particles are stabilized between pHs of 3-11, allowing their use for biological application.
Lee and Donahue (201 1 ) studied the coating that formed on TiO2 and CeO2 metal oxide nanoparticles in smog-chamber experiments in the presence of a-pinene and ozone. They also compared the
formation of this coating on bare metal oxide nanoparticles and those coated with poly(acrylic acid), and it was found that the organic vapors coat bare metal oxides more readily than those with the PAA
coating.
Cedervall et al. (2007) studied the nanoparticle-protein interactions that form the protein corona. Rates, affinities, and stoichiometries of protein association and dissociation from the particles were studied
using isothermal titration calorimetry. Rates of protein association and dissociation were studied using thiol-linked gold nanoparticles, exploiting their surface plasmon resonance properties. The binding
properties were found to depend on both protein identity and particle surface characteristics and size.
Lundqvist et al. (2008) determined the composition of the "hard" protein corona surrounding polystyrene nanoparticles of different size and charge, following immersion of the particles in human plasma. (The
hard corona is the portion of proteins that has a strong affinity for the nanoparticle, as opposed to the "soft" portion, which exhibits frequent exchange of proteins with the medium). The authors conducted a
systematic investigation of neutral, negatively charged (carboxyl-associated), and positively charged (amine-associated) polystyrene particles 50 and 1 00 nm in diameter. Among neutral particles, size did not
affect the corona composition. However, for charged particles, the particle size did appear to have an effect on the composition. The large particles showed more variation in protein composition than did the
small particles. Results of additional tests indicate that surface charge, rather than overall particle charge, maybe a driving factor behind protein corona composition.
Lynch and Dawson (2008) briefly review the state-of-the-art in protein-nanoparticle interactions, specifically the protein corona that forms on the surface of the nanoparticle in a biological medium. Various
topics are discussed, such as the effects of protein conformation on binding to nanoparticles, methods for characterizing nanoparticle-protein interactions, and the role nanoparticles may play in the fibrillation of
certain proteins. In addition, the utility that nanoparticles may have in probing protein-protein interactions is briefly discussed.
Complete Citation
Deonarine, A., Lau, B., Aiken, G.,
Ryan, J., and Hsu-Kim, H. 2011.
Effects of humic substances on
precipitation and aggregation of
zinc sulfide nanoparticles.
Environmental Science and
Technology, 45(8), 3217-3223.
Fauconnier, N., Pons, J., Roger,
J., and Bee, A. 1997. Thiolation
of maghemite nanoparticles by
dimercaptosuccinic acid. Journal
of Colloid and Interface Science,
194(2), 427-433.
Lee, J. and Donahue, N. 2011.
Secondary Organic Aerosol
Coating of Synthetic Metal-Oxide
Nanoparticles. Environmental
Science and Technology, 45(1 1 ),
4689-4695.
Cedervall, T., Lynch, I., Lindman,
S., Berggard, T., Thulin, E.,
Nilsson, H., Dawson, K., and
Linse, S. 2007. Understanding the
nanoparticle-protein corona using
methods to quantify exchange
rates and affinities of proteins for
nanoparticles. Proceedings of the
National Academy of Sciences,
104(7), 2050-2055.
Lundqvist, M., Sigler, J., Elia, G.,
Lynch, I., Cedervall, T., and
Dawson, K. 2008. Nanoparticle
size and surface properties
determine the protein corona with
possible implications for biological
impacts. Proceedings of the
National Academy of Sciences,
105(38), 14265-14270.
Lynch, I. and Dawson, K. 2008.
Protein-nanoparticle interactions.
Nano Today, 3(1), 40-47.
Page 21
-------
Doc ID
537
538
539
540
541
542
Title
Flow field-flow
fractionation for the
analysis and
characterization of
natural colloids and
manufactured
nanoparticles in
environmental
systems: a critical
review
Particle size
distributions of silver
nanoparticles at
environmentally
relevant conditions
Characterization of
structural and
surface speciation of
representative
commercially
available cerium
oxide nanoparticles
The effect of
environmentally
relevant conditions
on PVP stabilized
gold nanoparticles
What the cell "sees"
in bionanoscience
Analysis of gold
nanoparticle
mixtures: a
comparison of
hydrodynamic
chromatography
(HOC) and
asymmetrical flow
field-flow
fractionation (AF4)
coupled to ICP-MS
Authors
Baalousha, M.,
Stolpe, B., and
Lead, J.
Cumberland, S.
and Lead, J.
Baalousha, M.,
Coustumer, P.,
Jones, I., and
Lead, J.
Hitchman.A.,
Smith, G. , Ju-
Nami.Y.,
Sterling, M., and
Lead, J.
Walczyk, D.,
Bombelli, B.,
Monopoli, M.,
Lynch, I., and
Dawson, K.
Gray, E., Bruton,
T., Higgins, C.,
Halden, R.,
Westerhoff, P.,
and Ranville, J.
Year
2011
2009
2010
2013
2010
2012
Journal Title, Vol.
No., and Page No.
(or Year)
Journal of
Chromatography A,
121 8(27), 4078-41 03.
Journal of
Chromatography A,
1216(52), 9099-9105.
Environmental
Chemistry, 7(4), 377-
385.
Chemosphere, 90(2),
410-416
Journal of the
American Chemical
Society, 132(16),
5761-5768
Journal of Analytical
Atomic Spectrometry,
27(9), 1532-1539
Document
Type
Published
journal
Published
journal
Published
Journal
Published
journal
Published
Journal
Published
journal
Article Summary
Baalousha et al. (2011) provide an extensive review of flow field flow fractionation (FIFFF) and its application in the separation and characterization of nanomaterials, both engineered and natural, in the
environment. In addition to FI-FFF theory, the authors address experimental considerations such as calibration, detectors ,and sample preparation. FIFFF is also compared to other sizing and fractionation
techniques that have been commonly used in the analysis of nanoparticles in environmental samples.
Cumberland and Lead (2009) study the aggregation of 1 5-nm silver nanoparticles using flow field-flow fraction to both fractionate and size the nanoparticles. They found that in the presence of high ionic
strength, the particles aggregate and settle out of solution. The addition of humic substances stabilized the nanoparticles, as humic substances adsorbed onto the surfaces of the particles and provided a strong
negative charge that prevented aggregation.
Baalousha et al. (201 0) characterized commercially available cerium oxide nanoparticles using high resolution transmission electron microscopy coupled with electron energy loss spectroscopy. It was found
that nanoscale and bulk ceria have the same crystal structure and morphology; however, bulk ceria contain a higher proportion of Ce (IV), where as ceria nanoparticles are predominantly Ce (III). This
difference in oxidation state may play a significant role in the toxicology of these particles.
Hitchman et al. (2013) synthesized 7-nm gold nanoparticles stabilized with polyvinyl pyrrolidine (PVP). It was found that this sterically stabilized particle did not aggregate with changes to pH, ionic strength,
calcium concentration, and in the presence of dissolved organic matter (fulvic acid). Even at relatively high calcium concentrations (0.1 M Ca2+), these particles showed no aggregation. This suggests that
sterically stabilized particles may be highly mobile, and subsequently bioavailable in the environment.
Walczyk et al. (201 0) studied the protein corona that forms on dispersions of surface-carboxylated polystyrene nanoparticles, surface-sulfonated polystyrene nanoparticles, and silica particles by incubating
them in human blood plasma. The subsequent protein corona that forms on the particles was studied using differential centrifugation sedimentation (DCS), dynamic light scattering (DLS), and TEM. The
implications of the formation of a protein corona are discussed, for although a bare nanoparticle may have a stronger, non-specific affinity for cell membranes, those coated with a layer of proteins and
biomolecules may have more significant interactions with biological cells.
Gray et al. (201 2) compare two separation techniques for the detection and characterization of gold nanoparticles. It was found that AF4-ICP-MS held significantly greater resolution when separating mixtures
of particle sizes. However, recoveries from HDC-ICP-MS were consistently higher than that of AF4, as the AF4 recoveries were much lower for the largest of the nanoparticle sizes. The limit of detection for
this study was found to be approximately 5 ppb. In addition, HOC is able to separate dissolved signal from the particle signal, whereas the dissolved signal is lost in AF4-ICP-MS.
Complete Citation
Baalousha, M., Stolpe, B., and
Lead, J. 2011. Flow field-flow
fractionation for the analysis and
characterization of natural colloids
and manufactured nanoparticles
in environmental systems: a
critical review. Journal of
Chromatography A, 1218(27),
4078-4103.
Cumberland, S. and Lead, J.
2009. Particle size distributions of
silver nanoparticles at
environmentally relevant
conditions. Journal of
Chromatography A, 1216(52),
9099-9105.
Baalousha, M., Coustumer, P.,
Jones, I., and Lead, J. 2010.
Characterization of structural and
surface speciation of
representative commercially
available cerium oxide
nanoparticles. Environmental
Chemistry, 7(4), 377-385.
Hitchman, A., Smith, G., Ju-
Nami,Y, Sterling, M., and Lead,
J. 2013. The effect of
environmentally relevant
conditions on PVP stabilized gold
nanoparticles. Chemosphere,
90(2), 410-416.
Walczyk, D., Bombelli, B.,
Monopoli, M., Lynch, I., and
Dawson, K. 201 0. What the cell
"sees" in bionanoscience. Journal
of the American Chemical
Society, 132(16), 5761-5768.
Gray, E., Bruton, T., Higgins, C.,
Halden, R., Westerhoff, P., and
Ranville, J. 2012. Analysis of gold
nanoparticle mixtures: a
comparison of hydrodynamic
chromatography (H DC) and
asymmetrical flow field-flow
fractionation (AF4) coupled to
ICP-MS. Journal of Analytical
Atomic Spectrometry, 27(9),
1532-1539.
Page 22
-------
Doc ID
543
544
545
546
547
548
Title
Effect of Chloride on
the Dissolution Rate
of Silver
Nanoparticles and
Toxicity to E. coli
Environmental
transformations of
silver nanoparticles:
impact on stability
and toxicity
Transformation of
four silver/silver
chloride
nanoparticles during
anaerobic treatment
of wastewaterand
post-processing of
sewage sludge
Fate of zinc oxide
nanoparticles during
anaerobic digestion
of wastewaterand
post-treatment
processing of
sewage sludge
Sulfidation
processes of PVP-
coated silver
nanoparticles in
aqueous solution:
impact on dissolution
rate
Colloidal silver
nanoparticles:
photochemical
preparation and
interaction with O2,
CCI4, and some
metal ions
Authors
Levard, C.,
Mitra, S.,Yang,
T., Jew, A.,
Badiereddy, A.,
Lowry, G., and
Brown, Jr., G.
Levard C.,
Hotze, E.,
Lowry, G., and
Brown, Jr., G.
Lombi, E.,
Donner, E.,
Taheri, S.,
Tavakkoli, E.,
Jamting, A.,
McClure, S.,
Naidu, R., Miller,
B., Scheckel, K.,
and Vasilev, K.
Lombi, E.,
Donner, E.,
Tavakkoli, E.,
Tumey, T.,
Naidu, R., Miller,
B., and
Scheckel, K.
Levard, C.,
Reinsch, B.,
Michel, F.,
Oumahi, C.,
Lowry, G., and
Brown, Jr., G.
Henglein, A.
Year
2013
2012
2013
2012
2011
1998
Journal Title, Vol.
No., and Page No.
(or Year)
Environmental
Science and
Technology, 47(11),
5738-5745
Environmental
Science and
Technology, 46(1 3),
6900-6914
Environmental
Pollution, 176, 193-
197
Environmental
Science and
Technology, 46(16),
9089-9096
Environmental
Science and
Technology, 45(12),
5260-5266
Chemistry of
Materials, 10(1), 444-
450
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Levard et al. (201 3) studied the rate of silver dissolution in the presence of a chloride salt and the implications these dissolution rates hold for their toxicity to E.coli. The kinetics of silver nanoparticle dissolution
were studied using a Float-A-Lyzer G2 dialysis device with a nominal molar mass cutoff of 8-1 0 kDa. It was found that the kinetics of silver nanoparticle dissolution was highly dependent on the chlorine/silver
ratio, consistent with the themiodynamic speciation of silver in the presence of chloride. Toxicity to E. coli. was also found to be dependent on the speciation of silver, suggesting that the toxicity is a result of
the dissolved ions, rather than the silver nanoparticle itself.
Levard et al. (201 2) review the various processes that affect silver nanoparticles in the environment and how these processes affect nanoparticle toxicity. Processes such as the sulfidation of nanoparticles will
result in a decrease in their toxicity due to the inherent lower solubility of silver sulfide complexes. In addition to the discussion of these various environmental processes, future needs and research outlooks are
also discussed.
Lombi et al. (201 3) studied the speciation of silver nanoparticles capped with different surface groups (polyvinylpyrrolidone, citrate, mercaptosuccinic acid) when exposed to a wastewater sludge. The results
indicated that regardless of silver nanoparticle compositions and surface functionality, silver sulfide was formed for all particles. These results may have implications for the reactivity and behavior of silver
nanoparticles in environmental samples.
Lombi et al. (2012) investigated the speciation of ZnO nanoparticles during the anaerobic digestion of sewage sludge. It was found that the speciation of the zinc nanoparticles was the same as that of a
dissolved zinc salt after postprocessing of sewage sludge, indicating that all zinc species regardless of composition conform to a similar end-product. These results may have implications for the fate of
engineered nanomaterials in treatment processes.
Levard et al. (2011) used synchrotron XRD and EXAFS to study the formation of silver sulfide when silver nanoparticles are exposed to sulfur. It was found that the silver sulfide that forms creates bridges
between nanoparticles leading to chain-like structures. In addition, the sulfidation of these particles reduces the dissolution of the silver nanoparticles, which may impact toxicity, as the toxicity of silver
nanoparticles is dependent on the release of silver ions.
Henglein (1 998) produced 7-nm silver nanoparticles by illuminating silver perchlorate in the presence of polyethyleneimine. The particles produced possessed a narrow surface plasmon resonance. The
wavelength and peak width of the SPR band changed with the addition of oxygen and other metal ions such as cadmium, nickel, silver, and mercury, with the more electropositive metals resulting in the largest
change to the SPR.
Complete Citation
Levard, C., Mitra, S., Yang, T.,
Jew, A., Badiereddy, A., Lowry,
G., and Brown, Jr., G. 2013.
Effect of Chloride on the
Dissolution Rate of Silver
Nanoparticles andToxicity to E.
coli. Environmental Science and
Technology, 47(1 1 ), 5738-5745.
Levard C., Hotze, E., Lowry, G.,
and Brown, Jr., G. 2012.
Environmental transformations of
silver nanoparticles: impact on
stability and toxicity.
Environmental Science and
Technology, 46(13), 6900-6914.
Lombi, E., Donner, E., Taheri, S.,
Tavakkoli, E., Jamting, A.,
McClure, S., Naidu, R., Miller, B.,
Scheckel, K., and Vasilev, K.
2013. Transformation of four
silver/silver chloride nanoparticles
during anaerobic treatment of
wastewater and post-processing
of sewage sludge. Environmental
Pollution, 176, 193-197.
Lombi, E., Donner, E., Tavakkoli,
E. , Tumey, T., Naidu, R., Miller,
B., and Scheckel, K. 2012. Fate
of zinc oxide nanoparticles during
anaerobic digestion of
wastewaterand post-treatment
processing of sewage sludge.
Environmental Science and
Technology, 46(16), 9089-9096.
Levard, C., Reinsch, B., Michel,
F., Oumahi, C., Lowry, G., and
Brown, Jr., G. 201 1 . Sulfidation
processes of PVP-coated silver
nanoparticles in aqueous solution:
impact on dissolution rate.
Environmental Science and
Technology, 45(12), 5260-5266.
Henglein, A. 1998. Colloidal silver
nanoparticles: photochemical
preparation and interaction with
O2, CCI4, and some metal ions.
Chemistry of Materials, 10(1),
444-450.
Page 23
-------
Doc ID
549
550
551
552
553
554
555
556
Title
Silver nanoparticles:
partial oxidation and
antibacterial activities
TCE dechlorination
rates, pathways, and
efficiency of
nanoscale iron
particles with
different properties
Redox-active radical
scavenging
nanomaterials
Electrokinetic
characteristics of
some metal sulfide-
water interfaces
The surface acidity
of hydrous CdS (s)
Probing the
cytotoxicity of
semiconductor
quantum dots
Photochemical
transformation of
aqueous C6D clusters
in sunlight
Toxicity reduction of
polymer-stabilized
silver nanoparticles
by sunlight
Authors
Lok, C.-N., Ho,
C.-M.,Chen, R.,
He, Q.-Y.,Yu,
W.-Y,Sun, H.,
Tarn, P., Chiu, J,
F., and Che, C.-
M.
Liu, Y, Majetich,
S.,Tilton,R.,
Sholl, D., and
Lowry, G.
Karakoti, A.,
Singh, S.,
Dowding, J.,
Seal, S., and
Self, W.
Liu, J. and
Huang, C.
Park, S. and
Huang, C.
Derfus, A.,
Chan, W., and
Bhatia, S.
Hou,W. and
Jafvert, C.
Cheng, Y, Yin,
L.,Lin, S.,
Wiesner, M.,
Bemhardt, E.,
and Liu, J.
Year
2007
2005
2010
1992
1987
2004
2009
2011
No., and Page No.
(or Year)
Journal of Biological
Inorganic Chemistry,
12(4), 527-534
Environmental
Science and
Technology, 39(5),
1338-1345
Chemical Society
Reviews, 39(11),
4422-4432
Langmuir, 8(7), 1851-
1856
Journal of Colloid and
Interface Science,
117(2), 431-441
Nano Letters, 4(1),
11-18
Environmental
Science and
Technology, 43(2),
362-367
Journal of Physical
Chemistry C, 115(11),
4425-4432
Document
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Lok et al. (2007) studied the antibacterial properties of partially oxidized silver nanoparticles that had been formed via reduction by sodium borohydride. It was found that the partial oxidation of silver
nanoparticles led to a surface of chemisorbed silver ions, which correlated with higher toxicity to the bacterium. These results indicate that the toxicity of silver nanoparticles maybe dependent on levels of
chemisorbed Ag+, which is dependent on the oxygen levels in the system.
Liu et al. (2005) studied the rate of dechlorination of TCE (trichloroethylene) for both zero-valent iron produced by reduction of ferrous iron, and a commercially available zero valent iron nanoparticle. Different
conditions were tested, including iron-limiting and TCE-limiting reactions. It is suggested that the more crystalline magnetite shell (Fe3O4) present on the commercially available particle may be responsible for
the slower dechlorination rates, as less reactive iron is available. The addition of hydrogen gas also increased the rate of dechlorination, suggesting that a catalytic pathway may exist.
Karakoti et al. (201 0) discuss the potential of engineered nanomaterials to scavenge radical oxygen and nitrogen species, which are the cause of many neurodegenerative diseases. In particular the chemistry
and action by which these nanomaterials are able to protect biological systems from reactive oxygen species damage is discussed. Of the several ENPs in production, cerium oxide and fullerene nanomaterials
are expected to be promising materials for the purpose of radical species scavenging.
Liu and Huang (1 992) studied the electrokinetic potential for several metal sulfides and determined the isoelectric point for each material. They also investigated the role that crystal structure, crystal field
stabilization energies, and the ratio of cationic charge to ionic radius play in the electrokinetic behavior of these materials. For some metal sulfides (CuS, ZnS) the concentration of their corresponding cations
(Cu2+, Zn2+) can play a large role in determining their electrokinetic potential.
Park and Huang (1987) studied the surface acidity and electrokinetic potential of cadmium sulfide using titration methods. They determined that two surface sites existed, Bronsted sites (where OH- and H+ are
potential determining ions) and Lewis sites (where Cd2+ and S2- are potential determining ions). It was determined that pH plays a larger role in the ratio of Lewis and Bronsted sites than the concentration of
cadmium ions in solution.
Derfus et al. (2004) used primary hepatocytes isolated from rats to investigate the cytotoxicity of cadmium selenide semiconductor quantum dots. The primary pathway for quantum dot toxicity was found to be
the release of cadmium ions resulting from photo- and chemical oxidation of the quantum dot. The capping of these quantum dots with BSA (bovine serum albumin) or zinc sulfide was found to greatly reduce
their toxicity, most likely by protecting the cadmium selenide lattice from deterioration.
Hou and Jafvert (2009) investigated the photochemical transformation of C60 clusters under both sunlight and lamp light (300-400 nm). It was found that the C60 clusters degraded over time to form soluble
byproducts, as quantified byTOC measurements. The presence of humic substances and varying pH resulted in little change in the decay of these clusters. It was also found that the smaller clusters (~150 nm)
decayed at a faster rate than the larger clusters (500 nm). Lastly, the decay in deoxygenated water was much slower, indicating that the presence of oxygen is a necessary component in the photochemical
oxidation of these materials.
Cheng et al. (201 1 ) investigated the toxicity of 6- and 25-nm silver nanoparticles coated with both PVP and gum arable to Lolium muRiflora . It was found that exposure to U V irradiation resulted in irreversible
aggregation of the nanoparticles, reducing their toxicity. It was concluded that sunlight would be the primary driving force by inducing a strong oscillating dipole-dipole interaction, resulting in particle-particle
aggregation.
Complete Citation
Lok, C.-N., Ho, C.-M., Chen, R.,
He, Q.-Y,Yu,W.-Y,Sun, H.,
Tarn, P., Chiu, J.-F., and Che, C.-
M. 2007. Silver nanoparticles:
partial oxidation and antibacterial
activities. Journal of Biological
Inorganic Chemistry, 12(4), 527-
534.
Liu, Y, Majetich, S., Tilton, R.,
Sholl, D., and Lowry, G. 2005.
TCE dechlorination rates,
pathways, and efficiency of
nanoscale iron particles with
different properties.
Environmental Science and
Technology, 39(5), 1338-1345.
Karakoti, A., Singh, S., Dowding,
J., Seal, S., and Self, W. 2010.
Redox-active radical scavenging
nanomaterials. Chemical Society
Reviews, 39(1 1 ), 4422-4432.
Liu, J. and Huang, C. 1992.
Electrokinetic characteristics of
some metal sulfide-water
interfaces. Langmuir, 8(7), 1851-
1856.
Park, S. and Huang, C. 1987.
The surface acidity of hydrous
CdS (s). Journal of Colloid and
Interface Science, 117(2), 431-
441.
Derfus, A., Chan, W., and Bhatia,
S. 2004. Probing the cytotoxicity
of semiconductor quantum dots.
Nano Letters, 4(1), 11-18.
Hou,W. and Jafvert, C. 2009.
Photochemical transformation of
aqueous C60 clusters in sunlight.
Environmental Science and
Technology, 43(2), 362-367.
Cheng, Y, Yin, L, Lin, S.,
Wiesner, M., Bernhardt, E., and
Liu, J. 201 1 . Toxicity reduction of
polymer-stabilized silver
nanoparticles by sunlight. Journal
of Physical Chemistry C, 1 1 5(1 1 ),
4425-4432.
Page 24
-------
Doc ID
557
558
559
560
561
562
563
Title
Chemical
transformations
during aging of
zerovalent iron
nanoparticles in the
presence of common
groundwater
dissolved
constituents
Nanoparticle
aggregation:
Challenges to
understanding
transport and
reactivity in the
environment
Theoretical
framework for
nanoparticle
reactivity as a
function of
aggregation state
Impact of aggregate
size and structure on
the photo catalytic
properties ofTiO2
andZnO
nanoparticles
Characterization of
ZnS Nanoparticles
Aggregation using
Photoluminescence
Dissimilatory
reduction of
extracellular electron
acceptors in
anaerobic respiration
Biodegradation of
single-walled carton
nanotubes through
enzymatic catalysis
Authors
Reinsch, B.,
Forsberg, B.,
Penn, R., Kim,
C., and Lowry,
G.
Hotze, E.,
Phenrat.T., and
Lowry, G.
Hotze, E.,
Bottero, J., and
Wiesner, M.
Jassby, D.,
Budarz, J., and
Wiesner, M.
Jassby, D. and
Wiesner, M.
Richter, K.,
Schicklberger,
M., and
Gescher, J.
Allen, B.,
Kichambare, P.,
Gou,P., Vlasova,
l.,Kapralov,A.,
Kondum, N.,
Kagan, V., and
Star, A.
Year
2010
2010
2010
2012
2011
2012
2008
No., and Page No.
