United States
Environmental Protection
Agency
Proceedings
U.S. EPA 2004 Nanotechnology
Science To Achieve Results (S^AR)
Progress Review Workshop —
Nanotechnology and the Environmen
August
hiladelphia, P^
-------
-------
U.S.
of
DC
-------
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Table of Contents
Introduction xi
Executive Summary 1
Section 1. Green Manufacturing
Abstract: Green Engineering of Dispersed Nanoparticles: Measuring and Modeling Nanoparticle
Forces 21
Kristen Fichthorn
Environmental Implication/Application: Green Engineering of Dispersed Nanoparticles:
Measuring and Modeling Nanoparticle Forces 22
Darrell Velegal and Kristen Fichthorn
Abstract: Sustainable Biodegradable Green Nanocomposites From Bacterial Bioplastic for Automotive
Applications 23
Lawrence T. Drzal, Manjusri Misra, Amar K. Mohanty
Environmental Implication/Application: Sustainable Biodegradable Green Nanocomposites From
Bacterial Bioplastic for Automotive Applications 25
Lawrence T. Drzal, Manjusri Misra, Amar K. Mohanty
Abstract: Development of Nanocrystalline Zeolite Materials as Environmental Catalysts: From
Environmentally Benign Synthesis to Emission Abatement 26
Sarah Larsen
Environmental Implication/Application: Development of Nanocrystalline Zeolite Materials as
Environmental Catalysts: From Environmentally Benign Synthesis to Emission Abatement 27
Sarah Larsen
Abstract: Plasmon Sensitized Ti02 Nanoparticles as a Novel Photocatalyst for Solar Applications 29
George Chumanov
Environmental Implication/Application: Plasmon Sensitized Ti02 Nanoparticles as a Novel
Photocatalyst for Solar Applications 30
George Chumanov
Abstract: Graft Polymerization as a Route To Control Nanofiltration Membrane Surface Properties
To Manage Risk of EPA Candidate Contaminants and Reduce NOM Fouling 32
Georges Belfort
Environmental Implication/Application: Graft Polymerization as a Route To Control Nanofiltration
Membrane Surface Properties To Manage Risk of EPA Candidate Contaminants and Reduce NOM
Fouling 33
Georges Belfort
Abstract: Ecocomposites Reinforced With Cellulose Nanoparticles: An Alternative to Existing
Petroleum-Based Polymer Composites 34
William T. Winter
Environmental Implication/Application: Ecocomposites Reinforced With Cellulose Nanoparticles:
An Alternative to Existing Petroleum-Based Polymer Composites 35
William T. Winter
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Section 2. Aerosols
Abstract: Elemental Composition of Freshly Nucleated Particles 39
Murray Johnston
Environmental Implication/Application: Elemental Composition of Freshly Nucleated Particles 40
Murray Johnston
Abstract: Ion-Induced Nucleation of Atmospheric Aerosols 41
Peter McMurry, Kenjiro lida, FredEisele
Environmental Implication/Application: Ion-Induced Nucleation of Atmospheric Aerosols 42
Peter McMurry
Section 3. Sensors
Abstract: Nanostructured Porous Silicon and Luminescent Polysiloles as Chemical Sensors
for Carcinogenic Chromium(VI) and Arsenic(V) 45
William C. Trogler
Environmental Implication/Application: Nanostructured Porous Silicon and Luminescent
Polysiloles as Chemical Sensors for Carcinogenic Chromium(VI) and Arsenic(V) 46
William C. Trogler
Abstract: Nanosensors for Detection of Aquatic Toxins 47
Robert E. Gawley
Environmental Implication/Application: Nanosensors for Detection of Aquatic Toxins 48
Robert E. Gawley
Abstract: Micro-Integrated Sensing Systems by Controlled Self-Assembly of Nanoparticles 49
Somenath Mitra
Environmental Implication/Application: Micro-Integrated Sensing Systems by Controlled
Self-Assembly of Nanoparticles 50
Somenath Mitra
Abstract: Advanced Nanosensors for Continuous Monitoring of Heavy Metals 51
Adam K. Wanekaya, Daniel Andreescu, Omowunmi A. Sadik, Joseph Wang
Environmental Implication/Application: Advanced Nanosensors for Continuous Monitoring
of Heavy Metals 54
Adam K. Wanekaya, Daniel Andreescu, Omowunmi A. Sadik, Joseph Wang
Abstract: Metal Biosensors: Development and Environmental Testing 56
Anne J. Anderson, Charles D. Miller, Joan E. McLean
Environmental Implication/Application: Metal Biosensors: Development and Environmental
Testing 58
Anne J. Anderson, Charles D. Miller, Joan E. McLean
Abstract: Compound Specific Imprinted Microspheres for Optical Sensing 59
Barry K. Lavine
Environmental Implication/Application: Compound Specific Imprinted Microspheres for Optical
Sensing 60
Barry K. Lavine
vi The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Abstract: Ultrasensitive Pathogen Quantification in Drinking Water Using High Piezoelectric
PMN-PT Microcantilevers 61
Wan Y. Shih, Wei-Heng Shih
Environmental Implication/Application: Ultrasensitive Pathogen Quantification in Drinking Water
Using High Piezoelectric PMN-PT Microcantilevers 62
Wan Y. Shih
Abstract: Nanomaterial-Based Microchip Assays for Continuous Environmental Monitoring 63
Joseph Wang
Environmental Implication/Application: Nanomaterial-Based Microchip Assays for Continuous
Environmental Monitoring 64
Joseph Wang
Abstract: Low-Cost Organic Gas Sensors on Plastic for Distributed Environmental Monitoring 65
Vivek Subramanian
Environmental Implication/Application: Low-Cost Organic Gas Sensors on Plastic for Distributed
Environmental Monitoring 66
Vivek Subramanian
Abstract: The Silicon Olfactory Bulb: A Neuromorphic Approach to Molecular Sensing With
Chemoreceptive Neuron MOS Transistors (CvMOS) 67
Edwin C. Kan, Bradley A. Minch
Environmental Implication/Application: The Silicon Olfactory Bulb: A Neuromorphic Approach
to Molecular Sensing With Chemoreceptive Neuron MOS Transistors (CvMOS) 68
Edwin C. Kan, Bradley A. Minch
Abstract: A Nanocontact Sensor for Heavy Metal Ion Detection 69
Nongjian Tao
Environmental Implication/Application: A Nanocontact Sensor for Heavy Metal Ion Detection 71
Nongjian Tao
Section 4. Remediation
Abstract: Membrane-Based Nanostructured Metals for Reductive Degradation of Hazardous Organics
at Room Temperature 75
Dibakar Bhattacharyya, L. Bachas, D. Meyer, J. Xu, S. Ritchie, L. Wu
Environmental Implication/Application: Membrane-Based Nanostructured Metals for Reductive
Degradation of Hazardous Organics at Room Temperature 76
Dibakar Bhattacharyya
Abstract: Dendritic Nanoscale Chelating Agents: Synthesis, Characterization, Molecular Modeling,
and Environmental Applications 77
Mamadou Diallo, Lajos Balogh, William A. Goddard, James H. Johnson
Environmental Implication/Application: Dendritic Nanoscale Chelating Agents: Synthesis,
Characterization, Molecular Modeling, and Environmental Applications 78
Mamadou Diallo
Abstract: Synthesis, Characterization, and Manipulation of {FeS-PAMAM} Dendrimer
Nanocomposites 79
Xiangyang Shi, Lajos P. Balogh
Abstract: Hollow and Nanoporous Iron Particles 82
Wei-xian Zhang
The Office of Research and Development's National Center for Environmental Research vii
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Abstract: Developing Functional Fe°-Based Nanoparticles for In Situ Degradation of DNAPL
Chlorinated Organic Solvents 83
Gregory V. Lowry, YueqiangLiu, Sara A. Majetich, Kris Matyjaszewski, NavidSaleh,
Traian Sarbu, David S. Shall, Kevin Sirk, Robert D. Tilton
Environmental Implication/Application: Developing Functional Fe -Based Nanoparticles for In Situ
Degradation of DNAPL Chlorinated Organic Solvents 86
Gregory V. Lowry, Sara A. Majetich, KrisMatyjaszewski, Robert D. Tilton
Abstract: A Bioengineering Approach to Nanoparticle-Based Environmental Remediation 87
Daniel R. Strongin
Environmental Implication/Application: A Bioengineering Approach to Nanoparticle-Based
Environmental Remediation 90
Daniel R. Strongin
Section 5. Treatment
Abstract: NOX Reduction With Transition Metal Carbide Nanoparticles 93
S. Ismat Shah
Environmental Implication/Application: NOX Reduction With Transition Metal Carbide Nanoparticles 95
S. Ismat Shah
Abstract: Simultaneous Environmental Monitoring and Purification Through Smart Particles 96
Wolfgang Sigmund, C. Y. Wu, D. Mazyck
Environmental Implication/Application: Simultaneous Environmental Monitoring and Purification
Through Smart Particles 97
Wolfgang Sigmund
Abstract: Nanoscale Biopolymers With Tunable Properties for Improved Decontamination
and Recycling of Heavy Metals 98
Wilfred Chen
Environmental Implication/Application: Nanoscale Biopolymers With Tunable Properties
for Improved Decontamination and Recycling of Heavy Metals 99
Wilfred Chen
Environmental Implication/Application: Use of Ozonation in Combination With Nanocrystalline
Ceramic Membranes for Controlling Disinfection By-Products 100
Simon H. Davies
Section 6. Fate, Transport, and Tranformation
Abstract: Adsorption and Release of Contaminants Onto Engineered Nanoparticles 103
Mason B. Tomson
Environmental Implication/Application: Adsorption and Release of Contaminants Onto
Engineered Nanoparticles 104
Mason B. Tomson
Abstract: Impacts of Manufactured Nanomaterials on Human Health and the Environment: A Focus
on Nanoparticulate Aerosol and Atmospherically Processed Nanoparticulate Aerosol 105
VickiH. Grassian
Environmental Implication/Application: Impacts of Manufactured Nanomaterials on Human Health
and the Environment: A Focus on Nanoparticulate Aerosol and Atmospherically Processed
Nanoparticulate Aerosol 106
VickiH. Grassian
viii The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Abstract: Chemical and Biological Behavior of Carbon Nanotubes in Estuarine Sedimentary Systems 107
P. Lee Ferguson
Environmental Implication/Application: Chemical and Biological Behavior of Carbon Nanotubes
in Estuarine Sedimentary Systems 108
P. Lee Ferguson
Abstract: Transformations of Biologically Conjugated CdSe Quantum Dots Released Into Water
andBiofilms 109
Patricia A. Holden
Environmental Implication/Application: Transformations of Biologically Conjugated CdSe
Quantum Dots Released Into Water and Biofilms Ill
Patricia A. Holden, Jay L. Nadeau
Abstract: Repercussion of Carbon-Based Manufactured Nanoparticles on Microbial Processes in
Environmental Systems 112
Ronald F. Turco, Bruce M. Applegate, Timothy Filley
Environmental Implication/Application: Repercussion of Carbon-Based Manufactured Nanoparticles
on Microbial Processes in Environmental Systems 113
Ronald F. Turco, BrueeM. Applegate, Timothy Filley
Abstract: The Fate, Transport, Transformation, and Toxicity of Manufactured Nanomaterials
in Drinking Water 114
Yongsheng Chen, Paul Westerhoff, John Crittenden, David Capco
Section 7. Toxicology
Abstract: Short-Term Chronic Toxicity of Photocatalytic Nanoparticles to Bacteria, Algae,
and Zooplankton 117
Chin Pao Huang, Donald C. Phillips
Environmental Implication/Application: Short-Term Chronic Toxicity of Photocatalytic
Nanoparticles to Bacteria, Algae, and Zooplankton 118
Chin Pao Huang
Abstract: Evaluation of Nanoparticles Interactions With Skin 119
Nancy Ann Monteiro-Riviere
Environmental Implication/Application: Evaluation of Nanoparticles Interactions With Skin 120
Nancy Ann Monteiro-Riviere
Abstract: Physical and Chemical Determinants of Nanofiber/Nanotube Toxicity 121
Robert H. Hurt
Environmental Implication/Application: Physical and Chemical Determinants
of Nanofiber/Nanotube Toxicity 122
Robert H. Hurt, Agnes B. Kane
Section 8. Industrial Ecology
Abstract: Societal Implications of Nanotechnology: Benefits and Costs 125
EarlR. Beaver
Environmental Implication/Application: Societal Implications of Nanotechnology: Benefits
and Costs 126
EarlR. Beaver
The Office of Research and Development's National Center for Environmental Research ix
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Abstract: A Life-Cycle Assessment Approach for Evaluating Future Nanotechnology
Applications 127
Shannon M. Lloyd, Lester B. Lave
Environmental Implication/Application: A Life-Cycle Assessment Approach for Evaluating Future
Nanotechnology Applications 128
Shannon M. Lloyd, Lester B. Lave
Appendix
Agenda 131
Participants List 137
Index of Speakers, Authors, and Co-Authors 141
Cover Image:
Copyright. Dr. V.H. Crespi, Penn State University. Distributed under the Open Content License
(http://opencontent.org/opl/shtml).
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Introduction
Nanoscale science, engineering, and technology incorporate a variety of disciplines, including chemistry,
materials science, biology, engineering, electronics, and physics. The term nanotechnologies refers to tech-
nologies in the range of 1-100 nanometers and to the ability to work at the molecular level, atom by atom, to
create large structures with fundamentally new molecular organization. There is a potential for truly revolu-
tionary transformative capabilities for an entire host of products and processes, including those that enhance
environmental quality and sustainability through pollution prevention, treatment, and remediation. The poten-
tial also exists for adverse effects on human health and the environment. Understanding and preventing or
mitigating these effects is vital both for the responsible development of the technology and for the U.S. En-
vironmental Protection Agency (EPA) to carry out its mission.
EPA's Office of Research and Development (ORD), National Center for Environmental Research
(NCER), as part of its Science To Achieve Results (STAR) program, supports research leading to applications
of nanotechnology. EPA is interested in advances in nanotechnology that can improve the protection of human
health and the environment, including significant improvements in cost or performance to assess and solve
environmental problems. In anticipation of the significant impacts resulting from the development of nano-
technology, EPA is engaging in a variety of activities, including sponsoring research and development on the
potential environmental applications and implications of nanotechnology, coordinating and participating in
strategic research planning concerning the potential role(s) for emerging technologies with respect to en-
vironmental protection, and providing information at a variety of conferences and workshops composed of
academic, industry, government, and non-governmental organization (NGO) representatives dealing with
possible societal and environmental impacts of novel technologies.
Nanotechnology offers an opportunity to significantly impact environmental sensing research needs. For
example, nanotechnology makes it possible to develop parallel arrays of nanoscale sensor elements, which
would result in increased sensitivity, accuracy, and spatial resolution in the simultaneous detection of a large
number of compounds. Most sensors depend on interactions occurring at the molecular level; hence, nano-
technology-enabled sensors can have a tremendous effect on our capacity to monitor and protect the environ-
ment. Nanotechnology is certain to improve existing sensors and benefit the development of new ones.
However, there are many challenges such as reducing the cost of materials and devices, while improving
accuracy and sensitivity, and delivering the compound to the device when working with very dilute con-
centrations.
Treatment and remediation techniques also can be greatly improved through nanotechnology. The poten-
tial exists to develop inexpensive remediation and treatment technologies that enable the rapid and effective
cleanup of recalcitrant compounds, especially those located in inaccessible areas. Currently, many of the
methods that the Agency employs to remove toxic contaminants from the environment involve laborious, time-
consuming and expensive techniques. Such techniques often require pretreatment processes and removal of
portions of the surrounding environment with the consequent disturbance of the ecosystem. The development
of technologies that can perform in situ and that are able to reach into crevices, below aquifers, and other
difficult areas, eliminating the necessity for costly pump-and-treat operations, would greatly facilitate the re-
mediation of many contaminated sites, especially those contained on the Superfund list. Current challenges
include the need to increase the stability of nanoparticles utilized in remediation/treatment methodologies, the
need to develop manufacturing techniques for the mass production of these materials, and the need to develop
improved methods for monitoring the fate and transport of these materials once they enter the natural en-
vironment.
Environmentally benign manufacturing and processing methods enabled by nanotechnological advances
will result in the elimination of toxic wastes and by-products and facilitate bottom-up chemical and industrial
manufacturing that utilizes "green" processes. Such "green" or environmentally benign manufacturing pro-
cesses will not only eliminate waste streams (via precise manufacturing) as a resultant product, but also will
The Office of Research and Development's National Center for Environmental Research xi
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
reduce the risks associated with the use of hazardous reactants and solvents through the use of nonhazardous
starting materials. These processes also have the potential to significantly reduce the consumption of energy
and to make many of the alternative clean energy sources (e.g., solar, fuel cells) commercially viable.
Challenges to the development and adoption of these processes include the need to develop mass manu-
facturing techniques and the need to educate industry concerning their potential applicability.
NCER also supports research through STAR grants in understanding the implications of nanotechnologies.
There is a serious lack of information about the human health and environmental implications of manufactured
nanomaterials (e.g., nanoparticles, nanotubes, nanowires, fullerene derivatives, quantum dots, dendrimers, and
other nanoscale materials). Potentially harmful effects of nanotechnology might arise as a result of the nature
of the nanoparticles themselves, the characteristics of the products made from them, aspects of the manu-
facturing process involved, and the use of the products or the end-of-life disposal. The large surface area,
crystalline structure, type and degree of functionalization, and reactivity of some nanoparticles may facilitate
transport in the environment or lead to harm because of their interactions with cellular materials. Because size
matters on the nanoscale, harmful effects caused by the composition of the material itself could be increased.
EPA's research concerning environmental implications examines the potential persistence and possible
synergistic effects of nanomaterials with other contaminants or naturally occurring compounds in the
environment. Reactivity and the types of compounds that result are crucial degradation questions. There also is
the issue of the potential bioavailability, bioaccumulation, and biotransformation capacities of nanomaterials.
The capacity of these materials to accumulate in certain nanoparts of living systems in various species must be
explored along with the metabolic and alteration of these materials and their subsequent effects on living
systems. Knowledge about the transport of nanomaterials that reach the environment is important and is
currently unknown. How these materials move from one media to another, from one organism or ecosystem to
another, and from organisms to the environment and vice versa will be critical for understanding and imple-
menting proper manufacture, use, and end-of-life options. To effectively assess these impacts, a full life-cycle
analysis of the materials and products must be undertaken—from starting materials to the manufacture, use,
and eventual disposal or reuse.
EPA-sponsored nanotechnology research outlined in this document addresses these challenges and
concerns. Researchers in the areas of environmental applications and implications of nanotechnology presented
data and results from their work, some of which began in 2002. This Progress Review Workshop brings to-
gether EPA's extramural scientists as well as scientists and policymakers from government, academia, and
NGOs to consider both the environmental applications and implications of nanotechnology.
The research described in this report has not been subjected to the Agency's required peer review and policy reviews, and
does not necessarily reflect the views of the Agency. Therefore, no official endorsement should be inferred. Any opinions, find-
ings, conclusions, or recommendations expressed in this report are those of the investigators who participated in the research or
others participating in the Progress Review Workshop, and not necessarily those of EPA or the other federal agencies support-
ing the research.
For more information on EPA's nanotechnology research, please contact Barbara Karn, Ph.D., at 202-343-
9704 (karn.barbara@epa.gov); or Nora Savage, Ph.D., at 202-343-9858 (savage.nora@epa.gov).
xii The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress
Review Workshop—Nanotechnology and the Environment II
Loews Philadelphia Hotel
1200 Market Street
Philadelphia, PA 19107
August 18-20, 2004
Executive Summary
OVERVIEW
The U.S. Environmental Protection Agency's (EPA) 2004 Nanotechnology Science To Achieve Results
(STAR) Progress Review Workshop—Nanotechnology and the Environment II was held on August 18-
20, 2004, in Philadelphia, PA. The workshop brought together approximately 100 researchers from aca-
demia, industry, and government to discuss ongoing research on nanotechnology and the environment.
The workshop also served as a stimulus for increased collaborations among the various researchers and
resulted in improved knowledge of the environmental aspects of nanotechnology.
Welcome and Introductory Remarks
Steve Lingle, U.S. EPA
Mr. Lingle welcomed participants to the workshop, noting that EPA provides leadership for federal
efforts related to the environmental applications and implications of nanotechnology. The primary role of
EPA's National Center for Environmental Research in the Office of Research and Development (ORD) is
to support research carried out by the STAR and Small Business Innovation Research (SBIR) Programs.
ORD provides the scientific basis for regulatory policy decisions made by EPA and helps set EPA's
research agenda. ORD is partnering with the National Institute for Occupational Safety and Health
(NIOSH) and the National Science Foundation (NSF) as part of its efforts related to nanotechnology and
hopes to include a number of other agencies in these activities. ORD's goal also is attempting to build an
environmental nanotechnology research community.
National Initiative: Overview, Chances, and Risks
Mihail Roco, NSF
Dr. Roco spoke about the National Nanotechnology Initiative's (NNI) efforts to promote a multidomain
approach and interagency collaboration in nanotechnology research. One of the main drivers for nano-
technology, apart from scientific interest, is long-term societal effects. In the last 2-3 years, passive
nanostructures (e.g., quantum dots, nanotubes) have been created. The next generation of nanodevices
that soon will emerge as commercial prototypes are active nanodevices (e.g., actuators). It is anticipated
that in approximately 5 years, nanosystems with more complex applications will be in place.
The organizational structure and roles of the NNI were described. At present, there are approximately
40,000 U.S. workers in the field of nanotechnology. In 2000, only five academic institutions had graduate
courses related to nanotechnology; today, more than 270 have undergraduate and graduate courses in
nanotechnology. At present, the largest use of NNI funds for nanotechnology research is in the field of
electronics. About 4 percent of the NNI budget is dedicated to environmental research. Critical long-term
issues related to nanotechnology involve sustainable development, product lifecycle, measurement, miti-
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
gation, cleanup techniques, and interactions with living systems. NNI activities were discussed, including
coordination of research and development investments; evaluation and implementation of regulatory
standards; educational, health, and environmental implications meetings; and industry and international
collaborations. As a field, nanotechnology is growing very rapidly, and a coherent, exploratory plan that
includes a focus on societal implications is needed.
Nanotechnology and the Environment: A Charge to EPA Nanotechnology Grantees
Barbara Karn, U.S. EPA
The NNI defines nanotechnology as research and development at the atomic, molecular, or macro-
molecular levels, in the length scale of approximately 1-100 nm range; creating and using structures,
devices, and systems that have novel properties and functions because of their small and/or intermediate
size; and the ability to control or manipulate on the atomic scale. The challenge is to use nanotechnology
research to help clean up past environmental damage, correct present environmental problems, prevent
future environmental impacts, and help sustain the planet for future generations. A research framework
for nanotechnology and the environment includes applications that are reactive to existing problems or
proactive in preventing future problems (e.g., sensors, treatment, remediation, green manufacturing, green
energy) as well as the implications of interactions of nanomaterials with the environment and the possible
risks that may be posed by the use of nanotechnology (e.g., nano-geochemistry, toxicity, fate/transport/
transformation, exposure/bioavailability/bioaccumulation, and industrial ecology aspects). The NNI es-
tablished a set of nine Grand Challenges for Research in Nanotechnology. One of these Grand Chal-
lenges is Nanoscale Processes for Environmental Improvement, which includes applications for measure-
ment in the environment, applications for sustainable materials and resources, applications for sustainable
processes, implications in natural and global processes, and implications in health and environmental
safety.
PLENARY TALKS
Nanotechnology Applications for Environmental Sensors: Integrated Devices for Real-Time Analyses
Nongjian Tao, Arizona State University
Monitoring technology is moving in the direction of smaller devices with greater functionality. Nano-
technology will play a significant role in the development of integrated sensors, including sample de-
livery, sensing elements, and signal processing and transmission. One challenge is signal transduction,
which requires converting a chemical binding event into a readable signal. Projects utilizing nanoparticles
with a metal ion colorimetric sensor for optical detection and arrays of electrically wired nanosensing
elements for electrical detection were highlighted, as was a project that involves developing a palladium
nanowire hydrogen sensor. Another emerging technology is carbon nanotube field effect transistor (FET)
sensors. In a conventional FET, conduction through the channel is two-dimensional, but detection sen-
sitivity can be enhanced by narrowing the channel to one dimension. Nanotechnology offers several
unique features for making future generations of sensors smaller and more functional (e.g., reduced sam-
ple solutions, high degree of integration, high sensitivity for single molecule/ion analysis, and faster re-
sponse time). However, an integrated device needs to solve the interface between nano- and microtech-
nology, and challenges remain in terms of interconnectivity and sample delivery issues.
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Nanotechnology Applications for Treatment: Cost-Effective and Rapid Technologies,
Smart Materials or Active Surface Coatings
Wilfred Chen, University of California, Riverside
Nanomaterials provide the ability to manipulate, control, and bind materials at the same atomic and mo-
lecular level in addition to novel affinity, capacity, and selectivity because of their unique physical,
chemical, and biological properties. Types of nanomaterials that can be used for environmental treatments
include smart modified surfaces or membranes, nanostructured materials, molecularly imprinted polymers
(MIPs), and nanoscale biopolymers. One example of smart modified surfaces or membranes includes
active membranes modified with peptides for heavy metal removal. An array of different polypeptides
could be fine tuned for a variety of applications. Smart surfaces are being developed to address bio-
fouling. Poly(amidoamine) dendrimers are an example of nanostructured materials that can be used to
bind to metals. It may be possible to use combinations of functions in dendrimeric structures for a variety
of applications. MIPs are being developed for virus, phosphate, and perchlorate removal. Researchers are
developing a tunable biopolymer with metal-binding properties that could be applied to wastewater con-
tamination.
Nanotechnology Applications for Remediation: Cost-Effective and Rapid Technologies;
Removal of Contaminants From Soil, Groundwater, and Aqueous Environments
Gregory Wilson, U.S. EPA
A site conceptual model involving a trichloroethylene (TCE) plume at a U.S. Navy site was used to
describe the Record of Decision (ROD), part of the process that involves selecting the technology that
will be used to clean up a Superfund site. Fewer RODs are being implemented, but they are becoming
more complex with a greater mix of remedies. A greater amount of in situ treatment is occurring, which
addresses technically complex contamination problems. The Superfund Program is developing a nano-
technology component to many of its databases (e.g., the Reach It database) and is partnering with a
variety of federal agencies, including the Department of Energy (DOE). DOE's Office of Basic Energy
Science is working with NSF to support the construction of five Nanoscale Science Research Centers,
which will support nanotechnology research. The role of nanotechnology in environmental remediation
was discussed relative to three projects. One project involved nanoscale particle treatment of groundwater
at a naval air engineering station in Lakehurst, NJ. Nanoscale iron particles with a palladium catalyst were
injected below the surface, reducing TCE concentrations by up to 50 percent after a single injection.
Similar results were observed in a project on source area treatment with nanoscale particles at a naval air
station in Jacksonville, FL. This project indicated that nano approaches may be feasible from a cost-
effective as well as an environmentally effective standpoint. The third project involved micro-scale zero-
valent iron (ZVI) treatment of groundwater at Hunter's Point Shipyard in San Francisco, CA. In this
project, pneumatic fracturing was used to inject micro-scale ZVI, and 99.1 percent of chlorinated solvents
were removed.
Nanotechnology Applications for Green Manufacturing
Lawrence T. Drzal, Michigan State University
Nanotechnology can enable the transition of traditional manufacturing (the conversion of materials and
energy into useful products through a designed process utilizing a combination of chemical, biological,
and mechanical processes) to green manufacturing (manufacturing that reduces waste, minimizes pol-
lution, and protects human health and the environment). The morphologies, physical and chemical proper-
ties, and self-assembly characteristics of nanoparticles make them attractive to manufacturers, and a large
number of manufacturing operations will be impacted by nanotechnology. A number of projects in the
field of microelectronics were discussed, including those on nonvolatile computer memory through self-
assembly, epitaxial self-assembly of block copolymers on lithographically defined nanopatterned sub-
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
strates, self-assembled 3-D designer material, and enzyme "ink" for nanomanufacturing. The field of
structural polymer composites stands to benefit from nanotechnology. Nanoreinforcements can add multi-
functionality to polymers through small additions of these nanoparticles. Some examples include or-
ganically modified nanoclays, cellulose nanowhiskers, and graphite nanoplatelets. Other examples of
nanotechnology applications for green manufacturing include nanoparticle manufacturing using super-
critical CO2; incorporation of metal or metal oxide nanoparticles to produce coatings with anticorrosion
properties; self-assembled monolayers in mesoporous supports for improved selectivity in separations,
reactions, and sensing; reversible self-assembly for end-of-life and recyclability and reuse; and "demate-
rialization" through increased use of nanoscale materials to replace microscale elements. It is expected
that worldwide research and development spending in nanotechnology will rise about 10 percent this year
to $8.6 billion; in 2005, with the private sector likely outspending the public sector in this area.
Federal Nanotechnology Efforts: Toxicity and the Environment
Nora Savage, U.S. EPA
Federal agencies participating in the NNI, particularly the regulatory agencies, are aware of the current
observations, hypotheses, and deductions concerning nanomaterials. Environmental, societal and edu-
cational, and health nanotechnology funding by federal agencies has increased from approximately $80
million in 2001 to about $130 million in 2004. The environmental portion has increased from approxi-
mately $18 to 20 million (see Figure at the end of this summary). NNI activities related to health and the
environment include EPA and NSF research grants on health and environmental applications and
implications of nanotechnology; National Institutes of Health research on the effects of nanoscale mate-
rials inside the body; National Toxicology Program work on carbon nanotubes, quantum dots, and
titanium dioxide; and the joint NSF and DOE Nanoscale Science Research Centers. EPA is discussing
internally how nanomaterials should be approached under existing Toxic Substance Control Act (TSCA)
regulations and/or whether new regulations are needed. Potential environmental benefits of nano-
technology as seen by the Agency include improved monitoring and detection capabilities; ultra-green
manufacturing and chemical processing; waste minimization through designed pollution prevention at the
source; reduced energy usage; commercially viable, alternative clean energy sources; and inexpensive,
rapid remediation and treatment technologies. Nanotechnology also carries with it the potential to harm
the environment and human health. Human health and ecosystem implications include the potential
toxicity of novel materials; potential harm to the environment and/or ecosystem through use, manu-
facture, and/or disposal; unknown transport, transformation, and fate information of nanomaterials; and
potential bioaccumulation and biotransformation issues. At the American Chemical Society's (ACS) 2005
Annual Meeting, there will be a Nanotechnology and the Environment symposium with 11 sessions,
coordinated by Barbara Karn and Nora Savage. This is the third such symposium held at consecutive
ACS annual meetings. During this symposium, there will be a panel featuring representatives from
several nongovernment organizations who will give their perspectives on nanotechnology and societal
impacts.
SESSION 1: GREEN MANUFACTURING
Chair: Barbara Karn, U.S. EPA
Green Engineering of Dispersed Nanoparticles: Measuring and Modeling Nanoparticle Forces
Kristen Fichthorn, Pennsylvania State University
Nanoparticles are potential building blocks for new and existing materials; however, it is difficult to
disperse or assemble "bare" nanoparticles, and nanoparticle forces are poorly understood. In studying
nanoparticle forces, these researchers made the following conclusions: (1) current theories do not accu-
rately describe forces for small nanoparticles; (2) solvation forces can be important for colloidal nano-
particles; (3) solvation forces are strongly dependant on particle size, shape, surface, roughness, particle-
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
solvent interactions, and solvent structure; and (4) solvent-nanoparticle suspensions can be engineered for
stability, assembly, and environmental impact.
Sustainable Biodegradable Green Nanocomposites From Bacterial Bioplastic
for Automotive Applications
Lawrence T. Drzal, Michigan State University
The objectives of this project are to overcome inherent material limitations of polyhydroxybutyrate
(PHB)/polyhydroxyalkanoate (PHA) bioplastics, study the effect of PHB/PHA modification on the ther-
mal and morphological properties, and synthesize functionalized PHB/PHA as a compatibilizer in PHB/
PHA-based blends and nanocomposites. Reactive extrusion was used to graft functional groups onto a
PHB backbone through a solvent-free process; desired changes in the thermal and morphological proper-
ties of PHB can be achieved upon its functionalization. Optimum clay exfoliation and surface chemical
modification produced nanocomposites with enhanced properties capable of competing with toughened
polyolefin materials. The researchers currently are examining the use of ionic liquids as a new plasticizer
for a PHA polymer matrix (replacing pthalates) and as exfoliating agents for layered silicates in "green
nanocomposites" prepared from PHAs.
Development of Nanocrystalline Zeolite Materials as Environmental Catalysts
Sarah C. Larsen, University of Iowa
Zeolites are aluminosilicates with well-defined openings of molecular dimensions (0.4-10 nm). Zeolites
have a large number of applications in areas such as adsorption, catalysis, and ion exchange. Zeolite
particle size can be systematically tuned in the nanometer range by varying reaction conditions, and nano-
crystalline zeolites can be used as building blocks for hierarchical zeolite structures (e.g., fibers, films,
hollow zeolite structures). Environmental applications for nanocrystalline zeolites and hierarchical struc-
tures include adsorption of volatile organic compounds from aqueous solutions or humid environments on
functionalized zeolites, selective catalytic reduction of NO2 with hydrocarbons on nanocrystalline Y zeo-
lites, CR(VI) reduction on iron-loaded hollow zeolite structures, and bifunctional nanocrystalline zeolite
catalysts that exhibit different functionality on external and internal surfaces.