(or Year)
Environmental
Science and
Technology, 44(9),
3455-3461
Journal of
Environmental Quality,
39(6), 1909-1924
Langmuir, 26(13),
11170-11175
Environmental
Science and
Technology, 46(1 3),
6934-6941
Langmuir, 27(3), 902-
908
Applied and
Environmental
Microbiology, 78(4),
913-921
Nano Letters, 8(11),
3899-3903
Document
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Reinsch et al. (201 0) studied the aging of zerovalent iron nanoparticles under a variety of groundwater constituent and dissolved oxygen concentrations. Both fresh and aged NZVI particles were analyzed using
x-ray absorption near edge structure (XANES)to determine the oxidation state, while extended x-ray absorption fine structure (EXAFS) was used to quantify the different proportions of minerals present. Most
anions resulted in oxidation of the NZVI surface, whereas nitrate passivated the surface, preventing oxidation to the surface. Waters saturated with dissolved oxygen resulted in a rapid loss of zero-valent iron,
subsequently resulting in the evolution of magnetite and maghemite.
Hotze et al. (201 0) review aggregation processes as they relate to nanomaterials fate and transport in the environment. Whereas DLVO has been capable of sufficiently describing particle-particle interactions
in the past, nanoparticles provide new challenges to effectively utilizing this theory as their size, shape, and strong interactions with other molecules (i.e., humic substances) can greatly alter the behavior of
these particles.
Hotze et al. (201 0) develop a theoretical framework with which to describe reactive oxygen species (ROS) production in fullerene aggregates. In particular, their concern is to describe the paradox of higher
ROS production in fullerol suspensions (C6D(OH)22-24) than in aqueous fullerene aggregates (aquC60) despite C60 molecules having a greater quantum yield and thus greater potential for photosensitization.
The authors' theoretical framework qualitatively predicts higher singlet oxygen production from the fullerol aggregates than from the compact C60 aggregates. It is determined that the compact nature of C60
aggregates may result in triplet-triplet state annihilation between fullerene molecules in close proximity, leading to aggregation-suppressed ROS production. Fullerol aggregates, on the other hand have looser,
less-compact structures. Smaller aggregates and aggregates of lower fractal dimensions result in higher ROS production.
Jassby et al. (2012) studied the generation of free radicals from two photoactive nanomaterials (TiO2 and ZnO) as they underwent aggregation. Light scattering was used to determine the rate of aggregation
of these materials with increasing concentrations of electrolyte. The generation of radical species decreased with increasing aggregate size, most likely due to the reduced surface reactivity.
Jassby et al. (201 1 ) studied the photoluminescence of ZnS nanoparticles that undergo aggregation with increasing concentration of electrolyte. It is suspected that the aggregation of particles results in the
passivation of the electron-hole pairs of the surface, leading to an increase in photoluminescent intensity along the band edge as a result of a drop in surface tension. These findings show that temporal
changes in aggregate formation can be monitored using photoluminescent techniques.
Richter et al. (201 2) review the current knowledge of extracellular respiration. Their work shows that c-type chromosomes play an important role in the formation of extended respiratory chains. These
chromosomes are non-specific electron acceptors and donators that are suited for electron transfer.
Allen et al. (2008) demonstrate the biodegradability of carbon nanotubes using natural horseradish peroxidase (H RP) at low concentrations of hydrogen peroxide. The degradation of these materials was
monitored using several techniques, such as transmission electron microscopy, UV-vis, mass spectrometry, and dynamic light scattering. These results indicate that the degradation of carbon nanotubes is
possible in environmental systems.
Complete Citation
Reinsch, B., Forsberg, B., Penn,
R., Kim, C., and Lowry, G. 2010.
Chemical transformations during
aging of zerovalent iron
nanoparticles in the presence of
common groundwater dissolved
constituents. Environmental
Science and Technology, 44(9),
3455-3461 .
Hotze, E., Phenrat.T., and
Lowry, G. 2010. Nanoparticle
aggregation: Challenges to
understanding transport and
reactivity in the environment.
Journal of Environmental Quality,
39(6), 1909-1924.
Hotze, E., Bottero, J., and
Wiesner, M. 2010. Theoretical
framework for nanoparticle
reactivity as a function of
aggregation state. Langmuir,
26(13), 11170-11175.
Jassby, D., Budarz, J., and
Wiesner, M. 2012. Impact of
aggregate size and structure on
the photocatalytic properties of
TiO2 and ZnO nanoparticles.
Environmental Science and
Technology, 46(1 3), 6934-6941 .
Jassby, D. and Wiesner, M. 201 1 .
Characterization of ZnS
Nanoparticles Aggregation using
Photoluminescence. Langmuir,
27(3), 902-908.
Richter, K., Schicklberger, M.,
and Gescher, J. 2012.
Dissimilatory reduction of
extracellular electron acceptors in
anaerobic respiration. Applied
and Environmental Microbiology,
78(4), 913-921.
Allen, B., Kichambare, P.,
Gou,P., Vlasova, I., Kapralov, A.,
Kondum, N., Kagan, V., and Star,
A. 2008. Biodegradation of single-
walled carbon nanotubes through
enzymatic catalysis. Nano
Letters, 8(11), 3899-3903.
Page 25
-------
Doc ID
564
565
566
567
568
Title
Express it in
numbers: efforts to
quantify engineered
nanoparticles in
environmental
matrices advance
Characterization and
quantitative analysis
of single-walled
carbon nanotubes in
the aquatic
environment using
near-infrared
fluorescence
spectroscopy
Microbial
bioavailability of
covalently bound
polymer coatings on
model engineered
nanomaterials
Silver nanoparticle
characterization
using single particle
ICP-MS (SP-ICP-
MS)and
asymmetrical flow
field flow
fractionation ICP-MS
(AF4-ICP-MS)
Detection of single
walled carbon
nanotubes by
monitoring
embedded metals
Authors
Plata, D.,
Ferguson, P.,
and Westerhoff,
P.
Schierz,A.,
Parks, A.,
Washbum, K.,
Chandler, G.,
and Ferguson,
P.
Kirschling, T.,
Golas, P.,
Unrine, J.,
Matyjaszewski,
K., Gregory, K.,
Lowry, G., and
Tilton, R.
Mitrano, D.,
Barter, A.,
Bednar, A.,
Westerhoff, P.,
Higgins, C., and
Ranville, J.
Reed, R.,
Goodwin, D.,
Marsh, K.,
Capracotta, S.,
Higgins, C.,
Fairbrother, H.,
and Ranville, J.
Year
2012
2012
2011
2012
2013
Journal Title, Vol.
No., and Page No.
(or Year)
Environmental
Science and
Technology, 46(22),
12243-12245
Environmental
Science and
Technology, 46(22),
12262-12271
Environmental
Science and
Technology, 45(12),
5253-5259
Journal of Analytical
Atomic Spectrometry,
27(7), 1131-1142
Environmental
Science: Processes
and Impacts (201 3),
15
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Plata et al. (201 2) briefly overview the various new techniques being used to detect and characterize carton nano-tubes in biological and environmental samples. Near-infrared spectroscopy and single particle
ICP-MS are both discussed as feasible methods to detect CNTs in environmental samples.
Schierz et al. (2012) discuss the utility of near infrared spectroscopy for the selective and quantitative detection of semi-conducting carton nanotubes in environmental matrices. Using a set of known
standards, the chirality and diameters of these carton nanotubes can be determined. Detection limits for the instrument were determined to be in the ppb range in both aqueous and sediment environments.
Kirschling et al. (201 1 ) demonstrated that stabilizing polymers (polyethylene oxide)) covalently attached to the surface of engineered nanomaterials are bioavailable. The nanomaterials used in this study were
synthesized in such a way that biodegradation was the only feasible breakdown mechanism. The breakdown of the polymer coating was monitored by the protein and CO2 production of the PEO-degrading
enrichment culture. The biodegradation of the polymer coating maybe dependent on how the polymer is attached to the particle, as highly cross-linked polymer may be less available for degradation.
Mitrano et al. (2012) use both single particle ICP-MS and AF4-ICP-MS to characterize mixtures of silver nanoparticles. Though SP-ICP-MS is more sensitive than AF4-ICP-MS (ng/Lvs. ug/L), AF4 provides
greater size resolution, being able to size particles down to 2 nm (as opposed to 20 nm for SP-ICP-MS). The resolution between particle sizes is also demonstrated. In addition, the formation of silver
complexes from the dissolution of silver nanoparticles was demonstrated using AF4-ICP-MS. Both techniques can be useful for the detection and characterization of ENPs in environmental samples.
Reed et al. (2012) used single particle ICP-MS (SP-ICP-MS) to detect carton nanotubes by monitoring for metals that have been intercalated in the CNTas a result of the synthesis of these materials. Possible
metals to monitor for include yttrium, molybdenum, nickel, and cobalt. A clear correlation is shown between the mass loading of CNTs and the number of detection events, and the applicability of this technique
to monitor the release of CNTs from a polymer composite.
Complete Citation
Plata, D., Ferguson, P., and
Westerhoff, P. 2012. Express it in
numbers: efforts to quantify
engineered nanoparticles in
environmental matrices advance.
Environmental Science and
Technology, 46(22), 12243-
12245.
Schierz, A., Parks, A., Washbum,
K., Chandler, G., and Ferguson,
P. 2012. Characterization and
quantitative analysis of single-
walled carbon nanotubes in the
aquatic environment using near-
infrared fluorescence
spectroscopy. Environmental
Science and Technology, 46(22),
12262-12271.
Kirschling, T., Golas, P., Unrine,
J., Matyjaszewski, K., Gregory,
K., Lowry, G., and Tilton, R.
201 1 . Microbial bioavailability of
covalently bound polymer
coatings on model engineered
nanomaterials. Environmental
Science and Technology, 45(12),
5253-5259.
Mitrano, D., Barter, A., Bednar,
A., Westerhoff, P., Higgins, C.,
and Ranville, J. 2012. Silver
nanoparticle characterization
using single particle ICP-MS (SP-
ICP-MS) and asymmetrical flow
field flow fractionation ICP-MS
(AF4-ICP-MS). Journal of
Analytical Atomic Spectrometry,
27(7), 1131-1142.
Reed, R., Goodwin, D., Marsh,
K., Capracotta, S., Higgins, C.,
Fairbrother, H., and Ranville, J.
201 3. Detection of single walled
carbon nanotubes by monitoring
embedded metals. Environmental
Science: Processes and Impacts
(2013), 15.
Page 26
-------
Doc ID
569
570
571
572
573
574
Title
Separation and
characterization of
nanoparticles in
complex food and
environmental
samples by field-flow
fraction ation
Critical aspects of
sample handling for
direct nanoparticle
analysis and
analytical challenges
using asymmetric
field flow
fractionation in a
multi-detector
approach
Application of
hydrodynamic
chromatography- 1C P-
MS to investigate the
fate of silver
nanoparticles in
activated sludge
Partial validation of
cross flow
ultra filtration by
atomic force
microscopy
Measuring colloidal
and macromolecular
properties by FFF
Size fractionation
and characterization
of natural colloids by
flow-field flow
fractionation coupled
to multi-angle laser
light scattering
Authors
von der
Kammer, F.,
Legros, S.,
Larson, E.,
Loeschner, K.,
and Hofmann, T.
Ulrch, A., Losert,
S., Bendixen.N.,
AI-Kattan, A.,
Hagendorfer, H.,
Nowack, B.,
Adlhart, C.,
Ebert, J.,
Lattuada, M.,
and
Hungertiihler, K.
Tiede, K., Boxall,
A., Wang, X.,
Gore, D., Tiede,
D., Baxter, M.,
David, H.,Tear,
S., and Lewis, J.
Liu, R. and
Lead, J.
Giddings, J.
Baalousha, M.,
Kammer,
F.V.D.,Motelica-
Heino, M., Hilal,
H., and
Coustumer, P.
Year
2011
2012
2010
2006
1995
2006
Journal Title, Vol.
No., and Page No.
(or Year)
Trends in Analytical
Chemistry, 30(3), 425-
436
Journal of Analytical
Atomic Spectrometry,
27(7), 1120-1130
Journal of Analytical
Atomic Spectrometry,
25(7), 1149-1154
Analytical Chemistry,
78(23), 8105-8112
Analytical Chemistry,
67(19), 592A-598A
Journal of
ChromatographyA,
1104(1), 272-281
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
von der Kammer et al. (201 1 ) review the different ways that field flow fractionation (FFF) has been applied to the detection and characterization of engineered nanomaterials in food and environmental
samples. The type of information that can be obtained through FFF analysis is dependent on the type of detector that it is coupled to. The applicability of this technique is hindered by the method development
necessary to create conditions that allow for optimal resolution of the particles. However, this technique shows great promise and could be extremely useful in the detection of EN Ms in complex matrices.
Ulrich et al. (201 2) discuss the potential problems associated with the handling and analysis of engineered nanomaterials samples. Many different processes and sample preparation steps can result in the
aggregation of nanomaterials, resulting in false size information. Consequently, the authors recommend a fast-screening method for particle size such as dynamic light scattering prior to further analysis, to
monitor the formation of aggregates during sample handling and preparation.
In an earlier paper, Tiede et al. developed a method for using hydrodynamic chromatography coupled with plasma mass Spectrometry (HDC-ICP-MS) to detect and size nanoparticles. In this paper (2010) they
used the method to determine whether it could detect spiked silver nanoparticles in mixed liquor sewage sludge and to determine whether the size distribution of the nanoparticles changed as a result of contact
with the sludge (silver nanoparticles are used for antibacterial purposes). The authors found that more than 90 percent of added silver was removed from the supernatant and was assumed to be partitioned to
sludge. HDC-ICP-MS analysis indicated that the supernatant still contained silver nanoparticles (approximately 3 nm in diameter). The silver remaining in the supernatant could have ecological implications
since it is likely to be discharged to surface waters after the treatment process.
Liu and Lead (2006) investigated the efficacy of cross flow ultrafiltration for separating particle sizes by identifying the filtrate particle sizes using atomic force microscopy. The results recommend high cross
flow values for optimum particle separation. Though AFM is useful for validating particle sizes, it may not be useful for determining changes in particle conformation as a result of cross flow ultrafiltration.
Giddings (1995) reviews the theory and application of field flow fractionation (FFF). The different types of FFF are discussed including flow, sedimentation, thermal, and electrical FFF, as well as the theory of
FFF. In addition to particle size characterization, secondary measurements such as polymer molecular weight, surface characterization, and aggregation formation are also reviewed. This review makes
apparent the wide applicability of FFF to the characterization of colloidal/particulate systems.
Baalousha et al. (2006) use field-flow fractionation (FFF) coupled to multi-angle laser light scattering (MALLS) to size and characterize naturally occurring colloids. By obtaining the hydrodynamic diameter from
FFF, and the radius of gyration from MALLS, and determining the ratio of the two, one can describe the deviation of the particle from a hard-sphere colloid. The applicability of this technique was demonstrated
by studying a natural colloidal system, showing that the presence of calcium cartonate has the potential to act as a cement between particles, resulting in aggregation.
Complete Citation
von der Kammer, F., Legros, S.,
Larson, E., Loeschner, K., and
Hofmann, T. 2011. Separation
and characterization of
nanoparticles in complex food
and environmental samples by
field-flow fractionation. Trends in
Analytical Chemistry, 30(3), 425-
436.
Ulrch, A., Losert, S., Bendixen,
N., AI-Kattan, A., Hagendorfer,
H., Nowack, B., Adlhart, C.,
Ebert, J., Lattuada, M., and
Hungertuhler, K. 2012. Critical
aspects of sample handling for
direct nanoparticle analysis and
analytical challenges using
asymmetric field flow fractionation
in a multi-detector approach.
Journal of Analytical Atomic
Spectrometry, 27(7), 1 1 20-1 1 30.
Tiede, K., Boxall, A., Wang, X.,
Gore, D., Tiede, D., Baxter, M.,
David, H.,Tear, S., and Lewis, J.
2010. Application of
hydrodynamic chromatography-
ICP-MS to investigate the fate of
silver nanoparticles in activated
sludge. Journal of Analytical
Atomic Spectrometry, 25(7),
1149-1154.
Liu, R. and Lead, J. 2006. Partial
validation of cross flow
ultrafiltration by atomic force
microscopy. Analytical Chemistry,
78(23), 8105-8112.
Giddings, J. 1995. Measuring
colloidal and macromolecular
properties by FFF. Analytical
Chemistry, 67(19), 592A-598A.
Baalousha, M., Kammer, F.V.D.,
Motelica-Heino, M., Hilal, H., and
Coustumer, P. 2006. Size
fractionation and characterization
of natural colloids by flow-field
flow fractionation coupled to multi-
angle laser light scattering.
Journal of Chromatography A,
1104(1), 272-281.
Page 27
-------
Doc ID
575
576
577
578
579
580
581
Title
Detection,
separation, and
quantification of
unlabeled silica
nanoparticles in
biological media
using sedimentation
field-flow
fraction ation
Separation of Protein
Inclusion Bodies
from Escherichia
co// lysates using
Sedimentation Field-
flow Fractionation
Shape separation of
nanometer gold
particles by size-
exclusion
chromatography
Recycling size
exclusion
chromatography for
the analysis and
separation of
nanocrystalline gold
Characterization of
nanoparticulate
systems by
hydrodynamic
chromatography
Hydrodynamic
chromatography a
new approach to
particle size analysis
Measurement of
nanoparticles by light-
scattering techniques
Authors
Tadjik!, S.,
Assemi, S.,
Peering, C.,
Veranth, J., and
Miller, J.
Ratanathanawon
gs-Williams,
S.K., Raner, G.,
Ellis, Jr., W., and
Giddings, J.C.
Wei, G.-T., Liu,
F.-K., and
Wang, C.
Al-Somali, A.,
Kmeger, K.,
Falkner, J., and
Colvin, V.
Williams, A.,
Varela, E.,
Meehan, E., and
Tribe, K.
Small, H.,
Saunders, F.,
and Sole, J.
Brar, S. and
Vernia, M.
Year
2009
1997
1999
2004
2002
1976
2011
No., and Page No.
(or Year)
Journal of
Nanoparticle
Research, 11(4), 981-
988
Journal of
Microcolumn
Separation, 9(3), 233-
239
Analytical Chemistry,
71(11), 2085-2091
Analytical Chemistry,
76(19), 5903-5910
Journal of
Pharmaceutics,
242(1), 295-299
Advances in Colloid
and Interface Science,
6(4), 237-266
Trends in Analytical
Chemistry, 30(1), 4-1 7
Document
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Tadjik! et al. (2009) utilized sedimentation field-flow fractionation (Sed-FFF) to characterize silica nanoparticles extracted from rat and human endothelial cells. The silica nanoparticles were extracted via acid
digestion and analyzed using Sed-FFF, where the fraction collected at the peak maxima of the elution was further analyzed by transmission electron microscopy (TEM). Percent recoveries were also
determined for this technique. These results indicated that sedimentation FFF can be a useful technique for the sizing and characterization of extracted nanoparticles.
Ratanathanawongs-Williams et al. (1 997) studied the ability of sedimentation field-flow fractionation (Sed-FFF) to characterize myohemerythrin inclusion bodies amidst a background of growth media, soluble
proteins, and unlysed cells in E. co// cell lysates. In addition to the identification of the inclusion bodies, the presence of unlysed cells can also be determined by allowing the field to operate fora longer time.
Wei et al. (1 999) demonstrated the ability of size exclusion chromatography to separate gold nanoparticles based on size. This was achieved by using a surfactant mixture of sodium dodecyl sulfate (SDS) and
polyoxyethylene dodecanol, affecting the adsorption of the particles to the packing materials. The elution of the particles was then monitored using a diode-array detector, which produced a 3-D chromatogram.
The fractions collected at the peak maxima of elution were further characterized by transmission electron microscopy (TEM) to further validate their shape.
Al-somali et al. (2004) show that a dramatic increase in particle resolution can be achieved in the separation of gold nanoparticles by applying an alternate recycling method to size exclusion chromatography.
With alternate recycling, size resolution was increased to a point at which baseline separation between particles differing only 6A in size could be achieved. It was demonstrated that the resolution ratio of
separation increases with the square root of the cycle number, demonstrating the power of this technique to separate particles.
Williams et al. (2002) discuss the applicability of hydrodynamic chromatography (H DC) to the separation and sizing of polymers and particles. Separation is achieved through the retention of particles in a
packed column where the inter-particle channels retain smaller particles more effectively than larger particles, resulting in an elution order of large to small particles. The dynamic range of this technique allows
for the sizing of particles from the molecular size up to micron-sized materials.
Small et al. (2009) introduce hydrodynamic chromatography (HOC) as a powerful tool for sizing nanoparticle systems. In their review, the different parameters that affect retention time such as colloid size,
packing material size and ionic strength are discussed. In addition, the various properties that may affect transport such as the hydrodynamic effect, ionic strength effect and van der Waals forces are also
reviewed. Lastly, the development, calibration, and application of H DC to nanoparticle systems are discussed, showcasing its versatility in the characterization of colloidal systems.
Brar and Verma (201 1 ) review light scattering techniques as they apply to the detection and characterization of nanomaterials in food and environmental samples. The review discusses the theory and
application of dynamic light scattering (DLS) and static light scattering (SLS) and present different case studies for the analysis of nanomaterials in environmental samples, such as samples from a wastewater
treatment plant, and in food products, where materials such as nano-titanium dioxide are ubiquitous. The advantages of dynamic light scattering are the rapid analysis of the materials without the need for
calibration.
Complete Citation
Tadjik!, S., Assemi, S., Deering,
C. , Veranth, J., and Miller, J.
2009. Detection, separation, and
quantification of unlabeled silica
nanoparticles in biological media
using sedimentation field-flow
fractionation. Journal of
Nanoparticle Research, 11(4),
981-988.
Ratanathanawongs-Williams,
S.K., Raner, G., Ellis, Jr., W., and
Giddings, J.C. 1997. Separation
of Protein Inclusion Bodies from
Escherichia coli lysates using
Sedimentation Field-flow
Fractionation. Journal of
Microcolumn Separation, 9(3),
233-239.
Wei, G.-T., Liu, F.-K., and Wang,
C. 1999. Shape separation of
nanometer gold particles by size-
exclusion chromatography.
Analytical Chemistry, 71 (1 1 ),
2085-2091 .
Al-Somali, A., Krueger, K.,
Falkner, J., and Colvin, V. 2004.
Recycling size exclusion
chromatography for the analysis
and separation of nanocrystalline
gold. Analytical Chemistry,
76(19), 5903-5910.
Williams, A., Varela, E., Meehan,
E., and Tribe, K. 2002.
Characterization of
nanoparticulate systems by
hydrodynamic chromatography.
Journal of Pharmaceutics, 242(1),
295-299.
Small, H., Saunders, F., and
Sole, J. 1976. Hydrodynamic
chromatography a new approach
to particle size analysis.
Advances in Colloid and Interface
Science, 6(4), 237-266.
Brar, S. and Verma, M. 201 1 .
Measurement of nanoparticles by
light-scattering techniques.
Trends in Analytical Chemistry,
30(1), 4-17.
Page 28
-------
Doc ID
582
583
584
585
586
587
588
589
Title
Experimental
determination of the
extinction coefficient
of CdTe, CdSe, and
CdS nanocrystals
Surface plasmon
resonance sensors:
review
Evaluating
aggregation of gold
nanoparticles and
humic substances
using fluorescence
spectroscopy
Shape effects in
plasmon resonance
of individual colloidal
silver nanoparticles
Characterization of
nanomaterials by
physical methods
Characterization of
carbon nanotubes by
TEM and infrared
spectroscopy
Solid C60: a new
form of carton
Analysis of C60 and
C70fullerenes using
high-performance
liquid
urier transform
infrared
spectroscopy
Authors
Yu,W.,Qu, L,
Quo, W., and
Peng,X.
Homola, J., Yee,
S., andGauglitz,
G.
Pallem, V.,
Stretz, H., and
Wells, M.
Mock, J., Bartic,
M., Smith, D.,
Schultz, D., and
Schultz, S.
Rao, C. and
Biswas, K.
Branca, C.,
Frusteri, F.,
Magazu, V., and
Mangione, A.
Kratschmer, W.,
Lamb, L.,
Fostriopoulos,
K., and
Huffman, D.
Treubig, Jr., J.
and Brown, P.
Year
2003
1999
2009
2002
2009
2004
1990
2002
No., and Page No.