Plasmon-Sensitized TiO2 Nanoparticles as a Novel Photocatalyst for Solar Applications
George Chumanov, Clemson University
The efficiency of photocatalysis depends on how well charge recombination is prevented; metal nano-
particles can act as an electron sink, promoting interfacial charge transfer and reducing charge re-
combination. Titania-coated silver nanoparticles were synthesized using a sol-gel technique. In addition,
Fe3+-doped titania sensitive to visible light was synthesized. Experiments on the degradation of sulfor-
hodamine dye indicate that a true doping effect was observed in an Fe3+-doped titania photocatalyst.
Efforts are underway to coat silver nanoparticles with Fe3+-doped titania, and the photocatalytic activity
of Fe3+-doped titania and silver coated with Fe3+-doped titania will be compared.
Ecocomposites Reinforced With Cellulose Nanoparticles: An Alternative to Existing
Petroleum-Based Polymer Composites
William T. Winter, State University of New York
Cellulose nanoparticles can be made from almost any type of biomass; the properties of these particles
vary by source due to species-dependent differences in mean particle size. Sources such as apple pomace,
chitin, orange pulp, sugar beet, and wood have been utilized to create nanoparticles and make derivatives
such as acetates, maleates, and trimethylsilyl. Additional derivatives are planned. Scale-up of the project's
activities will allow for more widespread testing. New techniques are needed to characterize surface
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
chemistry and interactions. The challenges associated with scale-up include separation of particles from
acid, acid recycling, and minimizing reaggregation. Reactive extrusion may provide a route to stronger
composites, and an acid-free or reduced process may result from treating the nanoparticles as a coproduct
of ethanol production from biomass.
SESSION 2: AEROSOLS
Chair: Barbara Karn, U.S. EPA
Elemental Composition of Freshly Nucleated Particles
Murray V. Johnston, University of Delaware
Airborne particles are associated with societal implications related to human health and global climate
change. Real-time single particle mass spectrometry is used to measure ambient aerosol to determine the
chemical composition of individual particles as a function of particle size and to count particles as a
function of size and composition. Laser-induced plasma formation can determine the elemental compo-
sition of many particle types; the detection efficiency is independent of particle size and composition.
Fundamental limitations of nanoparticle transmission contribute to sampling rate limitation because of
aerodynamics and Brownian motion. Electrodynamic focusing, which requires particle charging as well
as electrodynamic trapping to increase the detection duty factor and overcome inefficient charging, may
be used to help address these issues.
Ion-Induced Nucleation of Atmospheric Aerosols
Peter H. McMurry, University of Minnesota
The objectives of this project are to determine whether ion-induced nucleation leads to the formation of
significant numbers of particles in the atmosphere, and to learn about the physics and chemistry of ion-
induced nucleation in the atmosphere. Inclined grid mobility analysis (IGMA) and nano-scanning mobil-
ity particle sizing (SMPS) were used to measure size distributions of particles during a nucleation event in
Boulder, CO. IGMA enables measurements on nucleated particles as small as 2 run, and it was deter-
mined that nucleation in Boulder is dominated by neutral molecules, not ions. In ongoing work, ion com-
position during nucleation events is being measured and new nano-SMPS for measuring total size distri-
butions of particles down to 1 nm is under development.
SESSION 3: SENSORS
Chair: Marti Otto, U.S. EPA
Nanostructured Porous Silicon and Luminescent Polysiloles as Chemical Sensors for TNT
and Carcinogenic Chromium (VI) and Arsenic (V)
William C. Trogler, University of California, San Diego
This project involves the use of fluorescent siloles as luminescent sensors. Siloles are sensitive, selective
sensors for nitroaromatic species. Through surface modification of siloles, it may be possible to use them
as selective sensors for inorganic oxoanions. The first known hydrosilation of a silole Si-H bond was
demonstrated in this work. Silole-amine was found to be less sensitive to some common aqueous oxo-
anions; however, an increase in luminescence was observed with other analytes. Development of porous
Si sensors for pollutants and miniature, low-power devices for integration into systems are underway. A
low-power, battery-powered sensor for volatile organic compounds (VOCs) has been built and tested, a
prototype for luminescence-based (polysilole) sensors has been constructed, surface chemistry that allows
the sensor to detect VOCs in the presence of background humidity was demonstrated, and a method to
construct active surface-enhanced Raman spectroscopy substrates on porous Si supports has been dis-
covered.
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Nanosensors for Detection of Aquatic Toxins
Robert E. Gawley, University of Miami
This project involves the development of nanosensors for detection of saxitoxin, which causes paralytic
shellfish poisoning, and other marine toxins that are problematic to human health, such as tetrodotoxin,
brevetoxin, ciguatoxin, and domoic acid. The objective of this project is to covalently attach fluorescent
dendrimers to a surface for sensing. To date, selective and sensitive fluorescent chemosensors have been
developed, dendrimers were attached to beads in a spatially resolved manner, and studies of toxic versus
nontoxic shellfish extracts have started. Challenges include making a water-soluble dendrimer, creating
combinatorial libraries, and developing a new fluorophore with absorption in the visible range to elimi-
nate matrix interference from the shellfish extract.
Self-Assembly of Nanoparticles in Sensing Platforms
Somenath Mitra, New Jersey Institute of Technology
The objective of this project is to take different steps of a measurement process and integrate them onto
one platform. This integration is especially important for environmental monitoring, which involves com-
plex metrics and low concentrations integrated into a single device. Specifically, a single device for
monitoring VOCs in air is being developed that exploits the self-assembly properties of carbon nanotubes
as they are grown on microstructures. Nanoparticles offer some distinct advantages, such as a very large
surface area and unique absorption characteristics. Fabrication requires self-assembly, and the process
needs to be fine tuned for each application.
Advanced Nanosensors for Continuous Monitoring of Heavy Metals
Omowunmi Sadik, State University of New York, Binghamton
The objectives of this project are to synthesize Au nanoparticles in organic medium using a short, simple,
and convenient method and to study the potential of the polyamic acid (PAA) metal nanoparticle films for
the analysis and removal of heavy metals from aqueous medium. Au nanoparticles were synthesized in
organic medium through use of PAA, which acts both as a reducing and capping agent. The potential of
the PAA-metal nanoparticle films in the analysis and removal of heavy metals from aqueous medium has
been demonstrated. Other metal salts of Co(II), Pd(II), and Ag(I) also can be used to form metal nano-
particles. Future work includes investigating the reduction of other metal salts with PAA and the use of
these metal nanoparticles in environmental and other applications.
Biosensors: Development and Environmental Testing
Anne J. Anderson, Utah State University
The goals of this project are to develop an array of promoter fusions that respond differentially and
specifically with light output upon exposure to toxic metals, and to create a gene chip array to detect
transcript abundance from cells responding to toxic metals (the pattern of gene activation would specify
the metal). Pseudomonas putida strains were used to test a luciferase biosensor for the detection of copper
and cadmium. luxAB::msertional mutants that detect copper and cadmium differentially have been identi-
fied, but gene loci await determination. Peptides that increase upon copper exposure have been detected,
and one has been correlated with a specific function.
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Compound-Specific Imprinted Microspheres for Optical Sensing
Barry K. Lavine, Oklahoma State University
Chemical sensing based on swellable polymers is a stable, low-cost approach with a fast reaction time.
This approach can be operated at near-infrared wavelengths for optical sensing. Using dispersion poly-
merization, polymeric nanospheres that selectively bind theophylline were prepared. Changes in the
swelling of the theophylline-imprinted particles are being measured using surface plasmon resonance
(SPR). In preparing a hydrogel membrane, polymer microspheres were directly applied to a gold surface,
where they are held in place by electrostatic attractions. Particle swelling can be increased at room
temperature by decreasing the amount of recognition monomer and template used in the formulation. A
new SPR instrument will be constructed with a sample chamber that will expose the gold to a larger
amount of sample, mitigating problems associated with alignment. Also, better stepping motors will be
used to control the movement of the rotational stages allowing greater control over the change in the
incident light angle.
Ultrasensitive Pathogen Quantification in Drinking Water Using High
Piezoelectric PMN-PT Microcantilevers
Wan Y. Shih, Drexel University
The objective of this project is to develop high piezoelectric microcantilever sensors for real-time, in situ,
ultrasensitive pathogen detection in water. Three tasks are involved: (1) developing highly piezoelectric
lead magnesium niobate-lead titante (PMN-PT) films for microcantilever miniaturization; (2) fabricating
and characterizing highly PMN-PT microcantilever sensors; and (3) using sub-millimeter piezoelectric
cantilevers for immediate pathogen detection. High piezoelectric PMN-PT films were successfully con-
structed with better than improved piezoelectric properties as compared to specially cut single crystals.
The in situ, real-time detection of Salmonella in standing water was demonstrated. The investigators
developed 0.4 mm long piezoelectric/glass cantilevers of 3 x 10"11 g/Hz sensitivity that are three to four
times more sensitive than 10 MHz quartz crystal microbalance (QCM) in protein/molecular detection and
six to seven times more sensitive than 10 MHz QCM planar detection in cell detection. Further sensitivity
improvement includes using PMN-PT/Cu microcantilevers with flow cells.
Nanomaterial-Based Microchip Environmental Assays
Joseph Wang, New Mexico State University
The inherent miniaturization and complete integration of electrochemical detection make it extremely at-
tractive for creating portable (and possibly disposable) stand-alone microsystems. Nanomaterials can be
used to facilitate detection, separation, preconcentration, and reaction processes, potentially leading to the
integration of multiple functions on a "lab-on-a-chip" device. Carbon nanotubes are useful for promoting
electron-transfer reactions and imparting higher resistance to surface fouling. In addition, the electro-
catalytic activity and resistance to surface fouling of carbon nanotube materials lead to improved sensi-
tivity, stability, and resolution compared to common carbon-electrode detectors. Nanomaterials offer
great promise for enhancing the performance of microchip devices. Such nanomaterials-based microchip
devices are expected to have a major impact on environmental monitoring and security surveillance appli-
cations.
Low-Cost Organic Gas Sensors on Plastic for Distributed Environmental Sensing
Vivek Subramanian, University of California, Berkeley
This project involves the development of arrayed organic FETs that are easily arrayed at low cost via
printing, flexible for easy dispersal, and trainable via electronic nose architecture. To ensure accuracy,
measurements are performed with a calibrated precision semiconductor parameter analyzer. The organic
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
FET-based sensors show promising responses, including transient behavior and cycle life. Future work
will optimize structure and process flow, particularly in terms of stability and reliability. Additional future
work includes integration of the latest sensing materials into printed device architecture, deployment in
testing of environmentally relevant analytes, and enhancement of specificity through functionalization/
doping.
Chemoreceptive Neuron MOS (CvMOS) Transistors for Environmental Monitoring: Detection in
Fluid and GasAmbients With Field Programmability and High Reliability
Edwin C. Kan, Cornell University
The objective of this project is to develop Chemoreceptive Neuron Metal-Oxide-Silicon (CuMOS) tran-
sistors for environmental monitoring that exhibit high sensitivity and selectivity, stability/reliability, sim-
ple reset, field reconfigurability, high bandwidth, low power, and low cost. Field Effect Transistor (FET)
devices with extended floating gates for chemical sensing have been developed; the floating-gate struc-
ture for electron tunneling operations provides more degrees of freedom for sensing. Indicators from I-V
characteristics include subthreshold slopes and threshold voltages. CuMOS integration enables more flex-
ible and controllable circuits. Future work involves an electrowetting actuator for potential microvalves
integrated with the sensors and conventional CuMOS circuitry for fluid delivery and confinement.
Nanocontact Sensor for Heavy Metal Ion Detection
Nongjian Tao, Arizona State University
Nanocontact sensors are being developed for the detection of heavy metal ions in water. The nanocontact
sensors include electrodes separated with atomic-scale gaps, so that a few ions can be detected when the
sensors are exposed to a water sample. A ppt-level of detection limit has been demonstrated. The nano-
contact sensors also exhibit the ability to selectively detect several different metal ions according to their
deposition and striping potentials. Efforts are underway to construct an integrated sensor for simultaneous
detection of different species using these nanocontact sensors as sensing elements in an array of elec-
trically wired nanojunctions. Conducting polymer nanojunctions that work for both small and large mole-
cular probes also are being developed.
SESSION 4: REMEDIATION
Chair: Philip Sayre, U.S. EPA
Graft Polymerization as a Route To Control Nanofiltration Membrane Surface Properties To Manage
Risk of EPA Candidate Contaminants and Reduce Natural Organic Matter Fouling
Georges Belfort, Rensselaer Polytechnic Institute
This project involves using graft polymerization to modify membrane surfaces for commercial use. The
objective is to use a patented technique, photooxidation of poly(ether sulfone) (PES), which is light sen-
sitive and inexpensive, to modify membranes to create a series of membranes by grafting monomers for a
variety of applications. This approach may improve the selection of candidate contaminants and reduce
natural organic matter (NOM) affinity. In studying the fundamental principles of photoinitiated poly-
merization, it was found that the degree of grafting increases reaction time and that wettability increases
with the degree of grafting (although it is not a good predictor with NOM), rejection and flux can be
tailored based on the degree of grafting, and a range of monomers can be grafted.
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Membrane-Based Nanostructured Metals for Reductive Degradation
of Hazardous Organics at Room Temperature
Dibakar Bhattacharyya, University of Kentucky
Functionalized materials and membranes can be used for ultra-high capacity metal sorption (Hg, Pb, etc.)
reactions and catalysis (nanosized metals, vitamin B12, enzymes) as well as tunable separations (with
polypeptides). Nanoparticles offer the advantages of high surface area, significant reduction in materials
use, reactivity, capacity for polymer surface coating to alter pollutant partitioning, alteration of reaction
pathways, bimetallic properties, and enhanced particle transport in groundwater. The synthesis of metal
nano- particles in membranes and polymers can be facilitated by chelation mixed-matrix cellulose acetate
mem- branes, thermolysis and sonication, and di-block copolymers. Nanostructured metal formation and
hazardous organic dechlorination with functionalized membranes (and with simultaneous recapture/reuse
of dissolved metals) was demonstrated. For example, TCE dechlorination by Fe/Ni and Fe/Pd nanoparti-
cles in a membrane was demonstrated.
Water Treatment by Dendrimer-Enhanced Filtration: Fundamental Principles and Applications
Mamadou S. Diallo, California Institute of Technology
Dendrimer-enhanced ultrafiltration has a number of advantages over polymer-supported ultrafiltration.
The process has a much higher metal binding capacity, and metal binding to dendrimers is much more
sensitive to pH due to their globular shape. Dendrimers have a much smaller intrinsic viscosity than linear
polymers with similar molar mass. Comparatively smaller operating pressure, energy consumption, and
loss of ligands by shear-induced mechanical breakdown could be achieved with dendrimers in tangential/
cross-flow ultrafiltration systems typically used to recover metal ions from contaminated water. Work in
progress includes metal ion binding measurements for Fe(III), Fe(II), Co(II), Ni(II), and Ag(I); investi-
gations of the effect of dendrimer generation and terminal group on dendrimer retention and membrane
fouling; and removal of Cu(II), Ag(I), and Co(II) from membrane concentrates by dendrimer-enhanced
ultrafiltration.
Synthesis, Characterization, and Manipulation of (FeS-PAMAM) Dendrimer Nanocomposites
Lajos Balogh, University of Michigan
Uniform iron sulfide (FeS) nanoparticles have been synthesized using surface-modified polyamidoamine
(PAMAM) dendrimers as templates. The nanocomposite particles are polycrystalline, and the nanoparti-
cle morphology can be varied from spherical to rod-like using different anions. The ultraviolet-visible ab-
sorbance spectra increase in the 250-1,000 nm range is proportional to the amount of FeS nanoparticles
present. FeS nanoparticles displayed different absorbance profiles when PAMAMs of different termini
were used as a template. Zeta potential measurements indicated that the formed FeS-PAMAM nano-
composites have the same polarity as the dendrimer templates. To deposit FeS nanoparticulate films onto
substrates, PAMAM/poly(sodium styrenesulfonate)(PSS) multilayers were constructed using a layer-by-
layer self-assembly method. The formed FeS nanoparticulate films exhibited less absorbance than the cor-
responding PAMAM/PSS multilayers.
Hollow and Nanoporous Iron Particles
Wei-xian Zhang, Lehigh University
This project is examining the use of highly porous zero valent iron (ZVI) particles and their applications
in degradation and transformation of contaminants. By making porous nanoparticles using an organic
polymer as a template, the surface area is greatly increased. Making the particles more porous allows
them to absorb more iron, reactive materials, or contaminants. Porous iron was used for testing the reac-
10 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
tivity to three standard contaminants, including Cr(VI). It was found that porous iron reduced Cr(VI)
concentrations by several orders of magnitude. New applications and efficiencies are being explored.
Developing Functional Fe°-Based Nanoparticles for In Situ Degradation
ofDNAPL Chlorinated Organic Solvents
Gregory V. Lowry, Carnegie Mellon University
The goal of this project is to synthesize surface-modified Fe°-based nanoparticles that can transport in a
saturated porous matrix, preferentially localize at the nonaqueous phase liquid (NAPL) water interface,
and degrade NAPL to nontoxic products. The approach is to: (1) understand the factors controlling reac-
tivity/lifetime of Fe° nanoparticles by comparing the effectiveness of two particle types; (2) identify block
copolymers that provide the desired transport and targeting behavior through polymer selection and
synthesizing polymer-coated particles; and (3) characterize polymer/particles in terms of size, NAPL-
water partitioning, and transport. Fe° nanoparticles are highly reactive, fully utilized, and very efficient in
TCE-water systems. Polymer-particle hybrid particles have been synthesized that are in the nano size
range (approximately 100 nm), have good NAPL-water partitioning, and exhibit good transportability.
Polymer-coated Fe° particles have been synthesized but not yet optimized.
A Bioengineering Approach to Environmental Remediation
Daniel R. Strongin, Temple University
The goals of this project are to examine the use of ferritin as a (photo)catalyst, study ferritin as a template
for the growth of oxide and metallic nanoparticles, and examine the functionalization of the ferritin shell.
Horse spleen ferritin and Listeria innocua, a ferritin-like protein, were studied. Researchers found that
ferritin facilitates the reduction of Cr(VI) to Cr(III). Ferritin can function as a template for the growth of
oxide and metallic nanoparticles. Functionalization of a ferritin-like protein shell to form a photosensitizer
also was demonstrated.
SESSIONS: IMPLICATIONS
Chair: Philip Sayre, U.S. EPA
Implications of Nanomaterials Manufacture and Use
Earl R. Beaver, Practical Sustainability, LLC
The approach of this project involves identifying sustainability aspects/impacts along the life cycle of
nanomaterials; constructing an inventory of resource use, waste, and emissions in manufacturing; and
expanding the analysis in upstream and downstream directions. Quantitative and qualitative aspects of
sustainability assessment are being integrated for emerging nanotechnologies, and the most important
sustainability cost and benefit drivers for near-term nanomaterials are being identified. Next steps include
continuing to develop the inventory, collecting safety and life cycle analysis (LCA) data on materials used
in manufacturing, expanding analysis of cost/benefit drivers to extraction and end of life, and soliciting
comments on the resulting product.
A Life Cycle Assessment Approach for Evaluating Future Nanotechnology Applications
Shannon Lloyd, Carnegie Mellon University
The motivation for applying an LCA approach includes reducing material and energy consumption,
reducing environmental discharge, using life cycle design early in product life cycles, optimizing econo-
mic and social value, identifying regulatory needs, and addressing public concerns. Two applications are
being examined: (1) life cycle implications of using nanocomposites for automotive body panel weight
reduction; and (2) life cycle implications of using nanofabrication to position and stabilize nanoscale
The Office of Research and Development's National Center for Environmental Research 11
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
particles in automotive catalysts. This work incorporated multiple LCA models, technology forecasting to
extend beyond environmental inventories, and expert elicitation to characterize expected impacts. A
framework was developed for making more informed decisions throughout research and development,
comparing current products to those expected from emerging technologies, and helping address public
concerns about emerging technologies. Specific nanotechnology LCA challenges include establishing an
inventory for nanomaterials and nanoprocesses, and determining whether risks are qualitatively/quanti-
tatively different.
SESSION 6: TREATMENT
Chair: Anita Street, U.S. EPA
Transition Metal Nanocarbides as De-NOx Catalysts
S. Ismat Shah, University of Delaware
An alternative catalyst is required to achieve mandated reductions of NOX emissions, considering the
limited availability of Pt-group metals. Transition metal carbides have catalytic properties similar to those
of Pt-group metals, and tungsten carbide (WC) has been used in isomerization reactions as a replacement
for Pt. WC nanoparticles effectively reduce NOX) with the WC composition and structure determining
conversion efficiency. CO emission can add to the conversion efficiency. Future steps include reactor
studies and quantification of catalysis data, systematic studies of the particle size effect on the de-NOx
activity and stability, intentional addition of oxygen to synthesize W-O-C to stabilize the catalyst, and
catalytic studies under a true exhaust mixture to measure the effect of CO/CO2 and S.
Simultaneous Environmental Monitoring and Purification Through Smart Particles
Wolfgang M. Sigmund, University of Florida
A multifunctional particle design was optimized to specific reactors. A TiO2/silica gel nanocomposite is
an effective alternative to carbon technology for removing elemental Hg. A high-efficiency anatase-
carbon nanotube photocatalyst more than a factor of 200 times more efficient based on TiO2 weight was
developed, but this work was stopped because of potential toxicity. A reduced-cost hard magnetic
composite photocatalyst comprised of barium ferrite, silica, and titania was developed. The specific
surface area was increased by two orders of magnitude from < 0.25 m2/g to 31.7 m2/g for magnetic
functional particles. A magnetically agitated photocatalytic reactor was optimized with respect to agita-
tion frequency based on modeling efforts.
Nanoscale Biopolymers With Customizable Properties for Heavy Metal Remediation
Ann Loi, University of California, Riverside
Metal chelating polymers require toxic solvents for synthesis, require ultrafiltration, and can clog mem-
branes. One solution is to develop metal-binding materials that can be recovered by environmental
stimuli. Metal chelating biopolymers are based on biological building blocks. They are nanoscale bio-
polymers that are specially preprogrammed within a DNA template, economically produced by bacteria,
environmentally friendly, and have tunable properties based on changes in environmental conditions (e.g.,
pH, temperature). Nanoscale elastin-like protein biopolymers can be designed with customized properties,
such as specificity and tunable transition. These biopolymers may provide a novel, environmentally
friendly, and green engineering method for the removal of heavy metals from water and soil.
12 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Combined Ozonation-Nanofiltration for Drinking Water Treatment
Simon Davies, Michigan State University
This project is studying a combined ozonation/nanofiltration process to reduce the problems associated
with use of these processes individually. Fouling studies indicate that ozonation at low dosages reduces
fouling; if ozone dosage is high enough, no fouling occurs. The reaction of ozone with foulants appears to
be enhanced at the membrane surface, presumably due to the catalytic degradation of ozone by TiO2.
Chlorination disinfection by-product (DBF) studies indicate that a combined ozonation/nanofiltration
process yields better results than with ozone alone. Lower DBF concentrations are obtained with tighter
membranes. In the range studied, ozone dosage has little effect on trihalomethane or haloacetic acid
precursor removal. A 1 kD molecular weight cutoff membrane results in good removal for all of the DBFs
studied; 5 kD yields good removal of chlorinated DBFs.
SESSION 7: FATE, TRANSPORT, AND TRANSFORMATION
Chair: Kevin Dreher
Adsorption and Release of Contaminants Onto Engineered Nanoparticles
Mason Tomson, Rice University
The objective of this project is to create the information needed to ensure that avoidable, deleterious
outcomes of nanomaterial production and use never materialize. The researchers aim to develop the infor-
mation needed to predict: the risk of nanomaterials related to adsorption and desorption of contaminants;
impact of naturally occurring sorbents, NOM, heavy metals, and surfactants; and fate of nanoparticles in
soil and water. This work is expected to provide information needed to assess whether there is a sub-
stantial risk posed by nanoparticles disposed of in groundwaters. It also should yield the necessary para-
meters for understanding the fate of engineered nanoparticles in the environment and for future develop-
ment of risk assessment of the engineered nanoparticles.
Impacts of Manufactured Nanomaterials on Human Health and the Environment: A Focus
on Nanoparticle Aerosol and Atmospherically Processed Nanoparticle Aerosol
Vicki Grassian, University of Iowa
The objectives of this project are to fully characterize a variety of manufactured nanomaterials in terms of
their size, shape, bulk, and surface properties; determine if engineered nanomaterials are particularly dele-
terious to health compared to particles from combustion processes that have been more extensively
studied; and evaluate the relative health effects caused by different surface coatings on the nanoparticles.
It is expected that these studies will help answer questions as to the potential impact of manufactured
nanomaterials on human health. Two important factors are the comparison of the potential health effects
of manufactured nanomaterials to other anthropogenic sources of ultrafine particles from combustion
processes and the effect of surface coatings, from manufacturing and atmospheric processing, on the
toxicity of these particles.
Chemical and Biological Behavior of Carbon Nanotubes in Estuarine Sedimentary Systems
P. Lee Ferguson, University of South Carolina
The four objectives of this project are to: (1) determine factors controlling the fate of single-wall
nanotubes (SWNTs) in estuarine seawater, sediment, and sediment-ingesting organisms; (2) examine the
impact of SWNTs on the disposition of model organic contaminants in estuarine sediments; (3) determine
whether the presence of SWNTs in estuarine sediments affects the bioavailability of model organic
contaminants to suspension- and deposit-feeding estuarine invertebrates; and (4) assess the toxicity of
SWNTs to a model deposit-feeding estuarine invertebrate in seawater and/or in combination with estua-
The Office of Research and Development's National Center for Environmental Research 13
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
rine sediments. Fate tracking in estuarine sediments is expected to provide information about potential
disposition of SWNTs discharged to the aquatic environment. Sorption and bioavailability studies will
reveal the possible impact of SWNTs on the fate and effect of hydrophobic organic contaminants in
estuarine sediments. In addition, toxicity studies are expected to lead to an increased understanding of the
potential effects of SWNTs on trophically important estuarine invertebrates in sediments.
Transformations of Biologically Conjugated CdSe Quantum Dots Released Into Water andBiofllms
Patricia Holden, University of California, Santa Barbara
The goals of this project are to determine the fate of CdSe quantum dots (QDs) under abiotic and biotic
conditions, toxicity of QDs to bacteria, damage of QDs to DNA, and the method by which QD coating or
conjugation alters effects. This project also will compare the effects of dissolved Cd and Se. QD break-
down in aqueous solutions will be quantified and pH, reducing conditions, light, and oxygen will be ex-
amined using bare, core-shell, conjugated QDs. Staphylococcus aureus and Pseodomonus aeroginosa will
be used to study growth effects, QD fates, and breakdown products. To investigate DNA damage, oxida-
tion of isolated guanine and adenine by time correlated single photon counting spectroscopy will be ex-
amined, as will the effects of bacterial biofilms.
Repercussion of Carbon-Based Manufactured Nanoparticles on Microbial
Processes in Environmental Systems
Ronald Turco, Purdue University
This project aims to answer the following questions: (1) How are environmental microorganisms im-
pacted by manufactured nanomaterials? (2) What is the ultimate fate of manufactured nanomaterial in the
environment? Investigators will examine how aerobic microorganisms in soil react to and alter them-
selves (or not) in the presence of carbon-based manufactured nanoparticles. They also will examine how
aerobic microorganisms in soil react to and alter carbon-based manufactured nanoparticles and how the
change in their chemical structure during this process affects toxicity and impacts soil processes. In
addition, baseline information on the toxic effects of carbon-based manufactured nanoparticles on aquatic
bacteria will be determined.
Fate, Transport, Transformation, and Toxicity of Nanomaterials
in Conventional Drinking Water Treatment Processes
Yongsheng Chen, Arizona State University
The goals of this project are to characterize the fundamental properties of nanomaterials in aquatic
environments, examine the interactions between nanomaterials and toxic pollutants and viruses, evaluate
the removal efficiency of nanomaterials by a sand filtration process, and test the toxicity of nanomaterials
in drinking water using the cell culture model of the epithelium. Results are expected to provide funda-
mental information about the fate, transport, and transformation of nanomaterials in drinking water
resources. This work may represent the first evidence that such nanomaterials can or cannot be removed
by conventional drinking water treatment processes. An improved toxicity assessment will be developed
for the potential exposure risks of nanomaterials in drinking water. This research will provide essential
information to support policy and decisionmaking regarding handling, disposal, and management of
nanomaterials in commerce, manufacturing, and the environment.
14 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
SESSIONS: TOXICOLOGY
Chair: Kevin Dreher, U.S. EPA
Short-Term Chronic Toxicity of Photocatalytic Nanoparticles to Bacteria, Algae, and Zooplankton
Chin-Pao Huang, University of Delaware
The objectives of this project are to determine: (1) the acute toxicity of photocatalytic nanoparticles to a
mixed bacterial culture; (2) the short-term chronic toxicity of photocatalytic nanoparticles to pure bac-
terial culture, daphnia, and green algae; (3) the short-term chronic toxicity of copper (II) to green algae in
the presence of photocatalytic nanoparticles; and (4) the short-term chronic toxicity of chlorinated phe-
nols to pure bacteria culture and daphnia in the presence of photocatalytic nanoparticles. This work
should provide insight into the mechanism of the ecotoxicity of nanoparticles with regard to particle size,
chemical composition, surface charges, and photocatalysis. The research also will help to understand the
ecotoxicity of chemical hazards as affected by photocatalytic nanoparticles.
Evaluation of Nanoparticle Interactions With Skin
Nancy Monteiro-Reviere, North Carolina State University
This project is focused on assessing the nature of the interactions between manufactured nanoparticles
and the skin (currently, there are few data on these interactions), particularly in terms of dermal absorp-
tion, cutaneous toxicity, and distribution to skin following systemic exposure. Nanoparticles to be studied
include carbon bucky balls and nanotubes, iron oxide nanocrystals, and cadmium selenide nanocrystals.
Model systems to be tested include human epidermal keratinocyte cell culture, porcine skin flow through
diffusion cells, and isolated perfused porcine skin flap. This work should provide data on the ability of a
range of manufactured nanoparticles to interact with skin, an initial assessment of potential vehicle
effects, and boundaries for a dermal risk assessment on manufactured nanoparticle exposure.
Physical and Chemical Determinants of Nanoflber/Nanotube Toxicity
Robert Hurt, Brown University
Carbon nanotubes/fibers share important properties with asbestos, such as high aspect ratio, small diam-
eter, durability, and transition metal content. It is hypothesized that fibrous geometry and surface-reactive
transition metal impurities are major determinants of toxicity. The approach includes fabricating nano-
materials, characterizing them postprocessing, mobilizing transition metals in vitro, and creating acute
cellular toxicity assays. Synthesis and characterization are underway for a panel of carbon nanoma-
terials.
CLOSING REMARKS
Barbara Karn, U.S. EPA
Dr. Karn thanked presenters and participants for their participation in the meeting, noting that a pro-
ceedings document will be published. A third nanotechnology grantees meeting is planned for October
2005, and investigators from the European Union and Canada may be asked to participate. Participants
were reminded that the ACS Annual Meeting will be held in March 2005. Other upcoming meetings that
will have at least one session on nanomaterials include the Society of Environmental Toxicology and
American Society of Mechanical Engineers. Grantees were informed that if they need assistance in pro-
moting environmental messages regarding nanotechnology at professional society meetings, EPA is
available to help with these efforts. Participants were invited to remain at the workshop for a presentation
by Dr. Raymond Oliver that was rescheduled and given immediately following Dr. Karn's closing
remarks.
The Office of Research and Development's National Center for Environmental Research 15
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Nanomanufacturing Futures: The Perceived Technological and Commercial Opportunities
and the Concerns Over Societal and Environmental Impact
Raymond Oliver, Leeds University
The Royal Academy Working Group Study, which began in the summer of 2003, was discussed. The
goals of the study were to define nanoscience and technology; summarize the current state of scientific
knowledge on nanotechnology; identify specific applications; identify what environmental, health and
safety, ethical, and social implications may arise; and identify areas where regulation should be con-
sidered. The study used corroborated evidence and input from academics, industry experts, representa-
tives of health and environmental groups, nongovernment organizations representatives, regulators, and
the public in Europe. Study findings indicate that nanotechnology offers great opportunities with many
benefits now and in the future. Public discussion has to be started and continued throughout the develop-
ment of nanotechnologies. Most nanotechnologies pose no new risks to health, safety, or the environment,
although there are concerns about the potential impacts of manufactured nanoparticles and nanotubes that
are free rather than embedded in other materials. Workplace exposure limits should be reviewed, and
manufactured nanoparticles should undergo a full and independent safety assessment by a scientific ad-
visory body before use. It is critical to take ethical considerations seriously with regard to nanotech-
nology. There is a large area of instrument development needed for inline and online tools that work at
the 20 nm to less than 1 nm scale. One of the ways through which nanoscience and technology will
become successful is the synthesis and assembly of highly organized structures. Significantly improved
material properties for performance and self-assembly and directed-assembly will become the cornerstone
of using synthetic materials to develop nano- and meso-scale structured materials.
16 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
D Environmental
• Societal and
Educational
D Health
DTOTAL
2001 2004
Figure 1. NNI nanotechnology funding.
The Office of Research and Development's National Center for Environmental Research
17
-------
-------
1.