(or Year)
Chemistry of
Materials, 15(14),
2854-2860
Sensors and
Actuators B:
Chemical, 54(1), 3-15
Environmental
Science and
Technology, 43(19),
7531-7535
Journal of Chemical
Physics, 116, 6755
Annual Review of
Analytical Chemistry,
2, 435-462
Journal of Physical
Chemistry B, 108(11),
3469-3473
Nature, 347(6291),
354-358
Journal of
ChromatographyA,
960(1), 135-142
Document
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Yu et al. (2003) determined the extinction coefficients for three different semi-conducting nanomaterials (CdSe, CdTe, and CdS) establishing a relationship between the size of the nanocrystal and its extinction
coefficient. The relationship between nanocrystal size and extinction coefficient was found to fall between a square and cubic dependence. Other factors, such as surface ligands, the solvents refractive index,
photoluminescent quantum yield, temperature, and synthesis methods were found to have a minimal effect on the extinction coefficient.
Homola et al. (1999) review surface plasmon resonance technologies for the application of sensitive detection. Surface plasmon resonance is a charge density oscillation phenomenon that occurs at the
interface of two media that have dielectric constants of opposite sign, such as a metal and a dielectric. The various applications of these materials are discussed, and their utility in the sensitive detection of
chemicals (i.e., NO2) and biological contaminants are also reviewed.
Pallem et al. (2009) study the interactions between gold nanoparticles capped with different surface ligands (B-D-glucose and citrate) and humic acid. Using UV-vis and fluorescence spectroscopy, changes in
humic acid fluorescence were monitored. The mixture of glucose-capped gold nanoparticles with humic acid showed a loss in fluorescence intensity, which was interpreted as the replacement of the glucose
surface groups with humic acids. In contrast, the mixture of citrate-capped gold nanoparticles with humic acids saw an enhancement in fluorescence intensity, potentially showing an overcoating of the citrate
surface groups by humic acid, leading to an increase in transfer distance for fluorescence resonance energy transfer and subsequent enhancement of the fluorescence signal.
Mock et al. (2002) investigated the effect that shape has on the surface plasmon resonance of colloidal silver particles. It was found that changes in shape lead to different spectral responses from the different
shapes. Through careful synthesis of these materials, homogenous populations of shapes and sizes can be obtained, allowing for a suite of multi-color nanomaterials that differ only in shape. These findings
indicate these particles may be useful in biological applications.
Rao and Biswa (2009) review several physical methods for the characterization of nanomaterials such as electron microscopy, scanning probe microscopy / atomic force microscopy, x-ray and neutron
diffraction, and various x-ray scattering techniques such as x-ray photoelectron spectroscopy and energy dispersive x-ray analysis. Other techniques such as raman spectroscopy or magnetic characterization
techniques such as vibrating sample magnetometer (VSM) and superconducting quantum interference devices are also discussed. Case studies illuminating the application of these techniques to the
and two-dimensional graphene.
Branca et al. (2004) characterize industrially produced single-walled carbon nanotubes and catalytically synthesized multi-walled carbon nanotubes using transmission electron microscopy (JEM) and Fourier
transform infrared spectroscopy (FTIR). The location of FTIR peaks can be sensitive to the diameter of the CNT, allowing for accurate characterization of these materials. The FTIR results produced are in
good agreement with the TEM characterization that was also performed.
Kratschmer et al. (1 990) describe the synthesis and characterization of C60 molecules formed from evaporating graphitic electrodes in an atmosphere of helium and subsequently subjecting the resulting soot
to several extraction procedures intended to purify the material. The material was then characterized using infrared spectroscopy and x-ray diffraction. Mass spectrometry confirmed the presence of C60
molecules with only a few percent C70 molecules present.
Treubig Jr. and Brown (2002) coupled a Fourier transform infrared spectroscopy (FTIR) to high performance liquid chromatography (HPLC)forthe characterization of C60 and C70 fullerenes. No changes
were needed to modify the instrumental set-up from the typical HPLC-UV instrumental set-up, using an octadecylsilane (ODS) column with a 1:1 acetonitrile-toluene mobile phase. Online FTIR spectra were
compared to literature results from offline IR spectra for these materials, showing good agreement. The results indicate HPLC-FTIR as an effective means of separation and characterization of these materials.
Complete Citation
Yu, W., Qu, L., Quo, W., and
Peng, X. 2003. Experimental
determination of the extinction
coefficient of CdTe, CdSe, and
CdS nanocrystals. Chemistry of
Materials, 15(14), 2854-2860.
Homola, J., Yee, S., and
Gauglitz, G. 1999. Surface
plasmon resonance sensors:
review. Sensors and Actuators B:
Chemical, 54(1), 3-15.
Pallem, V., Stretz, H., and Wells,
M. 2009. Evaluating aggregation
of gold nanoparticles and humic
substances using fluorescence
spectroscopy. Environmental
Science and Technology, 43(19),
7531-7535.
Mock, J., Bartic, M., Smith, D.,
Schultz, D., and Schultz, S. 2002.
Shape effects in plasmon
resonance of individual colloidal
silver nanoparticles. Journal of
Chemical Physics, 116, 6755.
Rao, C. and Biswas, K. 2009.
Characterization of nanomaterials
by physical methods. Annual
2, 435-462.
Branca, C., Fmsteri, F., Magazu,
V., and Mangione, A. 2004.
Characterization of carton
nanotubes by TEM and infrared
spectroscopy. Journal of Physical
Chemistry B, 1 08(1 1 ), 3469-
3473.
Kratschmer, W., Lamb, L.,
Fostriopoulos, K., and Huffman,
D. 1990. Solid C60: a new form
of carton. Nature, 347(6291),
354-358.
Treubig, Jr., J. and Brown, P.
2002. Analysis of C60 and C70
fullerenes using high-performance
liquid chromatography-Fourier
transform infrared spectroscopy.
Journal of Chromatography A,
960(1), 135-142.
Page 2
-------
Doc ID
590
591
592
593
594
595
Title
Comparative
analysis of two
aqueous-colloidal
solutions of C6D
fullerene with help of
FTIR reflectance and
UV-Vis
spectroscopy
Comprehensive
study of surface
chemistry of MCM-
41 using 29Si
CP/MAS NMR,
FTIR, Pyridine-TPD,
andTGA
Surface chemistry of
gold nanoparticles
produced by laser
ablation in aqueous
media
Characterization by
27AI NMR, X-ray
Absorption
Spectroscopy, and
Density Functional
Theory Techniques
of the Species
Responsible for
Benzene
Hydrogenation in Y
Zeolite-Supported
Carburized
Molybdenum
Catalysts
Characterization of
Nanocrystalline
Nanomaterials: NMR
of Zinc Phosphate as
a Case Study
Characterization of
phosphonic acid
capped SnO2
nanoparticles
Authors
Andrievsky, G.,
Klochkov,V.,
Bordyuh, A., and
Dovbeshko, G.
Zhao,X.,Lu,G.,
Whittaker,A.,
Millar, G., and
Zhu, H.
Sylvestre,J.-P.,
Poulin.S.,
Kabashin, A.,
Sacher, E.,
Meunier, M., and
Luong, J.
Rocha, A.S., da
Silva, V., Eon,
J., Menezes, S.,
Faro, Jr., A., and
Rocha, A.B.
Roming, M.,
Feldmann, C.,
Avadhut, Y., and
Schmedt auf der
Giinne, J.
Holland, G.,
Sharma, R.,
Agola, J., Amin,
S., Solomon, V.,
Singh,P.,Buttry,
D., and Yarger,
J.
Year
2002
1997
2004
2006
2008
2007
Journal Title, Vol.
No., and Page No.
(or Year)
Chemical Physics
Letters, 364(1), 8-17
Journal of Physical
Chemistry B, 101(33),
6525-6531
Journal of Physical
Chemistry B, 108(43),
16864-16869
Journal of Physical
Chemistry B, 110(32),
15803-15811
Chemistry of
Materials, 20(18),
5787-5795
Chemistry of
Materials, 19(10),
2519-2526
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Andrievsky et al. (2002) characterized two fullerene-water colloidal systems using several analytical techniques, specifically surface-enhanced infrared absorption (SEIRA) in FTIR reflectance mode. This
technique revealed vibrational bands in the 400-900cm"1 range, which are forbidden in infrared spectra. The results showed that the molecular-colloidal system of C60 shows isolated C60 molecules in a
hydrated state, with clusters of these C60 molecules.
Zhao et al. (1 997) used several techniques to characterize a sample of a mesoporous MCM-41 material. Spectroscopic techniques revealed the presence of three silanol groups (single, hydrogen-bonded, and
geminal groups). The number of silanol groups per area can be determined using silicon-29 magic angle spinning nuclear magnetic resonance. All silanol groups were shown to be active sites for pyridine
adsorption, but possessed different desorption energy values. It was also determined that the hydrogen-bound silanol groups can be removed or transformed to geminal silanol groups through heat treatment.
Sylvestre et al. (2004) synthesized gold nanoparticles through the ablation of a gold rod with a Ti/sapphire femtosecond laser. The particles produced were monodispersed and highly reactive due to partial
oxidation of the particle surface by oxygen present in the solution. As a result, anions greatly affected the net surface charge of the particles produced, allowing for strong electrostatic repulsion between
particles, and subsequently small particle growth. These results indicate that the size of the particles can be controlled through the use of different salts such as potassium chloride, sodium chloride, and sodium
hydroxide.
Rocha et al. (2006) investigated the capability and mechanism of benzene hydrogenation of three different carturized molybdenum catalysts that had been prepared from three different precursors (adsorption
of molybdenum hexacartonyl (5% and 1 0% Mo respectively) or impregnation of the aluminum substrate by aqueous ammonium heptamolybdate (5% Mo). Though each sample contained the carburized
molybdenum catalyst, the activity of each catalyst toward benzene hydrogenation differed. Those catalysts with the most initial activity showed the least stability and vice versa. The structure and activity of
these catalysts were studied using various spectroscopic techniques and were also described via density functional theory.
Roming et al. (2008) characterized zinc phosphate nanoparticles prepared through a polyol-mediated synthesis method, producing uniform, non-crystalline 20-nm particles. Various techniques were used to
size and characterize these particles including x-ray diffraction, TEM, SEM, and BET. 1H, 13C, and 31P magic angle spinning nuclear magnetic resonance were also used to characterize these nanomaterials. In
particular, 31P(1H) rotational echo double resonance experiments were used to differentiate between particles of homogenous and core-shell composition.
Holland et al. (2007) synthesized and characterized phosphonic acid capped SnO2 nanoparticles that were either water-soluble when capped with 2-carboxyethanephosphonic acid (CEPA), or water-insoluble
when capped with phenylphosphonic acid (PPA). Analysis by 1H NMR revealed an absence of acidic protons indicative of a P-O-Sn linkage between the ligand and the nanoparticle surface. The results of this
study suggest a bi- and/or tri-dentate bonding configuration of the surface ligand to the tin oxide nanoparticle surface.
Complete Citation
Andrievsky, G., Klochkov, V.,
Bordyuh, A., and Dovbeshko, G.
2002. Comparative analysis of
two aqueous-colloidal solutions of
C60 fullerene with help of FTIR
reflectance and UV-Vis
spectroscopy. Chemical Physics
Letters, 364(1), 8-17.
Zhao,X.,Lu, G.,Whittaker,A.,
Millar, G., and Zhu, H. 1997.
Comprehensive study of surface
chemistry of MCM-41 using 29Si
CP/MAS NMR, FTIR, Pyridine-
TPD, and TGA. Journal of
Physical Chemistry B, 101(33),
6525-6531 .
Sylvestre, J.-P., Poulin, S.,
Kabashin, A., Sacher, E.,
Meunier, M., and Luong, J. 2004.
Surface chemistry of gold
nanoparticles produced by laser
ablation in aqueous media.
Journal of Physical Chemistry B,
108(43), 16864-16869.
Rocha, A.S., da Silva, V., Eon, J.,
Menezes, S., Faro, Jr., A., and
Rocha, A.B. 2006.
Characterization by 27AI NMR, X-
ray Absorption Spectroscopy, and
Density Functional Theory
Techniques of the Species
Responsible for Benzene
Hydrogenation in YZeolite-
Supported Carburized
Molybdenum Catalysts. Journal of
Physical Chemist ryB, 110(32),
15803-15811.
Roming, M., Feldmann, C.,
Avadhut, Y., and Schmedt auf der
Gunne, J. 2008. Characterization
of Nanocrystalline Nanomaterials:
N MR of Zinc Phosphate as a
Case Study. Chemistry of
Materials, 20(18), 5787-5795.
Holland, G., Sharma, R., Agola,
J., Amin, S., Solomon, V., Singh,
P., Buttry, D., and Yarger, J.
2007. Characterization of
phosphonic acid capped SnO2
nanoparticles. Chemistry of
Materials, 19(10), 2519-2526.
Page 30
-------
Doc ID
596
597
598
599
600
601
602
Title
High resolution NMR
of water absorbed in
single-wall carton
nanotubes
Analysis of
environmental
particles by atomic
force microscopy,
scanning and
transmission electron
microscopy
New approach to
inter-technique
comparisons for
nanoparticle size
measurements;
using atomic force
microscopy,
nanoparticle tracking
analysis and
dynamic light
scattering
Determination of size
and concentration of
gold nanoparticles
from UV-vis spectra
Counting of particles
in aqueous solutions
by laser-induced
photoacoustic
breakdown detection
Sensors as tools for
quantitation,
nontoxicity and
nanomonitoring
assessment of
engineered
nanomaterials
Determination of size
and concentration of
gold nanoparticles
from extinction
spectra
Authors
Sekhaneh, W.,
Kotecha, M.,
Dettlaff-
Weglikowska,
U., and Veeman,
W.
Mavrocordatos,
D., Prank, W.,
and Boiler, M.
Boyd, R.,
Pichaimuthu, S.,
and Cuenat, A.
Haiss,W.,
Thanh, K.,
Averyard, J., and
Fernig, D.
Scherbaum, F.,
Knopp, R., and
Kim, J.
Sadik, O.,Zhou,
A., Kikandi, S.,
Du, N.,Wang,
Q., and Vamer,
K.
Khlebstov, N.
Year
2006
2004
2011
2007
1996
2009
2008
Journal Title, Vol.
No., and Page No.
(or Year)
Chemical Physics
Letters, 428(1), 143-
147
Water Sciences
Technology, 50(12), 9-
18
Colloids and Surfaces
A: Physicochemical
and Engineering
Aspects, 387(1), 35-
42
Analytical Chemistry,
79(11), 421 5-4221
Applied Physics B,
63(3), 299-306
Journal of
Environmental
Monitoring, 11(10),
1782-1800
Analytical Chemistry,
80(17), 6620-6625
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Sekhaneh et al. (2006) utilized 1H magic angle spinning nuclear magnetic resonance spectroscopy to study the absorption of water into single-walled carbon nanotubes that had been synthesized via an iron
catalyst. Using MAS NMR, two chemical shift regions were determined for water protons. Using temperature-controlled experiments, it was determined that these two regions represent water absorbed inside
and outside the carbon nanotubes.
Mavrocordatos, Pronk and Boiler (2004) review available microscopy techniques for the analysis of naturally occurring nanomaterials, and their applicability to studying how environmental processes can affect
these particles. Atomic force microscopy (AFM) has the ability to analyze these particles in situ , allowing for the direct observation of different transformation processes such as dissolution and aggregation. By
coupling transmission electron microscopy to electron energy loss spectrometry, one can perform sensitive chemical analysis, allowing for the determination of surface adsorption of different elements. Though
some of these techniques, particularly the electron microscopy methods that require vacuum, can introduce artifacts, these microscopy methods can be used to understand nanoparticle behavior beyond size
characterization.
Boyd et al. (201 1 ) compared various sizing techniques including single particle techniques (transmission electron microscopy and atomic force microscopy) as well as ensemble techniques (dynamic light
scattering and nanoparticle tracking analysis). There is currently no standard sizing technique for size measurements, so this paper compares the different information that can be obtained from these sizing
measurements.
Haiss et al. (2007) synthesized and characterized gold nanoparticles (5 nm to 1 00 nm in size) using transmission electron microscopy and UV-vis absorbance. Good agreement was found between
instrumental measurements and multipole scattering theory describing the size of the nanomaterials. These results show that size and concentration of the gold nanoparticles can be determined by UV-vis.
Schertaum et al. (1 996) demonstrates the ability of laser-induced photoacoustic breakdown detection as a technique for the detection of nanoparticles in aqueous media. The principles and application of this
technique are reviewed and applied to the detection of polystyrene latex, alumina, and thoriasol nanoparticles.
Sadik et al. (2009) review the application of nano-enabled sensors to the detection of nanomaterials and other contaminants in the environment. Nanosensors are typically divided into two broad classes: (i)
nanotechnology-enabled sensors that are either nanomaterials themselves, or contain nanosized components, and (ii) nanoproperty quantifiable sensors, those that measure nanoscale properties and
phenomena. As a great deal of literature is present on category I sensors, this review instead focuses on category II sensors, providing case studies in the detection of fullerenes and quantum dots.
Khlebstov (2008) discusses how size and concentration of gold nanoparticles can be determined from the extinction coefficient, which generally agrees with theoretical Mie theory calculations. However,
noticeable deviations are found when the nanoparticles deviate from a monodispersed spherical shape. These results indicate that there are limitations to the applicability of using the extinction spectra for the
characterization of nanomaterials.
Complete Citation
Sekhaneh, W., Kotecha, M.,
Dettlaff-Weglikowska, U., and
Veeman, W. 2006. High
resolution NMR of water
absorbed in single-wall carbon
nanotubes. Chemical Physics
Letters, 428(1), 143-147.
Mavrocordatos, D., Pronk, W.,
and Boiler, M. 2004. Analysis of
environmental particles by atomic
force microscopy, scanning and
transmission electron microscopy.
Water Science & Technology,
50(12), 9-18.
Boyd, R., Pichaimuthu, S., and
Cuenat, A. 201 1 . New approach
to inter-technique comparisons for
nanoparticle size measurements;
using atomic force microscopy,
nanoparticle tracking analysis and
dynamic light scattering. Colloids
and Surfaces A: Physicochemical
and Engineering Aspects, 387(1),
35-42.
Haiss, W., Thanh, K., Averyard,
J.,andFemig, D. 2007.
Determination of size and
concentration of gold
nanoparticles from UV-vis
spectra. Analytical Chemistry,
79(11), 421 5-4221.
Scherbaum, F., Knopp, R., and
Kim, J. 1996. Counting of
particles in aqueous solutions by
laser-induced photoacoustic
breakdown detection. Applied
Physics B, 63(3), 299-306.
Sadik, O., Zhou, A., Kikandi, S.,
Du, N., Wang, Q., and Varner, K.
2009. Sensors as tools for
quantitation, nontoxicity and
nanomonitoring assessment of
engineered nanomaterials.
Journal of Environmental
Monitoring, 11(10), 1782-1800.
Khlebstov, N. 2008.
Determination of size and
concentration of gold
nanoparticles from extinction
spectra. Analytical Chemistry,
80(17), 6620-6625.
Page 31
-------
Doc ID
603
604
605
606
607
Title
Extinction coefficient
of gold nanoparticles
with different sizes
and different capping
ligands
Characterization of
silver nanoparticles
using flow-field flow
fraction ation
interfaced to
inductively coupled
plasma mass
spectrometry
Overcoming
challenges in
analysis of
polydisperse metal-
containing
nanoparticles by
single particle
inductively coupled
plasma mass
spectrometry
Nanomaterialsfor
environmental
studies:
classification,
reference material
issues, and
strategies for physico
chemical
characterization
Characterizing
manufactured
nanoparticles in the
environment:
multimethod
deterni in ation of
particle sizes
Authors
Liu,X.,Atwater,
M.,Wang,J.,
andHuo, Q.
Poda.A.,
Bednar,A.,
Kennedy, A.,
Hull, M., Mitrano,
D., Ranville, J.,
and Steevens, J.
Reed, R.,
Higgins, C.,
Westerhoff, P.,
Tadjik!, S., and
Ranville, J.
Stone, V.,
Nowack, B.,
Baun, A., van
den Brink, N.,
von der
Kammer, F.,
Dusinska, M.,
Handy, R.,
Hankin.S.,
Hassellov, M.,
Joner, E., and
Fernandes, T.
Domingos, R.,
Baalousha, M.,
Ju-Nam, Y.,
Reid, M.,
Tufenkji, N.,
Lead, J.,
Leppard, G., and
Wilkinson, K.
Year
2007
2011
2012
2010
2009
Journal Title, Vol.
No., and Page No.
(or Year)
Colloids and Surfaces
B: Biointerfaces,
58(1), 3-7
Journal of
ChromatographyA,
121 8(27), 421 9-4225
Journal of Analytical
Atomic Spectrometry,
27(7), 1093-1100
Science of the Total
Environment, 408(7),
1745-1754
Environmental
Science and
Technology, 43(19),
7277-7284
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Liu et al. (2007) studied the extinction coefficients of gold nanoparticles of varying sizes capped with one of three capping agents (citrate, oleyamide, or decanethiol). The particles were characterized using high
resolution transmission electron microscopy (HRTEM) and UV-visible absorption spectroscopy. It was found that the extinction spectra of the nanoparticles is independent of the capping agent and the solvent
these nanomaterials are measured in, allowing for a linear relationship between extinction coefficient and diameter of the nanoparticles.
Poda et al. (2011) utilized flow-field flow fractionation coupled to ICP-MS to characterize silver nanoparticles extracted from Lumbriculus variegatus. The nanoparticles were also characterized using
transmission electron microscopy (TEM) and the hydrodynamic diameter results from FFF were compared to measurements obtained from dynamic light scattering (DLS). Silver nanoparticles extracted from
L. variegatus show an increase in primary particle size from 31 nm to 46 nm, indicating a change in particle size as a result of exposure. Overall, FFF-ICP-MS is a sensitive and selective method for the
characterization of nanomaterials in biological samples.
Reed et al. (201 2) used single particle inductively coupled plasma mass spectrometry (splCP-MS) to characterize a variety of nanomaterials such as silver nanowires, titanium dioxide, and cerium oxide
nanoparticles. Zinc oxide nanoparticle analysis was also attempted, but dissolution was too rapid for accurate analysis. This technique allows for sensitive and accurate characterization of engineered
nanomaterials, but can be hindered by a large concentration of particles, resulting in coincidence. Coincidence is reduced and characterization is optimized when the percentage of particle readings is
approximately 2.5%. Particle sizes determined from splCP-MS were compared to Sedimentation-FFF to validate accurate size measurement.
Stone et al. (2010) sought to address several questions regarding nanomaterials in the environment, including the determination of which nanomaterial properties are relevant to environmental studies, the
development of reference standards for environmental studies, and the classification of nanomaterials with respect to their environmental impact. The workshop determined that properties such as aggregation,
size, dissolution, surface charge, surface area and surface composition might be the most important properties with relevance to environmental studies, assuming chemical composition is known. Some
possible reference materials are titanium dioxide nanoparticles, polystyrene beads labeled with fluorescent dyes, and silver nanoparticles, though more work is required to standardize these materials for
environmental use. Though no consensus was reached on an appropriate classification system, it was generally accepted that a classification scheme based on chemistry is a likely starting point.
Domingos et al. (2009) compared several sizing techniques for the characterization of nanomaterials. Techniques such as transmission electron microscopy, fluorescence correlation spectroscopy, nanoparticle
tracking analysis, flow field-flow fractionation, atomic force microscopy, and dynamic light scattering are all reviewed and discussed. It was determined that no single technique is most effective at sizing and
characterizing nanomaterials, as each has its own inherent advantages and limitations. The techniques that are most commonly used (DLS and TEM) also happen to introduce the most artifacts during
analysis.
Complete Citation
Liu, X., Atwater, M., Wang, J.,
andHuo, Q. 2007. Extinction
coefficient of gold nanoparticles
with different sizes and different
capping ligands. Colloids and
Surfaces B: Biointerfaces, 58(1),
3-7.
Poda, A., Bednar, A., Kennedy,
A., Hull, M., Mitrano, D., Ranville,
J., and Steevens, J. 2011.
Characterization of silver
nanoparticles using flow-field flow
fractionation interfaced to
inductively coupled plasma mass
spectrometry. Journal of
ChromatographyA, 1218(27),
4219-4225.
Reed, R., Higgins, C.,
Westerhoff, P., Tadjik!, S., and
Ranville, J. 2012. Overcoming
challenges in analysis of
polydisperse metal-containing
nanoparticles by single particle
inductively coupled plasma mass
spectrometry. Journal of
Analytical Atomic Spectrometry,
27(7), 1093-1100.
Stone, V., Nowack, B., Baun, A.,
van den Brink, N., von der
Kammer, F., Dusinska, M.,
Handy, R., Hankin, S., Hassellov,
M., Joner, E., and Fernandes, T.
2010. Nanomaterialsfor
environmental studies:
classification, reference material
issues, and strategies for physico-
chemical characterization.
Science of the Total Environment,
408(7), 1745-1754.
Domingos, R., Baalousha, M., Ju-
Nam, Y., Reid, M., Tufenkji, N.,
Lead, J., Leppard, G., and
Wilkinson, K. 2009.
Characterizing manufactured
nanoparticles in the environment:
multimethod determination of
particle sizes. Environmental
Science and Technology, 43(19),
7277-7284.
Page 32
-------
Doc ID
608
609
610
611
612
Title
Comparison of
centrifugation and
filtration techniques
for the size
fractionation of
colloidal material in
soil suspensions
using sedimentation
field-flow
fractionation
Cloud point
extraction as an
advantageous
preconcentration
approach for
analysis of trace
silver nanoparticles
in environmental
waters
Physicochemical and
microbial
preservation of
colloid characteristics
of natural water
samples I:
Experimental
conditions
Imaging of
engineered
nanoparticles and
their aggregates
under fully liquid
conditions in
environmental
matrices
Selective
identification,
characterization and
determination of
dissolved silver (I)
and silver
nanoparticles based
on single particle
detection by
inductively coupled
plasma mass
spectrometry
Authors
Gimbert, L,
Haygarth, P.,
Beckett, R., and
Worsfold, P.
Liu, J.-F., Chao,
J.-B.,Liu,R.,
Tan,Z.-Q.,Yin-
Y.-G.,Wu,Y.,
and Jiang, G.-B.
Chen, Y.-W. and
Buffle, J.
Tiede, K., Tear,
S., David, H.,
and Boxall, A.
Laborda, F.,
Jimenez-
Lamana, J.,
Bolea, E., and
Castillo, J.
Year
2005
2009
1996
2009
2011
Journal Title, Vol.
No., and Page No.
(or Year)
Environmental
Science and
Technology, 39(6),
1731-1735
Analytical Chemistry,
81(15), 6496-6502
Water Research,
30(9), 2178-2184
Water Research,
43(13), 3335-3343
Journal of Analytical
Atomic Spectrometry,
26(7), 1362-1371
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Gimbert et al. (2005) used sedimentation field-flow fractionation (SdFFF) with a UV detector to compare both centrifugation and filtration for the size fractionation of a clay soil suspension. The results show that
membrane filtration underestimated the total mass of the particulate matter compared to centrifugation. This may have implication for accurately determining the colloidal and soluble fractions of naturally
occurring colloids.
Liu et al. (2009) demonstrate the ability of cloud point extraction with Triton X-1 14 to preconcentrate silver nanoparticles while still preserving their sizes and morphology. The most efficient extraction occurs on
the zero point charge pH and can be enhanced through the addition of salts such as sodium nitrate and sodium thiosulfate. The concentrated silver nanoparticles were characterized by electron microscopy and
UV-vis absorbance to demonstrate the preservation of size and shape. This technique allows for the concentration of nanoparticles found in environmental samples, particularly as humic acid does not affect
the extraction efficiency of the nanoparticles.
Chen et al. (1 996) examine the difficulties that may arise in the analysis of colloids in environmental samples. Particular attention is paid to the development of sample handling procedures that minimize sample
perturbation such that accurate analysis can be performed while minimizing artifacts. The different contaminants that can arise are also described; these include artifacts introduced by filtration membranes,
vessel and tubing walls, and atmospheric contaminants. Appropriate stabilizing compounds, apparatus, and experimental conditions for accurate analysis of environmental colloids are also discussed.
Tiede et al. (2009) characterize nanomaterials using WetSEM technology, which allows for in situ imaging of the nanomaterials by scanning electron microscopy. By using a capsule that uses a membrane
coating to attract the sample to the walls of the capsule, images can be obtained under fully liquid conditions. The results are apparent when using energy dispersive x-ray spectroscopy (EDS) for elemental
determination, as conventional SEM is subject to several of the other interferences present in the sample, whereas WetSEM is able to accurately determine the composition of the nanomaterial.
Laborda et al. (2011) present single particle inductively coupled plasma mass spectrometry (splCP-MS) as a selective and sensitive technique for the analysis of engineered nanoparticles. The use of ICP-MS
allows for mass detection limits at environmentally relevant concentrations of 10~9 g/L, and the method can detect as few as IxlO"4 particles/ L. The various means by which one may fit the data (i.e., Poisson,
lognormal) are also discussed, as are suggestions on how this technique can be improved.
Complete Citation
Gimbert, L., Haygarth, P.,
Beckett, R., and Worsfold, P.
2005. Comparison of
centrifugation and filtration
techniques for the size
fractionation of colloidal material
in soil suspensions using
sedimentation field-flow
fractionation. Environmental
Science and Technology, 39(6),
1731-1735.
Liu, J.-F., Chao, J.-B., Liu, R.,
Tan,Z.-Q.,Yin-Y.-G.,Wu,Y.,
and Jiang, G.-B. 2009. Cloud
point extraction as an
advantageous preconcentration
approach for analysis of trace
silver nanoparticles in
environmental waters. Analytical
Chemistry, 81(15), 6496-6502.
Chen, Y.-W. and Buffle, J. 1996.
Physicochemical and microbial
preservation of colloid
characteristics of natural water
samples I: Experimental
conditions. Water Research,
30(9), 2178-2184.
Tiede, K., Tear, S., David, H.,
and Boxall, A. 2009. Imaging of
engineered nanoparticles and
their aggregates under fully liquid
conditions in environmental
matrices. Water Research,
43(13), 3335-3343.
Laborda, F., Jimenez-Lamana, J.,
Bolea, E., and Castillo, J. 2011.
Selective identification,
characterization and
determination of dissolved silver
(I) and silver nanoparticles based
on single particle detection by
inductively coupled plasma mass
spectrometry. Journal of
Analytical Atomic Spectrometry,
26(7), 1362-1371.
Page 33
-------
Doc ID
613
614
615
616
617
Title
Synthesis of
isotopically modified
ZnO nanoparticles
nontoxicity tracers
Isotopically modified
nanoparticles for
enhanced detection
in bioaccumulation
studies
Evaluation of Stable
Isotope Tracing for
ZnO Nanomaterials--
New Constraints
from High Precision
Isotope Analyses
and Modeling
Parameter
Identifiability in
Application of Soft
Particle
Electrokinetic Theory
to Determine
Polymer and
Polyelectrolyte
Coating Thicknesses
on Colloids
Fate of Zinc Oxide
and Silver
Nanoparticles in a
Pilot Wastewater
Treatment Plant and
in Processed
Biosolids
Authors
Dybowska, A.,
Croteau, M.-N.,
Misra, S.,
Luoma, S.,
Christian, P.,
O'Brien, P., and
Valsami-Jones,
E.
Misra, S.,
Dybowska, A.,
Berhanu, D.,
Croteau, M.,
Luoma, S.,
Boccaccini, A.,
and Valsami-
Jones, E.
Larner, F. and
Rehkamper, M.
Louie, S.;
Pehnart,T.;
Small, M.;Tilton,
R. and Lowry, G.
Ma, R.; Levard,
C.; Judy, J.;
Unrine, J.;
Durenkamp, M.;
Martin, B.;
Jefferson, B.
and Lowry, G.
Year
2011
2011
2012
2012
2014
Journal Title, Vol.
No., and Page No.
(or Year)
Environmental
Pollution, 159(1), 266-
273
Environmental
Science and
Technology, 46(2),
1216-1222
Environmental
Science and
Technology, 46(7),
4149-4158
Langmuir, 28(28),
10334-10347
Environmental
Science &
Technology, 48(1),
104-112
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
Journal
Article Summary
Dybowska et al. (201 1 ) evaluate the use of a stable isotope zinc oxide nanoparticle tracer to further understand the uptake and behavior of nanoparticles. For this study S7ZnO nanoparticles were exposed to L.
stagnalis via amended diatoms. Using this tracer, the exposure concentration was found to be in the lower concentration range (below 15 (jg/g), which is avast improvement over the naturally occurring zinc
exposure concentration of 5000 |jg/g. The use of these isotopically modified tracers may provide an option to study environmentally relevant exposure concentrations.
Misra et al. (201 1 ) synthesized isotopically enriched copper oxide nanoparticles (65Cu) for use in ecotoxicological studies. The copper oxide nanomaterials were synthesized as rods (7x40 nm) and spheres (7
nm) and were characterized by transmission electron microscopy, atomic force microscopy, and zeta potentiometry. The use of a stable isotope tracer allowed for determining exposure concentration close to
that of the ambient concentration in freshwater systems (0.2-30 (jg/L), whereas the detection of newly accumulated 63Cu is problematic even at exposure concentrations greater than 1 mg/L.
Lamer et al. (201 2) evaluate the use of stable zinc isotopes for the study of nanomaterial toxicology and behavior. Initial experiments investigated the ratio of zinc isotopes in commercially available zinc oxide
nanoparticles compared to the natural abundance and found no discernible difference. Consequently, inexpensive isotopically modified zinc oxide nanomaterials were used. The results indicate that an
extremely low concentration of these modified nanoparticles (5 ng/g) can be identified amidst aZn background (100 (jg/g). In addition, the use of these isotopically modified materials allows for differentiation
between nanoparticles and their dissolved constituents.
Louie et al. (2012) undergo an investigation of the parameters necessary to correctly apply soft particle electrokinetic theory in determining the thickness of a polymer/polyelectrolyte coating on a particle.
Specifically, this paper compares fitted parameters (layer charge density, layer thickness, and permeability) to analytical and numerical electrokinetic models. Different particle sizes and particle coating types
were investigated, showing good agreement with the analytical model for particle having thin, lower-charged coatings, opposed to a greater uncertainty in particle with thick, highly-charged coatings.
Ma et al. (2014) utilized x-ray absorption spectroscopy to determine the chemical speciation of silver and zinc in sludge produced from a pilot wastewater treatment plant. Sources of silver and zinc included
PVP-coated 50nm silver nanoparticles, 30nm ZnO nanoparticles and their respective dissolved salt counterparts. In addition to examining the effects of activated sludge, additional treatment processes such as
lime and heat treatment were also investigated. It was determined that regardless of silver ion origin, all silver was converted to silver sulfide (AgS2). Zinc on the other hand was converted to three different zinc
species (zinc sulfide, zinc phosphate, and zinc associated with iron oxy/hydroxides). The ratio of these three zinc species depend on the redox state and water content available in the biosolids. Regardless of
the Zn and Ag input (nanoparticulate or dissolved) all ions were transformed into similar chemical forms in the waste water treatment process.
Complete Citation
Dybowska, A., Croteau, M.-N.,
Misra, S., Berhanu, D., Luoma,
S., Christian, P., O'Brien, P., and
Synthesis of isotopically modified
ZnO nanoparticles and their
potential as nontoxicity tracers.
Environmental Pollution, 159(1),
266-273.
Misra, S., Dybowska, A.,
Berhanu, D., Croteau, M., Luoma,
S., Boccaccini, A., and Valsami-
Jones, E. 2011. Isotopically
modified nanoparticles for
enhanced detection in
bioaccumulation studies.
Environmental Science and
Technology, 46(2), 1216-1222.
Larner, F. and Rehkamper, M.
2012. Evaluation of Stable
Isotope Tracing for ZnO
Nanomaterials-New Constraints
from High Precision Isotope
Analyses and Modeling.
Environmental Science and
Technology, 46(7), 4149^158.
Louie, S.; Pehnart, T.; Small, M.;
Tilton, R. and Lowry, G. 2012.
Parameter Identifiability in
Application of Soft Particle
Electrokinetic Theory to
Determine Polymer and
Polyelectrolyte Coating
Thicknesses on Colloids.
Langmuir, 28(28), 10334-10347.
Ma, R.; Levard, C.; Judy, J.;
Unrine, J.; Durenkamp, M.;
Martin, B.; Jefferson, B. and
Lowry, G. 2014. Fate of Zinc
Oxide and Silver Nanoparticles in
a Pilot Wastewater Treatment
Plant and in Processed Biosolids.
Environmental Science &
Technology, 48(1 ), 1 04-1 1 2.
Page 34
-------
Doc ID
618
619
620
621
622
623
Title
CuO andZnO
Nanoparticles:
Phytoxicity, Metal
Speciation, and
Induction of
Oxidative Stress in
Sand-Grown Wheat
Synchroton Micro-
XRF and Micro-
XANES
Confirmation of the
Uptake and
Translocation of
TiO2 Nanoparticles
in Cucumber
(Cucumis sativus)
Plants
International
Perspective on
Government
Nanotechnology
Funding in 2005
Gold Nanoparticles:
Assembly,
Supramolecular
Chemistry, Quantum-
size-related
Properties, and
Applications Toward
Biology, Catalysis,
and Nanotechnology
A Review of the
Antibacterial Effects
of Silver
Nanomaterials and
Potential Implications
for Human Health
and the Environment
Zero-valent Iron
Nanoparticles for
Abatement of
Environmental
Pollutants: Materials
and Engineering
Aspects
Authors
Dimkpa, C.;
McLean, J.;
Latta, D.;
Manangon, E.;
Britt, D.;
Johnson, W.;
Boyanov, M. and
Anderson, A.
Sen/in, A.;
Castillo-Michel,
H.; Hemandez-
Viezcas, J.;
Dias, B.; Peralta-
Videa, J. and
Gardea-
Torresdey, J.
Roco, M.
Daniel, M.-C.
and Astmc, D.
Marambio-
Jones, C. and
Hoek, E.
arid Zhang, W.-
X.
Year
2012
2012
2005
2004
2010
2006
Journal Title, Vol.
No., and Page No.
(or Year)
Journal of
Nanoparticle
Research, 14(9), 1-15
Environmental
Science and
Technology, 46(14),
7637-7643
Journal of
Nanoparticle
Research, 7(6), 707-
712
Chemical Reviews,
104(1), 293-346
Journal of
Nanoparticle
Research, 12(5), 1531
1551
Critical Reviews in
Solid State and
Materials Sciences,
31(4), 111-122
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Dimkpa et al. (201 2) studied the impact of commercial copper oxide and zinc oxide nanoparticles on wheat plants (Triticum aestivum) grown in sand. Analytical techniques such dynamic light scattering and
atomic force microscopy were used to investigate the aggregation of these materials, as well as the transformation ofZnO particles into elongated rods in the aqueous phase of the sand. Bulk equivalents of
copper and zinc added to the sand matrix were also investigated and showed significant reduction of root growth. Of the nanomaterials, only CuO impaired shoot growth, yet these growth reductions were less
than that of the bulk materials. Bioaccumulation of these materials in the form of copper(l)-sulfur and zinc-phosphate complexes were detected in the shoots of plants that had been exposed to the
nanomaterials. Oxidative stress was also present in nanoparticle treated plants, indicating increased production of reactive oxygen species.
Sen/in et al. (2012) evaluated the uptake and impact of titanium dioxide nanoparticles on hydroponically grown cucumber (Cucumis sativus) plants. Concentrations ofTiO2 nanoparticles ranging from 0 to
4000ppm were applied to seven day old seedlings. The plants were then harvested and the sizes of the roots and shoots were measured, and micro-XRF and micro-XAS were used to track the presence and
speciation of TiO2 within the plant. All TiO2 concentration significantly increased root length, and micro-XRF indicated the transport of Ti to the leaf trichomes. Micro-XANES indicated that the titanium present
in the plant tissues was in the form of TiO2, as opposed to another biotransformed chemical species.
Roco (2005) details the extent of government nanotechnology funding and its implications for the continued research and development of nanotechnology. The findings indicate the significant growth
(approximately nine-fold) of investment in nanotechnology research and development in the 8 years prior to 2005. This analysis was performed using the National Nanotechnology Initiative definition of
nanotechnology, using information ascertained from managers of nanotechnology research and development in the various countries.
Daniel and Astmc (2004) extensively reviewed various information pertaining to gold nanoparticles. Topics covered included synthesis, properties, and applications to catalysis, biomedical, and nano-
electronics. The various structures and properties of gold nanomaterials inform the variety of applications they are used for, and ensure their continued use in research and industry.
Marambio-Jones and Hoek (201 0) review the antibacterial effects of silver nanomaterials, as well as their potential toxicity to higher organisms and humans. Several nanomaterials are discussed including
nanoparticles, polymer composites, and activated carbon materials. Though some bactericidal effects are nanoparticle-specific, the main toxic action for most materials is a result of silver ion release which
results in potential increased membrane permeability, disruption of DNA replication, and other biological effects. The various factors governing particle characteristics (size, shape, capping agents) are also
discussed within the context of their stability and bioavailability.
Li et al. (2006) reviewed various aspects of zero-valent iron nanoparticles, specifically their applicability to the remediation of environmental pollutants. Topics covered include the synthesis and characterization
of these materials in addition to their application toward organic contaminants (i.e. TCE) and inorganic contaminants (i.e. uranium, arsenic). The fate and transport of these materials are also discussed within
the context of their environmental impact.
Complete Citation
Dimkpa, C.; McLean, J.; Latta,
D.; Manangon, E.; Britt, D.;
Johnson, W.; Boyanov, M. and
Anderson, A. 2012. CuO and
ZnO Nanoparticles: Phytoxicity,
Metal Speciation, and Induction of
Oxidative Stress in Sand-Grown
Wheat. Journal of Nanoparticle
Research, 14(9), 1-15.
Sen/in, A.; Castillo-Michel, H.;
Hernandez- Viezcas, J.; Dias, B.;
Peralta-Videa, J. and Gardea-
Torresdey, J. 2012. Synchroton
Micro-XRF and Micro-XANES
Confirmation of the Uptake and
Translocation of TiO2
Nanoparticles in Cucumber
(Cucumis sativus) Plants.
Environmental Science and
Technology, 46(14), 7637-7643.
Roco, M. 2005. International
Perspective on Government
Nanotechnology Funding in 2005.
Journal of Nanoparticle
Research, 7(6), 707-712.
Daniel, M.-C. and Astmc, D.
2004. Gold Nanoparticles:
Assembly, Supramolecular
Chemistry, Quantum-size-related
Properties, and Applications
Toward Biology, Catalysis, and
Nanotechnology. Chemical
Reviews, 104(1), 293-346.
Marambio-Jones, C. and Hoek,
E.2010.AReviewofthe
Antibacterial Effects of Silver
Nanomaterials and Potential
Implications for Human Health
and the Environment. Journal of
Nanoparticle Research, 12(5),
1531-1551.
Li,X.-Q.;Ellit, D. and Zhang, W.-
X. 2006. Zero-valent Iron
Nanoparticles for Abatement of
Environmental Pollutants:
Materials and Engineering
Aspects. Critical Reviews in Solid
State and Materials Sciences,
31(4), 111-122.
Page 35
-------
Doc ID
624
625
626
627
628
629
630
631
Title
Slurry Compositions
and Method for the
Chemical-
Mechanical Polishing
of Copper and
Copper Alloys
Titanium Dioxide and
Zinc Oxide
Nanoparticles in
Sunscreens: Focus
on their Safety and
Effectiveness
Experimental
Investigations on the
Effects of Cerium
Oxide Nanoparticle
Fuel Additives on
Biodiesel
Luminescent
Quantum Dots for
Multiplexed
Biological Detection
and Imaging
Carton Nanotubes-
The Route Toward
Applications
Nanomaterialsfor
Hydrogen Storage
Applications: A
Review
Dendrimers as
Therapeutic Agents:
A Systematic
Review
Turkevich Method for
Gold Nanoparticle
Synthesis Revisited
Authors
Mahulikar, D.;
Mravic, B.;
Pasqualoni, A.
Smijs, T. and
Pavel, S.
Sajith, V.;
Sobhan, C. and
Peterson, G.
Chan, W.;
Maxwell, D.;
Gao,X.; Bailey,
R. Han, M. and
Nie, S.
Baughman, R.;
Zakhidov, A. and
de Heer, W.
Niemann, M.;
Srinivasan, S.;
Phani,A.;
Kumar, A.;
Goswami, D.
and Stefanakos,
E.
Gajbhiye,V.;
Palanirajan, V.;
Tekade, R. and
Jain, N.
Kimling, J.;
Maier, M.;
Okenve, B.;
Kotaidis, V.;
Ballot, H. and
Plech.A.
Year
2000
2011
2010
2002
2002
2008
2009
2006
No., and Page No.
(or Year)
US Patent 5840629
Nanotechnology,
Science and
Application,4, 95
Advances in
Mechanical
Engineering, 2010, 1-
6
Current Opinion in
Biotechnology, 13(1),
40-46
Science, 297(5582),
787-792
Journal of
Nanomaterials, 2008,
1-9
Journal of Pharmacy
and Pharmacology,
61,989-1003
Journal of Physical
Chemistry B, 110(32),
15700-15707
Document
Patent
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Mahulikar et al. (2000) detail a method for polishing copper layer with high removal rates and reducing the amount of defects and erosion generated. This procedure uses two slurries, one comprised of a bulk
copper removal slurry that removes the majority of copper. The second slurry is a 1:1:1 mixture of copper/tantalum silicon dioxide that reduces the amount of dishing and erosion that occurs in the copper
arrays. The abrasive phase of the slurries is comprised of particles ranging from 10-800nm, where the liquid phase contains cartoxylic acid and an oxidizer capable of removing copper at a rate greater than
3000A/min.
Smijs and Pavel (201 1 ) review the efficacy of TiO2 and ZnO nanoparticles in protection against UVA and DVB radiation, in addition to the safety considerations these materials present. The extent of
protection against UVA and UVB radiation can be modified by altering the ratio of micro- and nano-sized ZnO and TiO2 nanoparticles in the sunscreen formulation. The most pressing safety issue is the
generation of free-radicals due to their photocatalytic activity. In addition, alteration to these particles can be generated from particle-particle, particle-skin, and skin-particle-light interactions that may result in
additional toxic effects.
Sajith et a. (201 0) investigate the influence on the addition of cerium oxide nanoparticles on the properties and performance of biodiesel. The viscosity and flash point of the biodiesel was found to increase with
the inclusion of the cerium oxide nanoparticles in relation to the concentration of nanoparticles added. The addition of these material also showed an increase in the efficiency of the engine tested. Lastly, the
emission levels of hydrocarbon and NOx are reduced upon addition of the cerium oxide nanoparticles.
Chan et al. (2002) review advances in the synthesis of semiconductor quantum dots modified with biorecognition molecules which can be used as fluorescent labels. These labels are water-soluble and
biocompatible which is advantageous over previously used organic dyes and lanthanide probes. The narrow emission wavelength of these materials, achieved by altering the size of the core nanocrystal, make
it particularly attractive for the utilization of multiple quantum dot types fluorescing upon excitation from a single light source. These properties make these materials particularly attractive for molecular
biotechnology and biomedical applications.
Baughman et al. (2002) review the synthesis, properties, and applications of carbon nanotubes. Their high electrical conductivity and tensile strength make them highly attractive for use in a variety of
applications such as hydrogen storage, energy conversion, and semiconductors. Though current cost and processing limitations hinder the wide-scale application of these materials, their novel properties
ensure their continued development and application in consumer and industrial products.
Niemann et al. (2008) review the application of nanomaterials for the purposes of hydrogen storage. The inherent high surface area to volume ratio of nanomaterials make them ideal candidates for hydrogen
and energy storage. Examples of such materials include carton nanotubes, magnesium hydrides, and metal -organic frameworks have all shown to be strong candidates for hydrogen storage. The various
properties pertaining to hydrogen storage and the efficacy of these materials is discussed within.
Gajbhiye et al. (2009) review the application of dendritic macromolecules as therapeutic agents. Their highly branched nature and low polydispersity make them ideal nanoscale container and excellent drug
delivery agents. Their properties prevent the formation of amyloid fibrils and viral adhesion which would reduce their efficacy as drug carriers. They have currently been demonstrated to be effective against
prion diseases, Alzheimer's, HIV and cancer.
Kimling et al. (2006) revisit the Turkevich method (citrate reduction) for the synthesis of gold nanoparticles. Specifically, the gold-to-reductant ratio is investigated, showing a clear relationship between the ratio
of these reagents and the final gold nanoparticle size, irrespective of absolute concentrations. Control over various parameters of this synthesis process can result in well-defined particle shapes and sizes.
Application of this procedure is also possible for the formation of platinum and palladium nanomaterials.