Nanotechnology offers the possibility of changing the manufacturing process in two ways: (1) incorporating
nanotechnology for efficient, controlled manufacturing would drastically reduce waste products; and (2) the
use of nanomaterials as catalysts for greater efficiency in current manufacturing processes would minimize or
eliminate the use of toxic materials and the generation of undesirable by-products and effluents. Research may
involve nanotechnology related to improved industrial processes and starting material requirements, develop-
ment of new chemical and industrial procedures, and materials to replace current hazardous constituents and
processes, resulting in reductions in energy, materials, and waste. Potential examples of types of nano-
technology research that may lead to reduction or elimination of pollutants of concern include: atomic-level
synthesis of new and improved catalysts for industrial processes; adding information into molecules (analo-
gous to DNA) that build new molecules; self-assembling molecules as the foundation for new chemicals and
materials; and building molecules "just in time" in microscale reactors.
-------
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Green Engineering of Dispersed Nanoparticles: Measuring
and Modeling Nanoparticle Forces
Kristen Fichthorn
Department of Chemical Engineering, Pennsylvania State University, University Park, PA
Abstract
Nanoparticles hold great promise for a diverse array of materials applications, ranging from electronic
circuits to bulk materials with novel mechanical properties to biological materials. Many applications involve
colloidal nanoparticles, whose effective use in nanotechnology hinges on their selective assembly or their sta-
bilization against aggregation. Various methods have been used to stabilize colloidal nanoparticles; however,
all involve dispersant molecules such as surfactants or polyelectrolytes. These dispersants not only alter the
chemistry and physics of nanoparticle systems, but also because they occupy a significant mass fraction of a
suspension, they produce a tremendous waste stream during processing. An improved understanding of the
forces between "bare" colloidal nanoparticles could lead to new and environmentally beneficial strategies for
engineering colloidal nanoparticle suspensions. Historically, Derjaguin-Landau-Verwey-Overbeek (DLVO)
theory has been used to describe electrostatic and van der Waals interactions in colloidal systems. However,
the assumptions of DLVO theory do not apply to nanoparticles. Further, recent studies suggest that forces that
are not taken into account by DLVO theory, such as solvation and depletion, could be important in colloidal
nanoparticle systems. From a theoretical point of view, it is now possible to simulate colloidal nanoparticles
using large-scale, parallel molecular dynamics (MD). These studies can yield atomic-scale detail that is not
currently accessible with experimental methods, and they can be used to resolve the origins and magnitudes of
forces between colloidal nanoparticles.
Parallel MD is used to simulate two solid nanoparticles immersed in a liquid solvent. In these studies, we
are interested in the interplay between solvation and van der Waals forces. The bulk solvent is simulated as
more than 100,000 Lennard-Jones (LJ) or n-decane molecules. Four different types of nanoparticles are being
studied: small (1.6 nm diameter) and large (6.0 nm diameter) rough, spherical nanoparticles, as well as cubic
and icosahedral crystals. To investigate the influence of surface roughness, the nanoparticles are rotated so that
they make contact from different angles and have different contacting surfaces. The nanoparticles can be either
solvophilic (solvent loving) or solvophobic (solvent fearing). Solvation forces for solvophilic and solvo-
phobic nanoparticles have been calculated for the different nanoparticle systems. In all of the solvophilic
nanoparticle systems, the solvation forces oscillate between attraction and repulsion. The oscillatory behavior
is caused by the solvent's ordering near the surface. This effect is particularly evident for the cubic nano-
particles, which exhibit the strongest solvation forces. A comparison of solvation forces and van der Waals
forces indicates that solvation forces can be comparable to van der Waals forces. This indicates that solvation
forces may be beneficial in preventing nanoparticles from aggregating and that stable nanoparticle dispersions
may be achieved in suitable nanoparticle-solvent systems. Solvophilic solvation forces can be highly sensitive
to the relative orientation of the nanoparticles and that these forces can cause the nanoparticles to rotate in
solution to minimize their free energy. This effect is especially pronounced for the icosahedral nanoparticles,
which alternate their relative orientation as they approach each other. In this case, solvation forces may be
utilized to align nanoparticles for applications in self assembly. Solvation forces for solvophobic nanoparticles
are always attractive. In this case, solvent molecules are repelled from the interparticle region and the density
there is lower than the bulk density. The solvophobic solvation forces for nanoparticles in n-decane are par-
ticularly interesting, as they exhibit a region of uniform attraction followed by a sudden jump of the forces to
zero. These attractive forces can be greater than the van der Waals forces. They arise from an interesting
ordering of n-decane around the nanoparticles, in which the molecules orient themselves normal to the particle
surfaces, to increase van der Waals attraction between the decane molecules and minimize contact with the
nanoparticles. In this orientation, solvent is repelled from the interparticle gap until the gap exceeds twice the
end-to-end distance of a decane molecule, at which point solvent enters the interparticle region and assumes a
bulk-like structure.
The Office of Research and Development's National Center for Environmental Research 21
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Green Engineering of Dispersed Nanoparticles: Measuring
and Modeling Nanoparticle Forces
Darrell Velegol and Kristen Fichthorn *
Department of Chemical Engineering (*also in Department of Physics),
Pennsylvania State University, University Park, PA
Environmental Implication/Application
Due to their remarkable electronic, optical, magnetic, and mechanical properties, nanoparticle systems will
play a central role in electronic and material systems (Kruis et al., 1998), biomedical materials and devices
(Gref et al., 1994; Gref et al., 1995; Hrkach, 1997), and environmental remediation systems (Ponder et al.,
2000). A central challenge in using nanoparticles is manufacturing bulk quantities of dispersed nanoparticles.
Manufacturers like MER Corporation and Carbolex produce carbon nanotubes but sell it by the gram. Nissan
Chemical Industries sells SNOWTEX silica nanoparticles in bulk; however, these are not dispersions of
discrete particles, but rather "a string of pearls made of 10 to 50 nm" particles. Nanotechnology is limited by
the ability to produce dispersed particles. The engineering challenge is how to stabilize bulk quantities of
nanoparticles without using a huge amount of adsorbed dispersant, which then later effects a large environ-
mental cost. For small batches, nanoparticle stability has been at least partially achieved in a manner similar to
that for micron size particles. Surfactants, polymers, or another material coating (Andres et al., 1998; Yang et
al., 2000) are added to the particles to stabilize them. However, for nanoparticle dispersions, these coatings can
negate some of the benefits of the nanoparticles. For example, by adding a surfactant layer onto the particles,
one adds two surfactant diameters to the particle size (often greater than 10 nm). Perhaps more importantly,
because the nanoparticles have a huge amount of surface area per volume (e.g., 10 nm silica particles have
-300,000 m2/g), huge amounts of the coating must be used, which will eventually end up as a large waste
stream. Nanotechnology will eventually require extensive production of particles, and so even commercially
scalable techniques like sol-gel processing will require knowing how to maintain stable dispersions of bare
nanoparticles. Our engineering goal is: Can suspensions of "bare" nanoparticles be dispersed, preventing a
huge waste stream of additives? Nanoparticles are synthesized by many methods, most of which can be
categorized into liquid-phase methods, aerosol methods, plasma methods, or mechanical methods. To achieve
a stable dispersion of nanoparticles, one must either liberate particles that are held in aggregates, or ensure that
the initial primary particles resist aggregation. Currently, nanoparticle stability cannot be controlled because
we do not understand nanoparticle forces. What little intuition does exist comes from extrapolating the
classical DLVO model (Hunter, 1986) for interparticle forces down to the nanometer regime. Not only does
DLVO theory often fail qualitatively, even for particles greater than 100 nm in diameter (Velegol et al., 1996;
Behrens et al., 1998; Behrens et al., 2000), but also it neglects phenomena such as fluid ordering (Israelachvili,
1992), which could be critical to nanoparticle systems.
This research project has three primary objectives: (1) model nanoparticle forces, especially van der
Waals, depletion, and solvation forces; (2) develop the experimental technique of "particle force light scatter-
ing" (PFLS) to measure nanoparticle forces; and (3) synergize the MD calculations and PFLS measurements to
study real systems (e.g., silica in water), including measurements of bulk stability or rheology. This research
project plans to synergize modeling and experiments, leading to predictive models for van der Waals, sol-
vation, and depletion forces. The essential feature of the project is to use molecular dynamics to model forces
(especially van der Waals, solvation, and depletion forces), and to verify the modeling using experiments. For
nanoparticle systems, these forces are poorly understood, and this limits the ability to control dispersion. The
modeling is important, as forces can be analyzed individually by turning them "on and off." The qualitative
(and perhaps quantitative) accuracy of the MD calculations will be verified by direct force measurements using
the technique of PFLS. This technique will be developed to measure sub-piconewton forces that are pertinent
to nanoparticle systems. These measurements will be compared with bulk stability and rheology measure-
ments, where possible, to see whether other factors (e.g., hydrodynamic shear) play a larger role in dispersion
than expected.
22 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Sustainable Biodegradable Green Nanocomposites From
Bacterial Bioplastic for Automotive Applications
Lawrence T. Drzal, Manjusri Misra, and Amur K. Mohanty
Michigan State University, East Lansing, MI
Abstract
Renewable resource-based "green" nanocomposites are the next generation of materials that provide a
combination of performance and environmental compatibility. This research project seeks to replace/substitute
existing petroleum-derived polypropylene (PP)/TPO (thermoplastic olefin) based nanocomposites with envi-
ronmentally friendly nanocomposites produced from bacterial-based bioplastic (polyhydroxyalkanoate, PHA)
reinforced with compatibilized nanoclay for automotive applications. These nanocomposites are "sustain-
able" materials because they are recyclable, stable in use but can be "triggered" to biodegrade under compost-
ing conditions, environmentally benign, and commercially viable. To achieve "sustainability," this research
project will address all of the critical components such as environment, economics, life-cycle analysis, energy,
and education.
The objectives of this research project are to synergistically combine biobased "green" plastic materials
technology and nanotechnology in a new manner that will have a positive impact on the environment through
its increased use in industrial applications. The objectives of this research project include: (1) nanoclay/bio-
plastics mechanical property optimization; (2) research into bioplastic toughening methods and into new alter-
native, ecofriendly compatibilizers; and (3) verification of sustainability through life-cycle analysis. A con-
current objective is to educate both graduate and undergraduate students on the importance of nanotech-
nology with special importance on the environmental benefits of "green" nanocomposites from an environ-
mental prospective.
The PHA bioplastic is the only water-resistant biopolymer from renewable resources with the potential for
automotive applications as a result of its highly crystalline morphology. The project is based on an interactive
approach that includes the interrelated topics of: (1) toughening of the bioplastic matrix with natural rubber to
mimic the properties of TPO; (2) plasticization with vegetable oil—to replace existing undesirable pthalates;
(3) synthesis of compatibilizer to bind clay and bioplastic; and (4) investigation and development of cost-
effective, reduced-step extrusion processing. A unique university-industry team composed of Michigan State
University, General Motors, Metabolix (bioplastic manufacturer), and Nanocor (producer of nanoclay) has
been assembled to ensure industrial and commercial viability.
Environmentally Benign Materials: Because the bioplastic is a renewable resource-based material, the
resulting green nanocomposites are eco-friendly because of their recyclability and compostability/biodegrada-
bility. This could result in a substantial reduction in greenhouse gases and reduction in the Nation's reliance on
oil and enhancement of national security.
Fuel Savings and Emissions Reduction Due to Lighter Auto Parts: The proposed lightweight green nano-
composites would reduce vehicle weight and would contribute significantly to fuel savings. About 7 L of fuel
per kg of vehicle weight could be saved over the life of a typical vehicle, or about 15 billion L annually. In
addition, approximately 3 kg of C02 are produced by combustion of 1 kg of fuel, thereby reducing C02 emis-
sions.
Replacement ofPhthalate Plasticizers: In the plastics industry, to improve processability, phthalate plasti-
cizers (a suspected endocrine disrupter) are used extensively in petroleum-based plastics. This research project
will use natural rubber as a toughening agent and derivitized soybean oil as a plasticizer, which would create a
significant positive impact on the environment as well as on the agricultural and manufacturing industries.
The Office of Research and Development's National Center for Environmental Research 23
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Industrial Impact: Petroleum-based plastics are nonbiodegradable and add to global warming. Although
performance limitations and high initial costs have restricted the adoption of bioplastics to niche markets, the
availability of higher performance "green" plastics will prove to be beneficial for the "greening" of U.S.
automobiles and for recycling.
24 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Sustainable Biodegradable Green Nanocomposites From
Bacterial Bioplastic for Automotive Applications
Lawrence T. Drzal, Manjusri Misra, and Amur K. Mohanty
Michigan State University, East Lansing, MI
Environmental Implication/Application
This research project is expected to create a basis for a new generation of green nanocomposites made
from bioplastic and commercial organically modified clay in the presence of a compatibilizer. The develop-
ment of a compatibilizer, formulation of the bioplastic and novel processing performed in this project have the
potential to produce high-impact and high-strength green nanocomposites that can substitute/replace petro-
leum-based nanocomposites.
New environmental regulations, societal concerns, and growing environmental awareness have triggered
the search for new products and processes that are compatible with the environment. This research will help to
develop the science and technology base necessary for sustainable green nanocomposite materials from renew-
able resources for automotive applications. These materials will replace petroleum plastic clay-based nano-
composites.
The Office of Research and Development's National Center for Environmental Research 25
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Development of Nanocrystalline Zeolite Materials as Environmental
Catalysts: From Environmentally Benign Synthesis
to Emission Abatement
Sarah Larsen
Department of Chemistry, University of Iowa, Iowa City, IA
Abstract
This research project involves the development of nanometer-sized zeolites and hierarchical zeolite
structures as environmental catalysts. Zeolites, which are widely used in applications in separations and cataly-
sis, are aluminosilicate molecular sieves with pores of molecular dimensions. The crystal size of zeolites form-
ed during conventional synthesis range in size from 1,000 to 10,000 nm. However, for some applications it
would be advantageous to employ much smaller nanometer-sized zeolite crystals in the range of 10 to 100 nm.
Specific advantages to be gained by using zeolite nanostructures include facile adsorption and desorption,
which will form dense films to facilitate separation applications and optical transparency.
A two-pronged approach based on: (1) the synthesis and characterization, and (2) subsequent application
of nanocrystalline zeolites as environmental catalysts has been undertaken. The first aspect involved the
synthesis and characterization of nanocrystalline silicalite (particle sizes ranging from 20 nm to 1,000 nm),
nanocrystalline ZSM-5 (particle sizes ranging from 15-200 nm), and nanocrystalline NaY (particle sizes of 25,
50, and 75 nm). The size-dependent properties of the nanocrystalline zeolites were investigated by powder x-
ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption isotherms, and solid state
nuclear magnetic resonance. Hierarchical structures such as rectangular fibers and hollow spheres and tubes
were formed from these nanocrystalline zeolites. The second aspect of this approach is the application of these
nanocrystalline zeolites and hierarchical structures for applications related to environmental catalysis. The use
of these nanocrystalline zeolites and hierarchical structures has been evaluated for the following potential
applications: (1) adsorption of volatile organic compounds (VOCs), such as toluene from air and water; (2)
selective catalytic reduction (SCR) of N02 with propylene (or urea) investigated by Fourier Transform In-
frared Spectroscopy and solid-state Nuclear Magnetic Resonance; and (3) reduction of Cr(VI) to Cr(III) using
iron-loaded hollow zeolite structures.
In the current phase of this project, reactivity studies are being undertaken to evaluate the activity of the
nanocrystalline zeolites as environmental catalysts. One unique characteristic of nanocrystalline zeolites rela-
tive to conventional zeolites is that the external surface area is the same order of magnitude as the internal
surface area. Applications are being examined in which the external surface of the nanocrystalline zeolite is
utilized for the decomposition of reactant molecules, and the internal surface is used for further reaction or for
storage. Functionalization of the external surface as a method of varying the hydrophobic/hydrophilic proper-
ties of the zeolites also is being examined. In addition, the adsorption of VOCs on the nanocrystalline zeolites
will be investigated further, particularly in humid environments and for a variety of different VOCs.
26 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Development of Nanocrystalline Zeolite Materials as Environmental
Catalysts: From Environmentally Benign Synthesis
to Emission Abatement
Sarah Larsen
Department of Chemistry, University of Iowa, Iowa City, IA
Environmental Implication/Application
Environmental catalysis involves the use of catalysts to solve environmental problems, in areas such as
emission abatement and environmentally benign synthesis. Many new catalysts and catalytic processes have
been developed to meet the challenges posed by environmental concerns. Recently, zeolites have emerged as
important materials for applications in environmental catalysis. Zeolites are aluminosilicate molecular sieves
with pores of molecular dimensions. Zeolites can be synthesized with a wide range of pore sizes and topolo-
gies and are used in applications such as catalysis and chemical separations. The crystal size of zeolites formed
during conventional synthesis range in size from 1,000 to 10,000 nm. However, for some applications it would
be advantageous to employ much smaller nanometer-sized zeolite crystals in the range of 10-100 nm. Specific
advantages to be gained by using zeolite nanostructures include facile adsorption and desorption, which will
form dense films to facilitate separations applications and optical transparency. Several applications of nano-
meter-sized zeolites to environmental catalysis are described below.
Environmental Remediation: NOX Emissions Abatement. The emission of NOX and N20 from stationary
and automotive sources, such as power plants and lean-burn engines, is a major environmental pollution issue.
NOX leads to the production of ground level ozone and acid rain, and N20 is a greenhouse gas. The catalytic
reduction of nitrogen oxides to N2 is an important environmental challenge for scientists and engineers. Re-
cently, the selective catalytic reduction of NOX and N20 by hydrocarbons (SCR-HC) over transition-metal
exchanged zeolites, particularly in the presence of oxygen, has attracted much interest for emission abatement
applications in stationary sources, such as natural gas fueled power plants. SCR-HC of NOX and N20 shows
promise for applications to lean-burn gasoline and diesel engines where noble-metal three-way catalysts are
not effective at reducing NOX in the presence of excess oxygen. The SCR activity of nanocrystalline zeolites,
such as NaY, has been investigated.
Environmental Remediation: Photocatalytic Decomposition of Organic Contaminants. The next system
that will be investigated involves the photocatalytic oxidation (PCO) of volatile organic compounds (VOCs)
and heavy metals such as chromium(IV). Photocatalysts, such as Ti02, can be used to degrade a wide range of
organic compounds found in polluted water and air. Ti02 photocatalysts are active at ambient temperatures and
pressures in the presence of UV irradiation and oxygen. Potential applications include purifying enclosed
atmospheres, such as those found in spacecrafts, offices, industrial plants, and homes. The major pollutants in
these applications are oxygenates and aromatics. Ti02 photocatalysts have been shown to oxidize toluene,
trichloroethylene (TCE), methanol/ethanol, and a number of other organic compounds. Additionally, iron
nanoparticles have been shown to reduce Cr(VI) to Cr(III) in solution using light. The use of nanometer-sized
zeolite Ti02 composites and iron-exchanged zeolites will be evaluated for applications in environmental
remediation of VOCs and chromium, respectively.
Adsorption of VOCs. Zeolites are extremely good adsorbents for many applications involving the
adsorption of VOCs from polluted water or air. In this last application, the advantages of nanocrystalline
zeolites for the adsorption of VOCs from water and air will be exploited. The nanocrystalline zeolites syn-
thesized in our laboratory will be evaluated for the adsorption of a representative VOC, such as toluene. The
adsorption properties of commercial and synthesized zeolites for toluene will be compared. In addition, the
nanocrystalline zeolites will be chemically modified to tailor the hydrophobic/hydrophilic properties for appli-
The Office of Research and Development's National Center for Environmental Research 27
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
cations in particular chemical environments. For example, nanocrystalline ZSM5 has been functionalized with
octamethylsilane such that the hydrophobicity was dramatically increased. The functionalized zeolites will be
evaluated for the adsorption of toluene in aqueous solution.
28 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Plasmon Sensitized TiO2 Nanoparticles as a Novel
Photocatalyst for Solar Applications
George Chumanov
Department of Chemistry, Biotechnology Research Center,
Clemson University, Clemson, SC
Abstract
Efficient conversion of sunlight into electrical and/or chemical energy is of great technological importance
for modern society and future generations. One attractive possibility for utilization of solar energy is based on
the ability of small semiconductor particles to function as photocatalysts promoting various oxidation and
reduction reactions under sunlight. Titanium dioxide (Ti02) is the most promising material for such appli-
cations because it is an efficient, environmentally friendly, and relatively inexpensive photocatalyst. However,
wide technological usage of this photocatalyst is largely hindered by the fact that ultraviolet (UV) light does
not constitute a significant fraction of the solar spectrum that is required for its activation. Any improvement of
photocatalytic efficiency of Ti02 by shifting its optical response from UV to the visible spectral range will
have a profoundly positive effect. The main objective of the proposed research is to synthesize and test a novel
photocatalyst that consists of small silver or gold nanoparticles covered with a thin Ti02 shell. Silver and gold
nanoparticles are very efficient systems for the interaction with visible light due to the excitation of plasmon
resonances. It is expected that, due to the coupling of plasmon resonances in the core with the electron-hole
pair generation in the shell, these hybrid Ag/Au Ti02 nanoparticles will exhibit photocatalytic activity in the
visible spectral range, thereby more efficiently utilizing solar energy.
A coating of silver and gold nanoparticles of different sizes with Ti02 layers of various thicknesses will be
accomplished by sol-gel chemical reactions. High temperature calcination and hydrothermal treatment will be
used to convert amorphous Ti02 layers into the anatase form. Other hybrid nanoparticles include an open Ti02
shell around metal cores, hollow Ti02 nanoparticles, and Ag/Au@Ti02 particles with small Ru02 and Pt
clusters attached to their surface. All particles will be characterized by UV-Vis absorption, luminescence and
Raman scattering spectroscopy, electron and scanning tunneling microscopy, and x-ray diffraction. The photo-
catalytic activity of hybrid nanoparticles will be assessed in model experiments using photoreduction of
methylviologen and photocatalytic degradation of 4-chlorophenol.
Ag/Au@Ti02 particles represent a new system with unknown chemical and physical properties. These
nanoparticles will exhibit enhanced photocatalytic activity as compared to Ti02 conventional catalyst. This
new material will have a positive impact on the development of new solar-based technologies, including
photoremediation of environmental pollutants, photovoltaic cells, photochemical splitting of water, and arti-
ficial photosynthesis. The synthetic approaches developed for the preparation of Ag/Au@Ti02 hybrid nano-
particles can be extended to include other metals and semiconductors. The proposed research will answer the
fundamental question about the possibility of utilization of energy stored in the form of plasmon resonances in
metal nanoparticles to carry different chemical reactions.
The Office of Research and Development's National Center for Environmental Research 29
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Plasmon Sensitized TiO2 Nanoparticles as a Novel
Photocatalyst for Solar Applications
George Chumanov
Department of Chemistry, Biotechnology Research Center,
Clemson University, Clemson, SC
Environmental Implication/Application
Efficient conversion of sunlight into electrical and/or chemical energy is of great technological importance
for modern society and future generations. Intensive research in this field in recent decades resulted in the
fundamental understanding of principles that govern photochemical reactions. This knowledge provides a
strong foundation for the development of an artificial photo synthetic system of practical significance. One
attractive possibility is to use the photoinduced heterogeneous electron transfer from small semiconductor
particles to drive different oxidation and reduction reactions. Titanium dioxide (Ti02) is considered the most
technologically promising material for these applications because it is an environmentally friendly, relatively
inexpensive, and potentially efficient photocatalyst. However, the photocatalytic activity of Ti02 requires the
sensitization with ultraviolet radiation that comprises only a small portion of the solar spectrum, thereby limit-
ing the solar efficiency of this material.
The main objective of this proposed research is to develop a novel hybrid photocatalyst that consists of
silver or gold nanoparticles encapsulated into a Ti02 shell (Ag/Au@Ti02). Silver and gold nanoparticles are
very efficient systems for capturing energy from the visible portion of the spectrum due to the excitation of
plasmon resonances. Thus, the hybrid Ag/Au@Ti02 nanoparticles will utilize solar energy for photochemical
reactions more efficiently than bare Ti02.
It is expected that the development of this novel photocatalyst will have a positive impact on the ad-
vancement of new, solar-based, environmentally friendly technologies. For example: (1) The hybrid photo-
catalysts will be used for photochemical destruction of the environmental pollutants, polychlorinated phenols.
Photooxidation of these pollutants using bare Ti02 particles was successfully accomplished in the field under
solar illumination. However, low solar efficiency of these photocatalysts limits its wide practical application.
(2) Based on Ag/Au@Ti02 nanoparticles, more procedures will be developed for photoremediation of a wide
range of organic and inorganic pollutants such as in the removal of heavy metals in purification of water by
sun-induced photoreduction processes. (3) This hybrid photocatalyst can be used for producing oxygen and
hydrogen from water using solar energy. It is difficult to overemphasize the importance of hydrogen-powered
technologies for the future. A vivid example is hydrogen-powered cars, an area of research and development in
which governments and the private sector around the world put a great deal of effort and resources. (4) Ag/
Au@Ti02 hybrid nanoparticles have a potential for the photovoltaic devices capable of direct conversion of
solar energy into electricity. Devices using Ti02 nanoparticles sensitized with organic chromophores already
have proved to be very efficient for photovoltaics. However, their lifetime and durability is limited by photo-
bleaching of organic molecules under prolonged solar irradiation. This problem is expected to be eradicated for
Ag/Au@Ti02 nanoparticles in which the inorganic metal core functions as a light-capturing chromophoric
species. (5) Ag/Au@Ti02 nanoparticles represent new systems with unknown chemical and physical proper-
ties. Further exploration of these materials may result in novel application in other areas such as pho-
tonics and microelectronics. (6) The synthetic approaches developed for the preparation of Ag/Au@Ti02
hybrid nanoparticles can be extended to include other metals and semiconductors. Other hybrid/semiconductor
nanoparticles also may find applications in various environmentally friendly, photochemical, solar tech-
nologies. The development of Ag/Au@Ti02 nanoparticles signifies a new field in material science with wide
possibilities for practical developments. (7) Finally, this proposed study addresses the fundamental question
about utilization of optical energy stored in the form of plasmon resonance for carrying out various chemical
reactions.
30 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
In summary, the potential impact of this research relates to the advancement of currently existing tech-
nologies and the development of new solar technologies, including photoremediation of environmental pol-
lutants, direct conversion of solar energy into electricity in photovoltaic devices, and splitting water to oxygen
and hydrogen.
The Office of Research and Development's National Center for Environmental Research 31
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Graft Polymerization as a Route To Control Nanofiltration Membrane
Surface Properties To Manage Risk of EPA Candidate
Contaminants and Reduce NOM Fouling
Georges Belfort
Department of Chemical Engineering, Rensselaer Polytechnic Institute, Troy, NY
Abstract
A UV-assisted photochemical graft polymerization technique was used to produce modified poly(ether
sulfone) ultrafiltration (UF) membranes that exhibit reduced interaction with natural organic matter (NOM), as
a route to reduce the fouling caused by NOM. Six different hydrophilic monomers were evaluated for their
ability to reduce fouling by NOM: two are neutral monomers, N-vinyl-2-pyrrolidinone (NVP) and 2-hydroxy-
ethyl methacrylate (HEMA); two are weakly acidic (carboxylic) monomers, acrylic acid (AA) and 2-acryl-
amidoglycolic acid (AAG); and two are strongly acidic (sulfonic) monomers, 3-sulfopropyl methacrylate
(SPMA) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS).
Grafting increased membrane surface wettability and shifted the membrane pore size distribution to
smaller sizes, which increased NOM rejection (except in the case of NVP). Total fouling appeared to depend
primarily on solute rejection, and varied in a complex way that could be interpreted in the context of the NOM
molecular weight distribution. Reversible fouling resulting from cake formation was only weakly dependent on
membrane surface chemistry; in contrast, irreversible fouling exhibited a marked dependence on surface
chemistry. Membranes modified with the weak acid AA monomer were able to reduce irreversible fouling to
zero, in contrast to other strongly hydrophilic monomers such as HEMA and AAG, which increased irrever-
sible fouling relative to the unmodified membrane. The wettability (or hydrophilicity) is not an appropriate pa-
rameter for estimating reduced fouling potential for NOM feeds, as it is for feeds containing protein. We
hypothesize that this is a consequence of the structural and chemical heterogeneity of NOM.
The AA-modified membranes exhibited excellent filtration performance over multiple runs, and outper-
formed a regenerated cellulose membrane having similar initial NOM rejection.
32 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Graft Polymerization as a Route To Control Nanofiltration Membrane
Surface Properties To Manage Risk of EPA Candidate
Contaminants and Reduce NOM Fouling
Georges Belfort
Department of Chemical Engineering, Rensselaer Polytechnic Institute, Troy, NY
Environmental Implication/Application
Results from this project will provide important treatability data for several contaminants from the
Candidate Contaminant List, and one contaminant (arsenic) that is currently regulated. The EPA has identified
this as a research priority. Treatability data will be provided using as-received nanofiltration membranes, and
membranes modified at the molecular scale. Such data will be collected in complex mixtures containing natu-
ral organic matter (NOM) that will be representative of water treatment conditions. Effects of organic matter
having a wide range of composition and properties on treatment will be quantified. Results from this project
also will provide new approaches to develop membrane materials that have superior performance charac-
teristics in terms of both enhanced rejection of contaminants and resistance to fouling by NOM. This project
will identify innovative and cost-effective ways to reduce the risk of organic and inorganic anions in potable
water sources, which will be of interest to practicing engineers who design water treatment facilities, re-
searchers in the membrane and water treatment fields, and membrane manufacturers.
The proposed research also will expand our understanding of the role of membrane charge and NOM
fouling layers on solute rejection by nanofiltration processes. This will identify new ways to assess treatment
technologies, and will assist practicing engineers and researchers in designing and implementing these tech-
nologies. The materials and processes developed in this research will provide new options for controlling risks
from contaminants in water supplies. In this way, we seek to protect human health, and improve the perfor-
mance of membrane treatment technologies while reducing their cost.
The Office of Research and Development's National Center for Environmental Research 33
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Ecocomposites Reinforced With Cellulose Nanoparticles: An
Alternative to Existing Petroleum-Based Polymer Composites
William T. Winter
College of Environmental Science and Forestry, State University of New York, Syracuse, NY
Abstract
The broad objective of this research project is to produce wholly biobased and biodegradable nano-
composites using cellulose nanocrystals and nanofibers dispersed in biodegradable matrices. These nanocom-
posites will be compared in terms of thermal, mechanical, and biodegradation properties with existing glass-
filled composites made from petrochemicals. During the past 4 months, a 22 L reactor has been acquired, and
the problems of scaleup in nanocrystal batch size are being explored. In addition, our own composite objects
will be extruded for testing, and biodegradation tests will be developed that are based on ASTM and ISO pro-
tocols.
34 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Ecocomposites Reinforced with Cellulose Nanoparticles: An
Alternative to Existing Petroleum-Based Polymer Composites
William T. Winter
College of Environmental Science and Forestry, State University of New York, Syracuse, NY
Environmental Implication/Application
The development of ecocomposites reinforced with cellulose nanoparticles as an alternative to existing
petroleum based polymer composites offers three principal environmental impacts. First, the particles being
used are made of cellulose, the most abundant and sustainable carbon compound on earth with some 1013 tons
biosynthesized each year and that replaces inorganic fillers such as chopped glass fiber. Second, because the
cellulose nanoparticles have lower densities and are used in smaller quantities to achieve a given level of rein-
forcement, products made with such composites will be lighter than corresponding glass-filled materials. In
transportation applications, lighter materials map into improved fuel economies as it takes more energy to
move a heavy object than it does to move a light one. Reduced fuel consumption, in turn, leads to lower emis-
sions of toxic gases. Finally, because the ecocomposites are made from both biodegradable matrices such as
polylactic acids, or seed oil-based polyesters and reinforced with biodegradable cellulose particles, it will be
demonstrated that the resulting composites are biodegradable under landfill or composting conditions. This
makes such materials particularly appropriate for single use applications such as the production of certain
packaging materials, Ag films, and many objects used in biomedical applications.
The Office of Research and Development's National Center for Environmental Research 35
-------
-------
Section 2. Aerosols
EPA is interested in furthering the scientific understanding of the microphysical phenomena of aerosol par-
ticles. Aerosols can be nanoscale, in the size range of 1-100 nm. Aerosol research will provide better data for
models used in atmospheric and stratospheric particle concentration predictions. Such understanding will lead
to protection of human health in terms of providing mechanisms for minimizing respiratory health effects, as
well as providing protection from stratospheric ozone depletion that results from particle deposition on cloud
condensation nuclei.
-------
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Elemental Composition of Freshly Nucleated Particles
Murray Johnston
University of Delaware, Newark, DE
Abstract
The objective of this research project is to develop a method for real-time sampling and analysis of
individual airborne nanoparticles between 5 and 100 nm in diameter. The size range covered by this method is
much smaller than existing single particle methods for chemical analysis. Because particles in this size range
have had relatively little time to grow or transform in the atmosphere, their chemical compositions should
more closely reflect particle formation mechanisms than larger particles that have undergone significant
transformation. Chemical composition measurements are performed with the use of a high-energy laser pulse
to create a laser induced plasma (LIP) that quantitatively converts the particle into positively charged atomic
ions.