Complete Citation
Mahulikar, D.; Mravic, B.;
Pasqualoni, A. 2000. Slurry
Compositions and Method for the
Chemical-Mechanical Polishing of
Copper and Copper Alloys. US
Patent 5840629.
Smijs, T. and Pavel, S. 2011.
Titanium Dioxide and Zinc Oxide
Nanoparticles in Sunscreens:
Focus on their Safety and
Effectiveness. Nanotechnology,
Science and Application, 4, 95.
Sajith, V.; Sobhan, C. and
Peterson, G. 2010. Experimental
Investigations on the Effects of
Cerium Oxide Nanoparticle Fuel
Additives on Biodiesel. Advances
in Mechanical Engineering, 2010,
1-6.
Chan, W.; Maxwell, D.; Gao, X.;
Bailey, R. Han, M. and Nie, S.
2002. Luminescent Quantum
Dots for Multiplexed Biological
Detection and Imaging. Current
Opinion in Biotechnology, 13(1),
40-46.
Baughman, R.; Zakhidov, A. and
de Heer, W. 2002. Carbon
Nanotubes-The Route Toward
Applications. Science, 297(5582),
787-792.
Niemann, M.; Srinivasan, S.;
Phani, A.; Kumar, A.; Goswami,
D. and Stefanakos, E. 2008.
Nanomaterials for Hydrogen
Storage Applications: A Review.
Journal of Nanomaterials, 2008, 1
9.
Gajbhiye, V.; Palanirajan, V.;
Tekade, R. and Jain, N. 2009.
Dendrimers as Therapeutic
Agents: A Systematic Review.
Journal of Pharmacy and
Pharmacology, 61, 989-1003.
Kimling, J.; Maier, M.; Okenve,
B. ; Kotaidis, V.; Ballot, H. and
Plech, A. 2006. Turkevich Method
for Gold Nanoparticle Synthesis
Revisited. Journal of Physical
Chemistry B, 110(32), 15700-
15707.
Page 36
-------
Doc ID
632
633
634
635
636
637
638
639
Title
Some Recent
Advances in
Nanostructure
Preparation from
Gold and Silver
Nanoparticles: A
Short Topical
Review
Sol-Gel Template
Synthesis of
Semiconductor
Nanostructures
A Review on Nano-
TiO2 Sol-Gel Type
Syntheses and Its
Applications
(CdSe)ZnS
Core-Shell Quantum
Dots: Synthesis and
Characterization of a
Size Series of Highly
Luminescent
Nanocrystallites
Carbon Nanotubes:
Synthesis,
Integration, and
Properties
Vapor-phase
Synthesis of
Nanoparticles
Nanoparticle-cored
Dendrimers:
Synthesis and
Characterization
Silver Nanoparticle
Protein Corona
Composition in Cell
Culture Media
Authors
Burst, M. and
Kiely, C.
Lakshmi, B.;
Dortiout, P. and
Martin, C.
Macwan, D.;
Dave, P. and
Chaturvedi, S.
Dabbousi, B.;
Rodriguez-Viejo,
J.;Mikulec, F.;
Heine, J.;
Mattoussi, H.;
Ober R.; Jensen,
K. and Bawendi,
M.
Dai, H.
Swihart, M.
Gopidas, K.;
Whitesell, J.and
Fox, M.
Shannahan, J.;
Lai,X.;Ke, P.;
Podila, R. and
Brown, J.
Year
2002
1997
2011
1997
2002
2003
2003
2013
Journal Title, Vol.
No., and Page No.
(or Year)
Colloids and Surfaces
A: Physicochemical
and Engineering
Aspects, 202(2), 175-
186
Chemistry of
Materials, 9(3), 857-
862
Journal of Materials
Science, 46(11), 3669-
3686
Journal of Physical
Chemistry B, 101(46),
9463-9475
Accounts of Chemical
Research, 35(12),
1035-1044
Current Opinion in
Colloid and Interface
Science, 8(1), 127-
133
Journal of the
American Chemical
Society, 125(21),
6491-6502
PLoSOne, 8(9), 1-10
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Burst and Kiely (2002) briefly review several aspects of gold and silver nanostructure self-assembly. An overview of the history and preparation of self-organized gold and silver superlattices are discussed.
Other nano-architectures such as those created from various templates and DMA base pair recognition are also discussed. The surface chemistry, optical properties, and potential for molecular recognition are
also reviewed in addition to current and future applications of these materials.
Lakshmi et al. (1 997) describes the use of sol-gel chemistry to prepare TiO2, WO3, and ZnO semiconductor nanomaterials. The TiO2 nanofibrils that formed were found to be single-crystalline anatase with
diameters of 22nm. Bundles of these fibrils were also found to be crystalline suggesting highly organized arrangement of these fibrils. The application of these nanomaterials was demonstrated through the
photocatalytic decomposition of salicylic acid using a 200nm TiO2 fibril.
Macwan et al. (2011) discuss the various sol-gel technique employed for the purposes of nano-TiO2 preparation. In this review various sol-gel techniques are discussed in addition to colloidal synthesis, solve-
thennal synthesis, and supersonically expanded plasma jet methods of synthesis. In addition to the preparation of these materials, their various applications are also reviewed.
Dabbousi et al. (1 997) synthesis several cadmium selenide-zinc sulfide composite quantum dots with core diameters ranging from 23-55 A. As expected, these materials possess a narrow photoluminescence
spanning the visible range, with quantum yields of approximately 30-50% at room temperature. X-ray spectroscopy, XPS, and TEM were used to characterize their chemical composition, size, size distribution,
shape, and structure. This research also investigated the growth of the zinc sulfide shell on the core to determine how the structure oftheZnS shell influences the photoluminescent properties of the quantum
dots.
Dai (2002) reviewed the various synthetic routes for the preparation of carton nanotubes. It was demonstrated that patterned growth of these materials is possible with catalytic nanoparticles, with the potential
to be scaled up for industrial application. The potential application of these materials in a variety of products is also reviewed.
Swihart (2003) reviews various methods for the preparation of nanomaterials through the vapor-phase synthesis. The principle behind this synthetic route is that conditions are achieved where the vapor phase
mixture is thermodynamically unstable, instead resorting to a more stable nanoparticulate form (typically achieved at chemical supersaturation). Various means of achieving these conditions are discussed
including laser pyrolysis, thermal plasma synthesis, and flame spray pyrolysis.
Gopidas et al. (2003) synthesize nanoparticle-cored dendrimers. These materials are prepared through the synthesis of a gold nanoparticle core (via reduction of chloroauric acid) follow by the self-assembly of
disulfide dendrimer wedges as the nanoparticle is formed. These materials were then characterized by TEM, TGA, UV-vis, IR, and NMR spectroscopy. As a large fraction of the surface area is not passivated,
these materials may still be suitable for catalytic activity.
Shannahan et al. (2013) studied the formation and composition of the protein corona that formed around a set of four different silver nanoparticles. To investigate the protein corona, a label-free mass
spectrometry-based proteomic approach was utilized. The form a protein corona, all silver nanoparticles were incubated in DMEM that had been supplemented with fetal bovine serum. The proteins were then
identified and quantified, showing that all silver nanoparticles associated with 1 1 proteins. The larger citrate and PVP-stabilized nanoparticles were found to bind the greatest number of proteins, suggesting that
protein corona formation may be based on surface curvature.
Complete Citation
Burst, M. and Kiely, C. 2002.
Some Recent Advances in
Nanostructure Preparation from
Gold and Silver Nanoparticles: A
Short Topical Review. Colloids
and Surfaces A: Physicochemical
and Engineering Aspects, 202(2),
175-186.
Lakshmi, B.; Dortiout, P. and
Martin, C. 1997. Sol-Gel
Template Synthesis of
Semiconductor Nanostructures.
Chemistry of Materials, 9(3), 857-
862.
Macwan, D.; Dave, P. and
Chaturvedi, S. 201 1 . A Review on
Nano-TiO2 Sol-Gel Type
Syntheses and Its Applications.
Journal of Materials Science,
46(11), 3669-3686.
Dabbousi, B.; Rodriguez-Viejo,
J.; Mikulec, F.; Heine, J.;
Mattoussi, H.; Ober R.; Jensen,
K. and Bawendi, M. 1997.
(CdSe)ZnS Core-Shell Quantum
Dots: Synthesis and
Characterization of a Size Series
of Highly Luminescent
Nanocrystallites. Journal of
Physical Chemistry B, 101(46),
9463-9475.
Dai, H. 2002. Carbon Nanotubes:
Synthesis, Integration, and
Properties. Accounts of Chemical
Research, 35(12), 1035-1044.
Swihart, M. 2003. Vapor-phase
Synthesis of Nanoparticles.
Current Opinion in Colloid and
Interface Science, 8(1 ), 1 27-1 33.
Gopidas, K.; Whitesell, J.and
Fox, M. 2003. Nanoparticle-cored
Dendrimers: Synthesis and
Characterization. Journal of the
American Chemical Society,
125(21), 6491-6502.
Shannahan, J.; Lai,X.; Ke, P.;
Podila, R. and Brown, J. 2013.
Silver Nanoparticle Protein
Corona Composition in Cell
Culture Media. PLoS One, 8(9), 1-
10.
Page 37
-------
Doc ID
640
641
642
643
644
645
Title
Comparative Eco-
Toxicity of
NanoscaleTiO2 ,
SiO, and ZnO Water
Suspensions
Size-controlled
Dissolution of
Organic-Coated
Silver Nanoparticles
Low Concentrations
of Silver
Nanoparticles in
Biosolids Cause
Adverse Ecosystem
Responses Under
Realistic Field
Scenario
Presence of
Nanoparticles in
Wash Water from
Conventional Silver
and Nano-Silver
Textiles
Langendorff heart: a
model system to
study cardiovascular
effects of engineered
nanoparticles
Distinguishing
Between Interlayer
and External
Sorption Sites of
Clay Minerals Using
X-ray Absorption
Spectroscopy
Authors
Adams, L; Lyon,
D. and Alvarez,
P.
Ma. R.; Levard,
C.; Marinakos,
S.; Cheng, Y.;
Liu, J.; Michel,
F.; Brown, Jr.,
G. and Lowry,
G.
Colman, B.;
Amaout, C.;
Anciaux, S.;
Gunsch, C.;
Hochella Jr., M.;
Kim, B.; Lowry,
G.; McGill, B.;
Reinsch, B.;
Richardson, C.;
Unrine, J.;
Wright, J.; Yin,
L. and
Bemhardt, E.
Mitrano, D.;
Rimmele, E.;
Wichser,A.;
Emi, R.; Height,
M. and Nowack,
B.
Stampfl, A.;
Maier, M.;
Radykewicz, R.;
Reitmeir, P.;
Gottlicher, M.
and Niessner, R.
Papelis, C. and
Hayes, K.
Year
2006
2012
2013
2014
2011
1996
Journal Title, Vol.
No., and Page No.
(or Year)
Water Research,
40(19), 3527-3532
Environmental
Science &
Technology, 46(2),
752-759
PLoSOne, 8(2),
e57189
ACS Nano, 8(7), 7208
7219
ACS Nano, 5(7), 5345
5353
Colloids and Surfaces
A: Physicochemical
and Engineering
Aspects, 107, 89-96
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Adams et al. (2006) investigated the eco-toxicity of titanium dioxide, silicon dioxide, and zinc oxide nanoparticle suspension to gram positive and gram negative bacteria. It was determined that silicon had the
highest antibacterial activity with zinc oxide having the lowest, and the gram positive B.. subtilis being the most susceptible to these effects. The most significant bacterial growth inhibition occurred under light
conditions, suggesting the role of reactive oxygen species.
Ma et al. (201 2) measured the solubility of different sizes of silver nanoparticles (diameters ranging from 5-80nm) that were synthesized using various methods and possessing different organic polymer
coatings. Transmission electron microscopy was used to characterize the size of the nanomaterials, where x-ray absorption spectroscopy (XAFS) and x-ray scattering were used to study the structure and
changes in the crystal lattice of the silver nanoparticle as a function of size. It was determined that lattice parameter does not change with particle size, down to a diameter of 6nm, indicating that particle
solubility can be estimated using a modified Kelvin equation for particles with sizes between 5-40nm.
Colman et al. (201 3) performed a long-term terrestrial mesocosm field experiment entailing the application of silver nanoparticles via a likely exposure route (sewage biosolids). At low concentrations of silver
(0.14 mg Ag kg-1 soil), the microorganism community was different in slurries that contained silver nanoparticles as determined byT-RLFP analysis of 16s-rRNA genes. The N2O flux was also higher in the
silver nanoparticle and slurry treatment than the slurry by itself, but both the N2Oflux and bacterial community composition converged to similar values after 50 days. In addition, it was demonstrated that these
responses were larger in magnitude when compared to a positive control of silver nitrate which had been added at a concentration four times higher than the mass concentration of nanoparticles.
Mitrano et al. (2014) simulated the house-hold laundering of nano-enabled textiles that had been prepared with known silver and silver nanoparticle treatments. Serial filtration separated various size fractions of
nanomaterials which were then characterized byTEM and EDX. Ionic silver showed the most release of total silver than those incorporating silver nanoparticles. Of the silver nanoparticle-enabled textiles,
those incorporated into the fabric, as opposed to surface treatment, saw less silver being released during the fabric washing process. Silver was found in various forms such as metallic silver, silver chloride,
and silver sulfide particles, which depended on the initial speciation of silver in the sock fabric.
Stampfl et al. (2011) studied the cardiovascular effects of ENPs on physiological systems by utilizing an isolated beating heart (Langendorff heart) as the model system. Using this model, a significant
correlation between heart rate and material type and concentration was found, with increased heart rate and arrhythmia occurring for all particle types aside from flame derived SiO2 (Aerosil) and
monodisperse polystyrene. The sensitivity of the Langendorff Heart to these effect may make it a suitable test model for studying ENP toxicity.
Papelis and Hayes (1996) utilized x-ray absorption spectroscopy to study the adsorption of cobalt onto smectite-clay minerals. It was demonstrated that at lowpH and low concentrations of sodium, the cobalt
will form an outer-sphere surface complex. However at increasing pH and sodium ion concentration, these interlayer sites are taken, resulting in polynuclear, external surface-hydroxyl complexes with cobalt.
This research demonstrates the utility of XAS in differentiating the interlayer and external site sorption of trace metals on clay minerals.
Complete Citation
Adams, L.; Lyon, D. and Alvarez,
P. 2006. Comparative Eco-
Toxicityof NanoscaleTiO2 , SiO,
and ZnO Water Suspensions.
Water Research, 40(19), 3527-
3532.
Ma. R.; Levard, C.; Marinakos,
S. ; Cheng, Y.; Liu, J.; Michel, F.;
Brown, Jr., G. and Lowry, G.
2012. Size-controlled Dissolution
of Organic-Coated Silver
Nanoparticles. Environmental
Science & Technology, 46(2),
752-759.
Colman, B.; Amaout, C.; Anciaux,
S. ; Gunsch, C.; Hochella Jr., M.;
Kim, B. ; Lowry, G.; McGill, B.;
Reinsch, B.; Richardson, C.;
Unrine, J.; Wright, J.; Yin, L. and
Bemhardt, E. 2013. Low
Concentrations of Silver
Nanoparticles in Biosolids Cause
Adverse Ecosystem Responses
Under Realistic Field Scenario.
PLoSOne, 8(2), e57189.
Mitrano, D.; Rimmele, E.;
Wichser, A.; Erni, R.; Height, M.
and Nowack, B. 2014. Presence
of Nanoparticles in Wash Water
from Conventional Silver and
Nano-Silver Textiles. ACS Nano,
8(7), 7208-7219.
Stampfl, A.; Maier, M.;
Radykewicz, R.; Reitmeir, P.;
Gottlicher, M. and Niessner, R.
2011. Langendorff heart: a model
system to study cardiovascular
effects of engineered
nanoparticles. ACS Nano, 5(7),
5345-5353.
Papelis, C. and Hayes, K. 1996.
Distinguishing Between Interlayer
and External Sorption Sites of
Clay Minerals Using X-ray
Absorption Spectroscopy.
Colloids and Surfaces A:
Physicochemical and Engineering
Aspects, 107, 89-96.
Page 38
-------
Doc ID
646
647
648
649
650
651
Title
Cerium Oxidation
State in Ceria
Nanoparticles
Studied with X-ray
Photoelectron
Spectroscopy and
Absorption Near
Edge Spectroscopy
Long-Term
Transformation and
Fate of
Manufactured Ag
Nanoparticles in a
Simulated Large
Scale Freshwater
Emergent Wetland.
Characterization of
Synthesized
Titanium Oxide
Nanoclusters by
MALDI-TOFMass
Spectrometry
Exposure to
engineered
nanoparticles: Model
and measurements
for accident
situations in
laboratories.
Toxicity and
penetration of TiO2
nanoparticles in
hairless mice and
porcine skin after
subchronic dermal
exposure
Multi-walled carbon
nanotube
interactions with
human epidermal
keratin ocytes
Authors
Zhang, F.;
Wang, P.;
Koberstein, J.;
Khalid, S. and
Chan, S.-W.
Lowry, G.;
Espinasse, B.;
Badireddy, A.;
Richardson, C.;
Reinsch, B.;
Bryant, L; Bone,
A.; Deonarine,
A.; Chae, S.;
Therezien, M.;
Colman, B.; Hsu-
Kim, H.;
Bemhardt, E.;
Matson, C. and
Wiesner, M.
Guan, B.; Lu,
W.; Fang, J. and
Cole, R.
Walser, T.;
Hellweg, S.;
Juraske, R.;
Luechinger, N.;
Wang, J. and
Fierz, M.
Wu, J.;Liu,W.;
Xue, C.; Zhou,
S.; Lan, F.; Bi,
L.;Xu,H.;Yang,
X. and Zeng, F.
Monteiro- Riviere,
N.; Nemanich,
R.; Inman, A.;
Wang, Y. and
Riviere, J.
Year
2004
2012
2007
2012
2009
2005
Journal Title, Vol.
No., and Page No.
(or Year)
Surface Science,
563(1-3), 74-82
Environmental
Science &
Technology, 46(13),
7027-7036
Journal of the
American Society for
Mass Spectrometry,
18(3), 517-524
Science of the Total
Environment, 420,
119-126
Toxicology Letters,
191(1), 1-8
Toxicology Letters,
155(3), 377-384
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Zhang et al. (2004) investigated the cerium oxidation state of ceria nanoparticles using both CPS andXANES. A comparison of the results revealed that x-ray photoelectron Spectroscopy overestimated the
concentration of cerium 3+ present inside the nanoparticles. It was suggested that surface reduction could occur within the XPS vacuum chamber. Additionally the fast reduction dynamics of ceria nanoparticles
and the diffuse depth profile of these materials may have also contributed to this error. This work highlights the importance of orthogonal analytical techniques in the characterization of nanomaterials.
Lowry et al. (201 2) studied the long-term behavior of PVP-capped silver nanoparticles in freshwater mesocosms to study their impact on an emergent wetland environment. The silver nanoparticles were
applied to either the water column or the soils, and the distribution of silver characterized after 18 months. It was determined that over 70 wt. % of the silver resided in the soils, and while most remained in their
initial dosing compartment, some exchange between soil and sediment was determined. Most of the silver was transformed into silver sulfides or silver-sulfhydryl compounds, and despite this sulfidation, a
fraction of silver was found to be bioaccumulated in plant biomass and some of the organisms present.
Guan et al. (2007) demonstrated the utility of MALDI-TOF-MS and LDI-TOF-MS for the characterization of titanium dioxide nanoparticles. The peak maxima obtained from these methods was found to
correlate with particle size, demonstrating their potential as particle sizing techniques. In addition, the particle size distribution obtained from these two mass Spectrometry techniques was found to be in good
agreement with the distribution obtained from transmission electron microscopy.
Wasler et al. (201 2) simulated three scenarios of equipment failure for processes used in gas phase production of nanomaterials to model potential nanomaterial exposure to workers. Release of
nanomaterials was monitored with high spatial and temporal resolution using nine charge-based aerosol samplers (MiniDiSC) that were compared to a conventional condensation particle counter (CPC). Worst
case release scenarios show that a very rapid dispersal event (60s) occurs with nanoparticle concentrations up to 1 06 particle / cm3 in a 300m2 work area. Particle number concentrations drop rapidly after this
even with proper ventilation, suggesting appropriate safety measures after accidental release.
Wu et al. (2009) studied the penetration oftoxicity of titanium dioxide nanoparticles to hairless mice and porcine skin following dermal exposure. In vitro results showed no penetration of titanium dioxide through
the stratum corneum. However, in vivo, TiO2 nanoparticles can penetrate through the horny layer of the porcine skin and reach the deep layer of epidermis. In the hairless mice, the TiO2 nanoparticle can
penetrate the skin and translocate to different tissue. The implications show that there may be a human health risk to TiO2 after prolonged dermal exposure.
Monteiro-Riviere et al.(2005) investigated the toxicity of carbon nanotubes to human epidermal keratinocytes, which were exposed to different concentrations of multi-walled carbon nanotubes. Transmission
electron microscopy measurements indicated the presence of MWCNTs in the cytoplasmic vacuoles of the cells at all time points. In addition, the MWCNTs resulted in the release of interieukin 8 (a
proinflammatory cytokine) indicating an irritative response from cell.
Complete Citation
Zhang, F.; Wang, P.; Koberstein,
J. ; Khalid, S. and Chan, S.-W.
2004. Cerium Oxidation State in
Ceria Nanoparticles Studied with
X-ray Photoelectron
Spectroscopy and Absorption
Near Edge Spectroscopy.
Surface Science, 563(1-3), 74-
82.
Lowry, G.; Espinasse, B.;
Badireddy, A.; Richardson, C.;
Reinsch, B.; Bryant, L.; Bone, A.;
Deonarine, A.; Chae, S.;
Therezien, M.; Colman, B.; Hsu-
Kim, H.; Bernhardt, E.; Matson,
C. and Wiesner, M. 2012. Long-
Term Transformation and Fate of
Manufactured Ag Nanoparticles in
a Simulated Large Scale
Freshwater Emergent Wetland..
Environmental Science &
Technology, 46(13), 7027-7036.
Guan, B.; Lu, W.; Fang, J. and
Cole, R. 2007. Characterization
of Synthesized Titanium Oxide
Nanoclusters by MALDI-TOF
Mass Spectrometry. Journal of
the American Society for Mass
Spectrometry, 18(3), 517-524.
Walser, T.; Hellweg, S.; Juraske,
R.; Luechinger, N.; Wang, J. and
Fierz, M. 2012. Exposure to
engineered nanoparticles: Model
and measurements for accident
situations in laboratories. .
Science of the Total Environment,
420,119-126.
Wu, J.; Liu, W.; Xue, C.; Zhou,
S. ; Lan, F.;Bi,L.;Xu,H.; Yang,
X. and Zeng, F. 2009. Toxicity
and penetration of TiO2
nanoparticles in hairless mice and
porcine skin after subchronic
dermal exposure. Toxicology
Letters, 191(1), 1-8.
Monteiro-Riviere, N.; Nemanich,
R.; Inman, A.; Wang, Y. and
Riviere, J. 2005. Multi-walled
carbon nanotube interactions with
human epidermal keratinocytes.
Toxicology Letters, 155(3), 377-
384.
Page 39
-------
Doc ID
652
653
654
655
656
657
Title
Estimation of
cumulative aquatic
exposure and risk
due to silver:
Contribution of nano-
functionalized
plastics and textiles
Characterization of
silver release from
commercially
available functional
(nano)textiles
Use of Nanoparticles
in Swiss Industry: A
Targeted Survey
Nanopesticides:
Guiding principles for
regulatory evaluation
of environmental
risks
Improvements in the
detection and
characterization of
engineered
nanoparticles using
splCP-MS with
microsecond dwell
times
Simultaneous mass
quantification of
nanoparticles of
different composition
in a mixture by
microdroplet
generator-
ICPTOFMS
Authors
Blaser, S.;
Scheringer, M.;
MacLeod, M.
and
Hungertuhler, K.
Lorenz, C.;
Windier, L; von
Goetz, N.;
Lehmann, R.;
Schuppler, M.;
Hungertuhler,
K.; Heuberger,
M.; Nowack, B.
Schmid, K. and
Riediker, M.
Kookana, R.;
Boxall, A.;
Reeves, P.;
Ashauer, R.;
Beulke, S.;
Chaudry, Q.;
Cornells, G.;
Fernandes, T.;
Gan, J.;Kah, M.;
Lynch, I.;
Ranville, J.;
Sinclair, C.;
Spurgeon, D.;
Tiede, K. and
Van den Brink,
P.