Relative to conventional laser ablation, which is used in most single particle experiments, the LIP is
produced with a lOOx higher laser fluence. The higher laser fluence is thought to completely disintegrate the
particle into atoms and then quantitatively convert the atoms to positively charged atomic ions. This concept
has been confirmed through the study of single particle mass spectra of particle compositions typically found
in urban air. In most cases, the measured relative peak areas of different atomic ions match, within experi-
mental error, the expected peak areas based on the elemental composition of the particle. Some important
exceptions are noted; for instance, transition and heavy metals tended to quench the LIP, inhibiting quantitative
analysis. An important advantage of LIP over conventional laser ablation is that the detection efficiency (de-
fined as the number of particles detected divided by the number of particles irradiated with the laser) remains
independent of particle size and composition. In particular, ammonium sulfate particles are detected by LIP
with the same efficiency as other particle composition types. In contrast, ammonium sulfate is very difficult to
detect with conventional laser ablation and has represented an important limitation of the technique in previous
field studies.
The Office of Research and Development's National Center for Environmental Research 39
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Elemental Composition of Freshly Nucleated Particles
Murray Johnston
University of Delaware, Newark, DE
Environmental Implication/Application
Ultrafine particles (defined as 100 nm in diameter and below) and nanoparticles (defined as 50 nm in di-
ameter and below) are important components of ambient aerosol that significantly influence global climate and
human health.
Nanoparticles are precursors for larger particles in the accumulation mode. Accumulation mode particles
affect the earth's temperature by directly and indirectly (through cloud formation) scattering incoming solar
radiation. Understanding the chemical composition of these particles and their precursors allows the impact of
human activities on climate change to be more accurately assessed.
There is growing evidence that ultrafine particles and nanoparticles are toxic and that particle number
concentration can be an important indicator of human health. Predicting the concentration of these particles in
the atmosphere requires an understanding of the processes that lead to new particle formation and to the
growth of existing particles. Insight into these processes can be gained through chemical composition measure-
ments. The chemical composition of an individual particle is determined by its origin (formation) and trans-
formation (growth) in the atmosphere. By performing chemical composition measurements on successively
smaller particles, we should be able to distinguish chemical components involved in formation from those
involved in growth and perhaps to quantify the relative contributions of the various sources to ambient particle
loadings.
40 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Ion-Induced Nucleation of Atmospheric Aerosols
Peter McMurry , Kenjiro lida , and Fred Eisele
Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN;
2Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, CO
Abstract
The goals of this research project are to determine whether or not regional nucleation events that have
been observed in the lower troposphere are due to ion-induced nucleation, and if so, to identify the chemical
species that participate in the formation and growth of ionic embryos. This project involves both atmospheric
observations and modeling to interpret those observations. An inclined grid mobility analyzer (IGMA) is being
used to measure the distributions of positive and negative ions in the 0.5-5 nm size range as well as a nano-
scanning mobility particle sizer (nano-SMPS) to measure mobility distributions of nanoparticles in the 3-40
nm diameter range, and a conventional SMPS and optical particle counter to measure particle size distri-
butions from 30 nm-2 um. In addition, measurements of ion composition are being made using a quadrupole
mass spectrometer. Measurements have been conducted in Atlanta, GA (August 2002), and Boulder, CO
(2004-2005).
Data from several nucleation events in Boulder have been analyzed, and it has been concluded that in most
cases nucleation is not ion-induced, but rather involves the clustering and subsequent growth of neutral spe-
cies. However, during several nucleation events, there is evidence that negative ion-induced nucleation occurs.
These conclusions are made by examining the transformation of size-dependent aerosol charge distributions
during nucleation events. As nucleated particles grow by condensation of species such as sulfuric acid, they
also collide with small ions. Due to such charge transfer processes, nucleated particles will eventually "forget"
their original charge states as they grow. However, if growth is sufficiently fast, then particles will "remember"
their initial charge state long enough to enable one to determine it by measuring the charge distributions of the
freshly nucleated particles. A model has been developed that accounts for charge transformation and growth,
and enables us to calculate size-dependent charge distributions that would be expected if nucleation were ion-
induced or neutral. The conclusions are obtained by comparing predictions of this model with our measure-
ments.
Currently, measured ion composition during nucleation events is being reconciled with theoretically
predicted ion composition, based on known kinetics of ion-molecule reactions. This work will enable us to
determine the chemical processes that are responsible for the ion-induced nucleation events.
The Office of Research and Development's National Center for Environmental Research 41
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Ion-Induced Nucleation of Atmospheric Aerosols
Peter McMurry
Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN
Environmental Implication/Application
It is necessary to understand nucleation to establish the relationship between anthropogenic and biogenic
emissions and atmospheric aerosol effects, including their effects on human health and global climate.
Nucleation, for example, can produce high concentrations of very small particles, and recent toxicology
research has shown that at a given mass concentration, particles in the 20 nm diameter range have a much
greater impact on the lung function of laboratory test animals than approximately 200 nm particles. Nucleated
particles also can grow into cloud condensation nuclei (CCN), and can thereby affect precipitation patterns and
albedo. Understanding such microphysical phenomena is essential to develop valid models for predicting
atmospheric aerosol size distributions and the effects of aerosols on the environment. This research project is
providing the tools to investigate the relative roles of homogeneous and ion-induced nucleation. In addition,
this research is continuing our pattern of developing new measurement methods, applying them in atmospheric
field studies, and comparing our measurements with model predictions.
42 The Office of Research and Development's National Center for Environmental Research
-------
Section 3. Sensors
Protection of human health and ecosystems requires rapid, precise sensors capable of detecting pollutants at
the molecular level. Major improvements in process control, compliance monitoring, and environmental
decision-making could be achieved if more accurate, less costly, more sensitive techniques were available.
Nanotechnology offers the possibility of sensors enabled to be selective or specific, detect multiple analytes,
and monitor their presence in real time. Examples of research in sensors include: the development of nano-
sensors for efficient and rapid in situ biochemical detection of pollutants, ultrafines, heavy metals and
pathogens in the environment; sensors capable of continuous measurement over large areas; integration of
nano-enabled sensors for real-time continuous monitoring; and sensors that utilize lab-on-a-chip technology.
Research also may involve sensors that can be used in monitoring or process control to detect or minimize
pollutants or their impact on the environment.
-------
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Nanostructured Porous Silicon and Luminescent
Polysiloles as Chemical Sensors for Carcinogenic
Chromium(VI) and Arsenic(V)
William C. Trogler
Department of Chemistry and Biochemistry, University of California at San Diego, San Diego, CA
Abstract
The chief goal of this research project is to develop new selective solid state sensors for carcinogenic and
toxic chromium(VI) and arsenic(V) based on redox quenching of the luminescence from nano-structured
porous silicon and polysiloles. Nano-structured porous silicon as well as polysilole nanowire coatings will be
chemically modified to enhance the binding of the chromate and arsenate anions. Chemical modification to
vary the redox potential of the polysilole excited state also will be used as a way to impart chemical selectivity.
Both approaches will be combined by encapsulating the polysilole in a nanotextured microcavity between two
Bragg stacks constructed from porous silicon. Such optical devices have been shown to provide significant
detection sensitivity enhancements. The nanoporous material will readily admit small inorganic analytes, such
as chromate and arsenate, and exclude biomolecules that might confound the measurements. Sensors based on
silicon wafer and polymer technologies also are readily adaptable to fabrication. The fluorescence quenching
detection modality also is manufacturable. The essential electronics require a blue or ultraviolet LED as the
excitation source and an inexpensive photodiode detector. Potential applications of such real-time detection
devices include remote sensing and industrial process control. The focus on chromium(VI) and arsenic(V)
detection is dictated by the redox quenching mechanism that is being used, as well as by the importance of
chromium(VI) and arsenic(V) as regulated chemicals under the Safe Drinking Water Act.
Chromium(VI) detectors will be developed that can sense the analyte at concentrations at least as low as
the 0.1 ppm action level mandated by the Safe Drinking Water Act with at least a 10 percent accuracy. For
arsenic(V), the target range is 10-50 ppb at the same level of analytical accuracy. The deployment of remote
sensors for natural waters and for industrial wastewater that could be used to signal alerts in real time would
become possible. An electronic sensor method would prove more beneficial than the grab-sampling procedure
currently used for detecting these problematic water contaminants. A second goal of this project is the develop-
ment of polymer-coated "litmus paper" for qualitative detection of chromium(VI) and arsenic(V). Given the
low expense of polymer-coated paper, this could prove to be a useful adjunct to current qualitative methods.
Those that benefit from remote sensing applications would include research scientists trying to understand
the variations in chromium and arsenic pollutants in natural waters, municipal source water monitoring, as well
as federal regulatory monitoring. Because electronic sensors can be engineered either wired or wireless, the
range of possible applications is truly immense. Industries involved in metal working and electroplating also
would benefit from the ability to monitor waste streams for continuous compliance (in real time) with pollution
regulations. Electronic sensors also could be employed to monitor mine runoff for the presence of toxic soluble
chromium and arsenic that could enter ground or natural water systems. Chromium is widely used as a cor-
rosion inhibitor in closed water boilers and chillers. Electronic sensors could be used to monitor leaks into
nearby groundwater as well as into heat exchange systems.
The simple "litmus paper" application of the thin film polymer indicators could prove useful for field
studies and monitoring. Such test strips also would find application in science education (both K-12 and
university level) for informing the public about metals in water supplies. Qualitative test strips would be most
economically feasible for monitoring water supplies for compliance at the tap, which is the ultimate measure of
safety.
The Office of Research and Development's National Center for Environmental Research 45
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Nanostructured Porous Silicon and Luminescent
Polysiloles as Chemical Sensors for Carcinogenic
Chromium(VI) and Arsenic(V)
William C. Trogler
Department of Chemistry and Biochemistry, University of California at San Diego, San Diego, CA
Environmental Implication/Application
There has been interest in the device properties of polymers since the first discovery of an electrolumi-
nescent organic polymer. The combination of good structural properties, fabrication, and high efficiency of
electroluminescence are important for the development of large-area, light-emitting displays. These same prop-
erties also make such materials excellent candidates for luminescent chemical sensors. This research project
has shown how luminescent polysiloles developed for LED applications also can be used as sensitive TNT and
picric acid (explosive) detectors. Chromium(VI) is an especially problematic contaminant of drinking water
because it has been identified as a human carcinogen due to its ease of uptake. In the case of chromium, it
could be argued that carcinogenic chromium(VI) should be regulated more stringently than the less toxic
chromium(III). Sensors with redox selectivity could be particularly useful in this regard. This project will sum-
marize how functionalization of polymer end groups, as well as those along the chain, can be used to modify
their sensor properties for organic vs. inorganic oxidants. Nanoparticles of the luminescent polymers and
monomers also can be prepared by rapid precipitation. Their high surface area and adsorptive properties offer
sensor detection levels far greater than for bulk phases. Laser scattering measurements support atomic force
microscopy (AFM) imaging studies, which show nanoparticle sizes in the 80-100 nm range.
46 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Nanosensors for Detection of Aquatic Toxins
Robert E. Gawley
University of Miami, Coral Gables, FL
Abstract
The objectives of this research project are to design and prepare nanoscale sensors for the detection of
marine toxins domoic acid, brevetoxin, ciguatoxin, cylindrospermopsin, and tetrodotoxin. Most of these ma-
rine toxins bind specifically to protein receptor sites with a high affinity (Kd typically in the nm range). The
protein receptor sites for several of these toxins have been characterized, and include two characteristic
features. One is an array of amino acid side chains that complement structural features of the toxin, which
facilitates and strengthens binding of the toxin into the receptor site. A second feature is a solvent-excluded
pocket in which the amino acid side chains are arrayed. This preorganized feature of toxin receptor sites will
be mimicked by design of synthetic receptors at the nanoscale (nanosensors). To optimize the sensitivity and
the selectivity of the nanosensor, combinatorial synthesis techniques will be employed to optimize binding in
libraries of peptidic host molecules immobilized on solid support (polystyrene beads). Unlike side chain arrays
in the native (protein) receptors, this study will not be limited to L-amino acids, or even to natural amino acids.
In this way, short peptide sequences will be produced that wrap around toxins and bind them by providing an
array of side chains similar to the native receptor. To mimic the solvent-excluded pocket of protein receptor
sites, the combinatorially designed peptide will be incorporated at the core of a dendritic polymer, still on a
solid support.
The marriage of combinatorial design and dendrimer synthesis on solid support will provide large libraries
(up to 100,000 members) of polypeptide hosts inside dendritic polymers, with each individual host molecule
attached uniquely to a polystyrene bead. This is a novel approach in nanosensor design. To our knowledge, this
is the first time combinatorially designed peptidic hosts have been incorporated into a dendrimer. Qualitative
evaluation of toxin binding can be done simply with a fluorescence microscope. Quantitative analysis will be
done with a specific host after it has been synthesized in bulk.
At present, environmental monitoring for aquatic toxins is most commonly done by mouse bioassay.
Alternative methods, such as liquid chromatography coupled with mass spectroscopy (LC-MS), are extra-
ordinarily expensive and not suitable for high-throughput analysis. To move away from mouse bioassay, an
inexpensive, fast method is needed. This project will identify nanoscale sensors attached to polystyrene beads
that can detect toxins using only a hand-held UV lamp and a magnifying glass. The science behind the design
of toxin sensors will lead to further developments as well. These synthetic receptors also could be used to
immobilize the toxins. Although beyond the scope of the present work, the same design features to be used for
mimicking toxin receptor sites also can be used to mimic enzyme receptor sites. Thus, by using models of
enzyme active sites, we anticipate being able to use this methodology to mimic enzyme reactions to produce
solid-phase catalysts.
The Office of Research and Development's National Center for Environmental Research 47
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Nanosensors for Detection of Aquatic Toxins
Robert E. Gawley
University of Miami, Coral Gables, FL
Environmental Implication/Application
This research is aimed at the development of efficient and rapid detection of the marine toxins such as
saxitoxin in environmental samples. Using our ability to work at the molecular level to create large structures
with fundamentally new molecular organization, preliminary data have been obtained showing that the toxin
can be detected at concentrations below that of the standard method of detection, mouse bioassay. At present,
most of the developmental work with toxin standards has been completed, but we recently obtained several
environmental samples for the Washington State Department of Health, and have begun to evaluate our sen-
sors on those samples.
Future work will be aimed at environmentally robust chemosensors that are small and portable, and which
will be able to detect saxitoxin quickly and inexpensively.
48 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Micro-Integrated Sensing Systems by Controlled
Self-Assembly of Nanoparticles
Somenath Mitra
Department of Chemistry, New Jersey Institute of Technology, Newark, NJ
Abstract
The increasing need for inexpensive, portable monitoring devices have added new impetus to miniaturi-
zation of chemical analysis systems. It is well known that miniaturization yields many functional and economi-
cal benefits because of the reduction of the sample size, decrease in reagent consumption, and inexpensive
mass production. Figures of merit necessary for different measurements are high sensitivity, selectivity, repro-
ducibility, short response time, and long-term stability. To solve real-world environmental problems, the sen-
sors need to meet these requirements. The limited success of the sensors in trace environmental monitoring is
due to the relatively low sensitivity and high detection limit of the sensors.
A method to enhance sensitivity in any analytical measurement is to preconcentrate the species of interest.
Sorbent trapping during air sampling and solid-phase extraction are common preconcentration techniques that
allow larger volumes of analyte to be concentrated and then released into the detector, thus resulting in a high
signal-to-noise ratio.
Methods of self-assembly of nanoparticles in micro-channels for analyte preconcentration will be pre-
sented. The first approach involves gas-phase preconcentration at the nanoscale via quantum interactions on
carbon annotates (CNTs) directly self-assembled on the devices. This is achieved by chemical vapor deposition
(CVD) techniques. The other approach involves solid-phase extraction in microfluidic channels on silica nano-
particles. The nanoparticles are self-assembled via sol-gel synthesis.
The Office of Research and Development's National Center for Environmental Research 49
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Micro-Integrated Sensing Systems by Controlled
Self-Assembly of Nanoparticles
Somenath Mitra
Department of Chemistry, New Jersey Institute of Technology, Newark, NJ
Environmental Implication/Application
At present, there is a need for the development of low cost micro-sensing and measurement devices that
can be used for real-time measurements with high sensitivity. Although microsensors have been around for
many years, their application in environmental sensing has been limited due to low sensitivity and high
detection limits. High sensitivity in the sensors proposed will be achieved by nanoscale quantum adsorption
and separation processes on self-assembled carbon nanotubes (CNTs). The sensing devices developed in this
project will be: (1) functionally simple and rugged; (2) completely automated for continuous monitoring; (3)
cost-effective; and (4) sensitive down to the ppb level. The sensing systems will be developed with air moni-
toring in mind. It can be used for regulatory purposes, in process control, or for monitoring fugitive emissions
from industry. It also will have applications in homeland defense applications, such as in monitoring chemical
warfare agents and explosive vapors. This research project also will develop new areas in next-generation
sensing and analysis and in nanotechnology. The major new developments will be: (1) fundamental under-
standing of a microconcentration on carbon nanotubes; (2) self-assembly of CNTs in microfluidic devices by
CVD; and (3) functionalization of CNTs.
50 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Advanced Nanosensors for Continuous Monitoring of Heavy Metals
Adam K. Wanekaya , Daniel Andreescu , Omowunmi A. Sadik , and Joseph Wang
Chemistry Department, State University of New York at Binghamton, Binghamton NY;
2Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM
Abstract
The overall objective of this research project is to utilize novel colloidal-metal nanoparticles that are
incorporated into a bed of electrically conducting polymers (ECPs) for the development of nanosensors. The
feasibility of designing advanced conducting materials for sensor and remediation applications has been ex-
plored. Specifically, the synthesis of: (1) polyamic acid (PAA)-silver nanoparticle composites membranes; (2)
polyoxy-dianiline films; and (3) electrochemical deposition of gold nanoparticle films on functionalized con-
ducting polymer substrates has been examined. A short description of our fast and simple synthetic approach
to gold nanoparticles will be presented. This one-step, synthesis of stable gold nanoparticles uses PAA as both
the reducing and stabilizing agents. The nanostructured materials were characterized using electrochemical and
morphological techniques such as Fourier-transform infrared spectroscopy, cyclic voltammetry, galvanostatic
methods, energy-dispersive spectroscopy, and transmission electron microscopy. Novel gold nanoparticles
were prepared through the reduction of AuCl3 by PAA in organic medium in less than 1 hour. The PAA acts as
a reducing agent of the metal salt and a stabilizing agent of the resulting gold (Au) nanoparticles. The pro-
cedure resulted in gold nanoparticles capped with the 7i-conjugated PAA. Depending on the reactant concen-
trations and ratios, the PAA-metal hybrid was synthesized either as well-dispersed or aggregated particles. The
size of the particles, which can be controlled by varying the PAA:AuCl3 ratios, ranged from 4.0 ± 0.7 nm to
7.8 ± 1.0 nm. Potential applications and environmental implications of the proposed materials also will be dis-
cussed.
Current widespread interest in metal nanomaterials is driven by a large number of potential applications,
including environmental catalysts, ultrafast optical switches, sensors and surface-enhanced spectroscopies.
Many of these applications require the nanoparticles to be stable and evenly distributed with precise control of
size, geometry, and morphology. The stable dispersion of nanoparticles in water is important to many appli-
cations. However, the water-based synthesis of nanoparticles is fraught with inherent problems such as ionic
interaction, low reactant concentration, and difficulty in removing the residue of stabilizers after synthesis.
Particles synthesized in organic solvents can be made at a relatively high concentration with a predefined size
and shape and with improved monodispersibility when compared with those prepared in aqueous media. Most
reports on the synthesis of gold nanoparticles in nonpolar organic solvents have followed the Brust protocol1,
wherein aqueous chloroaurate ions are transferred into the organic solvent using phase-transfer molecules
(tetraalkylammonium salts).
KBH4 or alcohol has been used for the reduction of the gold salt to form the nanoparticles before being
stabilized and protected by the linear polymer. Other researchers have since reported the stabilization of Au
nanoparticles using linear polymers. Polymer molecules that possess functional groups such as SH, CN, and
NH2, can provide sites to bind with Au nanoparticles and prevent them from aggregating because those func-
tional groups are known to have a high affinity for Au. Poly(dithiafulvene) represents the first example where
a polymer was used both as a reducing agent and a stabilizing agent in the preparation of gold nanoparticles in
organic medium. However, the reaction with poly(dithiafulvene) took 24 hours.
This study provides the first report on the synthesis and stabilization of gold nanoparticles using PAA both
as a reducing and stabilizing agent in the solution phase. This approach is based on the reduction of gold III
chloride by the PAA and its subsequent capping and stabilization of the resulting gold nanoparticles. Re-
duction of AuCl3 by this 7i-conjugated polymer at room temperature led to gold nanoparticles with narrow size
distribution and high dispersity, with the resulting oxidized conjugated polymers protecting the gold nano-
particles as stable colloidal solution. The size of the nanoparticles was controlled by simple variation in the
PAA:AuCl3 molar ratio. Unlike poly(amidoamine) dendrimer-encapsulated gold nanoparticles that are only
The Office of Research and Development's National Center for Environmental Research 51
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
stable for 1 day before sedimentation, the current synthesis and stabilization with PAA allows stability for
several months with no change in dispersion, nanoparticle density, size distribution, or absorption spectra
when stored at -20 °C. Furthermore, the PAA-capped gold nanoparticles are formed in less than 1 hour in a
rapid, one-step, single-phase synthesis compared to those produced in 12 hours to 1 day.2 Also, some current
approaches are performed in two phases and thus require extraction into the organic medium. The PAA
reaction enables the direct formation and stabilization of the nanoparticles in the organic medium.
In a typical reaction, AuCl3 crystals (1.5 mg, 5 x 10~6 moles) were dissolved in 6 mL of dimethylfor-
mamide (DMF) solutions containing various amounts of PAA (0.5 mg, 1.0 mg and 3.0 mg) and were left to
stand at room temperature. The resulting solutions contained PAA:AuCl3 in 1:100, 2:100, and 6:100 mole
ratios, respectively. PAA was synthesized by an adaptation of the method previously reported by Echigo. Its
average molecular weight was estimated to be about 10,000 using gel permeation chromatography (GPC).
Briefly, 0.010 mol of 4,4 oxydianiline (ODA) was dissolved in 125 mL of acetonitrile. 50 mL of aceto-
nitrile containing 0.01 mol of 1,2,4,5-benzenetetracarboxylic dianhydride (pyromellitic dianhydride - PMDA)
was then added dropwise for 1 hour to the stirred ODA solution. Yellow PAA precipitates were formed, and
the stirring was continued overnight. The PAA was filtered and dried at room temperature for 24 hours. The
Mw of PAA was estimated to be 10,000 using GPC. All solvation processes were achieved by sonication.
The reaction medium gradually changed color from yellow, through orange, and finally to purple (see
Figure 1). A control reaction with no PAA was run concurrently. There was no color change with this solution,
as the solution retained its original yellow color. The color change in the reaction with the PAA was attributed
to the reduction of the AuCl3 by PAA to produce the gold nanoparticles. PAA is simultaneously oxidized in
the process. Figure la also shows the ultraviolet-visible absorption spectrum of the reaction progress during
the formation of the PAA-capped gold nanoparticles in dimethylformamide. It is evident that there is a gradual
increase in intensity at 540 nm, indicating the formation of the gold nanoparticles. The shape and position of
the final band is characteristic of gold nanoparticles with a diameter below 10 nm. This has been attributed to
localized surface plasmon oscillation. The isosbestic point at 510 nm is indicative of the involvement of two
major species in the reaction medium. The reaction occurred in a similar manner in dimethylsulfoxide and
dimethylacetamide, although the rate of reaction was relatively much slower in the former solvent.
Figure Ib shows the transmission electron microscopy (TEM) of the PAA-capped gold nanoparticles when
a 2:100 mole ratio of PAA:AuCl3 was used for synthesis. The image clearly shows that the nanoparticles are
uniformly distributed and well dispersed throughout the polymer. No particle aggregation was seen. This
indicated that the re-conjugated PAA stabilized the gold nanoparticle and prevented the aggregation by both
steric and electrostatic stabilization mechanisms. The use of conjugation in the stabilizing nanoparticles is a
well-known concept. Additional stabilization also is believed to arise from the interaction of the gold with the
basic nitrogen centers in the polymer backbone. The average particle size in this case was 5.1 ± 0.9 nm. The
nanoparticles were very consistent in size and dispersion pattern. It is evident that the particles became smaller
in size to approximately 4.0 ± 0.7 nm when the PAA:AuCl3 mole ratio was increased to 6:100. This is due to
the presence of more PAA molecules that are available for the capping and stabilization of the gold
nanoparticles. On the other hand, the reduction of the PAA:AuCl3 mole ratio to 1:100 resulted in slightly larger
particles with more aggregation due to less PAA molecules in the reaction medium that are available to
stabilize the nanoparticles. The size of the nanoparticles in this case was in the range of 7.8 ± 1.0 nm. This
phenomenon of a higher polymer concentration giving rise to smaller particles has already been observed for
polymeric thiols.
This reaction was confirmed using HNMR spectroscopy.1 The chemical shifts of the hydrogens Ha and Hb
in the reactant PAA and the oxidized PAA were unchanged at § 10.5. The same applied to Hc (§ 8.3). This
meant that part of the PAA molecule remained unchanged after the reaction. On the other hand, the chemical
shifts of Hd (§ 7.7) and He (§ 6.8) in the reactant PAA are typical of a />ara-substituted benzene aromatic
system. However, the nature of the peaks and their chemical shifts after the reaction changed significantly (§ 7-
§ 8), and these could be attributed to the re-conjugated PAA stabilizing the nanoparticles.
52 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
The polymer nanoparticle hybrid was initially tested for the determination of copper using cysteine having
a strong affinity for the metal of interests. The effect of polymer-modified gold nanoparticles oxidation time on
the recovery of copper was investigated by keeping all factors constant and varying the times taken for the
polymer oxidation. The recovery of copper at 10, 100, 200, and 500 sec was 34.7, 75.0, 83.9, and 99.7 percent,
respectively. These results can be explained by the fact that more polymer oxidation time increases the number
of carbon atoms oxidized to COOH moieties, thus enabling more cysteine molecules to be covalently bonded.
Based on additional spectroscopic characterization, there is significant specificity of the materials towards the
metal even when it is sequestered within the polymers. Further work is required to prove the feasibility of this
technique for other metals.
In conclusion, this study shows the first example in which gold nanoparticles were prepared using the
reduction of AuCl3 by PAA in organic medium. The PAA was oxidized in the process, thus resulting in the
capping of the gold nanoparticles with the ^-conjugated PAA. Depending on the reactant concentrations, the
PAA-capped gold nanoparticles were synthesized either as well-dispersed or aggregated particles. Particle size
ranged from 4.0 ± 0.7 to 7.8 ± 1.0 nm. The size of the particles formed and whether aggregation of the
particles occurs or not depends on the PAA:AuCl3 mole ratio. This method can be applied to the preparation of
other PAA-capped metal nanoparticles and bimetallic particles in organic solvents.
350 450 550 650 750
Wavelength (nm)
-":.::=-„«!,
Figure 1. (a) The UV/Vis absorption spectrum for the formation of PAA capped gold
nanoparticles; (b) TEM image of reaction resulting from 2:100 mole ratio of
PAA:AuCl3 in DMF.
References:
1. (a) Brust M, Walker M, Bethell D, Schiffrin DJ, Whyman R. Synthesis of thiol derivatised gold nano-
particles in a two phase liquid/liquid system. Chemical Communications 1994;801. (b) Fink J, Kiely CJ,
Bethell D, Schiffrin DJ. Self-organisation of nanosized gold particles. Chemistry of Materials 1998;
10:922.
2. (a) Andreescu D, Sadik OA, Wang J. Fast and simple synthesis of stable gold nanoparticles using
polyamic acid as a reducing and stabilizing agent. Advanced Materials 2004 (submitted); (b) Andreescu D,
Sadik OA. Synthesis of gold-modified polyoxydianiline membranes: an electrochemical study. Macro-
molecules 2004 (submitted); (c) Andreescu D, Wanekaya AK, Sadik OA, Wang J. Nanostructured poly-
amic acid membranes as novel electrode materials. Langmuir 2004 (in review).
The Office of Research and Development's National Center for Environmental Research
53
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Advanced Nanosensors for Continuous Monitoring of Heavy Metals
Adam K. Wanekaya1, Daniel Andreescu1, Omowunmi A. Sadik1, and Joseph Wang2
Chemistry Department, State University of New York, Binghamton NY;
2Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM
Environmental Implication/Application
The early impact of nanotechnology research could be mostly in remediation and end-of-pipe treatment
technologies. Various reports have appeared on the use of a variety of nanoparticles for treatment and remedia-
tion of pollutants in the environment. For example, nanoparticles of various oxidants, reductants, and nutrients
have been suggested as useful for promoting contaminant transformation and stimulating microbial growth,
because their small size and larger surface area make them more reactive and more flexible in terms of
deployment.1 Nanoparticles could provide enormous flexibility for in situ remediation. For example, nano-
particles have been anchored onto a solid matrix such as carbon, zeolite, or membrane for enhanced treatment
of water, wastewater, or gaseous process streams.2 Direct subsurface injection of nanoscalc iron particles,
whether under gravity-feed or pressurized conditions, has already been shown to effectively degrade chlo-
rinated organics, such as trichloroethylene, to environmentally benign compounds.3 The technology also holds
great promise for immobilizing heavy metals and radionuclides. '" The oxidation of polyaniline modified gold
nanoparticles (PGN) has been investigated on the recovery of copper by keeping all parameters constant (see
Figure 1) and varying the times taken for the PGN oxidation. The results of this investigation showed that the
recovery at 10 sec, 100 sec, 200 sec, and 500 sec was 34.7 percent, 75.0 percent, 83.9 percent, and 99.7percent,
respectively.
HAuCI4
Au Nanoparticle +
polyaniline composite
NH2
HOOC
Cu Removal
P Buffer
pH5
NH2
HS.
COOH
NH2
Cysteine modified
Au Nanoparticle +
Polymer composite
Figure 1. Investigation of the removal of Cu"
nanostructured materials.
from aqueous and organic media using
54
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
References:
1. Masciangioli T. Zhang W-X. Environmental technologies at the nanoscale. Environmental Science and
Technology! 2003;! 02 A.
2. Fiijishima A. Rao TN, Tryk DA. UV enhancement of the gas sensing properties of TiCX Journal of
Photochemistry and Photobiology C: Photochemistry Rev 2000;! :1.
3. Kamat PV, Huehn R. Nicolaescu R. Photophysical, photochemical and photocatalytic aspects of metal
nanoparticies. Journal of Physical Chemistry B. 2002;106(32):7729-7744.
4. Subramanian V. Wolf E, Kamat PV. Semiconductor-metal composite nanostructures. To what extent do
metal nanoparticies improve the photocatalytic activity of Ti02 films? Journal ofPhvsical Chemistry B.
2001;105(46):11439-11446.
5. Ponder SM, Darab JG, Mallouk TE. Remediation of Cr(VI) and Pb(ll) aqueous solutions using supported,
nanoscale zero-valent iron. Environmental Science & Technology 20QQ;34:2564-2569.
The Office of Research and Development's National Center for Environmental Research 55
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Metal Biosensors: Development and Environmental Testing
Anne J. Anderson , Charles D. Miller , and Joan E. McLean
Department of Biology, College of Science, Utah State University, Logan, UT; Department of Biological
Engineering and Irrigation, College of Engineering, Utah State University, Logan, UT
Abstract
Environmental and health risks of toxic metals are based on total metal concentration assayed chemically.
However, chelation and sorption may influence metal bioavailabilty. The goal of this project is to use meta-
bolic changes induced in microbes on contact with the toxic metals to detect bioavailable copper (Cu) and cad-
mium (Cd). The deliverables will be two types of arrays, one based on live cell response and the second based
on gene sequences, to be employed in the specific detection of low doses of bioavailable metals in solution.
Metal detection using the cell array is based on increased production of light because the cells contain fusions
of a luxAB cassette, encoding light production, with promoters that increase in activity when they detect the
metal. Thus, one cell line in the array will emit light only when Cu is present and another only when Cd is
present. The gene array will be used by preparing RNA from the biosensor after metal exposure and assessing
which genes show changes in transcript level. The pattern of transcript abundance will be metal specific.
The microbe used in the construction of these molecular-based sensors is Pseudomonas putida strains
KT2440, selected because its genome is completely sequenced. Previous work with mutants of P. putida strain
Corvallis detected less than 1 mg/L free Cu. These mutants possessed fusions of the promoters of genes
involved in protecting the cells against oxidative stress with a luxAB cassette. Light emission from these
constructs decreased in the presence of toxic metals, but the responses had little metal specificity, presumably
because of induced cell death in the compromised mutants. However, the literature suggests that other
promoters, for example for genes encoding proteins involved in efflux, may respond with greater specificity
and with increased expression to low doses of the metals. To understand the issue of toxicity and its impact on
the biosensors, the threshold was determined for toxicity upon Cu exposure for wild-type KT2440. Loss in
culturability occurred at about 10 mg/L Cu for both KT2440 and Corvallis, a value more than tenfold higher
than the free Cu concentrations that we aim to detect.
To initiate the production of the cell and gene arrays, random promoter fusions were generated in KT2440
with inserts of the luxAB cassette and we measured how light emission changed after exposure to metal. In
trials examining 18 members of an insertion library with exposure to the lesser toxic Fe3+, six of these mutants
responded with increased rather than decreased light emission. By examining the site of the luxAB insertion,
one of the genes that increased in gene expression was found in GTP pyrophosphokinase. Its product,
guanosine 3',5'-bispyrophosphate (ppGpp), accumulates in bacteria in response to either amino acid or energy
source starvation. Consequently, to our knowledge this is a novel response of the bacterial cell to metal ex-
posure. Studies of responses to Cu and Cd are underway to determine whether this gene is another general
response gene or one with specificity. We propose that the cell arrays will consist of promoter fusions that
respond with increased light emission after Cu or Cd exposure. The genes identified through determining the
site on the KT2440 genome bearing the luxAB insertion will be used in the gene array.
The second approach to identify genes that would be likely candidates for promoter fusions and in the con-
struction of a gene array is based on reverse genetics. This method relies on the identification of the KT2440
proteins that change in accumulation in response to metals. Two-dimensional gel electrophoresis demonstrates
changes in levels of several distinct peptides after exposure of KT2440 to Cu and iron (Fe), showing degrees of
specificity in response to these different metals. By MALDITOF analysis, two of the peptides that changed in
response to 10 mg/L Cu were shown to correspond to a flagellin, which decreased threefold, and the lipoamide
dehydrogenase component of 2-oxoglutarate dehydrogenase (OGDH), which increased threefold. These pro-
teins are not among a published list of genes in KT2440 that are predicted to be involved in metal responses.
This finding illustrates the value in this reverse genomics approach. However, decreased flagellin production
has been correlated by other workers with water stress in the cell for P. putida. The increase in the OGDH
56 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
suggests that carbon flow through the tricarboxylic acid (TCA) cycle may be enhanced by Cu exposure as
anticipated from activated metabolism to overcome stress. The availability of the complete genomic sequence
of KT2440 permits synthesis of the promoters for these genes to directly construct the luxAB fusions. These
findings confirm that specific sequences in the genome of KT2440 can be harnessed for the detection of toxic
metals. Such detection is a prelude to the use of the constructs to probe the bioavailability of different metal
complexes occurring in the biological and geological world.
The Office of Research and Development's National Center for Environmental Research 57
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Metal Biosensors: Development and Environmental Testing
Anne J. Anderson , Charles D. Miller , and Joan E. McLean
Department of Biology, College of Science, Utah State University, Logan, UT; Department of Biological
Engineering and Irrigation, College of Engineering, Utah State University, Logan, UT
Environmental Implication/Application
Pseudomonads are common in soil and water, either free in the planktonic state or attached to soil and
biotic matter, including living plant roots. This research project demonstrates that two Pseudomonas putida
isolates, Corvallis and KT2440, respond by changes in gene expression to free ions of the toxic metals, Cu and
Cd. The cells are more susceptible to necrosis to Cu than to Cd. These findings indicate that bacteria when
exposed to these metals, such as from a mine site or from industrial waste, may show a dose-dependent
decrease in population. Such changes may have ecological effects, for example, in plant performance if the
pseudomonads are beneficial root colonizers or in biodegradation of pollutants if the pseudomonads have
bioremediation potential.
Changes in metabolism in response to Cu and Cd have been detected by observing altered production of
peptides and changes in promoter activities. Some of these changes are common to both metals, as expected in
responses that are triggered by oxidative stress, whereas others differ between these metals. Fusions made
between the promoters of the responding genes and luxAB genes, such that an active luciferase can be pro-
duced, have generated microbial cells that act as biosensors for the free metal ions at the 0.01 to 0.1 mg/L
metal ion concentration. These biosensors demonstrate that free ions of Cu and Cd are bioavailable and have
the potential to affect life forms. Thus, the biosensors offer the potential to determine bioavailability of metals,
such as Cu and Cd, in water samples and in pore waters from soils, in potentially contaminated locations.
58 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Compound Specific Imprinted Microspheres for Optical Sensing
Barry K. Lavine
Department of Chemistry, Oklahoma State University, Stillwater, OK
Abstract
The use of molecularly imprinted polymers is being investigated as the basis of a sensitive and selective
sensing method for the detection of pharmaceutical and other emerging organic contaminants, which are at
parts per billion levels, in aquatic environments. Moderately crosslinked molecularly imprinted polymeric
microspheres (ca. 1 micron in diameter), which are designed to swell and shrink as a function of analyte con-
centration in aqueous media, have been prepared. These microspheres are incorporated into hydrogel mem-
branes. Chemical sensing is based on changes in the refractive index of the membrane that accompanies
swelling of the molecularly imprinted microspheres. These changes are measured by surface plasmon reso-
nance (SPR) spectroscopy. For SPR, the polymer microspheres are directly applied to a gold surface where
they are held in place by electrostatic attraction. Encapsulation of the polymeric microspheres is achieved by
micropipetting the membrane formulation onto the surface of the SPR substrate, where it is distributed across
the gold surface by spatula prior to polymerization.
The prototype SPR sensor is both sensitive and specific. The addition of as little as 1.0 x 10~7 M theo-
phylline is sufficient to cause a change in the refractive index of the membrane, which was detected by SPR.
Higher concentrations of theophylline produced a larger change in refractive index. In contrast, the same
membrane showed no response to 1.0 x 10" M caffeine. (Caffeine and theophylline differ by only a single
methyl group.) This result, we believe, is significant for two reasons. First, selectivity has been introduced into
SPR analyses using these membranes. Studies where biological receptors have been used to functionalize gold
(Au) or silver (Ag) surfaces with analyte specific receptors for pollutant monitoring have often been un-
successful due to problems associated with antigen stability and crossreactivity. Second, the likelihood is high
that parts per billion detection limits for theophylline and other so-called emerging organic contaminants can
be achieved with this approach to chemical sensing once the polymeric formulation used to develop the
imprinted polymer and hydrogel membrane are optimized. Currently, a polymer formulation is being used,
which was developed from N-isopropylacrylamide or N-N-propylacrylamide (transduction monomer), metha-
crylic acid (recognition monomer), and moderate concentrations of methylenebisacrylamide (crosslinker), and
a template to prepare molecularly imprinted polymers that swell in the presence of the targeted analyte.
However, the concentration of the recognition monomer is probably too high. Furthermore, the thickness of the
membrane is approximately 75 mm, and the size of the microspheres is approximately 800 nm. The membrane
needs to be thinner to minimize diffusion distances, ensuring facile mass transfer. Smaller microspheres (ap-
proximately 200 nm) will mean that a larger number of polymer particles can be immobilized on the Au
surface, and the entire particle will lie within the region of the evanescent wave.
The proposed technology has several important advantages for chemical sensing. The hydrogel membrane
can serve as a "filter" to block out larger molecules (e.g., humic acid that might otherwise foul the micro-
spheres). Another advantage of this approach to sensing is that it can be implemented at any wavelength. The
microspheres are stable. They are not subject to photodegradation and can undergo multiple swelling and
shrinking cycles without degrading. Furthermore, swelling and shrinking of the microspheres has a minimal
effect on the size of the hydrogel, and does not generate enough force to affect adhesion of the hydrogel to a
substrate. By comparison, previously reported approaches to chemical sensing that involve polymer swelling
share the common feature that swelling introduces stress, causing the polymer to crack and tear as well as
delaminate.
The Office of Research and Development's National Center for Environmental Research 59
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Compound Specific Imprinted Microspheres for Optical Sensing
Barry K. Lavine
Department of Chemistry, Oklahoma State University, Stillwater, OK
Environmental Implication/Application
Steroids, hormones, antibiotics, and numerous other prescription and nonprescription drugs (e.g., caffeine
and ibuprofen) are present in streams throughout the United States at parts per billion (ppb) levels. These com-
pounds enter the environment through wastewater. Some of these compounds may be indicators of human and
animal fecal waste, whereas others have human or environmental health implications. As a first step towards
investigating the transport of these contaminants in the Nation's waterways, it will be necessary to develop
inexpensive field-based methods that can monitor the concentration of these organic contaminants in a variety
of aquatic environments. This research project includes the development of field deployable sensors specifical-
ly tuned towards these so-called emerging organic contaminants.
60 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Ultrasensitive Pathogen Quantification in Drinking Water Using
High Piezoelectric PMN-PT Microcantilevers
Wan Y. Shih and Wei-Heng Shih
Department of Materials Science and Engineering, Drexel University, Philadelphia, PA
Abstract
Highly piezoelectric cantilevers offer the advantages of simple electrical detection and better capabilities
to withstand damping in water. It is especially suitable for in situ aqueous detection of bioagents or microbes.
Binding of antigens to the antibody immobilized on the cantilever surface increases the cantilever's mass and
reduces its resonance frequency, which is detected by monitoring the resonance frequency shift. Detection of
cells, proteins, and specific antigen-antibody binding has been demonstrated with a lead zirconate titanate
(PZT)/stainless steel cantilever. In addition, we have shown that detection sensitivity increased with a de-
creasing cantilever size, L, as L"4. In this project, we have pursued both: (1) developing highly piezoelectric
lead magnesium niobate-lead titanate (PMN-PT) microcantilevers for better detection sensitivity; and (2) in-
vestigating in situ detection of water-born pathogens such as Salmonella typhimurium.
With PZT/glass cantilevers of less than 0.5 millimeter in length, we have: (1) achieved better than 3x10"
g/Hz mass detection sensitivity; (2) obtained resonance frequency shifts 3-7 times higher than those of a 10
MHz quartz crystal microbalance (QCM) in the same test conditions; and (3) demonstrated better than 104
cells/mL concentration detection sensitivity exceeding the infectious dosage of S. typhimurium (105 cells/mL)
and the concentration detection limit of commercial ELISA assays (105 cells/mL). Detection selectivity was
illustrated between Salmonella and yeast.
For PMN-PT microcantilever fabrication, an innovative low-temperature approach was developed to syn-
thesize freestanding lead magnesium niobate-lead titanate (PMN-PT) films as thin as 20 um thick with piezo-
electric properties better than those of specially-cut single crystals. After electroplating 4-um thick Cu, PMN-
PT/Cu microcantilevers were made by wire-saw cutting. With a 600 um length, PMN-PT/Cu microcantilevers
were shown to exhibit better than 10"12 g/Hz (less than the mass of a single cell) mass detection sensitivity. It is
expected that further reducing the cantilever length to less than 100 um will achieve better femtogram sen-
sitivity.
The Office of Research and Development's National Center for Environmental Research 61
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
.Ultrasensitive Pathogen Quantification in Drinking Water Using
High Piezoelectric PMN-PT Microcantilevers
Wan Y. Shih
Department of Materials Science and Engineering, Drexel University, Philadelphia, PA
Environmental Implication/Application
Current pathogen detection procedures rely on passing sample water collected from the environment
through a filter and examining the filter for colony formation a day later, which is slow and not quantitative.
The piezoelectric microcantilever sensors developed in our laboratory will detect and quantify pathogens
directly from the environment with unprecedented femtogram sensitivity. The sensors also are easily portable.
62 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Nanomaterial-Based Microchip Assays for Continuous
Environmental Monitoring
Joseph Wang
Arizona State University, Tempe, AZ
Abstract
This research project will address the needs for innovative nanotechnological tools for continuous environ-
mental monitoring of priority pollutants. The objective of this project is to create a novel nanomaterial-based
submersible microfluidic device for rapidly, continuously, and economically monitoring different classes of
priority pollutants. The unique properties of metal nanoparticles and carbon nanotubes will be exploited for
enhancing the separation and detection processes, respectively, in microchip environmental assays, and to
understand the relationship between the physical and chemical properties of these nanomaterials and the
observed behavior. The miniaturized "Laboratory-on-a-Cable" will incorporate all of the steps of the analytical
protocol into the submersible remotely deployed device.
This project will address the challenge of transforming the "Lab-on-a-Chip" concept to an effective en-
vironmental monitoring system and will exploit the unique properties of nanomaterials for enhancing such
chip-based environmental assays. "Lab-on-a-Chip" technologies can dramatically change the speed and scale
at which environmental analyses are performed. The ultimate goal of this project is to develop a submersible
microfluidic device, based on the integration of all the necessary sample handling/preparatory steps and nano-
material-based assays on a cable platform. The new "Laboratory-on-a-Cable" concept relies on the integration
of continuous sampling, sample pretreatment, particle-based separations, and a nanotube-based detection step
into a single-sealed miniaturized submersible package. Nanoparticle and nanotube materials will be examined
toward the enhancement of the separation and detection processes, respectively. Factors governing the im-
provements imparted by these nanomaterials will be identified, and structural-performance correlations will be
established. New "world-to-chip" interfaces will be examined toward the goal of effective online sample
introduction, and will assess the challenges of transforming the new microchip to a continuous monitoring
system. The parameters governing the microchip behavior will be optimized, and the analytical performance
will be characterized and validated.
This research project will enhance the understanding of the use of nanoparticles and carbon-nanotubes as
separation carriers and detectors, respectively, in chip-based environmental assays. The resulting submersible
microfluidic device will enable transporting the entire laboratory to the sample source, and will offer signi-
ficant advantages in terms of speed, cost, efficiency, sample/reagent consumption, and automation. Performing
in situ all of the necessary steps of the analytical protocol should have an enormous impact on the way
contaminated sites are monitored. Such development of a miniaturized system, with negligible waste pro-
duction, holds great promise for meeting the requirements of field "Green Analytical Chemistry."
Understanding the correlation between the properties of nanomaterials and the measurement processes will
have broader implications on the use of nanomaterials in analytical chemistry, on the fields of microfluidic
devices, and on nanotechnology, in general.
The Office of Research and Development's National Center for Environmental Research 63
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Nanomaterial-Based Microchip Assays for Continuous
Environmental Monitoring
Joseph Wang
Arizona State University, Tempe AZ
Environmental Implication/Application
"Lab-on-a-Chip" technologies can dramatically change the speed and scale at which environmental
analyses are performed. New and innovative nanomaterial-based strategies were introduced for enhancing the
performance of microchip devices for environmental assays. These developments indicate that nanomaterials
and microchip devices hold a great promise for environmental monitoring of priority pollutants. The resulting
microfluidic device will enable transporting the entire laboratory to the sample source, and will offer signi-
ficant advantages in terms of speed, cost, efficiency, sample/reagent consumption, and automation.
64 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Low-Cost Organic Gas Sensors on Plastic for Distributed
Environmental Monitoring
Vivek Subramanian
Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA
Abstract
The ability to monitor various chemical species in large expanses of currently unmonitored land resources
will enable proactive response to environmental problems and also will assist in the development of more
accurate models of environmental phenomena. Unfortunately, the widespread deployment of chemical sensors
is generally economically unfeasible using currently available sensor technology, primarily because individual
sensors are too expensive to be deployed on such large scales.
In recent years, there has been tremendous interest in organic transistors as a means of realizing ultra-low-
cost electronics, particularly because they may potentially be printed at extremely low cost on cheap substrates
such as plastic and paper. More recently, several groups have demonstrated that organic transistor channels
show tremendous environmental sensitivity, though they usually lack specificity. Specificity may be achieved
using arrays of organic transistors with different channel materials, thus generating unique, highly specific
signatures on chemical exposure. Because such devices may be formed entirely by solution-based processing
techniques, including inkjet printing, these are an attractive means of realizing low-cost gas sensors for en-
vironmental monitoring.
Our success in realizing such a sensor technology will be reported, and our development of arrayed
sensors based on organic transistors will be described. The repeatability and robustness of the same are being
studied as well as their usability in the detection of environmental contaminants, with the initial focus aimed at
organic solvents often used in industrial applications. Initial results indicate that robust, albeit slow, cycling of
organic sensors for reliable detection of several solvents is highly possible. This is promising, as most environ-
mental monitoring applications will not require high-speed responses. Also, simultaneous differential sensing
of various chemicals will be demonstrated, thus establishing the potential of these sensors in electronic noses.
The Office of Research and Development's National Center for Environmental Research 65
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Low-Cost Organic Gas Sensors on Plastic for Distributed
Environmental Monitoring
Vivek Subramanian
Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA
Environmental Implication/Application
In this research project, the development of low-cost arrayed sensors for distributed environmental
monitoring has the following environmental benefits: (1) It will result in the development of a ubiquitous
sensor technology for proactive environmental monitoring, thus enabling rapid response to environmental
contaminants. (2) The sensor technology itself has potentially low environmental impact relative to alternative
sensor technologies, because it is a low-cost, low-waste fabrication technology. As the technology matures, it
may enable replacement of these other, less environmentally benign, sensor technologies.
66 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
The Silicon Olfactory Bulb: A Neuromorphic Approach to Molecular
Sensing With Chemoreceptive Neuron MOS Transistors (CvMOS)
Edwin C. Kan and Bradley A. Minch
School of Electrical and Computer Engineering, Cornell University, Ithaca, NY
Abstract
An ideal microsensor for autonomously monitoring chemical and molecular environmental hazards in both
water and air should simultaneously have a high sensitivity, a high selectivity, a large dynamic range, a low
manufacturing cost, simple calibration/reset protocols, a long lifetime, field reconfigurability, and low power
consumption. These requirements arise from considering the rapid deployment and autonomous operation of a
microsensor network monitoring a large area. We have developed a Si-based neuron MOS transistor with a
novel extended floating-gate structure that permits molecular/chemical sensing. Our sensor, called a chemo-
receptive neuron MOS (CvMOS) transistor, is expected to simultaneously meet all of these requirements, and
can be fabricated by minor modification or simple postprocessing of conventional CMOS integrated circuits.
The modular structure and fabrication of this new device permits us to use CMOS devices optimized for high
sensitivity and large dynamic range and affords us complete flexibility in the design and composition of the
molecular/chemoreceptive sites. The performance of this new sensor has proved to be vastly superior to that of
existing chemical microsensors, such as the ion-sensitive FET (ISFET) and the CHEMFET, in nearly every
important respect resulting from the internal transistor gain, no need for a liquid reference potential, and much
better isolation between the electronics and microfluidics. During the first half of the project period, selectivity
between species like Na+ and K+ has been demonstrated with various nonfunctionalized polymer finger coat-
ings. Modification of contact angles in the microfluidic channel interface, sensitive to the ionic strength and
species, also has been demonstrated.
The preliminary process flow and testing of CvMOS transistors with generic molecular receptive areas for
vapor and liquid sensing (e.g., water, acetone, etc.) already have been established. The preliminary measure-
ments have validated most of our assumptions on the performance of these devices. In the 3-year proposed
effort, prototype arrays will be fabricated of these novel microsensors with various molecular/chemoreceptive
surface coatings, and their sensitivities will be characterized. Surface adsorption kinetics will be studied to
facilitate fast and reliable coating selection. This study will start with polymer coatings that have been used in
vapor and liquid sensors through volume expansion monitoring. A new table of target agents and coatings will
be gathered from CvMOS reading to achieve selectivity. Also, a micropower neuromorphic electronic inter-
face will be developed for such sensor arrays whose structure and function is based on what is known about the
olfactory and gustatory sensory systems of animals. This interface, called the silicon olfactory bulb, will
provide a distilled set of informative features that can be used by a recognition system to perform analysis and
risk assessment. During the first half of the project period, integrated sensing analog circuits have been
demonstrated to distinguish species and concentration without the use of the fluid potential. The required
analog circuit can be implemented on the same foundry chip with CvMOS.
A complete system, including both a sensor array and the silicon olfactory bulb, will be developed that can
be fully integrated, perhaps on a single chip, and that will dissipate only a few hundred microwatts of power in
total. Such devices could be manufactured in large numbers very inexpensively and deployed rapidly as
environmental sensors, running autonomously for long periods of time on either solar power or miniature
chemical batteries. During the first half of the project period, the characteristics of CvMOS have been
demonstrated in the proof-of-concept manner for sensitivity, selectivity, power consumption, and system in-
tegrability with CMOS technology and circuits. The developed CvMOS sensor with its all-around sensor
specification for an autonomous microsystem deployment can bring great benefit to the environmental sensing
in a wide deployment mode. The new sensor is inexpensive to be integrated with other necessary electronics
for data processing and communication (on the same chip), and can achieve a wide range of selectivity and
sensitivity. It is ready for product development to target at specific chemicals or molecules in ocean or in air.
The Office of Research and Development's National Center for Environmental Research 67
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
The Silicon Olfactory Bulb: A Neuromorphic Approach to Molecular
Sensing With Chemoreceptive Neuron MOS Transistors (CvMOS)
Edwin C. Kan and Bradley A. Minch
School of Electrical and Computer Engineering, Cornell University, Ithaca, NY
Environmental Implication/Application
This research project seeks to develop a complete system, including both a sensor array and the silicon
olfactory bulb, which can be a fully integrated monitoring device. This device, perhaps placed on a chip, will
dissipate only a few hundred microwatts of power in operation. Such devices could be manufactured in large
numbers very inexpensively and deployed rapidly as environmental sensors. Powering of these devices for
autonomous, lengthy operation can be accomplished using either solar or miniature chemical batteries.
68 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
A Nanocontact Sensor for Heavy Metal Ion Detection
Nongjian Tao
Department of Electrical Engineering, Arizona State University, Tempe, AZ
Abstract
Because of the toxicity of heavy metal ions to a broad range of living organisms, including humans, and
the fact that these pollutants are nonbiodegradable, there is an urgent demand for an in situ sensor that is
sensitive enough to monitor heavy metal ions before the concentration reaches a dangerous level. We have
been developing an integrated sensor chip to meet such demand. The sensor chip consists of an array of nano-
scale sensing elements. Three different sensing elements (nanocontacts, molecular junctions, and polymer
nanojunctions) were fabricated. Metal ion detections using these sensing elements were demonstrated. In
addition to metal ions, these sensing elements also are capable of detecting a variety of other chemical and
biological species. This research project's goal is to develop a highly integrated sensor for simultaneous de-
tection of a range of different chemical species.
Nanocontacts. This sensor starts with an array of electrode pairs fabricated on a silicon chip. The
separation between the two electrodes in each pair is as small as a few nm (see Figure 1). When the electrodes
are exposed to a solution containing heavy metal ions, the ions can be deposited into the gap by controlling the
electrode potentials. Once the deposited metal bridges the gap, a sudden jump in the conductance between the
electrodes occurs, which can be easily detected. Because the gap can be made as narrow as a few nm or less,
the deposition of even a few ions into the gap is enough to trigger a large change in the conductance, thus
providing a sensitive detection of metal ions. Previous experiments have shown that the conductance of such a
small bridge is quantized and given by NGO, where N is an integer and GO is conductance quantum (=2e2/h, e
is the electron charge and h is the Planck constant). For this reason, the bridge is often called quantum point
contact. The metal bridge also can be stripped off (or dissolved) by sweeping the potential anodically. The
potentials at which deposition and dissolution take place provide identity of the metal ions, a principle similar
to that of anodic stripping analysis. This nanocontact sensor is simple and can sensitively and selectively detect
heavy metal ions, but it is limited to metal ions. To detect other environmentally important species with the
same sensor chip, two other sensing elements, molecular junctions and conducting polymer junctions on the
sensor chip (described below), have been added.
Molecular Junction. Molecular junctions have been fabricated by bridging the narrow gaps of the elec-
trodes described above with molecules, which allows us to directly measure the conductance of the molecules
(see Figure 2). To demonstrate metal ion detections, peptides with different sequences were chosen to bridge
the gap. When a metal ion binds onto the peptides, a change in the conductance is detected. The metal ion-
induced conductance change is sensitive to the sequence of the peptides. By selecting appropriate sequences,
different metal ions on the peptides can be detected. Metal ion binding was studied on short peptides, and a
conductance increase was observed in each case. The conductance increase is highly sensitive to the sequence
of the peptide. For example, the binding of a Cu2+ onto cysteamine-Cys causes only a 10 percent conductance
increase, but the binding onto cysteamine-Gly-Gly-Cys increases the conductance approximately 300 times.
Therefore, the peptide sequence can be tuned to maximize the metal-ion binding-induced conductance change
for sensor applications. The conductance change also is dependent on the type of metal ions. For example, the
binding of Ni2+ onto cysteamine-Gly-Gly-Cys increases the conductance approximately 100 times, which is
several times smaller than the case of Cu2+ binding. This metal ion dependence shows that different metal ions
can be identified from the conductance measurement, even if they all bind to the peptide.
Conducting Polymer Junctions. Because most molecules are not good conductors, the molecular junction
approach is limited to relative small molecules (see Figure 2). To detect large biologically relevant molecules,
the gap between the nanoelectrodes was bridged with conducting polymers to form a metal-polymer-metal
junction. For selective detection of a particular target species, appropriate probe molecules were attached onto
the polymers such that a specific binding of the target species onto the probe molecules is detected as a change
The Office of Research and Development's National Center for Environmental Research 69
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
in the conductance of the polymer junction. For metal ion sensor applications, oligopeptides were attached to
the polymer junctions via peptide bonds. One example is to attach Gly-Gly-His to a polyaniline junction. The
tripeptide was chosen because of its large binding constant for copper ions. When exposing the sensor to other
metal ions, little response was detected, which shows the high degree of selectivity. The experiment demon-
strates the feasibility of detecting metal ions using the polymer junctions.
A
ions
SiN ®q I SiN
B
a
Figure 1. (A) A drop of sample solution is placed onto a pair of nanoelectrodes
separated with an atomic scale gap on a silicon chip. (B) Holding the nano-
electrodes at a negative potential, electrochemical deposition of a single or a few
metal atoms into the gap can form a nanocontact between the two nanoelectrodes
and result in a quantum jump in the conductance.
A
Figure 2. (A) A molecular junction is formed by bridging a pair of nanoelectrodes with
molecules terminated with linker groups that can bond to the nanoelectrodes
covalently. (B) Bridging the nanoelectrodes with conducting polymers results in
polymer junctions. By attaching different molecular probes onto the polymers,
specific interactions between a target species and the molecule probes are de-
tected as a change in the conductance of the polymer junction.
70
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
A Nanocontact Sensor for Heavy Metal Ion Detection
Nongjian Tao
Department of Electrical Engineering, Arizona State University, Tempe, AZ
Environmental Implication/Application
The threat of heavy metal pollution is a serious environmental concern because of the toxicity of such
metals on a broad range of living organisms, including humans, and the consequence of heavy metals not
being biodegradable. Due to the difficulty in the remediation of sites contaminated with heavy metals, there is
an urgent demand for an in situ sensor that is sensitive enough to monitor heavy metal ions before the
concentration reaches a dangerous level. To date, heavy metals in the environment are usually measured with
spectroscopic techniques, including atomic absorption and inductively coupled plasma-mass spectroscopy
(ICP-MS). These techniques are well established but require samples to be collected and transported to the
laboratory for analysis because the instrumentation is bulky, expensive, and requires significant maintenance
and operator expertise. Moreover, sample preservations and pretreatments, generally required by these tech-
niques, may cause sample contamination. In situ measurements, performed in the natural environment, are
highly desirable because they provide an early detection of trace metal contaminants while minimizing errors,
labor, and cost associated with collection, transport, and storage of samples for subsequent laboratory analysis.
A nanocontact sensor has been developed for in situ detection of heavy metal ion pollution in water. The sen-
sor can be extremely sensitive with the potential capability of detecting a few metal ions. The selectivity is
based on different redox potentials of metal ions, a principle that has been successfully used in anodic stripping
technique. The initial success has encouraged us to extend the nanocontacts sensor to an integrated nanosensor
that can detect not only metal ions but also other environmentally important species. The integrated nanosensor
includes both the nanocontact sensors and two other sensing elements, molecular junctions and conducting
polymer nanojunctions. The three types of sensing elements can be fabricated on a silicon chip using a com-
mon approach. Also, various chemical species, including metal ions, can be detected using these sensing ele-
ments. The sensor will be particularly suitable for an initial onsite screening test of polluted samples, thus lead-
ing to early warning and prevention of various chemical pollutions.
The Office of Research and Development's National Center for Environmental Research 71
-------
-------
Section 4. Remediation
Cost-effective remediation techniques pose a major challenge for EPA in the development of adequate hazard
removal techniques that protect the public and safeguard the environment. EPA supports research that ad-
dresses new remediation approaches that are more effective in removing contamination in a more cost-
effective manner than currently available techniques. Substances of significant concern in remediation of soils,
sediment, and groundwater include heavy metals (e.g., mercury, lead, cadmium) and organic compounds (e.g.,
benzene, chlorinated solvents, creosote, toluene). Nanotechnology offers the possibility of more effective
remediation due to the higher surface to volume ratios of nanomaterials, and it offers the possibility of novel
collection and separation protocols due to the unique physical properties of nanomaterials. Specific control and
design of materials at the molecular level may impart increased affinity, capacity, and selectivity for pollutants.
Reducing releases of such hazardous materials to the air and water, providing safe drinking water, and mini-
mizing quantities and exposure to hazardous wastes are among EPA's goals.
-------
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Membrane-Based Nanostructured Metals for Reductive Degradation
of Hazardous Organics at Room Temperature
Dibakar Bhattacharyya , L. Bachas1, D. Meyer1, J. Xu, S. Ritchie2, and L. Wu
1 Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY;
2Department of Chemical Engineering, University of Alabama, Tuscaloosa, AL
Abstract
The use of nanosized metals is emerging as an important technology for the detoxification of organics and
for green synthesis. Studies involving these particles have shown increased reaction rates by several orders of
magnitude. To obtain isolated nanoparticles with narrow size distributions, it is necessary to reduce the metal
ions in the presence of polymers or surfactants. Our present work addresses the reduction of chlorinated organ-
ics by bimetallic nanosystems comprised of nanoscale Fe/Ni particles confined within various polymeric mem-
brane matrices. The following synthesis techniques have been developed in support of this work: (1) direct
membrane-phase metal particle formation based on the classic phase-inversion method for membrane prepa-
ration, (2) use of metal chelating polymers on membrane supports, and (3) external particle synthesis in solu-
tion followed by membrane incorporation. Using these methods, we have obtained very exciting results both in
terms of synthesis of nanoparticles in membrane domain and resulting organic dechlorination. For the second
method, controlled separation of background toxic metals along with organic reduction also is possible.
Following U.S. EPA quality assurance guidelines, trichloroethylene (TCE) degradation behavior has been
quantified, resulting in ethane and Cl" formation using these nanocomposite membranes. Regardless of the
method employed, test membranes contained only milligram levels (rather than grams) of reactive metal par-
ticles. A comparison of both surface-area normalized rate constants and metal loadings with literature values
indicates significant enhancement to the traditional application of zero-valent metal nanoparticle technology.
Using in situ techniques to immobilize nanoparticles, one can reduce particle loss, prevent particle agglomera-
tion, and provide a means to recapture (and feasibly recycle) metal ions, which can form nonreactive
hydroxide coatings on the surfaces of particles. When ex situ particle synthesis is employed, the Fe/Ni particles
agglomerate during incorporation into the membrane phase. The agglomerates possess less available reactive
surface area (Fe/Ni/H20 interface), based on electron-microscopic characterization and comparison of dechlori-
nation rates. In addition, the use of membrane immobilization (as opposed to beads and direct ground in-
jection) allows for the potential application of this technology to novel hybridized separation/recycle processes
in the areas of industrial and municipal water treatment. Considering the performance of the bimetallic sys-
tems, the incorporation of a second metal with a high affinity for hydrogenolysis has the greatest impact on
reaction rates for the given set of variables investigated.
To date, this project successfully demonstrated: (1) formation of nanoscale particles directly in cellulose
acetate membranes in the 20-30 nm range; (2) crosslinking of polyacids (poly-acrylic acid) on conventional
microfiltration membrane supports to entrap metals and to form (after reduction) approximately 30 nm metal
particles; (3) the ability to synthesize immobilized Fe/Ni nanoparticles with a more uniform elemental dis-
tribution for superior dechlorination performance using a two-step deposition process (reduction of Fe fol-
lowed by electroless plating and reduction of Ni) as opposed to the simultaneous reduction of Fe and Ni; (4)
large conversions for TCE using a very small quantity of bimetallic (Fe/Ni ratio 4:1) nanoparticles in 60 min,
(5) production of ethane (identified in the headspace) with only trace levels (if any) of other chlorinated
intermediate by-products found in both the aqueous and headspace phases; (6) development of a novel method
for preparation of Fe nanoparticles and recovery as stable slurry using anaerobic synthesis conditions; and (7)
immobilization of Fe nanoparticles prepared in solution within a cellulose acetate matrix (as one example)
while avoiding metal oxidation. Preliminary results with membrane immobilized Fe/Pd nanoparticles showed
highly effective dechlorination of selected aromatics.
The Office of Research and Development's National Center for Environmental Research 75
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Membrane-Based Nanostructured Metals for Reductive Degradation
of Hazardous Organics at Room Temperature
Dibakar Bhattacharyya
Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY
Environmental Implication/Application
Chlorinated aromatics and aliphatics represent a class of commercially important but particularly toxic
chemicals that enter the environment from manufacturing operations and user applications. This research pro-
ject with nanostructured metals (Fe, Fe/Ni, Fe/Pd) immobilized in membrane phase is expected to have sig-
nificant positive impact on pollution remediation through compact and flexible dechlorination technology
development with high reaction rates at room temperature, significant reduction of metals usage, and improve-
ment in water quality.
Three separate methodologies have been established and refined successfully for the synthesis and incor-
poration of nano-sized metals into thin-film polymeric matrices. These methods include: (1) direct membrane-
phase Fe/Ni particle formation using a modified phase-inversion preparation of cellulose acetate; (2) in situ
reduction of Fe and Ni or Pd ions captured by polyacrylics supported on microfiltration membrane through ion
exchange/chelation; and (3) solution-phase synthesis of Fe and Fe/Ni nanoparticles followed by immobiliza-
tion in a celluose acetate thin-film under anaerobic conditions. Method #2 with metal chelating polyacrylic
acids (PAA), for example, provided highly controlled nanoparticles formation and allows metal reuse because
of recapture. In addition, to the rapid degradation (by Fe/Ni) of trichloroethylene (TCE) to ethane, complete
dechlorination of chlorobiphenyls was achieved using milligram quantities immobilized Fe/Pd nanoparticles in
membrane domain. The rapid and complete dechlorination of TCE and chloro-aromatics by milligram amount
of bimetallic nanoparticles synthesis in a membrane domain is a highly significant development for both re-
mediation and pollution prevention. Research dealing with highly improved reductive dechlorination techniques
should lead to substantial improvement in environmental quality.