Montafio, M.;
Baidei, H.;
Bazargan, S.
and Ranville, J.
Borovinskya, O.;
Gschwind, S.;
Hattendorf, B.;
Tanner, M. and
Gunther, D.
Year
2008
2012
2008
2014
2014
2014
Journal Title, Vol.
No., and Page No.
(or Year)
Science of the Total
Environment, 390(2-
3), 396^09
Chemosphere, 89(7),
817-824
Environmental
Science and
Technology, 42(7),
2253-2260
Journal of Agricultural
and Food Chemistry,
62(1 9), 4227-4240
Environmental
Science: Nano, 1, 338
346
Analytical Chemistry
Document
Type
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Published
journal
Article Summary
Blaser et al. (2008) performed risk analysis on the impact of nanosilver originating from biocidal plastics and textiles to freshwater ecosystems. Risk analysis was performed in several steps including the
assessment of silver fate, toxicity evaluation, estimation of predicted environmental concentrations (PECs), and predicted no-effect concentrations (PNECs), as well as risk characterization. Though the amount
of silver that truly reaches a freshwater ecosystem will depend on the ability of waste water treatment facilities to treat nanosilver, PEC/PN EC ratios greater than one are a distinct possibility.
Lorenz et al. (201 2) investigated the release of silver nanomaterials during a washing and rinsing cycle from several different (nano)functional textiles. The silver collected was size fractionated and
characterized using electron microscopy and EDX. The antimicrobial behavior of these silver nanomaterials was also investigated before and after a wash cycle. It was determined that the silver released after
a wash cycle can come in several different forms including a Ti/Si-AgCI nanocomposite, silver chloride and metallic silver nanoparticles, and silver sulfide particles. One textile in particular showed a reduction in
microbial toxicity after washing, which had been attributed to the formation of the less bioavailable silver sulfide, reducing its toxicity.
Schmid and Riediker (2008) evaluated the use of nanomaterials, the safety measures taken to protect workers, and the number of workers currently exposed to engineered nanomaterials in the Swiss Industry.
The research was performed by a targeted telephone survey of 197 different Swiss companies. It was determined that several of these companies had been creating or using engineered nanomaterials, and
that some import and trade prepackaged goods containing nanomaterials. The use of nanomaterials extends beyond companies specifically in the nanotechnology field, and has entered into some traditional
industries such as paints. Some of the most commonly used nanomaterials (>1000 kg /yr/ company) are silver, aluminum and iron oxides, silica, and titania.
Kookana et al. (2014) review the current approaches for the environmental risk assessment of pesticides and their applicability to an emerging class of nano-pesticides. These new materials show promise in
increasing the efficacy of pesticides while simultaneously preserving human and ecological health. However, there are still several issues that need to be addressed. Among these are a clear definition of what
constitutes a nano-pesticide, improved analytical methodology to characterize these materials, and an adaptive regulatory framework to respond to the continued development of these nanomaterials.
Montafio et al. (2014) demonstrate the utility of microsecond dwell times in the analysis of engineered nanomaterials by splCP-MS. Their findings indicate a significantly improved working range from a particle
number concentration stand-point, as well as an improved ability to discern nanoparticulate and dissolved signals at proportionally high dissolved background concentrations. In addition, the utilization of these
short data acquistions times may open the door for multi-element analysis on a particle-by-particle basis, resulting in a potential way to differentiate naturally occurring and engineered nanomaterials.
Borovinskya et al. (2014) investigated the use of a inductively coupled plasma time-of-flight mass spectrometer for the analysis of gold, silver, and gold core-silver shell nanomaterials. The utilization of thetime-
of-flight allowed for simultaneous mass quantification of the different nanoparticles. By utilizing these high temporal resolution of this technique, these three particles can be differentiated from one another. In
addition, the limits-of-detection for this technique were also discussed, along with the demonstration of using this technique to investigate differences in vaporization behavior.
Complete Citation
Blaser, S.; Scheringer, M.;
MacLeod, M. and Hungerbiihler,
K. 2008. Estimation of cumulative
aquatic exposure and risk due to
silver: Contribution of nano-
functionalized plastics and
textiles. Science of the Total
Environment, 390(2-3), 396-409.
Lorenz, C.; Windier, L.; von
Goetz, N.; Lehmann, R.;
Schuppler, M.; Hungertuhler, K.;
Heuberger, M.; Nowack, B. 2012.
Characterization of silver release
from commercially available
functional (nano)textiles.
Chemosphere, 89(7), 817-824.
Schmid, K. and Riediker, M.
2008. Use of Nanoparticles in
Swiss Industry: A Targeted
Survey. Environmental Science
and Technology, 42(7), 2253-
2260.
Kookana, R.; Boxall, A.; Reeves,
P.; Ashauer, R.; Beulke, S.;
Chaudry, Q.; Cornells, G.;
Fernandes, T.; Gan, J.; Kah, M.;
Lynch, I.; Ranville, J.; Sinclair, C.;
Spurgeon, D.; Tiede, K. and Van
den Brink, P. 2014.
Nanopesticides: Guiding
principles for regulatory
evaluation of environmental risks.
Journal of Agricultural and Food
Chemistry, 62(19), 4227-4240.
Montafio, M.; Baidei, H.;
Bazargan, S. and Ranville, J.
2014. Improvements in the
detection and characterization of
engineered nanoparticles using
splCP-MS with microsecond
dwell times. Environmental
Science: Nano, 1,338-346.
Borovinskya, O.; Gschwind, S.;
Hattendorf, B.; Tanner, M. and
Gunther, D. 2014. Simultaneous
mass quantification of
nanoparticles of different
composition in a mixture by
microdroplet generator-
ICPTOFMS. Analytical Chemistry.
Page 40
-------
Doc ID
658
Title
A prototype of a new
inductively coupled
plasma time-of-flight
mass spectrometer
providing temporally
resolved, multi-
element detection of
short signals
generated by single
particles and
droplets
Authors
Borovinskya, O.;
Hattendorf, B.;
Tanner, M.;
Gschwind, S.
and Giinther, D.
Year
2013
Journal Title, Vol.
No., and Page No.
(or Year)
Journal of Analytical
Atomic Spectrometry,
28, 226-233
Document
Type
Published
journal
Article Summary
Borovinskya et al. (2014) demonstrated the use of a prototype ICP-TOF-MS for the characterization of single nanoparticles. The quasi-simultaneous detection (acquisition time 33 microseconds) allows for the
monitoring of the short temporal signals originating from the nanoparticle. The size detection limits for silver, gold and uranium nanoparticles are determined. This analytical technique also allows for the
monitoring of multiple elements within a given particles.
Complete Citation
Borovinskya, O.; Hattendorf, B.;
Tanner, M.; Gschwind, S. and
Gunther, D. 2013. A prototype of
a new inductively coupled plasma
time-of-flight mass spectrometer
providing temporally resolved,
multi-element detection of short
signals generated by single
particles and droplets. Journal of
Analytical Atomic Spectrometry,
28, 226-233.
Page 41
-------
United States EPA/600/R-14/244
Environmental Protection tr/vouu/rc i^f/z^f
Agency
Image library in support of:
Detection and characterization of engineered nanomaterials in the environment:
current state-of-the-art and future directions
Report, annotated bibliography, and image library
RESEARCH AND DEVELOPMENT
-------
August 2014
www.epa.gov
Image library in support of:
Detection and characterization of engineered nanomaterials in the environment:
current state-of-the-art and future directions
EPA Contract EP-C-11-039
Task Order 5
Steven P. Gardner
U.S. Environmental Protection Agency
Office of Research and Development
National Environmental Research Laboratory
Environmental Sciences Division
Characterization and Monitoring Branch
944 E. Harmon Ave.
Las Vegas, NV 89119
Manuel Montano1
James F. Ranville, Ph.D.1
Julie Blue, Ph.D.2
Nupur Hiremath2
Clare Stankwitz2
Gregory V. Lowry, Ph.D.3
1Colorado School of Mines
1500 Illinois Street
Golden, CO 80401
2The Cadmus Group, Inc.
100 5th Avenue, Suite 100
Waltham, MA 02451
3Carnegie Mellon University
5000 Forbes Avenue
Pittsburgh, PA 15213
Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy. Mention of trade names and commercial products does not constitute
endorsement or recommendation for use.
U.S. Environmental Protection Agency
Office of Research and Development
Washington DC 20460
-------
Disclaimer
The United States Environmental Protection Agency through its Office of Research and Development funded and managed the research
described here. It has been peer reviewed by the EPA and approved for publication.
-------
Current Status and Future Directions for Examining Engineered Nanoparticles in Natural
Systems - Image Library Appendix
The purpose of this image library is to provide examples of engineered nanoparticles and
contrast them to images of their naturally occurring and/or biogenically produced counterparts.
Images are provide (where possible) of the engineered particles in a product and in some cases,
an image of an engineered particle that demonstrates obvious weathering effects.
Apparent in most images is the similarity between the engineered nanomaterial and it's
naturally occurring analogue. Though the engineered particles showed a greater degree of
monodispersity, most particles both manufactured and natural have similar morphologies. The
similarity between these images show the need for corroborative measurements to verify the
identity and origin of these materials.
There are some engineered materials that will possess very unique morphologies and surface
coatings that are noticeably different than naturally occurring materials of the same
composition (Slide 40). However, alterations made to these features upon entry into the
environment is still a topic of research and not well understood. It is possible these highly-
engineered material properties may be changed and altered to reflect materials more similar to
those found in the environment as a result of chemical changes and weathering that may occur.
It should be noted that imaging alone may not be sufficient to determine the origin and
identity of nanomaterials. Other techniques that exploit key physio-chemical differences
between these particles are necessary to detect and characterize these engineered
nanomaterials upon entry into the environment.
-------
Carbon nanotubes - Images
SEM image of Purified CNTs (Lu et al., 2006)
5 % CNTs in PVOH (Fairbrother, unpublished data)
Organic filaments in lake (Buffle and Leppard, 1995)
-------
Carbon nanotubes - References (Clockwise from top left)
1) Scanning electron microscope image of purified multi-walled carbon nanotubes.
1) Imaged by SEM.
2) Lu, C; Chung, Y.-L; Chang, K.-F. Adsorption thermodynamic and kinetic studies of
trihalomethanes on multiwalled carbon nanotubes. Journal of Hazardous Materials B.
2006,138, pp. 304-310
2) 5% CNTs in polyvinyl alcohol.
1) Imaged by SEM
2) Howard Fairbrother. John Hopkins University. Unpublished Data
3) Organic filaments in lake water.
1) Observed by transmission electron microscopy.
2) Buffle, J.; Leppard, G. G. Characterization of aquatic colloids and macromolecules. 1.
Structure and Behavior of Colloidal Material. Environmental Science and Technology.
1995, 29, pp. 2169-2175.
-------
ZnO nanoparticles- Images
ZnO nanoparticles imaged by SEM (Dybowska et al., 2011)
100000: 1
ZnO applied to a cotton textile (Behceri et al. 2008)
200nm
ZnO nanoparticles contained in a surface coating (Vorbau et al., 2009)
-------
ZnO nanoparticles- References (Clockwise from top left)
1) Images of isotopically modified ZnO nanoparticles
1) Imaged by SEM (at micron scale)
2) Dybowska, A.; Croteau, M-N.; Misra, S.; Berhanu, D.; Luoma, S.; Christian, P.; O'Brien, P.;
Valsami-Jones, E. Synthesis of isotopically modified ZnO nanoparticles and their
potential as nanotoxicity tracers. Environmental Pollution, 2011,159, pp. 266-273.
2) ZnO nanoparticles applied to a cotton textile
1) Imaged by SEM (at micron scale)
2) Becheri, A.; Durr, M.; Lo Nostro, P.; Baglioni, P. Synthesis and characterization of zinc
oxide nanoparticles: application to textiles as UV-absorbers. Journal of Nanoparticle
Research, 2008,10, pp. 679-689.
3) ZnO nanoparticles released from a surface coating via abrasion.
1) Imaged by TEM.
2) Vorbau, M.; Hillemann, L; Stintz, M. Method for the characterization of the abrasion
induced nanoparticle release into air from surface coatings. Aerosol Science, 2009, 40,
pp. 209-217.
-------
Ag nanoparticles- Images
100 nm
M
Ag nanoparticles prepared by silver ammonia reduction
(Panaceketal., 2006)
Ag nanoparticles found in sock fabric (Benn and Westerhoff, 2008)
Ag nanoparticles found in wash water (Benn and
Westerhoff, 2007)
Ag nanoparticles synthesized by Aspergillusflavus (Vigneshwaran et al., 2007)
-------
Ag nanoparticles- References (Clockwise from top left)
1) Ag nanoparticles formed via the reduction of silver ammoniate by glucose
1) Imaged by TEM
2) Panacek, A.; Kvitek, L; Prucek, R.; Kolaf, M.; Vecefova, R.; Pizurova, N.; Sharma, V.; Nevecna, T.;
Zbofil, R. Silver Colloid Nanoparticles: Synthesis, Characterization, and Their Antibacterial Activity.
Journal of Physical Chemistry B, 2006,110, pp. 16248-16253.
2) Ag nanoparticles found in ashed sock fabric (EDX inset)
1) Imaged by SEM (at micron scale)
2) Benn, T.; Westerhoff, P. Nanoparticle Silver Released into Water from Commercially Available Sock
Fabrics. Environmental Science and Technology, 2008, 42, pp. 4133-4139.
3) Silver nanoparticles formed from the reduction of silver nitrate byAspergillusflavus
1) Imaged by SEM
2) Vigneshwaran, N.; Ashtaputre, N.; Varadarajan, P.; Nachane, R.; Paralikar, K.; Balasubramanya, R.
Biological synthesis of silver nanoparticles using the fungus Aspergillusflavus. Materials Letters,
2007, 61, pp. 1413-1418.
4) Ag nanoparticles found in wash water from sock fabrics (inset is EDX)
1) Imaged by TEM
2) Benn, T; Westerhoff, P. Nanoparticle Silver Released into Water from Commercially Available Sock
Fabrics. Environmental Science and Technology, 2008, 42, pp. 4133-4139.
-------
TiO, nanoparticles- Images
Ti02 nanoparticles imaged byTEM (Oskam et al., 2003)
V
20 nm
Ti02 nanoparticles in toothpaste (Kiser et al., 2008)
Weathered Ti02 particle in sunscreen (Nowack et al., 2012)
Ti-containing mineral in a biosolid (Kiser et al., 2008)
-------
TiO2 nanoparticles- References (Clockwise from top left)
1) Image of Ti02 nanoparticles prepared from titanium (IV) isoprepoxide
1) Imaged by TEM
2) Oskam, G.; Nellore, A.; Penn, R. L; Searson, P. The Growth Kinetics of Ti02 Nanoparticles from
Titanium (IV) Alkoxide at High Water/Titanium Ratio. Journal of Physical Chemistry B. 2003,107,
pp. 1734-1738.
2) Ti02 nanoparticles in toothpaste
1) Imaged by SEM
2) Kiser, M.; Westerhoff, P.; Benn, T; Wang, Y.; Perez-Rivera, J.; Hristovski, K. Titanium Nanomaterial
Removal and Release from Wastewater Treatment. Environmental Science and Technology. 2008,
43, pp. 6757-6763.
3) Titanium containing mineral in a biosolid
1) Observed by SEM (at micron scale)
2) Kiser, M.; Westerhoff, P.; Benn, T; Wang, Y.; Perez-Rivera, J.; Hristovski, K. Titanium Nanomaterial
Removal and Release from Wastewater Treatment. Environmental Science and Technology. 2008,
43, pp. 6757-6763.
4) Weathered titania nanoparticle released from sunscreen
1) Observed by TEM
2) Nowack, B.; Ranville, J.; Diamond, S.; Gallego-Urrea, J.; Metcalfe, C.; Rose, J.; Home, N.; Koelmans,
A.; Klaine, S. Potential Scenarios for Nanomaterial Release and Subsequent Alteration in the
Environment. Environmental Toxicology and Chemistry, 2012, 31, pp. 50-59.
-------
Au nanoparticles- Images
Gold nanoparticles synthesized by reduction of
chloroauric acid (Cichomski et al., 2011)
Aggregated acrylate capped gold nanoparticles at pH=2
(Diegolietal., 2008)
Catalytic gold nanoparticles deposited on a
ZnO support (Catillejos et al., 2012)
D
*
Gold nanoparticles found in weathered gold deposits
(Hough etal., 2008)
-------
Au nanoparticles- References (Clockwise from top left)
1) Gold nanoparticles synthesized via reduction of chloroauric acid by trisodium citrate
1) Imaged by SEM
2) Cichomski, M.; Tomaszewska, E.; Kosla, K.; Kozlowski, W.; Kowalczyk, P.; Grobelny, J. Study of dithiol
monolayer as the interface for controlled deposition of gold nanoparticles. Materials
Characterization, 2011, 42, pp. 268-274.
2) Catalytic gold nanoparticles deposited on a ZnO support
1) Imaged by TEM
2) Castillejos, E.; Gallegos-Suarez, E.; Bachiller-Baeza, B.; Bacsa, R.; Serp, P.; Guerrero-Ruiz, A.;
Rodriguez-Ramos, I. Deposition of gold nanoparticles on ZnO and their catalytic activity for
hydrogenation applications. Catalysis Communications, 2012, 22, pp. 79-82.
3) Gold nanoparticles found in weather gold deposits
1) Imaged by SEM
2) Hough, R.; Noble, R.; Hitchen, G.; Hart, R.; Reddy, S.; Saunders, M.; Clode, P.; Vaughan, D.; Lowe, J.;
Gray, D.; Anand, R.; Butt, C.; Verrall, M. Naturally occurring gold nanoparticles and nanoplates.
Geology, 2008, 36, pp. 571-574.
4) Aggregated acrylate-capped gold nanoparticles at pH=2.
1) Imaged by TEM
2) Diegoli, S.; Manciulea, A.; Begum, S.; Jones, I.; Lead, J.; Preece, J. Interaction between
manufactured gold nanoparticles and naturally occurring macromolecules. Science of the Total
Environ ment,2QQS, 402, pp. 51-61.
-------
1) CeO, nanoparticles- Images
Cerium oxide nanoparticles prepared at 70°C (Chen and
Chang, 2005)
Ce02 particles adhered to a silty loam (von der Kammer et
al., 2012)
100 nm
Cerium oxide adhered to diesel particles in fuel additive (Jung et
al., 2005)
Ce02 nano-cluster found in a floodplain (von der Kammer
etal., 2012)
-------
CeO2 nanoparticles- References (Clockwise from top left)
1) Cerium oxide nanoparticles prepared from the oxidation of cerium ammoniate at 70° C.
1) Imaged by TEM
2) Chen, H.; Chang, H. Synthesis of nanocrystalline cerium oxide particles by the precipitation
method. Ceramic International, 2005, 31, pp. 795-802.
2) Cerium oxide nanoparticles found on diesel particles
1) Imaged by TEM
2) Jung, H.; Kittelson, D.; Zachariah, M. The influence of a cerium additive on ultrafine diesel particle
emissions and kinetics of oxidation. Combustion and Flame, 2005,142, pp. 276-288.
3) Natural Ce-containing nanoparticle cluster from the floodplain of Clark Fork River, Montana, USA
1) Imaged by TEM (scale not specified)
2) von der Kammer, R; Ferguson, P.; Holden, P.; Mason, A.; Rogers, K.; Klaine, S.; Koelmans, A.; Home,
N.; Unrine, J. Analysis of Engineered Nanomaterials in Complex Matrices (Environment and Biota):
General Consideration and Conceptual Case Studies. Environmental Toxicology and Chemistry,
2012, 31, pp. 32-49.
4) Cerium dioxide nanoparticles adhered to the surface of a silty loam
1) Imaged by SEM (at micron scale)
2) von der Kammer, F.; Ferguson, P.; Holden, P.; Mason, A.; Rogers, K.; Klaine, S.; Koelmans, A.; Home,
N.; Unrine, J. Analysis of Engineered Nanomaterials in Complex Matrices (Environment and Biota):
General Consideration and Conceptual Case Studies. Environmental Toxicology and Chemistry,
2012, 31, pp. 32-49.
-------
Zero valent iron nanoparticles- Images
Pristine zero valent iron NP (Kanel et al., 2006)
As(V) adsorbed to a ZVI reactive barrier (Kanel et al., 2006)
Zero valent iron NP with an oxide shell (Ramos et al., 2009)
Magnetite particles formed from photoxidation (Silva et al., 2012)
-------
Zero valent iron nanoparticles- References (Clockwise from top left)
1) Pristine zero valent iron nanoparticles
1) Imaged by TEM
2) Kanel, S.; Greneche, J.; Choi, H. Arsenic (V) Removal from Groundwater Using Nano Scale Zero-
Valent Iron as a Colloidal Reactive Barrier Material. Environmental Science and Technology, 2006,
40, pp. 2045-2050.
2) Arsenic (V) adsorbed onto a reactive barrier of zero valent iron nanoparticles
1) Imaged by SEM (at micron scale)
2) Kanel, S.; Greneche, J.; Choi, H. Arsenic (V) Removal from Groundwater Using Nano Scale Zero-
Valent Iron as a Colloidal Reactive Barrier Material. Environmental Science and Technology, 2006,
40, pp. 2045-2050.
3) Magnetite particles formed from the precipitation and photooxidation of acid mine drainage
1) Imaged by SEM (at micron scale)
2) Silva, R.; Castro, C.; Viganico, E.; Petter, C.; Schneider, I. Selective precipitation/UV production of
magnetite particles obtained from the iron recovered from acid mine drainage. Minerals
Engineering, 2012, 29, pp. 22-27.
4) Zero valent iron nanoparticle with a formed oxide coating
1) Imaged by TEM
2) Ramos, M.; Van, W.; Li, X.; Koel, B.; Zhang, W. Simultaneous Oxidation and Reduction of Arsenic by
Zero-Valent Iron Nanoparticles: Understanding the Significance of the Core-Shell Structure. Journal
of Physical Chemistry C Letters, 2009,113, pp. 14591-14594.
-------
WOa nanoparticles- Images
W03 nanoparticles prepared by acid precipitation (Supothina et
al. 2007)
Tungsten oxide nanoparticles used for N02 gas sensing
(Rossinyol etal., 2007)
-------
Zero valent iron nanoparticles- References (Clockwise from top left)
1) Pristine tungsten oxide (W03) nanoplates
1) Imaged by SEM
2) Supothina, S.; Seeharaj, P.; Yoriya, S.; Sriyudthsak, M. Synthesis of tungsten oxide nanoparticles by
acid precipitation method. Ceramics International, 2007, 33, pp. 931-936.
2) Tungsten oxide nanoparticles templated on a KIT-6 structure for gas-sensing applications
1) Imaged by TEM
2) Rossinyol, E.; Prim, A.; Pellicer, E.; Arbio, J.; Hernandez-Ramirez, R; Peiro, R; Cornet, A.; Morante, J.;
Solovyov, L; Tian, B.; Bo, T, Zhao, D. Synthesis and Characterization of Chromium-Doped
Mesoporous Tungsten Oxide for Gas-sensing Applications. Advanced Functional Materials, 2007,
17, pp. 1801-1806.
-------
MnO,nanoparticles- Images
Pristine MnO, nanoparticles (Ching et al., 2011)
Carbon coated Mn02 nanoparticles for catalysis (Roche
etal., 2008)
Mn02 aggregation in the presence of biomolecules and divalent
cations (Huangfu et al., 2013)
Biogenically synthesized manganese oxides
(Miyataetal., 2007)
-------
MnO2 - References (Clockwise from top left)
1) Pristine manganese oxide (Mn02) nanoparticles
1) Imaged by SEM (at micron scale)
2) Ching, S.; Kriz, D.; Luthy, K.; Njagi, E.; Suib, S. Self-assembly of manganese oxide nanoparticles and
hollow spheres. Catalytic activity in carbon monoxide oxidation. Chemical Communications, 2011,
47, pp. 8286-8288.
2) Manganese oxide / carbon electrocatalysts
1) Imaged by TEM
2) Roche, I.; ChaTnet, E.; Chatenet, M.; Vondrak, J. Durability of carbon-supported manganese oxide
nanoparticles for the oxygen reduction reaction (ORR) in alkaline medium. Journal of Applied
Electrochemistry, 2008, 38,pp. 1195-1201.
3) Manganese (II) oxidation byAcremonium sp. Strain KR21-2 to form manganese oxides
1) Imaged by TEM
2) Miyata, N.; Tani, Y.; Sakata, M.; Iwahori, K. Microbial Manganese Oxide Formation and Interaction
with Toxic Metal Ions. Journal of Bioscience and Bioengineering, 2007,104, pp. 1-8.
4) Aggregated Mn2 nanoparticles in the presence of lOmM calcium nitrate and 2 mg/L alginate
1) Imaged by TEM
2) Huangfu, X.; Jiang, J.; Ma, J.; Yongze, L; Jing, Y. Aggregation Kinetics of Manganese Dioxide Colloids
in Aqueous Solution: Influence of Humic Substances and Biomacromolecules. Environmental
Science and Technology, 2013, Just Accepted.
-------
ALO, nanoparticles- Images
500 nm
a-AI203 nanoparticles formed in the presence of Na(AOT) (Park et al.,
2005)
Nano-porous anodised alumina coating on titanium (Briggs
etal., 2004)
Silica-alumina nanoparticle heteroaggregation (Garcia-Perez et al., 2006)
-------
AI2O3 - References (Clockwise from top left)
1) a-AI203 nanoparticles form in the presence of sodium bis(2-ethylhexyl) sulfosuccinate
1) Imaged by SEM
2) Park, Y.; Tadd, E.; Zubris, M.; Tannenbaum, R. Size-controlled synthesis of alumina nanoparticles
from aluminum alkoxides. Materials Research Bulletin, 2005, 40, pp.1506-1512.
2) Nano-porous anodised alumina coating on titanium for surgical implants
1) Imaged by SEM
2) Briggs, E.; Walpole, A.; Wilshaw, P.; Karlsson, M.; Palsgard, E. Formation of highly adherent nano-
porous alumina on Ti-based substrates: a novel bone implant coating. Journal of Materials Science:
Materials In Medicine, 2004,15, pp. 1021-1029.
1) Alumina colloids heteroaggregated with silica nanoparticles
1) Imaged by Cryo-FEG-SEM
2) Garcia-Perez, P.; Pagnoux, C; Rossignol, F.; Baumard, J. Heterocoagulation between Si02
nanoparticles and AI203 submicronparticles; influence of the background electrolyte. Colloids and
Surfaces A: Physiochemical Engineering Aspects, 2006, 281, pp. 58-66.
-------
UO, nanoparticles- Images
50 nm
Uraninite nanoparticles precipitated on green rusts
(O'Loughlinetal.,2003)
Uranium nanoparticles precipitated from bio-reduction of U(VI)
by Shewanella oneidensis (Burgos et al., 2008)
-------
UO2 - References (Clockwise from top left)
1) Uraninite nanoparticles precipitated on mixed Fe(ll)/Fe(lll) hydroxides
1) Imaged by TEM
2) O'Loughlin, E.; Kelly, S.; Cook, R.; Csencsits, R.; Kemner, K. Reduction of Uranium (VI) by Mixed Iron
(ll)/ Iron(lll) Hydroxide (Green Rusts: Formation of U2 Nanoparticles. Environmental Science and
Technology, 2003, 37, pp. 721-727.
2) Uraninite nanoparticles precipitated from soluble U(VI) by Shewanella oneidensis MR-1 strain
1) Imaged by SEM (at micron scale)
2) Burgos, W.; McDonough, J.; Senko, J.; Zhang, G.; Dohnalkova, A.; Kelly, S.; Gorby, Y.; Kemner, K.
Characterization of uraninite nanoparticles produced by Shewanella oneidensis MR-1. Geochimica
etCosmochimicaActa, 2008, 72, pp. 4901-4915.
-------
Graphene - Images
Grapheme layer produced by chemical vapor deposition
(Park etal., 2010)
Graphene sheets with embedded gold nanoparticles
(Muszynskietal., 2008)
-------
Graphene - References (Clockwise from top left)
1) Graphene prepared by chemical vapor deposition
1) Imaged by TEM
2) Park, H.; Meyer, J.; Rother, S.; Skakalova, V. Growth and properties of few-layer graphene prepared
by chemical vapor deposition. Carbon, 2010, 48, pp. 1088-1094.
2) Graphene sheets with embedded gold nanoparticles for catalysis applications
1) Imaged by SEM (at micron scale)
2) Muszynski, R.; Seger, B.; Kamat, P. Decorating Graphene Sheets with Gold Nanoparticles. Journal of
Physical Chemistry C Letters, 2008,112, pp. 5263-5266.
-------
Fullerenes- Images
SEM image of C60 powder (Gusev et al., 1999)
.-
o
' '-': .'~''---'^1''l:''' '!:-Vv;,f;yV'.'.''- '^-,''' ':', 5 HPTI
Fullerene-like soot from a EurolV diesel engine (Su et al., 2004)
Fullerene particles found in precambrian rocks
from Russia (Buseck et al., 1992)
-------
Fullerenes- References (Clockwise from top left)
1) SEM image of C60 powder
1) Imaged by SEM
2) Gusez, Y.; Ruetsch, S.; Popeko, L; Popeko, I. Nitrogen and Argon Adsorption and SEM
Characterization of C60 And C60/70 Fullerenes: Comparison with Graphite. Journal of Physical
Chemistry B, 1999,103, pp. 6498-6503.
2) TEM images of fullerenes found in a precambrian rock from Russia
1) Imaged by TEM
2) Buseck, P.; Tsipursky, S.; Hettich, R. Fullerenes from the Geological Environment. Science, 1992,
257, pp. 215-217.
3) TEM image of fullerene-like soot from EurolV diesel engine
1) Imaged by TEM
2) Su, D.; Muller, J.-O; Jentoft, R.; Rothe, D.; Jacob, E.; Schlogl, R. Fullerene-like soot from EurolV
diesel engine: consequences for catalytic automotive pollution control. Topics In Catalysis, 2004,
30/31, pp. 241-245.
-------
1) Fe,Oa- Images
TEM image of hematite nanoparticles coated with HPC (Jing
and Wu, 2004)
100 nm
u
20 nm
Hematite nanoparticles found in free-drifting icebergs (Shaw et
al., 2011)
*»**
Aggregated alginate-coated hematite nanoparticles (Chen et al.,
2006)
-------
Graphene - References (Clockwise from top left)
1) TEM image of hematite nanoparticles coated with hexadecyipyridinium chloride (HPC)
1) Imaged by TEM
2) Jing, Z.; Wu, S. Synthesis and characterization of monodisperse hematite nanoparticles modified by
surfactants via hydrothermal approach. Materials Letters, 2004, 58, pp.3637-3640.
2) N/A hematite nanoparticle in a product
3) Hematite nanoparticles found in free-drifting icebergs
1) Imaged by TEM
2) Shaw, T; Raiswell, R.; Hexel, C.; Vu, H.; Moore, W.; Dudgeon, R.; Smith Jr., K. Input, composition,
and potential impact of terrigenous material from free-drifting icebergs in the Weddell Sea. Deep-
Sea Research II, 2011, 58, pp. 1376-1383.
4) Aggregated alginate-coated hematite nanoparticles in the presence of divalent salts
1) Imaged by TEM
2) Chen, K.; Mylon, S.; Elimelech, M. Aggregation Kinetics of Alignate-Coated Hematite Nanoparticles
in Monovalent and Divalent Electrolytes. Environment Science and Technology, 2006, 40, pp. 1516-
1523.
-------
Quantum dots - Images
TEM images of various quantum dots (Alivisatos, 1996)
3. suhtifis &
weathered QD<
PbS Quantum dots in solar cells (Jean et al., 2013)
TEM images of weathered quantum dot clusters
(Mahendraetal., 2008)
Spherical aggregates of ZnS nanoparticles formed in a biofilm (Labrenz et
al., 2000)
-------
Quantum dots - References (Clockwise from top left)
1) TEM images of various quantum dots lattices
1) Imaged by TEM
2) Alivisatos, A. Semiconductor Clusters, Nanocrystals, and Quantum Dots. Science, 1996, 271, pp.
933-937.
2) Lead sulfide quantum dots in solar cells
1) Imaged by SEM
2) Jean, J.; Chang, S.; Brown, P.; Cheng, J.; Rekemeyer, P.; Bawendi, M.; Gradecak, S.; Bulovic, V. ZnO
Nanowire Arrays for Enhanced Photocurrent in PbS Quantum Dot Solar Cells. Advanced Materials,
2013, 25, pp. 2790-2796.
3) Spherical aggregates of ZnS nanoparticles formed in a biofilm
1) Imaged by SEM (at micron scale)
2) Labrenz, M.; Druschel, G.; Thomsen-Ebert, T.; Gilbert, B.; Welch, S.; Stasio, G.; Bond, P.; Lai, B.;
Kelly, S.; Banfield, J. Formation of Sphalerite (ZnS) Deposits in Natural Biofilms of Sulfate-Reducing
Bacteria. Science, 2000, 290, pp. 1744-1747.
4) Weathered quantum dots clusters with Bacillus subtilis
1) Imaged by TEM
2) Mahendra, S.; Zhu, H.; Colvin, V.; Alvarez, P. Quantum Dot Weathering Results in Microbial Toxicity.
Environmental Science and Technology, 2008, 42, pp. 9424-9430.
-------
SiO, nanoparticles - Images
TEM image of mesoporous silica (Slowing et
al., 2008)
e
Endocytosed mesoporous silica in a HeLa cell (Slowing et al., 2008)
Silicified filamentous microbes in geothermal waters (Inagaki et al., 2003)
-------
SiO2 nanoparticles - References (Clockwise from top left)
1) Mesoporous silica imaged perpendicular to pores
1) Imaged by TEM
2) Slowing, I.; Vivero-Escoto, J.; Wu, C.; Lin, V. Mesoporous silica nanoparticles as controlled release
drug delivery and gene transfection carriers. Advanced Drug Delivery Review, 2008, 60, pp. 1278-
1288.
2) Mesoporous silica endocytosed by HeLa cells
1) Imaged by TEM (at micron scale)
2) Slowing, I.; Vivero-Escoto, J.; Wu, C.; Lin, V. Mesoporous silica nanoparticles as controlled release
drug delivery and gene transfection carriers. Advanced Drug Delivery Review, 2008, 60, pp. 1278-
1288.
3) Silicified filamentous microbes found in geothermal waters
1) Imaged by SEM (at micron scale)
2) Inagaki, R; Motomura, Y.; Ogata, S. Microbial silica deposition in geothermal hot waters. Applied
Microbiology and Biotechnology, 2003, 60, pp. 605-611.
-------
Nanoclay composites - Images
TEM of HDPE/nanoclay composite (Faruk et
al., 2008)
TEM image of silicone/montmorillonite composite containing
siloxane-modified montmorillonite clay (Simon et al., 2008)
SEM image of phyllosciliate grains from regolith (Murphy et al.,
1998)
-------
Nanoclay composites - References (Clockwise from top left)
1) TEM image of HDPE/nanoclay composites
1) Imaged by TEM
2) Faruk, 0.; Matuana, L. Nanoclay reinforced HOPE as a matrix for wood-plastic composites.
Composites Science and Technology, 2008, 68, pp. 2073-2077.
2) TEM micrograph of silicone/montmorillonite composite containing 5 wt% siloxane-modified
montmorillonite clay
1) Imaged by TEM
2) Simon, M.; Stafford, K.; Ou, D. Nanoclay Reinforcement of Liquid Silicone Rubber. Journal of
Inorganic and Organometallic Polymers and Materials, 2008,18, pp. 364-373.
3) Regolith grain consisting of biotite and kaolinite clay.
1) Imaged by SEM (at micron scale)
2) Murphy, S.; Brantley, S.; Blum, A.; White, A.; Dong, H. Chemical weathering in a tropical watershed,
Liquillo Mountains, Puerto Rico: II. Rate and mechanism of biotite weathering. Geochimica et
Cosmochimica Acta, 1998, 62m pp. 227-243.
-------
Zeolites - Images
Solid zeolite particles from resin templating (Tosheva et al., 2005)
Zeolite 4A for use as a detergent builder (Hui and Chao, 2006)
SEM image of a naturally occuring Chilean zeolite (Englert
and Rubio, 2005)
-------
Zeolites - References (Clockwise from top left)
1) Solid zeolite particle from resin templating
1) Imaged by SEM (at micron scale)
2) Tosheva, L; Valtchev, V. Nanozeolites: Synthesis, Crystallization Mechanisms, and Applications.
Chemistry of Materials, 2005,17, pp. 2494-2513.
2) Zeolite 4A synthesized from coal fly ash
1) Imaged by SEM (at micron scale)
2) Hui, K.; Chao, C. Pure, single phase, high crystalline, camfered-edge zeolite 4A synthesized from
coal fly ash for use as a builder in detergents. Journal of Hazardous Materials B, 2006,137, pp.
401-409.
3) Image of a grain of a naturally occurring Chilean zeolite
1) Imaged by SEM (at micron scale)
2) Englert, A.; Rubio, J. Characterization and environmental application of a Chilean natural zeolite.
InternationalJournal of Mineral Processing, 2005, 75, pp. 21-29.
-------
Chitosan nanoparticles - Images
Image of 10% cross-linked chitosan nanoparticles
(Banerjeeetal., 2002)
;>
100 nm
Chitosan nanoparticle loaded with cyclosporin A
(De Campos etal., 2001)
-------
Chitosan nanoparticles - References (Clockwise from top left)
1) 10% cross-linked chitosan nanoparticles
1) Imaged by TEM
2) Banerjee, T.; Mitra, S.; Singh, A.; Sharma, R.; Maitra, A. Preparation, characterization and
biodistribution of ultrafine chitosan nanoparticles. InternationalJournal of Pharmaceutics, 2002,
243, pp. 93-105.
2) Chistosan nanoparticle loaded with cyclosporin A
1) Imaged by TEM
2) De Campos, A.; Sanchez, A.; Alonso, M. Chitosan nanoparticles: a new vehicle for the improvement
of the delivery of drugs to the ocular surface. Application to cyclosporin A. InternationalJournal of
Pharmaceutics, 2001, 224, pp. 159-168.
-------
Highly functionalized nanoparticles - Images
MWCNT-A
o
Residual metal catalyst embedded in carbon
nanotube (Pumera, 2007)
100 nm
^^H
Silver nanoparticle decahedron formed in DMF (Tsuji et al., 2010)
I
/c^*^\
I \
50 nm
Quantum dot nanoparticle surrounded by a PLGA shell to
form a core-shell nanocomposite (Lee et al., 2010)
O
Double-walled Sn02 nano-coccon with an a-Fe203
spindle embedded inside (Lou et al., 2007)
-------
Highly functionalized nanoparticles - References (Clockwise from top left)
1) Residual metal catalyst embedded in carbon nanotube
1) Imaged by TEM
2) Pumera, M. Carbon Nanotubes Contain Residual Metal Catalyst Nanoparticles even after Washing
with Nitric Acid at Elevated Temperature Because These Metal Nanoparticles Are Sheathed by
Several Graphene Sheets. Langmuir, 2007, 23, pp. 6453-6458.
2) Quantum dot nanoparticle surrounded by a PLGA shell to form a core-shell nanocomposite
1) Imaged by TEM
2) Lee, P.-W.; Hsu, S.-H.; Tsai, J.-S.; Chen, F.-R.; Huang, P.-J.; Ke, C.-J.; Liao, Z.-X.; Hsiao, C.-W.; Lin, H.-J.;
Sung, H.-W. Multifunctional core-shell polymeric nanoparticles for transdermal DNA delivery and
epidermal Langerhans cells tracking. Biomaterials, 2010, 31, pp. 2425-2434.
3) Silver nanoparticle decahedron formed in DMF
1) Imaged by SEM
2) Tsuji, M.; Ogino, M.; Matsuo, R.; Kumagae, H.; Hikino, S.; Kim, T; Yoon, S.-H. Stepwise Growth of
Decahedral and Icosahedral Silver Nanocrystals in DMF. Crystal Growth & Design, 2010,10, pp.
296-301.
4) Double-walled Sn02 nano-cocoon with an ct-Fe203 spindle embedded inside
1) Imaged by TEM
2) Lou, X.; Yuan, C.; Archer, L. Double-walled Sn02 Nano-Cocoons with Movable Magnetic Cores.
Advanced Materials, 2007,19, pp. 3328-3332.
-------
Current Status and Future Directions for Examining Engineered Nanoparticles in Natural
Systems - Image Library Appendix
The purpose of this image library is to provide examples of engineered nanoparticles and
contrast them to images of their naturally occurring and/or biogenically produced counterparts.
Images are provide (where possible) of the engineered particles in a product and in some cases,
an image of an engineered particle that demonstrates obvious weathering effects.
Apparent in most images is the similarity between the engineered nanomaterial and it's
naturally occurring analogue. Though the engineered particles showed a greater degree of
monodispersity, most particles both manufactured and natural have similar morphologies. The
similarity between these images show the need for corroborative measurements to verify the
identity and origin of these materials.
There are some engineered materials that will possess very unique morphologies and surface
coatings that are noticeably different than naturally occurring materials of the same
composition (Slide 40). However, alterations made to these features upon entry into the
environment is still a topic of research and not well understood. It is possible these highly-
engineered material properties may be changed and altered to reflect materials more similar to
those found in the environment as a result of chemical changes and weathering that may occur.
It should be noted that imaging alone may not be sufficient to determine the origin and
identity of nanomaterials. Other techniques that exploit key physio-chemical differences
between these particles are necessary to detect and characterize these engineered
nanomaterials upon entry into the environment.
-------
Carbon nanotubes - Images
SEM image of Purified CNTs (Lu et al., 2006)
5 % CNTs in PVOH (Fairbrother, unpublished data)
Organic filaments in lake (Buffle and Leppard, 1995)
-------
Carbon nanotubes - References (Clockwise from top left)
1) Scanning electron microscope image of purified multi-walled carbon nanotubes.
1) Imaged by SEM.
2) Lu, C; Chung, Y.-L; Chang, K.-F. Adsorption thermodynamic and kinetic studies of
trihalomethanes on multiwalled carbon nanotubes. Journal of Hazardous Materials B.
2006,138, pp. 304-310
2) 5% CNTs in polyvinyl alcohol.
1) Imaged by SEM
2) Howard Fairbrother. John Hopkins University. Unpublished Data
3) Organic filaments in lake water.
1) Observed by transmission electron microscopy.
2) Buffle, J.; Leppard, G. G. Characterization of aquatic colloids and macromolecules. 1.
Structure and Behavior of Colloidal Material. Environmental Science and Technology.
1995, 29, pp. 2169-2175.
-------
ZnO nanoparticles- Images
ZnO nanoparticles imaged by SEM (Dybowska et al., 2011)
100000: 1
ZnO applied to a cotton textile (Behceri et al. 2008)
200nm
ZnO nanoparticles contained in a surface coating (Vorbau et al., 2009)
-------
ZnO nanoparticles- References (Clockwise from top left)
1) Images of isotopically modified ZnO nanoparticles
1) Imaged by SEM (at micron scale)
2) Dybowska, A.; Croteau, M-N.; Misra, S.; Berhanu, D.; Luoma, S.; Christian, P.; O'Brien, P.;
Valsami-Jones, E. Synthesis of isotopically modified ZnO nanoparticles and their
potential as nanotoxicity tracers. Environmental Pollution, 2011,159, pp. 266-273.
2) ZnO nanoparticles applied to a cotton textile
1) Imaged by SEM (at micron scale)
2) Becheri, A.; Durr, M.; Lo Nostro, P.; Baglioni, P. Synthesis and characterization of zinc
oxide nanoparticles: application to textiles as UV-absorbers. Journal of Nanoparticle
Research, 2008,10, pp. 679-689.
3) ZnO nanoparticles released from a surface coating via abrasion.
1) Imaged by TEM.
2) Vorbau, M.; Hillemann, L; Stintz, M. Method for the characterization of the abrasion
induced nanoparticle release into air from surface coatings. Aerosol Science, 2009, 40,
pp. 209-217.
-------
Ag nanoparticles- Images
100 nm
M
Ag nanoparticles prepared by silver ammonia reduction
(Panaceketal., 2006)
Ag nanoparticles found in sock fabric (Benn and Westerhoff, 2008)
Ag nanoparticles found in wash water (Benn and
Westerhoff, 2007)
Ag nanoparticles synthesized by Aspergillusflavus (Vigneshwaran et al., 2007)
-------
Ag nanoparticles- References (Clockwise from top left)
1) Ag nanoparticles formed via the reduction of silver ammoniate by glucose
1) Imaged by TEM
2) Panacek, A.; Kvitek, L; Prucek, R.; Kolaf, M.; Vecefova, R.; Pizurova, N.; Sharma, V.; Nevecna, T.;
Zbofil, R. Silver Colloid Nanoparticles: Synthesis, Characterization, and Their Antibacterial Activity.
Journal of Physical Chemistry B, 2006,110, pp. 16248-16253.
2) Ag nanoparticles found in ashed sock fabric (EDX inset)
1) Imaged by SEM (at micron scale)
2) Benn, T.; Westerhoff, P. Nanoparticle Silver Released into Water from Commercially Available Sock
Fabrics. Environmental Science and Technology, 2008, 42, pp. 4133-4139.
3) Silver nanoparticles formed from the reduction of silver nitrate byAspergillusflavus
1) Imaged by SEM
2) Vigneshwaran, N.; Ashtaputre, N.; Varadarajan, P.; Nachane, R.; Paralikar, K.; Balasubramanya, R.
Biological synthesis of silver nanoparticles using the fungus Aspergillusflavus. Materials Letters,
2007, 61, pp. 1413-1418.
4) Ag nanoparticles found in wash water from sock fabrics (inset is EDX)
1) Imaged by TEM
2) Benn, T; Westerhoff, P. Nanoparticle Silver Released into Water from Commercially Available Sock
Fabrics. Environmental Science and Technology, 2008, 42, pp. 4133-4139.
-------
TiO, nanoparticles- Images
o
15 nm
Ti02 nanoparticles imaged byTEM (Oskam et al., 2003)
V
20 nm
Ti02 nanoparticles in toothpaste (Kiser et al., 2008)
Weathered Ti02 particle in sunscreen (Nowack et al., 2012)
Ti-containing mineral in a biosolid (Kiser et al., 2008)
-------
TiO2 nanoparticles- References (Clockwise from top left)
1) Image of Ti02 nanoparticles prepared from titanium (IV) isoprepoxide
1) Imaged by TEM
2) Oskam, G.; Nellore, A.; Penn, R. L; Searson, P. The Growth Kinetics of Ti02 Nanoparticles from
Titanium (IV) Alkoxide at High Water/Titanium Ratio. Journal of Physical Chemistry B. 2003,107,
pp. 1734-1738.
2) Ti02 nanoparticles in toothpaste
1) Imaged by SEM
2) Kiser, M.; Westerhoff, P.; Benn, T; Wang, Y.; Perez-Rivera, J.; Hristovski, K. Titanium Nanomaterial
Removal and Release from Wastewater Treatment. Environmental Science and Technology. 2008,
43, pp. 6757-6763.
3) Titanium containing mineral in a biosolid
1) Observed by SEM (at micron scale)
2) Kiser, M.; Westerhoff, P.; Benn, T; Wang, Y.; Perez-Rivera, J.; Hristovski, K. Titanium Nanomaterial
Removal and Release from Wastewater Treatment. Environmental Science and Technology. 2008,
43, pp. 6757-6763.
4) Weathered titania nanoparticle released from sunscreen
1) Observed by TEM
2) Nowack, B.; Ranville, J.; Diamond, S.; Gallego-Urrea, J.; Metcalfe, C.; Rose, J.; Home, N.; Koelmans,
A.; Klaine, S. Potential Scenarios for Nanomaterial Release and Subsequent Alteration in the
Environment. Environmental Toxicology and Chemistry, 2012, 31, pp. 50-59.
-------
Au nanoparticles- Images
Gold nanoparticles synthesized by reduction of
chloroauric acid (Cichomski et al., 2011)
Aggregated acrylate capped gold nanoparticles at pH=2
(Diegolietal., 2008)
Catalytic gold nanoparticles deposited on a
ZnO support (Catillejos et al., 2012)
D
*
Gold nanoparticles found in weathered gold deposits
(Hough etal., 2008)
-------
Au nanoparticles- References (Clockwise from top left)
1) Gold nanoparticles synthesized via reduction of chloroauric acid by trisodium citrate
1) Imaged by SEM
2) Cichomski, M.; Tomaszewska, E.; Kosla, K.; Kozlowski, W.; Kowalczyk, P.; Grobelny, J. Study of dithiol
monolayer as the interface for controlled deposition of gold nanoparticles. Materials
Characterization, 2011, 42, pp. 268-274.