76 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Dendritic Nanoscale Chelating Agents: Synthesis, Characterization,
Molecular Modeling and Environmental Applications
Mamadou S. Diallo1, Lajos Balogh2, William A Goddard3, and James H. Johnson1
toward University, Washington, DC;2 University of Michigan, Ann Arbor, MI;
3California Institute of Technology, Pasadena, CA
Abstract
Dendrimers are monodisperse and highly branched nanostructures with controlled composition and
architecture. Poly(amidoamine) (PAMAM) dendrimers possess functional nitrogen and amide groups arranged
in regular "branched upon branched" patterns. This high density of nitrogen ligands enclosed within a nano-
scale container makes PAMAM dendrimers particularly attractive as high-capacity chelating agents for toxic
metal ions [Cu(II)], electron transfer mediators [Fe(II)], redox active metal clusters [FeS], and metal clusters
with catalytic properties [Pt(II)]. PAMAM dendrimers also can be functionalized with surface groups that
make them soluble in appropriate media or bind onto appropriate surfaces. This research project explores the
fundamental science of metal ion uptake by PAMAM dendrimers in aqueous solutions and assesses the extent
to which this fundamental knowledge can be used to develop: (1) high-capacity and reusable chelating agents
for industrial and environmental separations; and (2) FeS laden nanoparticles with enhanced reactivity, selec-
tivity, and longevity for reductive detoxification of perchloroethylene (PCE) in aqueous solutions and sub-
surface formations.
To achieve these objectives, an integrated project is proposed that combines: (1) materials synthesis and
characterization; (2) bench-scale measurements of metal ion [Cu(II), Fe(II), Co(II), Ni(II), Cd(II), and Ag(I)]
uptake by PAMAM dendrimers in aqueous solutions; (3) x-ray absorption spectroscopic (XAS) investigations
of metal ion-PAMAM dendrimer complexes in aqueous solutions; (4) bench-scale measurements and spectro-
scopic investigations of the reduction of PCE by water soluble FeS-PAMAM dendrimer nanocomposites and
solid particles coated with FeS-PAMAM dendrimer nanocomposites; and (5) molecular modeling of (a) metal
ion uptake by PAMAM dendrimers in aqueous solutions; and (b) PCE reductive dechlorination by FeS clus-
ters.
The successful completion of this research is expected to result in: (1) more effective functional materials
for recovering precious metal ions [e.g., Ag (I)] and toxic metal ions [e.g., Cu (II)] from industrial wastewater
solutions by low-cost, membrane-based processes (e.g., ultrafiltration); and (2) more effective reactive media
for reductive detoxification of PCE in aqueous solutions and subsurface formations.
The Office of Research and Development's National Center for Environmental Research 77
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Dendritic Nanoscale Chelating Agents: Synthesis, Characterization,
Molecular Modeling, and Environmental Applications
Mamadou Diallo
Howard University, Washington, DC
Environmental Implication/Application
Clean water is essential to human health. It also is a critical feedstock in a variety of key industries
including the electronics, pharmaceutical, and food industries. The world is facing formidable challenges in
meeting rising demands of clean water when the available supplies of surface water and groundwater are
steadily decreasing due to increasing pollution. The ability to design and synthesize water-soluble dendrimer-
based functional nanostructures with: (1) metal ion chelating functional groups; (2) redox active metal ions
and clusters; (3) catalytically active metal ions and clusters; (4) hydrophobic cavities; and (5) bioactive active
agents to provide new and unprecedented opportunities for developing a new generation of efficient, cost-
effective, and environmentally acceptable functional materials for water treatment processes. The Dendrimer
Enhanced Filtration (DEF) process (Diallo MS, U.S. Patent Pending) exploits these unique properties of den-
drimers and other dendritic polymers to develop a new generation of water purification technologies. The DEF
process is structured around three unit operations: (1) a reaction unit; (2) a clean water recovery unit; and (3) a
dendrimer recovery unit. In the reaction unit, contaminated water is mixed with a solution of functionalized
dendritic polymers to carry out the specific reactions of interest, including metal ion chelation, organic solu-
bilization, contaminant oxidation-reduction, contaminant hydrolysis, and microbial/viral disinfection. Follow-
ing completion of the reaction, the resulting solution is passed through a filtration membrane (Filtration Unit)
to recover the clean water. The contaminant laden dendrimer solutions are subsequently sent to the Reactive
Filtration Unit to recover and recycle the functionalized dendritic polymers. The key novel feature of the
proposed DEF process is the combination of dendritic polymers with multiple chemical functionalities with the
well-established technology of nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF). This allows
the development of a new generation of water treatment processes that are flexible, reconfigurable, and
scalable. The flexibility of DEF is illustrated by its modular design approach. DEF systems will be designed to
be "hardware invariant" and thus reconfigurable in most cases by simply changing the "dendrimer formu-
lation" and "dendrimer recovery system" for the targeted contaminants. Finally, because DEF is a membrane
process, it is a fully scalable process. Thus, DEF could be used to develop small mobile membrane-based
water treatment systems as well as larger and fixed treatment systems.
78 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Synthesis, Characterization, and Manipulation of {FeS-PAMAM}
Dendrimer Nanocomposites
Xiangyang Shi and Lajos P. Balogh
Center for Biologic Nanotechnology, University of Michigan, Ann Arbor, MI
Abstract
Nanoparticles have received great scientific and technological interest in environmental remediation. It is
expected that nano-sized FeS particles have much higher reactivity than FeS-based minerals because of their
higher surface area. Dendrimers are a novel class of polymers with a spherical shape and narrow size-distri-
bution that are used as templates to form monodispersed dendrimer nanocomposites containing metal sulfides.
In this research study, FeS nanoparticles were synthesized using generation 4 polyamidoamine (PAMAM)
dendrimers with amine (E4.NH2), hydroxyl (E4.N(Gly)OH), and carboxyl (E4.SAH) terminal groups as tem-
plates. These {FeS-PAMAM} nanocomposites were characterized by ultraviolet (UV)-Vis spectroscopy, zeta
potential measurements, transmission electron microscopy (TEM), selected area electron diffraction (SAED),
and energy dispersive spectroscopy (EDS).
Synthesis and Characterization of Nanocomposites. Upon addition of sulfide anions to the Fe(II)-PAMAM
complexes, monodisperse {FeS} DNC particles form as a result of homogenous nucleation and simultaneous
cluster growth. Figure 1 shows the UV-Vis spectra of {FeS-E4.NH2} nanocomposites in aqueous solution.
K4-VKcS(l mi.)
K4-N-KcS(O.Sml,)
K4-N-KrS(0.25ml.)
0
200 300 400 500 600 700 800 900 1000
Wavelength (nm)
Figure 1. UV-Vis Spectra of FeS-E4.NH2 nanocomposites containing different
amount of FeS nano-particles.
In the presence of {FeS} nanocomposites, a strong buildup in absorbance at 250-1,000 nm is observed in
the spectra, indicating the formation of FeS clusters. The peak at 630 nm may be attributed to interparticle
interactions. In the case of {FeS-E4.N(Gly)OH} nanocomposites after the formation of FeS nano-domains, a
prominent broad band develops at 250-800 nm as well as another one at 610 nm. With the increase of the
{FeS} concentration, the intensity of these bands increases. The UV-Vis spectra of {FeS-E4.SAH nano-
composites are quite different from those of {FeS-E4.NH2} and {FeS-E4.N(Gly)OH}. The absorbance profile
of {FeS-E4.SAH} nanocomposites is quite similar to the template E4.SAH dendrimer in the low molar con-
centration range. When the FeS amount is increased, a broad band profile at 250-1,000 nm also can be ob-
served. The sensitivity of FeS clusters to oxidation makes the exact assignment of the peaks in the UV-Vis
The Office of Research and Development's National Center for Environmental Research
79
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
spectra difficult. All of the {FeS-PAMAM} nanocomposites are quite stable and soluble under anaerobic con-
ditions.
Surface charge of {FeS-PAMAM} nanocomposites was determined by zeta-potential measurements. All
of the {FeS-PAMAM} nanocomposites have the same polarity as the PAMAM templates. It was found that
although the zeta potential values are fairly similar, the morphologies of {FeS-E4.NH2} prepared from dif-
ferent iron (II) salts are different, as demonstrated by TEM.
Figure 2 shows the TEM images of {FeS-E4.NH2} nanocomposites. It is clear that the formed particles
are dominantly spherical with a diameter of d= 4-6 nm. Only a small portion of needle-shaped nanocrystals can
be found in the TEM images (Figure 2a). High-resolution TEM image confirms the polycrystalline nature of
the particles (see Figure 2b). SAED pattern (inset of Figure 2a), which is composed of rings and bright dots,
further verifies the polycrystalline phase of the formed FeS-E4.NH2 nanocrystals. It is interesting to note that
the morphology of FeS-E4.NH2 nanocomposites can be tuned by varying the different anions from predomi-
nantly round-shaped {FeS-E4.NH2} nanocomposite particles to a needle-like shape with the length of 15-32
nm and diameter of about 2 nm. The composition of the FeS-PAMAM nanocomposites has been confirmed by
EDS.
i «*&•! -JSkftiJ ti: "*t: 3VSl: £
Figure 2. TEM images of {FeS-E4.NH2} (Sample ID: 3xys89-3) nanocomposites. (a) low magni-
fication TEM image; Inset: SAED pattern; (b) high-resolution TEM image showing indi-
vidual nanocomposite particles.
Fabrication of Multilayer Structures. To fabricate {FeS} nanocomposite films, either nanocomposites
were deposited or preassembled multilayers of PAMAM/poly(styrenesulfonate) (PSS) were employed as ma-
trices to facilitate the binding of Fe(II) ions. Polyelectrolyte multilayers are useful matrixes to confine inor-
ganic nanoparticles, because the mass transfer of the nanoparticles within the multilayers is significantly limit-
ed as compared with the solution synthesis, thus overgrowth and aggregation of nanoparticles can be pre-
vented.
The conditions for layer assembly of PAMAM/PSS multilayers were optimized by varying the deposition
parameters (molecular weight of PSS, adsorption time, dendrimer generation, and dendrimer terminal groups).
The formed nanoparticulate films were characterized by UV-Vis spectrometry and x-ray Photoelectron Spec-
troscopy (XPS).
80
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
The absorption peak at 227 nm was used to monitor the growth of PSS multilayers. It is clear that after
each layer buildup of PAMAM, regular removal of PSS also is observed. E5.NH2/PSS multilayers release less
PSS than E4.NH2/PSS multilayers. In addition, we found that higher Mw of PSS facilitates the multilayer
construction and that longer PSS adsorption times and short PAMAM adsorption times decreased the PSS
removal. Construction of E4.N(Gly)OH/PSS multilayers was unsuccessful. Structure and composition of the
PAMAM/PSS multilayers did not change considerably during storage at 4 °C within 10 days. Figure 3 shows
the UV-Vis Spectra of PAMAM/PSS multilayers before and after nanoparticle formation. An interesting ob-
servation is that after the formation of FeS nanoparticles, the absorbance of PSS at 227 nm decreases sig-
nificantly (see Figures 3a and 3b). The FeS nanoparticulate films were not stable for more than 10 days'storage
at 4 °C, probably due to partial oxidation of FeS because of exposure to air during UV-Vis measurements. XPS
spectroscopy was used to confirm the composition of FeS nanoparticulate films.
0.08
0.12
§J
0.08
»
«
1 0.06
.Q
i 0.04
.fit
^0.02
0
IiSIKSNH /PSS-t-KcS
200 250 300 350 400 450 500 S50 600
Wavelength (nm)
200 250 300 350
Wavelength (nm)
400
Figure 3. (a) UV-Vis spectra of (E4/PSS)5 multilayers before complexation with iron ions (solid line),
complexed with Fe(II) ions (dashed line), and formation of FeS nanoparticulate films (dotted
line), (b) UV-Vis spectra of (E5/PSS)5 multilayers (solid line) and the respective FeS nano-
particulate films (dashed line) using (E5/PSS)5 multilayers as matrixes.
Nanocomposite Deposition Onto Silica Gel. Preliminary experiments to deposit {FeS} nanocomposites
onto mesoporous silica gels also has been conducted. Preliminary zeta-potential measurements show that the
surface charge of silica gels was successfully reversed from negative to positive, indicating the formation of
coating by the{FeS} nanocomposites.
Conclusion. Uniform {FeS} nanoparticles have been successfully synthesized using surface-modified
PAMAM dendrimers as templates. The formed nanocomposite particles were found to be polycrystalline by
high-resolution TEM and SAED. The nanoparticle morphology can be varied from spherical to rod-like using
different anions. The UV-Vis absorbance spectra increase in the 250-1,000 nm range is proportional to the
amount of FeS nanoparticles present. {FeS} nanoparticles displayed different absorbance profiles when PAM-
AMs of different termini were used as a template. Zeta potential measurements indicated that the formed {FeS-
PAMAM} nanocomposites have the same polarity as the dendrimer templates. To deposit FeS nanoparticulate
films onto substrates, PAMAM/PSS multilayers were constructed by the layer-by-layer self-assembly method,
and these preassembled multilayers also were used as host matrices to prepare {FeS} nanoparticles. The
formed FeS nanoparticulate films exhibited less absorbance than the corresponding PAMAM/PSS multilayers.
x-ray spectroscopy qualitatively confirms the presence of both iron and sulfur elements. In addition, depo-
sition of {FeS-PAMAM} onto mesoporous silica gels also was confirmed by zeta-potential measurements,
showing reversal of surface charge after the deposition of {FeS} nanocomposites.
The Office of Research and Development's National Center for Environmental Research
81
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Hollow and Nanoporous Iron Particles
Wei-Xian Zhang
Department of Environmental Engineering, Lehigh University, Bethlehem, PA
Abstract
Hollow iron spheres with micro- and nano-scale pores were prepared using template-directed synthesis.
Iron nanoparticles were deposited on the surfaces of polymeric resin by reductive precipitation. The resin was
subsequently removed by heat treatment. Pores ranging in size from nanometers (~80 percent, <100 nm) to
several micrometers were observed on the shell. Specific surface area of the resulting iron spheres (0.4 mm
dia.) was 2,100 m2/kg, that is 1,250 times bigger than the theoretical specific surface area of solid iron
particles at the same size. Tests further suggested that the iron spheres are effective for the reduction of several
common environmental pollutants, including azo dyes and chlorinated aliphatic compounds. Surface area
normalized rate for the reduction of trichloroethene was 17 percent higher than that of conventional microscale
iron particles. The reaction rate per unit of iron mass was approximately 1,461 times higher than that of solid
iron particles at the same size. The nanoporous iron has broad potential in groundwater remediation and
industrial waste treatment.
82 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Developing Functional Fe°-Based Nanoparticles for In Situ
Degradation of DNAPL Chlorinated Organic Solvents
Gregory V. Lowry , Yueqiang Liu , Sara A. Majetich , Kris Matyjaszewski, Navid Saleh ,
Traian Sarbu3, David S. Shall3, Kevin Sirk3, and Robert D. Tilton3
Department of Civil and Environmental Engineering, Physics Department, Department
of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA
Abstract
Dense non-aqueous phase liquids (DNAPLs) in the subsurface remain an important and costly environ-
mental liability. DNAPL serves as a continuous long-term source of groundwater contamination. This project
integrates several basic science fields to advance a particle-based strategy for in situ DNAPL degradation by
providing targeted delivery of reactive particles directly to the DNAPL.
Over the past decade, laboratory and field studies have demonstrated that zero-valent iron and bimetallic
colloids (Fe/Pd) can rapidly transform dissolved chlorinated organic solvents into nontoxic compounds.1 This
emerging technology also has the potential to address DNAPL contamination, a vexing contamination prob-
lem. The objective of this research is to develop and test reactive nanoscale particles for in situ delivery to, and
degradation of, chlorinated solvents that are present as DNAPLs in the subsurface. The hypothesis under con-
sideration is that the surfaces of reactive Fe°-based nanoparticles can be modified with amphiphilic block
copolymers to maintain a stable suspension of the particles in water for transport in a porous matrix, as well as
create an affinity for the water-DNAPL interface. Delivering reactive particles directly to the surface of the
DNAPL-water interface will decompose the pollutant into benign materials, reduce the migration of pollutant
during treatment, and reduce the time needed to remove residual pollution by other means, such as natural
attenuation.
Research in the first year of the project has focused on: (1) identifying suitable Fe° nanoparticles and
understanding the properties that control their reactivity with trichloroethylene (TCE); (2) synthesizing amphi-
philic polymer blocks and attaching these blocks to Si02 nanoparticles; and (3) evaluating the properties of the
resulting polymer-modified functional nanoparticles, including their hydrodynamic radius, stability, TCE-
water partitioning behavior, and mobility in a porous matrix.
The TCE reaction rates, pathways, and efficiency of two types of nanoscale Fe° particles were measured in
batch reactors; particles were synthesized from sodium borohydride reduction of ferrous iron (Fe/B), and
commercially available particles (RNIP) were synthesized from the gas phase reduction of Fe-oxides in H2.
Particle characterization indicated many similarities between the particles, but several distinct differences be-
tween the particle types were found. TEM micrographs of the particles evaluated are given in Figure l(a,b).
Both particle types showed a core-shell morphology. RNIP particles had an Fe° core and a magnetite (Fe304)
shell. No other Fe-oxides were detected. Electron diffraction indicated that the core of the Fe/B (borohydride
reduced particles) contains a-Fe°; however, early reports on metallic nanoparticles made from borohydride re-
duction of dissolved iron identified these particles as a Fe-B alloy rather than pure a-Fe . ' The boron content
measured in these particles was approximately 4 wt percent, which is nearly 18 mol percent. Boron pre-
cipitated on the outer shell of the particles (as borate) accounts for approximately 0.2-1 wt percent, so the
remaining boron is most likely present as a Fe-B alloy as previously suggested, or as distinct phases of Fe° and
B°. No Fe-oxides could be detected on Fe/B, also suggesting that the shell may be a boron-oxide (borate)
rather than a Fe-oxide. The effect of boron on the reactivity of these particles remains unclear.
The Office of Research and Development's National Center for Environmental Research 83
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Ouuu
Figure 1. (a) Borohydride reduction
methods.
(b) H2 reduction method.
Reactivity was determined under iron limited (high [TCE]) and excess iron (low [TCE]) conditions, and
with and without added H2. The reactivity and efficiency of the two particle types were very different and
strongly influenced by the oxide shell properties and the presence of boron.4 For example, the main reaction
products using Fe/B were primarily saturated (e.g., ethane, butane), but the reaction products using RNIP were
primarily unsaturated (e.g., acetylene, ethane). A concentration dependence on the TCE reaction rate and pro-
duct distribution was observed. The addition of H2 to the reactor headspace increased the reactivity of Fe/B,
and these particles were able to use externally supplied H2 to reduce TCE, suggesting that these particles are
catalytic. RNIP particles did not display this behavior. The ability of Fe/B to catalyze the hydrodehalogenation
of TCE may be because they are a Fe-B alloy rather than pure Fe°.
This research project involved synthesizing amphiphilic polymer blocks, grafting polymers to Si02
nanoparticles, and evaluating the properties of the resulting polymer-modified functional nanoparticles. Atom
Transfer Radical Polymerization (ATRP) was used to synthesize tailored block copolymers for hybrid nano-
particles.5'6 Concerning the synthesis of Fe° nanomaterials, a technique was developed for building hydro-
phobic-hydrophilic hybrids that consist of a short anchoring poly(methacrylic acid) block, a hydrophobic
PMMA protective shell, and a hydrophilic SPSt outer block (see Figure 2). Polystyrene and poly(methyl
methacrylate) have been identified as good candidates for the hydrophobic blocks. Sulfonated polystyrene has
excellent water solubility and makes a good hydrophilic block. Additional methods for grafting polymers to
Fe° are under investigation. ATRP also was used to synthesize particles (dp~100 nm) with an inorganic core
(Si02), and an amphiphilic polymer shell has been synthesized (see Figure 3). The particles were water solu-
ble, formed stable suspensions, and partition to the TCE (DNAPL)-water interface. Bench-scale transport stud-
ies demonstrate that the nanoparticles are readily transported through a saturated porous matrix, suggesting that
they will be transportable in the subsurface.
SO3H
Figure 2. Hydrophobic-hydrophilic triblock copolymers containing
a short anchoring group.
84
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Figure 3. Polymer decorated Si02 nanoparticles.
References:
1. Zhang W-X. Journal ofNanoparticle Research 2003;5(3-4):323-332.
2. Wonterghem J, Morup S, Koch C, Charles S, Wells S. Nature 1986;322:622-623.
3. Shen J, Li Z, Yan Q, Chen Y. Journal of Physical Chemistry 1993;97:8504-8511.
4. Liu Y, Majetich SA, Tilton RD, Sholl DS, Lowry GV. TCE dechlorination rates, pathways, and efficiency
of nanoscale iron particles with different properties, (submitted to Environmental Science & Technology,
May 31,2004)
5. Wang JS, Matyjaszewski KJ. Controlled/"Living" radical polymerization. ATRP in the presence of tran-
sition-metal complexes. American Chemical Society 1995;! 17:5614.
6. Matyjaszewski K, Wang JS. (Co)polymers and a novel polymerization process based on atom (or group)
transfer radical polymerization. U.S. Patent 5,763,548, 1995.
The Office of Research and Development's National Center for Environmental Research
85
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Developing Functional Fe(0)-Based Nanoparticles for In Situ
Degradation of DNAPL Chlorinated Organic Solvents
Gregory V. Lowry1, Sara A, Majetich2, Kris Matyjaszewski3, and Robert D. Tilton3
Department of Civil and Environmental Engineering, Physics Department, Department
of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA
Environmental Implication/Application
Groundwater contamination by chlorinated organic solvents poses a significant health hazard. Dense non-
aqueous phase liquid (DNAPL) present at these sites acts as a long-term source. Remediation is costly and
poses significant technical challenges.1 This project develops and evaluates a new class of affinity-targeted
nanoscale remediation agents for efficient in situ remediation of DNAPL source areas in aquifers. By locating
and maintaining reactive nanoiron particles at the DNAPL-water interface, fewer particles will be required and
more efficient DNAPL remediation is possible relative to other methods (e.g., surfactant and alcohol flooding,
bio-augmentation, and chemical oxidation). Even though the benefits of mass removal from a source zone in
meeting regulatory goals are controversial, reducing entrapped DNAPL mass will lower the longevity of the
source and reduce mass flux. This can mitigate future human and ecological exposure risk and the duration and
cost of treatment.2 Additional advantages of in situ treatment with nanoiron include the ability to provide
significant DNAPL mass reduction without generating secondary waste streams and exposure pathways, the
ability to control the delivery distance (e.g., selective placement of subsurface treatment zones), and the ability
to provide residual treatment capacity to mitigate mass flux from diffusion-controlled low permeability zones.
Nanoiron also has the potential for lower initial capital and life-cycle costs compared to other source zone
treatments. Realizing these benefits, however, requires a fundamental understanding of the factors affecting the
migration and distribution of nanoiron in the naturally heterogeneous subsurface.
References:
1. Stroo H, Unger M, Ward CH, Kavanaugh M, Vogel C, Leeson A, Marquesee J, Smith B. Remediating
chlorinated solvent source zones. Environmental Science & Technology 2003;3711:193a-232a.
2. U.S. EPA Expert Panel on DNAPL Remediation. The DNAPL remediation challenge: is there a case for
source depletion? Publication Number EPA/600/R-03/143, December 2003.
86 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
A Bioengineering Approach to Nanoparticle-Based
Environmental Remediation
Daniel R. Strongin
Department of Chemistry, Temple University, Philadelphia, PA
Abstract
Research has investigated the potential use of ferritin, and ferritin-derived compounds, as templates to syn-
thesize nanomaterials and to use these materials as substrates for environmental degradation processes. Speci-
fically, recent research has developed a synthetic route for the assembly of supported nano-metal oxide parti-
cles by assembling them in the biological protein ferritin and then removing the protein shell. This methodolo-
gy has been further exploited to allow production of nanometallic particles of homogeneous size. Also, the
fundamental chemistry of ferritin-derived systems and their activity for the remediation of toxic metals in the
presence and absence of light have been investigated recently.
Horse Spleen Ferritin (HS-Fn) as a Precursor to Supported Metal Oxide and Metallic Nanoparticles.
Figure 1 shows a Tapping Mode™ AFM image of ferrihydrite nanoparticles prepared by ultraviolet (UV)-
ozone treatment of 2,500 Fe loaded ferritin dispersed on an Si02 substrate. The accompanying cross-section
shows the full range of height values to be 6.5 nm, with a root-mean-square (RMS) roughness (standard
deviation of the height about the average value) of 1.46 nm. The peak-to-valley height differences for the large
features in the cross-section are in the 4-6 nm range. The lateral full widths at half maximum (FWHM) of the
individual particles are several times larger than the heights due to tip convolution effects.
E
•£
JC
en
'55
I
5.0
4.0
3.0
2C
1.0
0.0
-1.0
; . ^ :* -( /\
j ' ' I i ^
.* ; [ ', ; . ; '• ' \
'(•'*.: ' • * 1 '
• ' ' : I ': , *
• i ; ;.^ ;•.:-_, s ,: ^ _,: > '•.
V."- ' r" ... / -..-,,» - • ,-
25
50 75
100 125 150 175 200 225 250 275
Figure 1. AFM Tapping Mode™ micrographs (top view) of FeOOH nanoparticles
prepared by UV-ozone treatment of 2,500 Fe loaded ferritin for 60 mins
at 100 °C under oxygen (< 5psi); section analysis.
Reduction of the ferrihydrite nanoparticles to the Fe metal was conducted in a reaction cell coupled to the
ultra-high vacuum (UHV) chamber. The sample was then transferred directly into the UHV chamber where X-
Ray Photoelectron Spectroscopy (XPS) was conducted. The AFM image of these particular particles (see Fig-
ure 2) shows a similar morphology to the particles prior to reduction. Again, the peak-to-valley height differ-
ences for the large features in the cross-section are in the 4-6 nm range, and in this case the RMS roughness is
1.47.
Formation of Reactive Cu Nanoparticles Encapsulated Within the Protein Cage of Ferritin. The photo-
lysis of Cu(II) in the presence of iron oxide-mineralized ferritin and a sacrificial reductant such as citrate or
tartrate resulted in the formation of a wine-red color after 1 hour. Control reactions photolyzed in the absence
of Cu(II), tartrate/citrate, or iron oxide mineralized ferritin, did not change color over the same period. No
reaction was observed when solutions were left in the dark or in the presence of the unmineralized (apo)
ferritin. In addition, Fe(II) alone was not observed to spontaneously reduce Cu(II) in deaerated solutions. Ex-
The Office of Research and Development's National Center for Environmental Research
87
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
animation of the photolysis products by transmission electron microscopy (TEM) revealed electron-dense
spherical particles (see Figure 3), with the Cu(II):ferritin ratio serving as the major determinant of particle size.
Histograms of particle sizes were fit to Gaussian distributions. Higher Cu(II):ferritin ratios led to larger particle
sizes, with loadings of 250, 500, 1,000, and 2,000 leading to average particle diameters of 4.5 ± 0.8, 9.7 ± 4.2,
12.7 ± 3.6, and 31.4 ± 10.1 nm, respectively. The reactivity of these nano-Cu particles will be investigated with
regard to environmental remediation reactions.
'* 1.0
120 160 200
Position fnml
Figure 2. AFM Tapping Mode™ micrographs (top view) of iron nanoparticles
prepared by heating 2,500 Fe loaded FeOOH nanoparticles in a re-
ducing environment; section analysis.
Figure 3. Metallic Cu particles grown within ferritin.
Formation of F^Oj and TiO? Nanoparticles Within the Protein Cage of Ferritin. Mineralization of
mammalian ferritin using high oxidation state transition metal ions as starting materials can be achieved using
a photoreduction process. The Fn cages with Fe-oxhydroxide and Ti-oxhydroxide nanoparticles have been
mineralized successfully, in a spatially selective manner, and the resultant nanoparticles within the protein ca-
ges were encapsulated. The composite materials, synthesized in this way, have particle sizes that are highly
monodisperse. This represents a new synthetic approach to the formation of protein encapsulated metal oxy-
hydroxide materials in the nanoscale size regime.
Photolysis of a solution of Fe(III) or Ti(IV) citrate in the presence of the apo-ferritin cage results in the
formation of small amounts of Fe(II) and Ti(III), respectively. In the presence of oxygen, these reoxidize and
hydrolyze to form nanoparticles within the protein cage. The Fe reaction could be monitored spectroscopically
by the development of the ligand-to-metal charge transfer absorbance characteristic of Fe(III)-oxo polymers.
When the reaction was performed in the absence of the protein cages, the development of the color was clearly
associated with the formation of a rust colored precipitate. When Ti(IV)citrate was used as a starting material,
there was no change in color during the photolysis reaction. In the presence of the protein cages, the reaction
solution remained homogeneous, but in control reactions in the absence of the protein cage, a white precipitate
88
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
formed as the photolysis proceeded. If the photolysis was performed under inert atmosphere, the characteristic
purple color of dl Ti(III) species could be observed. The Ti-oxyhydroxide material was tested for its ability to
catalyze the photoreduction of Cr042 under Xe-arc lamp illumination (see Figure 4). This material exhibited a
catalytic behavior similar to that observed previously for Fe203-ferritin.
E
c
CM
m
o>
J2
3*
o«
-10-
-20.
-30.
-40.
-50-
-6Qx1D"3.
» & -
J3
<
a*
«
^7r;:.._ ^.^^^.^^
^C-: ': . , r. . Xj/
\-- '""''- -.. .-•• ' -/
v- •'./
\j/
T T i if i it ^ K 1
320 340 360 380 -300 420 440 460
WaveSength(min)
*
» . *
10 15
20
Figure 4. The plot shows the loss of Cr(VI) (reflected in the loss of absorbance at 372 nm)
from solution as the Ti-oxyhydroxide catalyzes its reduction to Cr(III) in the pres-
ence of light.
The Office of Research and Development's National Center for Environmental Research
89
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
A Bioengineering Approach to Nanoparticle-Based
Environmental Remediation
Daniel R. Strorigin
Department of Chemistry, Temple University, Philadelphia, PA
Environmental Implication/Application
This research project is a multidisciplinary effort to develop a firm understanding of the properties of
nano-size metal oxide compounds within the protein shell (or cage) of the iron storage protein, ferritin
(spherical with a 120 D diameter). Prior to this research effort, these systems were relatively unexplored in
terms of their potential use in remediation processes or as a method for synthesis of nano-scale particles of
metal compounds. The entire system, consisting of the inorganic core material and protein shell, provides
opportunities for the development of new catalysts for beneficial environmental chemistry by manipulating the
composition and size of the core material, as well as chemically functionalizing the surrounding protein shell.
The bioengineering approach proposed here has allowed us to investigate the reactivity of a variety of metal
oxides (with a primary emphasis on iron oxyhydroxide), with variable nano-dimensions that may have great
potential benefits to chemical and photochemical remediation schemes. Both the thermal chemistry and photo-
chemistry of the particles toward the redox chemistry of toxic metals have been probed. The nanomaterials
used in this research are ubiquitous components of soils, aquatic systems, and related environments, and have
found uses in remediation strategies, but not at the nano-scale. Furthermore, results have demonstrated the
ability to reduce the metal oxide core of ferritin to yield nano-sized zero-valent metal particles. Hence, our
bioengineering approach yields a synthetic route to well-defined, nano-metal particles for environmental
chemistry. At least one prior impediment to fully investigating and ultimately testing the utility of nano-
structures has been the difficulty that their preparation and stabilization presents. The bioengineering approach
has addressed this issue and has helped circumvent these difficulties in an environmentally benign and
biodegradable system. The low band gap energy of most Fe(III) bearing iron oxides allows them to harness a
significant amount of the solar spectrum to carry out photochemical processes. Because of its attractive
semiconductor properties and low cost, iron oxides have been investigated as photocatalysts for the degra-
dation of environmental toxins (e.g., chlorocarbons and metals). Their potential use, however, is limited due to
their undergoing photoreduction (i.e, conversion of Fe(III) to Fe(II)), resulting in the deterioration of the
catalytic particle. In this study, the nano-catalyst is encapsulated by a protein cage that stabilizes the iron oxide
against photoreduction. Ferritin is engineered by nature to convert Fe(II) to Fe(III) so a hypothesis has been
that any Fe(II) produced by photoreduction will be rapidly converted back to Fe(III) in the presence of 02. This
stabilization by the protein shell will be a significant advantage over, for example, a free-standing iron oxide
particle photocatalyst. While the protein cage stabilizes the core, its presence still allows the iron oxide core to
drive important environmental chemistry. In our laboratory, for example, photoexcited ferritin mediates the
rapid reduction of toxic Cr(VI) to the immobile Cr(III) species.