2) Catalytic gold nanoparticles deposited on a ZnO support
1) Imaged by TEM
2) Castillejos, E.; Gallegos-Suarez, E.; Bachiller-Baeza, B.; Bacsa, R.; Serp, P.; Guerrero-Ruiz, A.;
Rodriguez-Ramos, I. Deposition of gold nanoparticles on ZnO and their catalytic activity for
hydrogenation applications. Catalysis Communications, 2012, 22, pp. 79-82.
3) Gold nanoparticles found in weather gold deposits
1) Imaged by SEM
2) Hough, R.; Noble, R.; Hitchen, G.; Hart, R.; Reddy, S.; Saunders, M.; Clode, P.; Vaughan, D.; Lowe, J.;
Gray, D.; Anand, R.; Butt, C; Verrall, M. Naturally occurring gold nanoparticles and nanoplates.
Geology, 2008, 36, pp. 571-574.
4) Aggregated acrylate-capped gold nanoparticles at pH=2.
1) Imaged by TEM
2) Diegoli, S.; Manciulea, A.; Begum, S.; Jones, I.; Lead, J.; Preece, J. Interaction between
manufactured gold nanoparticles and naturally occurring macromolecules. Science of the Total
Environ ment,2QQS, 402, pp. 51-61.
-------
1) CeO, nanoparticles- Images
Cerium oxide nanoparticles prepared at 70°C (Chen and
Chang, 2005)
Ce02 particles adhered to a silty loam (von der Kammer et
al., 2012)
100 nm
Cerium oxide adhered to diesel particles in fuel additive (Jung et
al., 2005)
Ce02 nano-cluster found in a floodplain (von der Kammer
etal., 2012)
-------
CeO2 nanoparticles- References (Clockwise from top left)
1) Cerium oxide nanoparticles prepared from the oxidation of cerium ammoniate at 70° C.
1) Imaged by TEM
2) Chen, H.; Chang, H. Synthesis of nanocrystalline cerium oxide particles by the precipitation
method. Ceramic International, 2005, 31, pp. 795-802.
2) Cerium oxide nanoparticles found on diesel particles
1) Imaged by TEM
2) Jung, H.; Kittelson, D.; Zachariah, M. The influence of a cerium additive on ultrafine diesel particle
emissions and kinetics of oxidation. Combustion and Flame, 2005,142, pp. 276-288.
3) Natural Ce-containing nanoparticle cluster from the floodplain of Clark Fork River, Montana, USA
1) Imaged by TEM (scale not specified)
2) von der Kammer, R; Ferguson, P.; Holden, P.; Mason, A.; Rogers, K.; Klaine, S.; Koelmans, A.; Home,
N.; Unrine, J. Analysis of Engineered Nanomaterials in Complex Matrices (Environment and Biota):
General Consideration and Conceptual Case Studies. Environmental Toxicology and Chemistry,
2012, 31, pp. 32-49.
4) Cerium dioxide nanoparticles adhered to the surface of a silty loam
1) Imaged by SEM (at micron scale)
2) von der Kammer, F.; Ferguson, P.; Holden, P.; Mason, A.; Rogers, K.; Klaine, S.; Koelmans, A.; Home,
N.; Unrine, J. Analysis of Engineered Nanomaterials in Complex Matrices (Environment and Biota):
General Consideration and Conceptual Case Studies. Environmental Toxicology and Chemistry,
2012, 31, pp. 32-49.
-------
Zero valent iron nanoparticles- Images
Pristine zero valent iron NP (Kanel et al., 2006)
As(V) adsorbed to a ZVI reactive barrier (Kanel et al., 2006)
Zero valent iron NP with an oxide shell (Ramos et al., 2009)
Magnetite particles formed from photoxidation (Silva et al., 2012)
-------
Zero valent iron nanoparticles- References (Clockwise from top left)
1) Pristine zero valent iron nanoparticles
1) Imaged by TEM
2) Kanel, S.; Greneche, J.; Choi, H. Arsenic (V) Removal from Groundwater Using Nano Scale Zero-
Valent Iron as a Colloidal Reactive Barrier Material. Environmental Science and Technology, 2006,
40, pp. 2045-2050.
2) Arsenic (V) adsorbed onto a reactive barrier of zero valent iron nanoparticles
1) Imaged by SEM (at micron scale)
2) Kanel, S.; Greneche, J.; Choi, H. Arsenic (V) Removal from Groundwater Using Nano Scale Zero-
Valent Iron as a Colloidal Reactive Barrier Material. Environmental Science and Technology, 2006,
40, pp. 2045-2050.
3) Magnetite particles formed from the precipitation and photooxidation of acid mine drainage
1) Imaged by SEM (at micron scale)
2) Silva, R.; Castro, C.; Viganico, E.; Petter, C; Schneider, I. Selective precipitation/UV production of
magnetite particles obtained from the iron recovered from acid mine drainage. Minerals
Engineering, 2012, 29, pp. 22-27.
4) Zero valent iron nanoparticle with a formed oxide coating
1) Imaged by TEM
2) Ramos, M.; Van, W.; Li, X.; Koel, B.; Zhang, W. Simultaneous Oxidation and Reduction of Arsenic by
Zero-Valent Iron Nanoparticles: Understanding the Significance of the Core-Shell Structure. Journal
of Physical Chemistry C Letters, 2009,113, pp. 14591-14594.
-------
WOa nanoparticles- Images
W03 nanoparticles prepared by acid precipitation (Supothina et
al. 2007)
Tungsten oxide nanoparticles used for N02 gas sensing
(Rossinyol etal., 2007)
-------
Zero valent iron nanoparticles- References (Clockwise from top left)
1) Pristine tungsten oxide (W03) nanoplates
1) Imaged by SEM
2) Supothina, S.; Seeharaj, P.; Yoriya, S.; Sriyudthsak, M. Synthesis of tungsten oxide nanoparticles by
acid precipitation method. Ceramics International, 2007, 33, pp. 931-936.
2) Tungsten oxide nanoparticles templated on a KIT-6 structure for gas-sensing applications
1) Imaged by TEM
2) Rossinyol, E.; Prim, A.; Pellicer, E.; Arbio, J.; Hernandez-Ramirez, R; Peiro, R; Cornet, A.; Morante, J.;
Solovyov, L; Tian, B.; Bo, T, Zhao, D. Synthesis and Characterization of Chromium-Doped
Mesoporous Tungsten Oxide for Gas-sensing Applications. Advanced Functional Materials, 2007,
17, pp. 1801-1806.
-------
MnO,nanoparticles- Images
Pristine MnO, nanoparticles (Ching et al., 2011)
Carbon coated Mn02 nanoparticles for catalysis (Roche
etal., 2008)
Mn02 aggregation in the presence of biomolecules and divalent
cations (Huangfu et al., 2013)
Biogenically synthesized manganese oxides
(Miyataetal., 2007)
-------
MnO2 - References (Clockwise from top left)
1) Pristine manganese oxide (Mn02) nanoparticles
1) Imaged by SEM (at micron scale)
2) Ching, S.; Kriz, D.; Luthy, K.; Njagi, E.; Suib, S. Self-assembly of manganese oxide nanoparticles and
hollow spheres. Catalytic activity in carbon monoxide oxidation. Chemical Communications, 2011,
47, pp. 8286-8288.
2) Manganese oxide / carbon electrocatalysts
1) Imaged by TEM
2) Roche, I.; ChaTnet, E.; Chatenet, M.; Vondrak, J. Durability of carbon-supported manganese oxide
nanoparticles for the oxygen reduction reaction (ORR) in alkaline medium. Journal of Applied
Electrochemistry, 2008, 38, pp. 1195-1201.
3) Manganese (II) oxidation byAcremonium sp. Strain KR21-2 to form manganese oxides
1) Imaged by TEM
2) Miyata, N.; Tani, Y.; Sakata, M.; Iwahori, K. Microbial Manganese Oxide Formation and Interaction
with Toxic Metal Ions. Journal of Bioscience and Bioengineering, 2007,104, pp. 1-8.
4) Aggregated Mn2 nanoparticles in the presence of lOmM calcium nitrate and 2 mg/L alginate
1) Imaged by TEM
2) Huangfu, X.; Jiang, J.; Ma, J.; Yongze, L; Jing, Y. Aggregation Kinetics of Manganese Dioxide Colloids
in Aqueous Solution: Influence of Humic Substances and Biomacromolecules. Environmental
Science and Technology, 2013, Just Accepted.
-------
ALO, nanoparticles- Images
500 nm
a-AI203 nanoparticles formed in the presence of Na(AOT) (Park et al.,
2005)
Nano-porous anodised alumina coating on titanium (Briggs
etal., 2004)
Silica-alumina nanoparticle heteroaggregation (Garcia-Perez et al., 2006)
-------
AI2O3 - References (Clockwise from top left)
1) a-AI203 nanoparticles form in the presence of sodium bis(2-ethylhexyl) sulfosuccinate
1) Imaged by SEM
2) Park, Y.; Tadd, E.; Zubris, M.; Tannenbaum, R. Size-controlled synthesis of alumina nanoparticles
from aluminum alkoxides. Materials Research Bulletin, 2005, 40, pp.1506-1512.
2) Nano-porous anodised alumina coating on titanium for surgical implants
1) Imaged by SEM
2) Briggs, E.; Walpole, A.; Wilshaw, P.; Karlsson, M.; Palsgard, E. Formation of highly adherent nano-
porous alumina on Ti-based substrates: a novel bone implant coating. Journal of Materials Science:
Materials In Medicine, 2004,15, pp. 1021-1029.
1) Alumina colloids heteroaggregated with silica nanoparticles
1) Imaged by Cryo-FEG-SEM
2) Garcia-Perez, P.; Pagnoux, C.; Rossignol, F.; Baumard, J. Heterocoagulation between Si02
nanoparticles and AI203 submicronparticles; influence of the background electrolyte. Colloids and
Surfaces A: Physiochemical Engineering Aspects, 2006, 281, pp. 58-66.
-------
UO, nanoparticles- Images
50 nm
Uraninite nanoparticles precipitated on green rusts
(O'Loughlinetal.,2003)
Uranium nanoparticles precipitated from bio-reduction of U(VI)
by Shewanella oneidensis (Burgos et al., 2008)
-------
UO2 - References (Clockwise from top left)
1) Uraninite nanoparticles precipitated on mixed Fe(ll)/Fe(lll) hydroxides
1) Imaged by TEM
2) O'Loughlin, E.; Kelly, S.; Cook, R.; Csencsits, R.; Kemner, K. Reduction of Uranium (VI) by Mixed Iron
(ll)/ Iron(lll) Hydroxide (Green Rusts: Formation of U2 Nanoparticles. Environmental Science and
Technology, 2003, 37, pp. 721-727.
2) Uraninite nanoparticles precipitated from soluble U(VI) by Shewanella oneidensis MR-1 strain
1) Imaged by SEM (at micron scale)
2) Burgos, W.; McDonough, J.; Senko, J.; Zhang, G.; Dohnalkova, A.; Kelly, S.; Gorby, Y.; Kemner, K.
Characterization of uraninite nanoparticles produced by Shewanella oneidensis MR-1. Geochimica
etCosmochimicaActa, 2008, 72, pp. 4901-4915.
-------
Graphene - Images
Grapheme layer produced by chemical vapor deposition
(Park etal., 2010)
Graphene sheets with embedded gold nanoparticles
(Muszynskietal., 2008)
-------
Graphene - References (Clockwise from top left)
1) Graphene prepared by chemical vapor deposition
1) Imaged by TEM
2) Park, H.; Meyer, J.; Rother, S.; Skakalova, V. Growth and properties of few-layer graphene prepared
by chemical vapor deposition. Carbon, 2010, 48, pp. 1088-1094.
2) Graphene sheets with embedded gold nanoparticles for catalysis applications
1) Imaged by SEM (at micron scale)
2) Muszynski, R.; Seger, B.; Kamat, P. Decorating Graphene Sheets with Gold Nanoparticles. Journal of
Physical Chemistry C Letters, 2008,112, pp. 5263-5266.
-------
Fullerenes- Images
SEM image of C60 powder (Gusev et al., 1999)
.-
o
' '-': .'~''---'^1''l:''' '!:-Vv;,f;yV'.'.''- '^-,''' ':', 5 HPTI
Fullerene-like soot from a EurolV diesel engine (Su et al., 2004)
Fullerene particles found in precambrian rocks
from Russia (Buseck et al., 1992)
-------
Fullerenes- References (Clockwise from top left)
1) SEM image of C60 powder
1) Imaged by SEM
2) Gusez, Y.; Ruetsch, S.; Popeko, L; Popeko, I. Nitrogen and Argon Adsorption and SEM
Characterization of C60 And C60/70 Fullerenes: Comparison with Graphite. Journal of Physical
Chemistry B, 1999,103, pp. 6498-6503.
2) TEM images of fullerenes found in a precambrian rock from Russia
1) Imaged by TEM
2) Buseck, P.; Tsipursky, S.; Hettich, R. Fullerenes from the Geological Environment. Science, 1992,
257, pp. 215-217.
3) TEM image of fullerene-like soot from EurolV diesel engine
1) Imaged by TEM
2) Su, D.; Muller, J.-O; Jentoft, R.; Rothe, D.; Jacob, E.; Schlogl, R. Fullerene-like soot from EurolV
diesel engine: consequences for catalytic automotive pollution control. Topics In Catalysis, 2004,
30/31, pp. 241-245.
-------
1) Fe,Oa- Images
TEM image of hematite nanoparticles coated with HPC (Jing
and Wu, 2004)
100 nm
u
20 nm
Hematite nanoparticles found in free-drifting icebergs (Shaw et
al., 2011)
*»**
Aggregated alginate-coated hematite nanoparticles (Chen et al.,
2006)
-------
Graphene - References (Clockwise from top left)
1) TEM image of hematite nanoparticles coated with hexadecyipyridinium chloride (HPC)
1) Imaged by TEM
2) Jing, Z.; Wu, S. Synthesis and characterization of monodisperse hematite nanoparticles modified by
surfactants via hydrothermal approach. Materials Letters, 2004, 58, pp.3637-3640.
2) N/A hematite nanoparticle in a product
3) Hematite nanoparticles found in free-drifting icebergs
1) Imaged by TEM
2) Shaw, T; Raiswell, R.; Hexel, C.; Vu, H.; Moore, W.; Dudgeon, R.; Smith Jr., K. Input, composition,
and potential impact of terrigenous material from free-drifting icebergs in the Weddell Sea. Deep-
Sea Research II, 2011, 58, pp. 1376-1383.
4) Aggregated alginate-coated hematite nanoparticles in the presence of divalent salts
1) Imaged by TEM
2) Chen, K.; Mylon, S.; Elimelech, M. Aggregation Kinetics of Alignate-Coated Hematite Nanoparticles
in Monovalent and Divalent Electrolytes. Environment Science and Technology, 2006, 40, pp. 1516-
1523.
-------
Quantum dots - Images
TEM images of various quantum dots (Alivisatos, 1996)
3. suhtifis &
weathered QD<
PbS Quantum dots in solar cells (Jean et al., 2013)
TEM images of weathered quantum dot clusters
(Mahendraetal., 2008)
Spherical aggregates of ZnS nanoparticles formed in a biofilm (Labrenz et
al., 2000)
-------
Quantum dots - References (Clockwise from top left)
1) TEM images of various quantum dots lattices
1) Imaged by TEM
2) Alivisatos, A. Semiconductor Clusters, Nanocrystals, and Quantum Dots. Science, 1996, 271, pp.
933-937.
2) Lead sulfide quantum dots in solar cells
1) Imaged by SEM
2) Jean, J.; Chang, S.; Brown, P.; Cheng, J.; Rekemeyer, P.; Bawendi, M.; Gradecak, S.; Bulovic, V. ZnO
Nanowire Arrays for Enhanced Photocurrent in PbS Quantum Dot Solar Cells. Advanced Materials,
2013, 25, pp. 2790-2796.
3) Spherical aggregates of ZnS nanoparticles formed in a biofilm
1) Imaged by SEM (at micron scale)
2) Labrenz, M.; Druschel, G.; Thomsen-Ebert, T.; Gilbert, B.; Welch, S.; Stasio, G.; Bond, P.; Lai, B.;
Kelly, S.; Banfield, J. Formation of Sphalerite (ZnS) Deposits in Natural Biofilms of Sulfate-Reducing
Bacteria. Science, 2000, 290, pp. 1744-1747.
4) Weathered quantum dots clusters with Bacillus subtilis
1) Imaged by TEM
2) Mahendra, S.; Zhu, H.; Colvin, V.; Alvarez, P. Quantum Dot Weathering Results in Microbial Toxicity.
Environmental Science and Technology, 2008, 42, pp. 9424-9430.
-------
SiO, nanoparticles - Images
TEM image of mesoporous silica (Slowing et
al., 2008)
(a)
*
Endocytosed mesoporous silica in a HeLa cell (Slowing et al., 2008)
Silicified filamentous microbes in geothermal waters (Inagaki et al., 2003)
-------
SiO2 nanoparticles - References (Clockwise from top left)
1) Mesoporous silica imaged perpendicular to pores
1) Imaged by TEM
2) Slowing, I.; Vivero-Escoto, J.; Wu, C.; Lin, V. Mesoporous silica nanoparticles as controlled release
drug delivery and gene transfection carriers. Advanced Drug Delivery Review, 2008, 60, pp. 1278-
1288.
2) Mesoporous silica endocytosed by HeLa cells
1) Imaged by TEM (at micron scale)
2) Slowing, I.; Vivero-Escoto, J.; Wu, C.; Lin, V. Mesoporous silica nanoparticles as controlled release
drug delivery and gene transfection carriers. Advanced Drug Delivery Review, 2008, 60, pp. 1278-
1288.
3) Silicified filamentous microbes found in geothermal waters
1) Imaged by SEM (at micron scale)
2) Inagaki, R; Motomura, Y.; Ogata, S. Microbial silica deposition in geothermal hot waters. Applied
Microbiology and Biotechnology, 2003, 60, pp. 605-611.
-------
Nanoclay composites - Images
TEM of HDPE/nanoclay composite (Faruk et
al., 2008)
TEM image of silicone/montmorillonite composite containing
siloxane-modified montmorillonite clay (Simon et al., 2008)
SEM image of phyllosciliate grains from regolith (Murphy et al.,
1998)
-------
Nanoclay composites - References (Clockwise from top left)
1) TEM image of HDPE/nanoclay composites
1) Imaged by TEM
2) Faruk, 0.; Matuana, L. Nanoclay reinforced HOPE as a matrix for wood-plastic composites.
Composites Science and Technology, 2008, 68, pp. 2073-2077.
2) TEM micrograph of silicone/montmorillonite composite containing 5 wt% siloxane-modified
montmorillonite clay
1) Imaged by TEM
2) Simon, M.; Stafford, K.; Ou, D. Nanoclay Reinforcement of Liquid Silicone Rubber. Journal of
Inorganic and Organometallic Polymers and Materials, 2008,18, pp. 364-373.
3) Regolith grain consisting of biotite and kaolinite clay.
1) Imaged by SEM (at micron scale)
2) Murphy, S.; Brantley, S.; Blum, A.; White, A.; Dong, H. Chemical weathering in a tropical watershed,
Liquillo Mountains, Puerto Rico: II. Rate and mechanism of biotite weathering. Geochimica et
Cosmochimica Ada, 1998, 62m pp. 227-243.
-------
Zeolites - Images
Solid zeolite particles from resin templating (Tosheva et al., 2005)
Zeolite 4A for use as a detergent builder (Hui and Chao, 2006)
SEM image of a naturally occuring Chilean zeolite (Englert
and Rubio, 2005)
-------
Zeolites - References (Clockwise from top left)
1) Solid zeolite particle from resin templating
1) Imaged by SEM (at micron scale)
2) Tosheva, L; Valtchev, V. Nanozeolites: Synthesis, Crystallization Mechanisms, and Applications.
Chemistry of Materials, 2005,17, pp. 2494-2513.
2) Zeolite 4A synthesized from coal fly ash
1) Imaged by SEM (at micron scale)
2) Hui, K.; Chao, C. Pure, single phase, high crystalline, camfered-edge zeolite 4A synthesized from
coal fly ash for use as a builder in detergents. Journal of Hazardous Materials B, 2006,137, pp.
401-409.
3) Image of a grain of a naturally occurring Chilean zeolite
1) Imaged by SEM (at micron scale)
2) Englert, A.; Rubio, J. Characterization and environmental application of a Chilean natural zeolite.
InternationalJournal of Mineral Processing, 2005, 75, pp. 21-29.
-------
Chitosan nanoparticles - Images
Image of 10% cross-linked chitosan nanoparticles
(Banerjeeetal., 2002)
;>
100 nm
Chitosan nanoparticle loaded with cyclosporin A
(De Campos etal., 2001)
-------
Chitosan nanoparticles - References (Clockwise from top left)
1) 10% cross-linked chitosan nanoparticles
1) Imaged by TEM
2) Banerjee, T.; Mitra, S.; Singh, A.; Sharma, R.; Maitra, A. Preparation, characterization and
biodistribution of ultrafine chitosan nanoparticles. InternationalJournal of Pharmaceutics, 2002,
243, pp. 93-105.
2) Chistosan nanoparticle loaded with cyclosporin A
1) Imaged by TEM
2) De Campos, A.; Sanchez, A.; Alonso, M. Chitosan nanoparticles: a new vehicle for the improvement
of the delivery of drugs to the ocular surface. Application to cyclosporin A. InternationalJournal of
Pharmaceutics, 2001, 224, pp. 159-168.
-------
Highly functionalized nanoparticles - Images
MWCNT-A
o
Residual metal catalyst embedded in carbon
nanotube (Pumera, 2007)
100 nm
^^H
Silver nanoparticle decahedron formed in DMF (Tsuji et al., 2010)
I
/c^*^\
I \
50 nm
Quantum dot nanoparticle surrounded by a PLGA shell to
form a core-shell nanocomposite (Lee et al., 2010)
O
Double-walled Sn02 nano-coccon with an a-Fe203
spindle embedded inside (Lou et al., 2007)
-------
Highly functionalized nanoparticles - References (Clockwise from top left)
1) Residual metal catalyst embedded in carbon nanotube
1) Imaged by TEM
2) Pumera, M. Carbon Nanotubes Contain Residual Metal Catalyst Nanoparticles even after Washing
with Nitric Acid at Elevated Temperature Because These Metal Nanoparticles Are Sheathed by
Several Graphene Sheets. Langmuir, 2007, 23, pp. 6453-6458.
2) Quantum dot nanoparticle surrounded by a PLGA shell to form a core-shell nanocomposite
1) Imaged by TEM
2) Lee, P.-W.; Hsu, S.-H.; Tsai, J.-S.; Chen, F.-R.; Huang, P.-J.; Ke, C.-J.; Liao, Z.-X.; Hsiao, C.-W.; Lin, H.-J.;
Sung, H.-W. Multifunctional core-shell polymeric nanoparticles for transdermal DNA delivery and
epidermal Langerhans cells tracking. Biomaterials, 2010, 31, pp. 2425-2434.
3) Silver nanoparticle decahedron formed in DMF
1) Imaged by SEM
2) Tsuji, M.; Ogino, M.; Matsuo, R.; Kumagae, H.; Hikino, S.; Kim, T; Yoon, S.-H. Stepwise Growth of
Decahedral and Icosahedral Silver Nanocrystals in DMF. Crystal Growth & Design, 2010,10, pp.
296-301.
4) Double-walled Sn02 nano-cocoon with an ct-Fe203 spindle embedded inside
1) Imaged by TEM
2) Lou, X.; Yuan, C; Archer, L. Double-walled Sn02 Nano-Cocoons with Movable Magnetic Cores.
Advanced Materials, 2007,19, pp. 3328-3332.
-------
&EPA
United States
Environmental Protection
Agency
Office of Research
and Development (8101R)
Washington, DC 20460
Official Business
Penalty for Private Use
$300
EPA/600/R-14/244
August 2014
www.epa.gov
Please make all necessary changes on the below label, detach
or copy and return to the address in the upper left hand corner.
If you do not wish to receive these reports CHECK HERE n!
detach, or copy this cover, and return to the address in the
upper left hand corner.
PRESORTED STANDARD
POSTAGE & FEES PAID
EPA PER MIT No, G-35
Recy cl ed/Recy cl able
Printed with vegetable-based ink on
paper that contains a minimum of
50% post-consumer fiber content
processed chlorine free
------- |