90 The Office of Research and Development's National Center for Environmental Research
-------
Section 5. Treatment
Cost-effective treatment of pollutants poses a challenge for EPA and others in the development of effective
risk management strategies. EPA supports research that addresses new treatment approaches that are more
effective in reducing contaminant levels and more cost effective than currently available techniques. A variety
of pollutants at different concentrations requiring removal may exist at contaminated sites, in groundwater, or
in process fluids. Nanotechnology offers the possibility of more effective treatment of gases, soil, and water
due to the higher surface to volume ratios of nanomaterials. In addition, collection and separation mechanisms
may be more effective due to unique physical properties at the nanoscale. Specific control and design of ma-
terials at the molecular level may impart increased affinity, capacity, and selectivity for pollutants.
-------
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
NOX Reduction With Transition Metal Carbide Nanoparticles
S. Ismat Shah
Department of Materials Science and Engineering, University of Delaware, Newark, DE
Abstract
This research project deals with exploring the possibility of using alternative catalytic materials, transition
metal carbides (TMC) and oxycarbides (defined as oxygen-modified carbides), to replace platinum (Pt)-group
metals for the reduction of NOX. The carbides and oxycarbides of Groups 4-6 early transition metals are char-
acterized by many unique and intriguing catalytic properties. The catalytic properties of TMC and transition
metal oxycarbides (TMOC) have been the subject of many investigations in the fields of catalysis and surface
science. From the catalysis literature, it is now well established that the catalytic properties of TMC and
TMOC often show strong similarities to those of the more expensive Pt-group metals (Ru, Rh, Ir, Pd, and Pt).
In the past few years, several surface science groups have performed fundamental investigations of the cata-
lytic properties of TMC and TMOC. For example, our research group has performed extensive studies aimed
at directly comparing the chemical reactivity of carbide surfaces with that of Pt-group metals. The results pro-
vided conclusive evidence that the decomposition of a variety of hydrocarbon molecules on TMC occurs via
reaction mechanisms that are characteristic of Pt, Rh, and Pd. Furthermore, comparative studies have been
performed on the decomposition of NO on the bulk surfaces of molybdenum (Mo) and tungsten (W) carbides
and oxycarbides. Preliminary results clearly demonstrate that carbides and oxycarbides of Mo and W are very
efficient in the conversion of the toxic NO pollutants into the harmless N2 molecules, with catalytic activity
and selectivity being similar or better than those of the expensive Pt-group metals.
Decomposition of NO on Carbide Modified W(lll) Surface. It is relatively easier to study the decompo-
sition pathways of NO on carbide modified single crystal W surfaces. This study will be extended to include
the WC and WOC nanoparticles. The decomposition pathways are investigated using a combination of tem-
perature programmed desorption, auger electron spectroscopy, high-resolution electron energy loss spec-
troscopy, and soft x-ray photoelectron spectroscopy. All of these surfaces exhibit high activity toward the de-
composition of NO, and the only N-containing products are N2 and N20. Furthermore, all three surfaces
preferentially produce N2 over N20 from the decomposition of NO. Oxygen atoms, produced from the de-
composition of NO, react with carbide surfaces to produce gas-phase CO at high temperatures. In addition, the
results demonstrate that cycles of alternate NO/hydrocarbon treatments can regenerate the carbide overlayer on
W(l 11), and the regenerated C/W(111) surface remains active in the decomposition of NO.
EXAFS Study of the Nanoparticles. Extended X-ray Absorption Fine Structure (EXAFS) analysis shows
the nearest neighbor coordination in materials. These studies are important because WC surfaces have catalytic
behavior for NO decomposition similar to that of Pt. If the same electronic structure and local chemistry in the
WC nanoparticles are observed as in the bulk surfaces, their catalytic properties can be correlated. Previously,
it was reported that the synthesis process can be modified to obtain desired surfaces. EXAFS is used to
compare the local chemistry of the nanoparticles with that of bulk surfaces. Figure la shows the comparison of
the W K-edge oscillation for the nanoparticle film, with spectra from the bulk and theory (FEFF). Figure Ib
shows the edge oscillations of the nanoparticles and the bulk only. The similarity on the structure is readily
observable, indicating that the local chemistry of the nanoparticles is similar to that of the bulk; therefore,
catalytic properties of the nanoparticles should be similar to that of the bulk.
NOX Decomposition With WCX Nanoparticles. Preliminary experiments to study NOX decomposition with
WCX nanoparticles were conducted in an in-line reactor. The reactor setup is shown in Figure 2. The tem-
perature of the reactor can be controlled from RT to 1,000 °C. Currently, only the nitrogen column in the gas
chromatograph (GC) is being used. This will be expanded to include the NO column very shortly. A mixture of
1 percent NO with He is used as the test gas. Flow rates are adjusted by using mass flow controllers. A base
line for the experiment is obtained by passing the gas mixture through the reactor, without any catalyst. The
The Office of Research and Development's National Center for Environmental Research 93
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
base line is shown in Figure 2. With the addition of the catalyst, the direct decomposition of NOX occurs
according to the reaction: NOX -> N2 + 02.
The N2 signal is detected by GC. Figure 2 shows the increase in the N2 signal intensity as a function of the
reactor temperature. The decomposition reaction starts to occur at temperatures above 200 °C, increases rapid-
ly up to about 500 °C, and becomes constant beyond 500 °C. We think that the leveling off is a result of the
loss of some carbon form of the nanocatalyst. The next set of experiments includes the addition of hydro-
carbon to the feed gas. This will not only imitate the automobile exhaust better, it also will stabilize the carbon
concentration in the nanoparticles and enhance the activity further with the temperature.
60-
\k)30:
-30-
-60-
, Kb I- I
- v, \> $ ',-•• i. u, if- '•',' si^ijK
('! • lr (v ''! ^[j S
! ! i ja
4 6 8 10 12 14 16
k/A1
Figure 1. EXAF results comparing the nanoparticles, bulk and
theoretical spectra.
/With WC Nanopartlcles
3ase Line^No Catalyst
Figure 2. NOX decomposition with and without the catalyst.
94
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
NOX Reduction With Transition Metal Carbide Nanoparticles
S. Ismat Shah
Department of Materials Science and Engineering, University of Delaware, Newark, DE
Environmental Implication/Application
One of the major environmental pollution sources is from automobile exhaust, which causes smog and
acid rain. Since 1975, the automobile manufacturers have taken a variety of steps to reduce the level of
harmful emission gases, including NOX, CO, and unburned hydrocarbons (HC). At present, the emission levels
of these gases can be reduced by catalytic reactions in the catalytic converter via the following chemical
reactions: CO + 02 -> C02, CO Oxidation; HC + 02 -> C02 + H20, HC Oxidation; NOX + HC -> N2 + H20 +
C02, NOX Reduction by HC; NOX + CO -> N2 + C02 NOX, Reduction by CO. In these reactions, the harmful
pollutants are converted into relatively harmless molecules such as C02, N2 and H20. These reactions occur
inside the automobile catalytic converters in the presence of catalysts, which consist of mixtures of platinum-
group metals, such as rhodium (Rh), platinum (Pt), and palladium (Pd). Due to their limited natural abundance
in the Earth's crust, the platinum-group metals are among the most expensive elements. For example, the
current price for a troy ounce of Rh is about $2,500, which is about three times more expensive than gold. For
the reason of cost effectiveness, the Pt-group metals in the catalytic converter are always kept at a minimum
amount, as long as it is sufficient to reduce the emission levels to meet the government regulations.
Recently, the U.S. Environmental Protection Agency (EPA) and the California Air Resources Board
(CARB) have defined specific future targets for the reduction of emission gases of NOX, CO, and HC. For
example, the target emission levels for the 1997-2003 Ultra Low Emission Vehicle (ULEV) are 0.04, 1.7, and
0.2 g/mile of HC, CO, and NOX, respectively. An even more stringent target, set by the 2004 ULEV2 Act,
requires that the level of NOX be further reduced to 0.05 g/mile. The current catalytic converter technology is
able to reach the 1997-2003 targets. However, it is insufficient to achieve a further decrease, by a factor of
four, in the level of NOX by the year 2004. Although one of the obvious solutions is to increase the con-
centrations of the Pt-group metals in the catalytic converter, the cost effectiveness would eventually become a
major issue for automobile manufacturers and catalyst vendors.
This research project attempts to explore the possibility of using alternative catalytic materials, transition
metal carbides and oxycarbides (defined as oxygen-modified carbides), to replace Pt-group metals for the
reduction of NOX. The carbides and oxycarbides of Groups 4-6 early transition metals are characterized by
many unique and intriguing catalytic properties. Ever since the landmark paper by Levy and Boudart regarding
the Pt-like properties of tungsten carbides, the catalytic properties of transition metal carbides (TMC) and
oxycarbides (TMOC) have been the subject of many investigations in the fields of catalysis and surface
science. From the catalysis literature, it is now well established that the catalytic properties of TMC and
TMOC often show strong similarities to those of the more expensive Pt-group metals (Ru, Rh, Ir, Pd, and Pt).
In the past few years, several surface science groups have performed fundamental investigations of the
catalytic properties of TMC and TMOC. For example, our research group has performed extensive studies
aimed at directly comparing the chemical reactivity of carbide surfaces with that of Pt-group metals. The
results provided conclusive evidence that the decomposition of a variety of hydrocarbon molecules on TMC
occurs via reaction mechanisms that are characteristic of Pt, Rh, and Pd. Furthermore, comparative studies
were performed on the decomposition of NO on the bulk surfaces of Mo and W carbides and oxycarbides.
Preliminary results clearly demonstrate that carbides and oxycarbides of Mo and W are very efficient in the
conversion of the toxic NO pollutants into the harmless N2 molecules, with catalytic activity and selectivity
being similar or better than those of the expensive Pt-group metals. Nanoparticles of TMC and TMOC offer
the means of obtaining the phase and crystal surface required for efficient NO reduction. If successful, the
replacement of Pt-group metals by TMC or TMOC nanoparticles would offer enormous economic incentives
for the effective reduction of NOX. More importantly, it might offer one of the more realistic ways to achieve
the NOX emission level, 0.05 g/mile, because of the prohibitively high price of the Pt-group metal catalysts.
The Office of Research and Development's National Center for Environmental Research 95
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Simultaneous Environmental Monitoring and Purification
Through Smart Particles
Wolfgang Sigmund, C. Y. Wu, andD. Mazyck
Department of Materials Science and Engineering, University of Florida, Gainesville, FL
Abstract
This research project has resulted in the development of two multifunctional composite materials. The first
composite material consists of a hard magnetic core, an intermediate silica layer, and a photocatalytic titania
shell (7.7 nm primary particle size). Figure 1 shows a TEM micrograph of the material (the region between the
white arrows is the silica layer. The high surface area titania shell is responsible for photocatalytic oxidation of
pollutants when illuminated by ultraviolet (UV) light. Under an external magnetic field as in the newly de-
signed MAPR (Magnetically Agitated Photocatalytic Reactor), the composite can be magnetically fluidized,
thus providing enhanced mixing with pollutants to be treated and enhanced exposure to UV light. The resultant
advantage is improved pollutant destruction. An additional advantage is the retrieval of the material from the
treated air or water media. The novel composite has been demonstrated to outperform the benchmark Degussa
P25 in the destruction of phenol in laboratory tests.
The project team also has developed a silica-titania composite that possesses synergistic photocatalytic
oxidation and adsorption. The nanostructured silica substrates provides high surface area, but the nanosized
titania particles are responsible for photocatalytic oxidation of pollutants. Excellent removal of elemental
mercury vapor has been demonstrated. A unique feature of the novel composite is that the adsorption improves
over time as shown in Figure 2. Based on the mechanisms identified, the team has developed a second genera-
tion composite that has extraordinary mercury removal capability without the excitation of UV light.
UVon UVon UVon UV on UVon UV on
0.0
100 120
Figure 1. TEM micrograph of
titania/silica/magnet
composite.
40 60 80
Time (min)
Figure 2. Fractional Hg° concentration at reactor outlet
(showing improved adsorption over time).
96
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Simultaneous Environmental Monitoring and Purification
Through Smart Particles
Wolfgang Sigmund
Department of Materials Science and Engineering, University of Florida, Gainesville, FL
Environmental Implication/Application
Photocatalytic Ti02 nanoparticles have been well recognized for their superior ability to oxidize pollu-
tants. However, its separation from treated water has been a serious limitation. Unintentional release of nano-
particles into the environment also causes concerns due to their potential toxicity. Mass transfer limitation for
Ti02 nanoparticles coated on tubes or beads is another constraint of the current Ti02 technology. The multi-
functional magnetic silica-titania composite material developed by the University of Florida has overcome
these limitations and brings several advantages to the environment. Magnetic fluidization of the material
allows its enhanced mixing with pollutants to be treated and enhanced by exposure to a light source. Pollutant
destruction kinetics is improved, thus reducing the amount and energy required for pollutant treatment. Its
movement can be well adjusted and confined to a prescribed space using a controlled magnetic field. Retrieval
of the material from treated air or water media also can be accomplished easily by magnetic separation. By
incorporating silica, photo-dissociation of the magnetic core, which commonly occurs with other magnetic
materials, does not exist anymore. This prevents introduction of heavy metals into water and reduces un-
necessary consumption of materials. In short, the magnetic silica-titania based nanotechnology enables us to
improve environmental quality with less consumption of materials and energy.
In parallel, a nanostructured silica-titania composite has been developed that possesses synergistic
photocatalytic oxidation and adsorption capabilities. The nanostructured silica provides high surface area for
adsorbing pollutants as a concentrator while the nanosized Ti02 particles can photocatalytically oxidize
pollutants. The synergistic combination allows a reduced energy requirement as the light source only needs to
be provided. This material has been successfully tested for removing elemental mercury vapor in air. The
material changes its color as oxidized mercury accumulates on the material. The change of material color
provides a convenient tool to identify the state of the material. The concentrated accumulation of oxidized
mercury can be recycled by heat treatment or vacuum treatment. The recycle reduces demand of mercury from
mining, which is known to yield significant environmental damages. The silica-titania composite is regenerat-
ed in the meantime. The regeneration prolongs the lifetime of the material, thus reducing the required amount
of material to be supplied. Furthermore, no hazardous waste is generated by this technology, which is in
contrast to current carbon-based technology. Hazardous waste disposal of mercury-loaded carbon is costly and
may have a long-term environmental impact. During the research, a unique feature of improved adsorption
over time has been observed, which has never been reported before. The mechanism of this feature has been
identified, which led to the development of a second generation composite. The benefit of this new material is
its independence from ultraviolet light, thus reducing the energy requirement.
The Office of Research and Development's National Center for Environmental Research 97
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Nanoscale Biopolymers With Tunable Properties for Improved
Decontamination and Recycling of Heavy Metals
Wilfred Chen
Department of Chemical and Environmental Engineering, University of California, Riverside, CA
Abstract
Heavy metal ions are major sources for pollution of the biosphere, and they are usually found as co-
contaminants in many Superfund sites. Current technologies are inadequate to reduce metal concentrations to
acceptable standards and to separate these heavy metals from a waste mixture for potential recycling. The goal
of this project is to develop a technology utilizing nanoscale metal-binding biopolymers with customizable
properties for the differential sequestration and recovery of different heavy metals in a mixed-metal waste.
Tunable biopolymers based on elastin-like polypeptides (ELP) will be generated to demonstrate this feasibility
by specifically incorporating different metal binding domains into ELP biopolymers with dramatically dif-
ferent transition temperatures. Initial feasibility studies will utilize two different ELP building blocks contain-
ing either polyhistidine or synthetic phytochelatin as the metal-binding domain. Application of this technology
for soil remediation also will be discussed. This technology serves as an example to provide an efficient and
nontoxic solution to the removal and separation of heavy metal contamination.
98 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Nanoscale Biopolymers With Tunable Properties for Improved
Decontamination and Recycling of Heavy Metals
Wilfred Chen
Department of Chemistry and Environmental Engineering, University of Calif ornia, Riverside, CA
Environmental Implication/Application
The biosynthetic approach is environmentally friendly and allows precise and independent control of the
length, composition, and charge density of the interacting end blocks and metal-binding domains, thus
allowing the flexibility in designing tunable biopolymers that can undergo transition from water-soluble into
aggregate forms under a wide range of conditions. Such precise control is valuable to satisfy the needs of dif-
ferent process conditions. Compared to conventional chemical chelators or chelating polymers, the proposed
biopolymers are environmentally friendly because no toxic chemical is required for their synthesis and re-
generation can be achieved easily. This strategy, if successful, will provide a low-cost and environmentally
benign technology for heavy metal removal.
The Office of Research and Development's National Center for Environmental Research 99
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Use of Ozonation in Combination With Nanocrystalline Ceramic
Membranes for Controlling Disinfection By-Products
Simon H. Davies
Michigan State University, East Lansing, MI
Environmental Implication/Application
The production of disinfection by-products (DBFs) during the disinfection process in drinking water is a
very important issue since some DBFs, such as trihalomethanes (THMs), are carcinogenic or potentially car-
cinogenic. In addition, THMs in drinking water have been linked to miscarriages, premature births and low
birth weight babies. Because of their greater perceived health risk, under Stage 1 of the Disinfectants/Disin-
fection By-Products (D/DBP) Rule, which was promulgated in December 1998, the maximum contaminant
level (MCL) for total THMs (TTHMs) was lowered from 100 |ig/L to 80 |ig/L, and that for the sum of five
haloacetic acids (HAAS). The proposed Stage 2 regulations will further limit the levels of THMs and other
DBFs. Therefore, novel ways to further remove DBF precursors to meet the more stringent regulations con-
cerning DBFs must be developed.
This proposed ozonation/membrane process combines ozonation and membrane technology to control
DBF precursors and raise the quality of treated water. Inactivation of pathogens in the residual stream, re-
duction of membrane fouling, and an increase in the efficiency of natural organic matter (NOM) destruction by
ozone could be achieved in this process as well. If this proposed process is successfully developed, it will help
drinking water treatment plants upgrade or retrofit their conventional system and comply with the Stage 2
D/DBP standards.
100 The Office of Research and Development's National Center for Environmental Research
-------
Section 6. Fate, Transport, and Transformation
As nanotechnology progresses from research and development to commercialization and use, manufactured
nanomaterials may be released into the environment. EPA is interested in determining the routes through
which manufactured nanomaterials enter the environment and their modes of dispersion, interaction, and
degradation within the environment: soil, water, atmosphere, and biosphere. Persistence and bioaccumulation/
biomagnification are factors that offer guidance for determining whether substances are classified as hazar-
dous. Although the short-term effects of a toxic nanomaterial may result from a single exposure, the long-term
effects due to bioaccumulation and persistency may be more severe, ranging from lasting health problems to
organ damage. Biomagnification, a side effect of bioaccumulation, is the amplification of the concentrations of
nanomaterials in each successive step in the food chain. Keeping in mind the novel properties of nano-
materials, new or modified test methods, basic datasets for environmental fate/transport endpoints, and
applications of new or existing air dispersion, soil transport, groundwater models may be needed.
-------
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Adsorption and Release of Contaminants
Onto Engineered Nanoparticles
Mason B. Tomson
Rice University, Houston, TX
Abstract
As nanotechnology develops into a mature industry, the environmental and health effects of its core
materials become of increasing importance. This research project aims to evaluate the sorption and release of
contaminants onto the surfaces of engineered nanoparticles. Specifically, four hypotheses will be tested in this
research: (1) carbon nanostructures have a high capacity for sorption/desorption hysteresis with polynuclear
aromatic hydrocarbons and other common organic contaminants; (2) the sorption capacity of inorganic nano-
materials for heavy metals is the same as the corresponding bulk crystals, when corrected for surface area; (3)
the sorption of naturally occurring humic materials and surfactants to metal oxide and carbon nanomaterials
will diminish the sorption capacity of heavy metals on oxides and increase the sorption of hydrocarbons on
carbon nanomaterials; and (4) the transport of nanoparticles in soils, sediments, and porous medial will be
vastly greater than the corresponding colloids or bulk materials.
This project is motivated by the interest in collecting data needed for risk assessments of nanoparticle
materials. It is never too early in an emerging technology to consider issues of environmental impact; for nano-
technology, sound technical data concerning the health risks and potential exposure of nanomaterials in water
will allow nanomaterials to be targeted at the most appropriate applications. Such information also will allow
environmental issues to factor in early into manufacturing development, leading to a greener and ultimately
more economic industry. There is no existing technical literature that speaks to the issue of the environmental
impacts of nanoengineered materials. However, related areas concerning contaminant sorption to minerals and
clays, as well as the importance of particle-mediated transport to exposure calculations are quite relevant and
have informed our thinking about this problem.
The introduction of a new class of materials into consumer products will require information about the
potential behavior and risks that these systems pose to the environment and people. The high surface area of
nanoparticles means that even weak sorption of contaminants to surfaces can introduce a significant new
pathway for exposure, or removal, of molecular contaminants in biological systems. This research project
provides the information needed to assess whether this risk is substantial for nanoparticles disposed of in
groundwaters. It is expected that this research would yield the necessary parameters to understand the fate of
engineered nanoparticles in the environment and to yield the necessary parameters for future development of
risk assessment of the engineered nanoparticles. The research group has conducted the first groundwater con-
tamination studies. Recently, a dual equilibrium desorption equation was developed and it has been considered
by many consulting companies and regulatory agencies for adoption into their remediation scheme and
regulatory guidelines.
The Office of Research and Development's National Center for Environmental Research 103
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Adsorption and Release of Contaminants
Onto Engineered Nanoparticles
Mason B. Tomson
Rice University, Houston, TX
Environmental Implication/Application
The introduction of a new class of materials into consumer products will require information about the
potential behavior and risks these systems pose to the environment and people. The high surface area of nano-
particles means that even weak sorption of contaminants to surfaces can introduce a significant new pathway
for exposure, or removal, of molecular contaminants in biological systems. This research project provides the
information needed to assess whether this risk is substantial for nanoparticles disposed of in groundwaters. It is
expected that this research would yield the necessary parameters to understand the fate of engineered
nanoparticles in the environment and to yield the necessary parameters for future development of risk
assessment of the engineered nanoparticles. The first groundwater contamination studies have been completed.
Recently, a dual equilibrium desorption equation was developed, and it has been considered by many con-
sulting companies and a regulatory agency for adoption into their remediation scheme and regulatory guide-
line.
104 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Impacts of Manufactured Nanomaterials on Human Health and the
Environment: A Focus on Nanoparticulate Aerosol and
Atmospherically Processed Nanoparticulate Aerosol
VickiH. Grassian
Department of Chemistry, University of Iowa, Iowa City, IA
Abstract
The goal of this research project is to determine the potential effects of manufactured nanomaterial aerosol
on human health. Manufactured nanomaterials will be characterized using a wide variety of techniques and
analysis methods, including surface spectroscopy so that both bulk and surfaces properties can be understood
on a molecular level. Because a number of physical and chemical properties are size-dependent on nanometer
length scales, it is important to fully characterize the nanoparticles used in these studies. These well-charac-
terized particles will then be used for inhalation and exposure studies using laboratory animals. There will be
additional characterization once the aerosol has been generated to determine if the particles aggregate or retain
the size distribution determined prior to aerosol generation. Toxicology assessments of the animals will in-
clude murine acute pulmonary inflammation assay, murine subacute pulmonary toxicology evaluation, and
murine microbial challenge host resistance evaluation to screen for acute and subchronic pulmonary effects.
The Office of Research and Development's National Center for Environmental Research 105
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Impacts of Manufactured Nanomaterials on Human Health and the
Environment—A Focus on Nanoparticulate Aerosol and
Atmospherically Processed Nanoparticulate Aerosol
VickiH. Grassian, Patrick O'Shaughnessy, and Peter Thorne
University of Iowa, Iowa City, IA
Environmental Implication/Application
In this work, the potential effects of manufactured nanomaterial aerosol on human health will be investigated.
It is expected that these studies will help answer questions as to the potential impact of manufactured nano-
material aerosol on human health as there is clearly a lack of information in this regard. Two important factors of
the proposed activities are the comparison of the potential health effects of manufactured nanomaterials to other
anthropogenic sources of ultrafine particles from combustion processes and the effect of surface coatings, from
manufacturing and atmospheric processing, on the toxicity of these particles.
106 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Chemical and Biological Behavior of Carbon Nanotubes
in Estuarine Sedimentary Systems
P. Lee Ferguson
Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC
Abstract
The general objectives of the proposed research are to: (1) determine factors controlling the fate of single-
walled carbon nanotubes (SWNTs) and their synthetic by-products in estuarine seawater, sediment, and sedi-
ment-ingesting organisms; (2) examine the impact of SWNTs and by-products on the disposition of model
organic contaminants in estuarine sediments; (3) determine whether the presence of SWNTs and by-products
in estuarine sediments affects the bioavailability of model organic contaminants to estuarine invertebrates; and
(4) assess the toxicity of SWNTs and by-products to suspension- and deposit-feeding estuarine invertebrate
models in seawater suspension alone, and/or in combination with estuarine sediments.
This research project will address these objectives through a series of experiments designed to provide a
holistic picture of the behavior of SWNTs and their synthetic by-products on entry into the estuarine environ-
ment. These experiments will include tracing the fate and phase-association of 14C-SWNTs and by-products
under simulated estuarine conditions and through ingestion by deposit-feeding organisms, batch sorption stud-
ies to examine the affinity of SWNTs for model hydrophobic organic contaminants (HOC) in the estuarine
environment, laboratory-scale bioaccumulation experiments designed to test modulation of HOC bioavaila-
bility by co-occurring SWNTs in estuarine sediments, and dose-response experiments designed to test the
potential for SWNTs and by-products to directly cause adverse effects on a sensitive estuarine infaunal inverte-
brate (the harpacticoid copepod, Amphisascus tenuiremus).
The proposed work will, for the first time, address the physical, chemical, and biological behavior of novel
and emerging carbon nanotube materials under environmental conditions typical of estuaries. In total, this
study will address not only the potential for SWNTs to be transported, accumulate, and cause direct deleterious
effects within estuarine environments, but also the potential for linked effects on the biological and chemical
behaviors of known priority pollutants common in estuarine sediments. This combined approach represents a
novel way of addressing the environmental impact of an emerging synthetic nanomaterial and will thus provide
the U.S. Environmental Protection Agency and the scientific community with an entirely new and highly
relevant dataset for risk assessment of SWNT-derived contaminant discharge. Further, the work will generate
new scientific knowledge related to the behavior of these highly novel nanomaterials under conditions not
normally tested in the course of nanoscience research (e.g., nonmammalian biological systems, highly saline
aqueous solutions, and complex sediment media). This knowledge may become useful in designing new
nanoscale technologies in, for example, environmental engineering or "green" manufacturing techniques.
The Office of Research and Development's National Center for Environmental Research 107
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Chemical and Biological Behavior of Carbon Nanotubes
in Estuarine Sedimentary Systems
P. Lee Ferguson
Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC
Environmental Implication/Application
This research project will illuminate the potential for commercially relevant single wall carbon nanotube
(SWNT) material to adversely affect estuarine environments on intentional or inadvertent release. The phy-
sical, chemical, and biological behavior of these novel and emerging materials will be studied under environ-
mental conditions typical of estuaries. Specifically, this study will provide information on the phase-behavior
(physico-chemical partitioning) of SWNTs among estuarine water, colloidal suspension, and suspended/
bedded sediments. The resulting data will be crucial for predicting/modeling the environmental fate, transport,
and risk of these materials in impacted estuaries.
In addition, this work will provide detailed and valuable information on the potential for adverse effects of
these materials (possibly related to differential feeding selection or gut/feeding appendage fouling) on trophy-
cally important members of the estuarine food web. This work will be structured to address the relevance to the
fate of priority pollutants in estuarine sediments impacted by SWNTs. Furthermore, this research will generate
new scientific knowledge related to the behavior of these novel nanomaterials under estuarine conditions,
which may prove useful in the design of new nanoscale technologies.
108 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Transformations of Biologically Conjugated CdSe Quantum Dots
Released Into Water and Biofilms
Patricia A. Holden
Donald Bren School of Environmental Science and Management, University of California,
Santa Barbara, CA
Abstract
Semiconductor nanocrystals (quantum dots [QDs]) differ in important ways from bulk semiconductor
materials. Their increased band gap means that they function as strong oxidizing and/or reducing agents, and
their small size allows them to pass into living cells. Conjugation of biomolecules to the crystal surface can
alter any or all of these properties. In preliminary experiments, it was observed that nucleobase-conjugated
cadmium selenide (CdSe) QDs were actively taken up by soil and aquatic bacteria (e.g., Bacillus subtilis and
Escherichia coll). Effects on microbial viability attributed to the presence of the QDs included slower doubling
times, heavy metal sequestration, and "blebbing" of metals into the environment. In this project, these effects
will be quantified using a variety of biologically conjugated QDs and an assortment of microbial species,
monitoring the process of quantum dot uptake and breakdown, and characterizing the breakdown products that
result from bacterial metabolism of these particles. Possible hazards to microbial populations with extrapola-
tion to humans through contamination of soil and water with quantum dot breakdown products will be ana-
lyzed and quantified.
Bare, core-shell and biologically conjugated QDs will be studied. Abiotic breakdown kinetics and products
in aqueous environments will be determined by inductively coupled plasma (ICP) spectrometry for QDs as a
function of exposure to light, pH, and oxidizing or reducing conditions. In preliminary experiments, biologi-
cally conjugated QDs are easily taken up by B. subtilis, but the process is light and pH dependent. Some
breakdown occurs inside and outside of cells. Working with Pseudomonas aeruginosa and Staphylococcus
aureus to represent Cd-sensitive and Cd-resistant strains, population growth and fluorescence for pure liquid
cultures previously exposed to QDs will be quantified. Conventional methods (shake flask, viable and direct
counting over time) will be used to assess the effects of labeling on bacterial growth rates under high and low
nutrient conditions. QD fluorescence will be monitored throughout, adjusting final results for the dilution
effect of growing populations. Concentrations of Cd and Se will be assessed inside and outside cells, and
membrane associations of whole QDs and breakdown products will be quantified. The relationship of QD re-
lease and breakdown to cell viability will be assessed. DNA damage in bacteria will be assessed by quanti-
fying 8-oxoguanine, a product of oxidative DNA damage, by microscopy and a commercially available fluo-
rescent label. These experiments will provide basic insight into cellular interactions with QDs. The potential
for single base pair damage from whole QDs and breakdown products will be assessed using time-correlated
single photon counting techniques. Because most bacteria exist as biofilms in nature, mono- and dual-species
bacterial biofilms will be cultured under continuous flow conditions in a commercially available flow cell.
Using digital photomicroscopy and computerized image analysis, the effects of QD labeling on biofilm growth
will be assessed. Unsaturated biofilms also will be cultured on membranes to assess the effects of QD labeling
on development under soil-like conditions and as a function of nutrient and water availability. Cryo-environ-
mental scanning electron microscopy (ESEM) coupled with energy dispersive spectrometry (EDS) will be used
to visualize ultrastructural QD associations. Biofilms cultured in the absence of QDs will be exposed under a
range of experimental conditions and assessed over time for viability and QD content. For all biofilm experi-
ments, QD effects on exopolymeric substances (EPS) can be quantified by gas chromatography-mass spectro-
metry of derivatized glycosyl residues, and DNA and protein content can be determined by standard fluoro-
metric and colorimetric methods, respectively.
Finally, column studies, using packed porous media under saturated and unsaturated conditions, will be
conducted to assess QD and Cd mobility as a function of bacterial colonization. Because EPS is expected to
chelate Cd, whole QDs, Cd, Se, and biopolymers will be quantified in breakthrough experiments, followed by
The Office of Research and Development's National Center for Environmental Research 109
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
sacrificial characterization of residual analytes. Overall, this research project is intended to provide a compre-
hensive investigation into bacterial-QD interactions, which is needed to understand the impact and fates of
these nanoparticles in the environment.
110 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Transformations of Biologically Conjugated CdSe Quantum Dots
Released Into Water and Biofilm
Patricia A. Holden1 and Jay L. Nadeau2
Donald Bren School of Environmental Science and Management, University of California,
Santa Barbara, CA; McGill University, Montreal, Quebec, Canada
Environmental Implication/Application
Cadmium selenide (CdSe) quantum dots (QDs) are nanoscale semiconductors that have widespread appli-
cations in biotechnology and medicine. The broad applications of these particles in medical diagnostics and
other settings brings into question their impacts on nontarget organisms in the natural environment. This pro-
ject seeks to discover the fates of CdSe QDs under abiotic and biotic conditions characteristic of the natural
environment. CdSe QDs are altered by solution chemistry as well as sunlight. CdSe QDs damage DNA, but by
what mechanism? CdSe QDs are likely to affect bacteria in water and biofilms, which could have implications
for how these particles are transferred to higher life forms. Very little is known regarding the fates of CdSe
particles in the environment. This research project will seek to discover the physical and biological transfor-
mation of these particles and the effects, relative to dissolved Cd ions, on bacterial function. The results will be
important for strategically planning the handling and disposal of CdSe QDs and their overall management, so
that potential CdSe-mediated environmental degradation can be circumvented.
The Office of Research and Development's National Center for Environmental Research 111
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Repercussion of Carbon-Based Manufactured Nanoparticles
on Microbial Processes in Environmental Systems
Ronald F. Turco, Bruce M. Applegate, and Timothy Filley
Purdue University, West Lafayette, IN
Abstract
The use of nanotechnology has tremendous potential for economic growth and is a key feature of sus-
tainable development. Despite the impending increase in industrial production and the certain releases of
Carbon Based Manufactured Nanoparticles (CMNPs) to the environment, almost nothing is known about their
environmental impact. To engage in a publicly transparent evaluation of risks and benefits, and to develop
public policy and technology to manage potential risks, fundamental scientific environmental research must be
completed. The goal of this research project is to provide fundamental information about the impact of CMNPs
on water, soil, and subsurface ecosystems.
Objective 1: There will be a shift in the structure of soil microbial populations in systems exposed to
CMNPs as the nanomaterial will exert pressure on the microbial population. The intrinsic features describing
activity will be estimated in four ways, including: (1) drawing information from the ratio of key fatty acids
taken from the phospholipid fatty acids fraction (PLFA) and relating it to a background status of the soil
microbial populations; (2) using genetic approaches, for example, density gradient gel electrophoresis (DGGE)
with both bacterial and fungal primers; (3) using enzyme assays for dehydrogenase, urease, and cellubiase; and
(4) respirating and trapping C02 to estimate aerobic activity in the presence of CMNPs.
Objective 2: The long-term fate of CMNPs in the environment and their entrance into soil and aquatic
biogeochemical cycles mostly will be a function of the activity of the specific oxygenase, ligninase, laccase,
and fenton systems resident in microbial populations. Using 13C-fullerenes in soil microcosm studies outlined
in Hypothesis 1, CMNP carbon will be tracked to determine how the soil microbial biomass responds to
CMNPs. The degree to which CMNP carbon is assimilated into microbial biomass, or is converted to a form
bound with soil carbon, also will be assessed. Additionally, various litter forms (wood and leaves) spiked with
13C-labeled fullerene with aggressive decay fungi will be inoculated to assess the degree to which CMNP
carbon is assimilated into fungal biomass or converted to functionalized forms (free and bound).
Objective 3: Water-borne CMNPs represent an, as yet, unassessed toxicological risk to aquatic organisms
because of their capacity to physically interact with cell membranes, possibly causing harm to the cells. A lux-
gfp based assay will be used to estimate the impact of CMNPs on the processes of respiration and growth,
allowing development of the first CMNP structure-to-microbial function model. This objective will involve
monitoring bacterial bioluminescence to evaluate the impact of CMNPs (amount or structure) on bacterial
response in aqueous systems.
The expected results of this research project are very substantial. The knowledge gained from this research
will be used by government and industry for developing public policy and technology for the management of
any environmental risks from CMNPs. This research also can be integrated with educational programs and
used to disseminate knowledge about the behavior of nanomaterials.
112 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Repercussion of Carbon-Based Manufactured Nanoparticles
on Microbial Processes in Environmental Systems
Ronald F. Turco, Bruce M. Applegate, and Timothy Filley
Purdue University, West Lafayette, IN
Environmental Implication/Application
This research project will provide the scientific community with a method for assessing the toxicity of
carbon-based manufactured nanoparticles. This project will result in fundamental information regarding the
impact on soil, water, and subsurface ecosystems. In addition, this project will study the shift in the structure of
microbial populations in systems exposed to these materials, and the resulting effect(s) mostly will be a func-
tion of the activity of specific enzyme systems within the microbial systems.
The Office of Research and Development's National Center for Environmental Research 113
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
The Fate, Transport, Transformation, and Toxicity of Manufactured
Nanomaterials in Drinking Water
Yongsheng Chen, Paul Westerhoff, John Crittenden, and David Capco
Department of Civil and Environmental Engineering and Department of Biology,
Arizona State University, Tempe, AZ
Abstract
Although the current market for nanomaterials is small and their concentration may not be high enough in
the environment to cause human health or environmental problems, this market is increasing rapidly and the
discharge of nanomaterials to the environment in the near future could be significant as manufacturing costs
decrease and new applications are discovered. The accumulation of nanomaterials in cells may have significant
environmental and human impacts. However, at present, very little is known about the fate, transport, trans-
formation, and toxicity of these man-made nanomaterials in the environment.
The objectives of this project are to: (1) characterize the fundamental properties of nanomaterials in aqua-
tic environments, (2) examine the interactions between nanomaterials and toxic organic pollutants and patho-
gens (viruses), (3) evaluate the removal efficiency of nanomaterials by drinking water unit processes, and
(4) test the toxicity of nanomaterials in drinking water using a cell culture model system of the epithelium.
This study considers the physical, chemical, and biological implications of nanomaterial fate and toxicity in
systems that will provide insight into the potential for nanomaterials to be present and of health concern in
finished drinking water.
The proposed work will provide fundamental information about the fate, transport, and transformation of
nanomaterials in the drinking water resources and the first evidence that such nanomaterials can or cannot be
removed by conventional drinking water treatment processes. An improved assessment will be developed for
the potential exposure risks of nanomaterials in drinking water. This research would ultimately provide essen-
tial information that would support policy and decision-making regarding handling, disposal, and management
of nanoscale materials in commerce, manufacturing, and the environment.
114 The Office of Research and Development's National Center for Environmental Research
-------
Section 7. Toxicology
As nanotechnology progresses from research and development to commercialization and use, it is likely that
manufactured nanomaterials and nanoproducts will be released into the environment. EPA is charged with
protecting human health and the environment, as well as ensuring that the application of engineered nano-
technology products occur without unreasonable harm to human health or the environment. The unique
features of manufactured nanomaterials and a lack of experience with these materials hinder the risk evaluation
that is needed to inform decisions about pollution prevention, environmental clean-up and other control
measures, including regulation. Beyond the usual concerns for most toxic materials, such as physical and
chemical properties, uptake, distribution, absorption, and interactions with organs, the immune system and the
environment, the adequacy of current toxicity tests for chemicals needs to be assessed to develop an effective
approach for evaluating the toxicity of nanomaterials. To the extent that nanoparticles are redox active or elicit
novel biological responses, these concerns need to be accounted for in toxicity testing to provide relevant
information needed for risk assessment to inform decision making.
-------
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Short-Term Chronic Toxicity of Photocatalytic Nanoparticles
to Bacteria, Algae, and Zooplankton
Chin Pao Huang and Donald C. Phillips
Department of Civil and Environmental Engineering, University of Delaware, Newark, DE
Abstract
The unique physical and chemical properties of photocatalysts can stress the aquatic environment. This re-
search project will evaluate the short-term chronic toxicity of photocatalytic nanoparticles to bacteria, algae,
and daphnia. Properties such as particle size, location and level of the band gap energy, surface charge, and
chemical composition are keys to the ecotoxicity of photocatalytic nanoparticles. Generally, as the particle size
decreases, the toxicity of the photocatalysts increases and the band gap energy may shift toward the visible end
of the light spectrum, making smaller photocatalysts more sensitive to visible light. Photocatalysts can exhibit
oxidation or reduction reactions or both. Photooxidation and photoreduction can have significant impacts on
microorganisms. Nanoparticles in the aqueous environment also can acquire surface charges, which can affect
specific chemical interactions between the nanoparticles and the microorganisms of interest.
This research project will assess the short-term chronic toxicity of photocatalytic nanoparticles to selected
aquatic microorganisms. Nanoparticles possessing photocatalytic or semiconducting properties, including in-
frared (IR) sensitive CdSe and MoS2, visible light sensitive GaP, CdS, and ultraviolet (UV) light sensitive
Ti02, ZnO, and Sn02 will be studied. Testing organisms will cover three trophic levels: bacteria, algae, and
primary consumers (e.g., zooplankton). Escherichia coli and a mixed commercial bacterial culture, Sele-
nastrum capricornutum (green algae) and Ceriodaphnia bubia (daphnia), will be selected as the testing
organisms. The specific objectives are to determine: (1) the acute toxicity of photocatalytic nanoparticles to a
mixed bacterial culture; (2) the short-term chronic toxicity of photocatalytic nanoparticles to a pure bacterial
culture of E. coli; (3) the short-term chronic toxicity of photocatalytic nanoparticles to C. dubia; (4) the short-
term chronic toxicity of photocatalytic nanoparticles to S. capricornutum', (5) the short-term chronic toxicity of
copper(II) to S. capricornutum in the presence of photocatalytic nanoparticles; (6) the short-term chronic toxi-
city of chlorinated phenols to E. coli and C. dubia in the presence of photocatalytic nanoparticles; and (7) the
short-term toxicity of photocatalytic nanoparticles to freshwater algal assemblages.
As a result of the proposed study, it is expected that systematic information on the short-term chronic toxi-
city of photocatalytic nanoparticles to bacteria, algae, and daphnia, which covers three successive trophic
levels in the ecosystem, will be established.
The Office of Research and Development's National Center for Environmental Research 117
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Short-Term Chronic Toxicity of Photocatalytic Nanoparticles
to Bacteria, Algae, and Zooplankton
Chin Pao Huang
Department of Civil and Environmental Engineering, University of Delaware, Newark, DE
Environmental Implication/Application
This research project addresses four major nano-ecotoxicity issues: (1) the general ecotoxicity of nano-
particles, (2) the additional effect of photocatalysis of nanoparticles to aquatic organisms; (3) the ecotoxicity of
organisms of three subsequent trophic levels; and (4) the response of the natural algal community to nano-
particles. Information obtained from this project will serve a wider purpose to both the regulatory and the
scientific communities. Specifically, the information to be obtained in this research including the EC50, IC25,
and IC50 values of various nanophotocatalysts for bacteria (e.g., Escherichia coli), green algae (e.g., Sele-
nastrum capricornutum), and daphnia (e.g., Ceriodaphnia dubia) will be useful for assessing the general eco-
toxicity of nanophotoctalysts. Because these three test organisms represent three successive trophic levels, the
toxicity effect displayed by these selected organisms can be extrapolated readily to species of higher orders in
trophic scale. Based on the feeding capacity and behavior of each organism and the information obtained in
this research such as EC50 and IC50, it is possible to estimate with first approximation the tolerable amount of
uptake of the corresponding nanoparticles by organisms of higher order in the trophic structure. The muta-
genicity of photocatalysts to aquatic bacteria, exemplified by E. coli and to be assessed with direct DNA se-
quencing technique, will shed much light on the ecotoxicity of nanophotocatalysts at the molecular-biological
level. The synergistic and antagonistic effects of photocatalytic nanoparticles, examined by copper toxicity to
green algae and chlorinated phenols toxicity to daphnia, will greatly aid in a better understanding of the inter-
species toxicity mechanisms. The response of the natural algal community to nanoparticles also will be assess-
ed. Algal community is among the most sensitive to environmental contaminants. Overall, information obtain-
ed from this project will prove to be most useful to the design of toxicity mitigation strategy for photocatalytic
nanoparticles in aquatic systems.
118 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Evaluation of Nanoparticles Interactions With Skin
Nancy Ann Monteiro-Riviere
Center for Chemical Toxicology Research and Pharmacokinetics, Department of Clinical Sciences,
College of Veterinary Medicine, North Carolina State University, Raleigh NC
Abstract
This research project proposes to address whether manufactured nanoparticles can gain access to the
epidermis after topical exposure, the first step in a toxicological reaction. Exposure to metallic nanoparticles,
whose physical properties would allow them to catalyze a number of biomolecular interactions, potentially
could produce adverse toxicological effects. The difference between nanoparticles and "traditional" hazardous
chemical exposure is that decontamination of nanoparticles would be significantly more difficult than chemi-
cals, as solubilization or dilution, the two hallmarks of post-exposure decontamination, might be less effi-
cacious for these solid structures.
The focus of this research project is to assess the nature of interaction between manufactured nanoparticles
and the skin; including dermal absorption, cutaneous toxicity, as well as the ability to distribute to the skin
after systemic exposure. The skin is a primary route of potential exposure to toxicants, including novel nano-
particles. However, there is no information on whether particles are absorbed across the stratum corneum bar-
rier or whether systemically administered particles can accumulate in dermal tissue. Our laboratory has
developed a well-validated humane alternative animal model that is predictive of in vivo human dermal
absorption, which is ideally suited to assess both the dermal absorption of nanoparticles as well as their
potential accumulation in skin after systemic exposure. These studies will utilize iron oxide nanocrystals, cad-
mium selenide nanocrystals, and carbon fullerene nanoparticles, which are representative of the broad spec-
trum of nanoparticles presently being used by industry. Eight particle types selected from these commercially
relevant manufactured nanoparticles will be studied to allow assessment of size, shape, and composition on
absorption, distribution, or toxicity to the skin. These data would provide a preliminary but relevant assessment
of both systemic exposure after topical administration as well as cutaneous hazard after both topical or sys-
temic exposure, the two essential components of any risk assessment. If carbon nanoparticles are accidentally
modified or if exposure occurs before cleansing, they could have untoward consequences if they gain entry to
tissues.
All studies will be conducted in three well-characterized in vitro skin models: human skin keratinocyte
cell cultures, porcine skin flow-through diffusion cells, and the isolated perfused porcine skin flap (IPPSF).
Nanoparticles will be applied topically in three exposure scenarios (neat, water, mineral oil) at two doses to
assess potential dermal absorption in the diffusion cell studies and to assess cellular toxicity (light and electron
microscopy, viability) and irritation (IL-8 release) in cell culture. Those particles that penetrate skin or cause
direct irritation will be completely characterized in IPPSF studies, which have previously been shown to be
predictive of in vivo absorption in humans. Similarly, to model nanoparticle uptake into skin after systemic
exposure, nanoparticles will be infused into the arterial blood supply of the IPPSF to assess the ability to
distribute out of the vasculature into the skin. Deposition of particles in epidermal tissue after both infusion
and topical exposure will be evaluated using high-resolution electron microscopy.
Presently, there are minimal data available on the interaction between manufactured nanoparticles and
biological tissues. The basic requirement for any risk assessment includes information on hazard (e.g., toxicity)
and exposure (e.g., absorption). This research project focuses on the health effects of nanoparticle interactions
with the skin. This integrated research program will generate data on the ability of nanoparticles to be toxic to
keratinocytes as well as assess the ability of nanoparticles to either be absorbed into skin after topical expo-
sure, or distribute into skin as would occur after systemic exposure by an alternate route of administration. At
the conclusion of the research, the boundaries of a dermal risk assessment for manufactured nanoparticle
exposure will be available.
The Office of Research and Development's National Center for Environmental Research 119
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Evaluation of Nanoparticles Interactions With Skin
Nancy Ann Monteiro-Riviere
Center for Chemical Toxicology Research and Pharmacokinetics, Department of Clinical Sciences,
College of Veterinary Medicine, North Carolina State University, Raleigh NC
Environmental Implication/Application
There is a serious lack of information about the human health and environmental implications of manu-
factured nanomaterials. The purpose of this research is to address this deficiency in the area of skin absorp-
tion and toxicity to set bounds for future risk assessments. It is anticipated that this research will generate data
in three specific areas relative to assessing the potential health effects of manufactured nanomaterials to
humans: (1) Are nanoparticles absorbed across the skin? (2) Are nanoparticles irritating to cultured human
keratinocytes? (3) Can nanoparticles distribute into skin after systemic administration?
There has not been any systematic investigation into the factors that determine whether these phenomenon
can occur. Should minimal absorption or toxicity be detected, then this finding can be interpreted based on our
previous data with other chemicals. The results should provide insight into the nature of the potential hazard to
nanoparticles and provide an initial estimate of dermal exposure parameters that can be used to design more
definitive studies. For example, information would be available on what is an appropriate vehicle and what is a
"high" dose?
120 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Physical and Chemical Determinants
of Nanofiber/Nanotube Toxicity
Robert H. Hurt
Division of Engineering, Brown University, Providence, RI
Abstract
Tubular and fibrous materials play a very special role in emerging nanotechnologies, but may show
asbestos-like toxicity in humans upon inhalation. For asbestos fibers, it is known that both surface-reactive
transition metals and fibrous geometry are major determinants of toxicity. Most commercial nanotubes/fibers
are complex materials containing transition metal catalysts or residues and exhibiting complex distributions of
length and diameter, as well as variability in defect density and surface functional groups.
The objective the proposed project is to conduct a carefully designed parametric study of the physical and
chemical factors that underlie nanofiber/tube toxicity, in which shape, size, purity, and redox activity are care-
fully isolated by special synthesis techniques developed at Brown University.
This project uses model carbon nanofibers and nanotubes synthesized by non-catalytic templating routes
from high-purity liquid-phase precursors. This approach allows explicit control of size and shape, and the as-
produced materials are essentially free of transition metal impurities. Subsequent metal doping of these pure
nanocarbons is then carried out to assess directly the effects of redox-active metals. A panel of fibrous and
tubular nanocarbons have been synthesized, post-processed, and characterized, and the following toxicologic
endpoints are being determined over a range of doses: (1) phagocytosis; (2) cell toxicity; (3) induction of
proinflammatory gene expression; and (4) genotoxicity. These short-term toxicologic assays will establish the
toxicity of these nanomaterials relative to carcinogenic asbestos fibers and nontoxic titanium dioxide nano-
particles. The work is being extended to commercial carbon nanotube samples, where metal residues can be
partially or wholly encapsulated by carbon and the bioavailability of nanophase metals as a function of mate-
rial processing and oxidation becomes a key issue.
We hypothesize that reactive transition metal catalyst residues are important determinants of carbon
nanofiber/tube toxicity. On the basis of the preliminary data, we predict that nanomaterials doped with tran-
sition metals will be more toxic than pure carbon nanomaterials. This mechanistic study will provide guidance
for the manufacturing of nanomaterials with minimal human health impact (e.g., through catalyst selection,
purification, and control of mechanical damage that gives access to encapsulated metals), while maintaining
desirable material properties and functions.
The Office of Research and Development's National Center for Environmental Research 121
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Physical and Chemical Determinants
of Nanofiber/Nanotube Toxicity
Robert H. Hurt and Agnes B. Kane
Division of Engineering, Brown University, Providence, RI
Environmental Implication/Application
This research project will characterize and document the potential health effects associated with exposure
to carbon nanotubes and nanofibers. These materials are among the most promising new products of the U.S.
nanotechnology initiative, but a better understanding of their potential toxicity is needed before widespread
commercialization can occur.
Manufactured batches of carbon nanotubes and nanofibers are complex materials that typically contain a
variety of carbon forms as well as inorganic catalyst residues that may be partially or wholly encapsulated by
carbon. Many catalyst compositions include reduced forms of iron, which are already known to play an impor-
tant role in the inhalation toxicity of asbestos.
The specific objective of this project is to understand the role of iron residues in the potential toxicity of
carbon nanotubes to macrophage cells. This mechanistic project will determine if and how iron nanoparticles
mediate toxicity, and will provide guidelines on the threshold allowable amounts of bioaccessible iron residue
in commercial nanomaterials. The data will help define nanotube fabrication and purification procedures that
ensure intrinsically safe products and thus protect nanotechnology workers, users, and the environment.
122 The Office of Research and Development's National Center for Environmental Research
-------
Section 8. Industrial Ecology
As new nanomaterials are discovered and dynamic patterns of commercial and environmental opportunity and
risk are observed, there is an important need for EPA to improve its ability to respond to these emerging
opportunities and risks as early as possible. Information is needed to engage in efforts to encourage the early
redesign of products and services and effectively prevent the impacts of these materials on human health and
the environment. A multidisciplinary and coordinated policy approach, including an analysis of product life
cycle impacts, along with a materials flow analysis, starting with the conversion of raw materials, manufacture,
use, and disposal, is necessary to encourage a culture of stewardship in relationship to the development and
application of emerging nanotechnologies and materials.
-------
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Societal Implications of Nanotechnology: Benefits and Costs
EarlR. Beaver
Institute for Sustainability, New York, NY; Practical Sustainability, LLC, Chesterfield, MO;
and BRIDGES to Sustainability, Houston, TX
Abstract
As each new technology emerges, there are implications that often are unforeseen. Surprises tend to be at
least 50 percent negative. Using tools such as "Total Benefit and Cost Assessment" provide mechanisms for
identifying and examining the surprises in advance. This presentation will report the work done by Practical
Sustainability, LLC, and BRIDGES to Sustainability™ to identify and prioritize the issues surrounding the
realm of nanotechnology. The excitement, in particular the interest by the U.S. federal government, provides
incentives for accelerating the growth of this field. Researchers actively involved in the field have no reason to
raise red flags and, yet, the earlier those flags are raised, the more thoroughly they can be explored. The odds
of problems can be reduced, the magnitude of problems can be reduced, and the benefits of new technology
can be maximized.
The Office of Research and Development's National Center for Environmental Research 125
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Societal Implications of Nanotechnology: Benefits and Costs
EarlR. Beaver
Institute for Sustainability, New York, NY; Practical Sustainability, LLC, Chesterfield, MO;
and BRIDGES to Sustainability, Houston, TX
Environmental Implication/Application
The benefits of this research project are to: (1) contribute to the U.S. Environmental Protection Agency's
goal of developing "theoretically consistent, empirically feasible, and policy relevant estimates of values for
changes in ecological benefits (the products, services, and amenities provided by ecosystems, including non-
use values) caused by environmental influences"; (2) identify candidate societal implications for developers to
utilize in considering positive and negative potential implications of nanotechnology; and (3) offer a method
for researchers to make product development decisions. One way to contribute to those goals is to develop
improved methodologies for assessing the environmental costs and benefits of alternative actions, because
cost-benefit analysis (Total Benefit and Cost Assessment) is so widely used as a framework for evaluating
policy choices, setting priorities, and allocating resources. Critics of new technologies, for example, argue that
regulatory agencies fail to address the most serious risks, and that identifying the costs and benefits of alter-
native actions will help steer them towards the initiatives that promise to accomplish the most good with the
resources expended. Total Benefit and Cost Assessment also is championed as a way to avoid policies such as
overly stringent regulations that impose major compliance costs but produce limited value and to ensure that
only worthwhile projects are undertaken. Because the costs and benefits of policy and regulatory choices vary
significantly, Total Benefit and Cost Assessment can help ensure that risks are regulated and desirable actions
encouraged in comparable, fair ways. The approach here is to follow the successful abbreviated valuation
methods developed within the past 4 years and applied to "harmless odors" and "eutrophication of waterways."
126 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
A Life-Cycle Assessment Approach for Evaluating
Future Nanotechnology Applications
Shannon M. Lloyd and Lester B. Lave
Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA
Abstract
By reducing the energy and materials required to provide goods and services, nanotechnology has the
potential to provide more appealing products while improving environmental performance and sustainability.
However, while nanotechnology offers great potential, it is unlikely to be the first entirely benign technology.
A technological push towards greater investment in nanotechnology without a commensurate consideration of
the net environmental benefits will likely lead to cases where the nanotechnology substitute is environmentally
inferior to the product or process replaced. Whether and how soon the promise of improved environmental
quality could be realized depends on phrasing life-cycle questions during research and development and pur-
suing commercialization intelligently.
A framework will be presented for a quantitative analysis of the life-cycle implications of projected
nanotechnology-based products. We use technology scenarios and prospective hybrid life-cycle assessment to
estimate the economic and environmental life-cycle implications of two projected nanotechnology-based
products. In the case of using nanocomposites in light-duty vehicle body panels, the ability to disperse nano-
scale particles in polymers would reduce vehicle weight thereby improving fuel economy. In the case of nano-
fabricated catalysts, the ability to position and stabilize platinum-group metal particles in automotive catalyst
would reduce the amount of platinum-group metal required to meet emissions standards, thereby reducing
mining and refining activities. For each application, a conventional product is compared to its nanotech-
nology-based substitute to assess whether the nanotechnology substitute can be cost effective and improve
environmental quality.
The Office of Research and Development's National Center for Environmental Research 127
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
A Life-Cycle Assessment Approach for Evaluating
Future Nanotechnology Applications
Shannon M. Lloyd and Lester B. Lave
Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA
Environmental Implication/Application
Evaluating the sustainability, and environmental and human health implications of consumer goods and
services requires analysis of material and energy usage, as well as environmental discharges associated with
each life-cycle stage. This life-cycle analysis goes from extraction of raw materials, to production, use, and
end-of-life. The importance of evaluating product performance over a product's entire life cycle can be illus-
trated by considering a possible nanotechnology application. Advances in nanotechnology are expected to of-
fer increased understanding of, and control over, catalyst design and performance. For example, bottom-up
assembly may be used to synthesize catalytically active sites by positioning atoms or molecules one-by-one,
thereby utilizing materials more efficiently. This precise positioning would result in less material use during
catalyst production and perhaps less energy use during catalyst use. However, because catalysts require large
numbers of active sites, efficient methods for positioning atoms or molecules will be needed to ensure that any
materials savings from production or energy savings during use are not offset by the energy required to syn-
thesize active sites one-by-one.
Life-cycle assessment is a systematic, analytical process for assessing the inputs and outputs associated
with each life-cycle stage of a product or process. Life-cycle assessment is typically used to estimate the re-
source and environmental implications associated with existing products. Changing a product to reduce its
environmental impact after the product has been developed can cost orders of magnitude more than making the
change during research and development. Our framework employs technology scenarios and prospective hy-
brid life-cycle assessment to estimate the economic and environmental life-cycle implications of projected
nanotechnology-based products. Conventional products are compared to nanotechnology-based substitutes to
assess whether the nanotechnology substitutes can be cost effective and improve environmental quality. By
employing this framework, policy makers and industry can identify technology scenarios and employ pro-
spective life-cycle assessment during early research and development to evaluate future nanotechnology-based
products and emerging nanotechnologies. The ability to evaluate life-cycle implications of alternative courses
of action during research and development improves the ability to evaluate tradeoffs, optimize products for all
aspects of life-cycle performance, and make more strategic R&D choices. A more informed understanding of
the commercial, societal, and technological possibilities and consequences will enable better decisions in re-
gard to the selection, development, and commercialization of nanotechnology.
128 The Office of Research and Development's National Center for Environmental Research
-------
Appendix
-------
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR)
Progress Review Workshop — Nanotechnology and the Environment II
Loews Philadelphia Hotel
1200 Market Street
Philadelphia, PA 19107
August 18 - 20, 2004
Agenda
Wednesday. August 18. 2004
9:30 - 10:00 a.m. Registration
Overview
10:00 - 10:15 a.m. Welcome - Stephen A. Lingle
Director, Environmental Engineering Research Division,
IS. EPA, ORD, NCER
10:15 - 10:40 a.m. Overview of Nanotechnology—Responsible Research
and Development of Nanotechnology
Mihail Roco, Chair, Nanoscale Science, Engineering and
Technology ^ISET)
EPA's Nanotechnology Program—Vision of How
Nanotechnology Can Be Used To Protect, Inform,
Manage, and Improve the Environment and How
Harm From Nanotechnology Can Be Studied
and Prevented
Barbara Karn, SEP A, ORD, NCER, Washington, DC
10:40-11:05 a.m.
Plenary Talks
11:05-11:35a.m.
Nanotechnology Applications for Environmental
Sensors: Rapid and Precise Monitoring; Lab-on-a-Chip
Devices; Real-Time Analyses; Remote, In Situ, and
Continuous Devices
Nongjian Tao, Arizona State diversity
11:35 a.m. - 12:05 p.m. Nanotechnology Applications for Treatment:
Cost-Effective and Rapid Technologies; Smart Materials
or Active Surface Coatings
131 Wilfred Chen, diversity of CaliforniaRiverside
The Office of Research and Development's National Center for Environmental Research 131
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
12:05 — 12:35 p.m. Nanotechnology Applications for Remediation: Cost-
Effective and Rapid Technologies; Removal of
Contaminants From Soil, Ground Water, and Aqueous
Environments
Gregory Wilson, The American Association for the
Advancement of Science
12:35-1:35 p.m.
3:35-4:00 p.m.
Lunch
1:35-2:05 p.m.
2:05-2:35 p.m.
Green Manufacturing
Barbara Karn, Chair
2:35-2:55 p.m.
2:55-3:15 p.m.
3:15-3:35 p.m.
Break
4:00-4:20 p.m.
4:20- 4:40 p.m.
4:40-5:00 p.m.
Nanotechnology Applications for Green Manufacturing:
Minimize Harmful Emissions and Generated Wastes;
Reuse; Recycle; Benign Chemical Processes;
Self-Assembly
Lawrence T. Drzal, Michigan State diversity
Nanotechnology Implications in the Environment and
Human Health: Life Cycle Assessment, Ecosystem
Health, Persistence, Toxicity, Fate and Transport,
Bioavailability, Bioaccumulation/Biotransformation
Nora Savage, BEPA, ORD, NCER, Washington, DC
Green Engineering of Dispersed Nanoparticles:
Measuring and Modeling Nanoparticle Forces
Kristen Fichthorn, The Pennsylvania State diversity
Sustainable Biodegradable Green Nanocomposites From
Bacterial Bioplastic for Automotive Applications
Lawrence T. Drzal, Michigan State diversity
Development of Nanocrystalline Zeolite Materials as
Environmental Catalysts: From Environmentally
Benign Synthesis to Emission Abatement
Sarah C. Larsen, diversity of Iowa
Plasmon-Sensitized TiO2 Nanoparticles as a Novel
Photocatalyst for Solar Applications
George Chumanov, Clemson diversity
Graft Polymerization as a Route To Control Nano-
filtration Membrane Surface Properties To Manage
Risk of EPA Candidate Contaminants and Reduce NOM
Fouling
Georges Belfort, Rensselaer Polytechnic Institute
Ecocomposites Reinforced With Cellulose
Nanoparticles: An Alternative to Existing Petroleum-
Based Polymer Composites
William T. Winter, The State diversity of New York
132
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
5:00-5:20 p.m. Break
6:00 p.m.
Aerosols
Maria Rodriguez, Chair
5:20-5:40 p.m.
5:40-6:00 p.m.
Adjourn
Elemental Composition of Freshly Nucleated Particles
Murray V. Johnston, diversity of Delaware
Ion-Induced Nucleation of Atmospheric Aerosols
Peter H. McMurry, diversity of Minnesota
Thursday. August 19. 2004
8:40 a.m. - 1:50 p.m. Sensors
Marti Otto, Chair
8:40-9:00 a.m.
9:00-9:20 a.m.
9:20-9:40 a.m.
9:40-10:00 a.m.
10:00-10:20 a.m.
10:20 -10:40 a.m. Break
10:40-11:00 a.m.
11:00-11:20a.m.
11:20-11:40 a.m.
Nanostructured Porous Silicon and Luminescent
Polysiloles as Chemical Sensors for Carcinogenic
Chromium (VI) and Arsenic (V)
William C. Trogler, diversity of CaliforniaSan Diego
Nanosensors for Detection of Aquatic Toxins
Robert E. Gawley, diversity of Arkansas
Micro-Integrated Sensing Systems by Controlled Self
Assembly of Nanoparticles
Somenath Mitra, New Jersey Institute of Technology
Advanced Nanosensors for Continuous Monitoring of
Heavy Metals
Omowunmi Sadik, State diversity of New
YorkBinghamton
Metal Biosensors: Development and Environmental
Testing
Anne J. Anderson, tali State diversity
Compound Specific Imprinted Microspheres for Optical
Sensing
Barry K. Lavine, Oklahoma State diversity
Ultrasensitive Pathogen Quantification in Drinking
Water Using Highly Piezoelectric PMN-PT
Microcantilevers
Wan Y. Shih, Drexel diversity
Nanomaterial-Based Microchip Assays for Continuous
Environmental Monitoring
Joseph Wang, New Mexico State diversity
The Office of Research and Development's National Center for Environmental Research 133
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
12:20- 1:30 p.m.
3:10-3:30 p.m.
11:40-12:00 noon
12:00-12:20 p.m.
Lunch
1:30-1:50 p.m.
Remediation
Philip Sayre, Chair
1:50-2:10 p.m.
2:10-2:30 p.m.
2:30-2:50 p.m.
2:50-3:10 p.m.
Break
3:30-3:50 p.m.
3:50-4:10 p.m.
Implications
Philip Sayre, Chair
4:10-4:30 p.m.
Low-Cost Organic Gas Sensors on Plastic for
Distributed Environmental Monitoring
Vivek Subramanian, Mvers ity of CaliforniaBerkeley
The Silicon Olfactory Bulb: A Neuromorphic Approach
to Molecular Sensing With Chemoreceptive Neuron
MOS Transistors (CvMOS)
Edwin C. Kan, Cornell diversity
A Nanocontact Sensor for Heavy Metal Ion Detection
Nongjian Tao, Arizona State Mversity
Membrane-Based Nanostructured Metals for Reductive
Degradation of Hazardous Organics at Room
Temperature
Dibakar Bhattacharyya, Mversity of Kentucky
Dendritic Nanoscale Chelating Agents: Synthesis,
Characterization, Molecular Modeling, and
Environmental Applications
Mamadou S. Diallo, California Institute of Technology
Synthesis, Characterization, and Manipulation of
(FeS-PAMAM) Dendrimer Nanocomposites
Lajos Balogh, Mversity of Michigan
Hollow and Nanoporous Iron Particles
Wei-Xian Zhang, Lehigh Mversity
Developing Functional Fe°-Based Nanoparticles for In
Situ Degradation ofDNAPL Chlorinated Organic
Solvents
Gregory V. Lowry, Carnegie Mellon Mversity
A Bioengineering Approach to Nanoparticle-Based
Environmental Remediation
Daniel R. Strongin, Temple Mversity
Societal Implications of Nanotechnology: Benefits and
Costs
Earl R. Beaver, Practical Sustainability, LLC
134
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
4:50 p.m.
4:30-4:50 p.m.
Adjourn
A Life-Cycle Analysis Approach for Evaluating Future
Nanotechnology Applications
Shannon Lloyd, Carnegie Mellon Mversity
Friday. August 20. 2004
10:00-10:30 a.m.
Treatment
Anita Street, Chair
8:40-9:00 a.m.
9:00-9:20 a.m.
9:20-9:40 a.m.
9:40-10:00 a.m.
Break
NOX Reduction With Transition Metal Carbide
Nan opar'tides
S. Ismat Shah, Mversity of Delaware
Simultaneous Environmental Monitoring and
Purification Through Smart Particles
Wolfgang M. Sigmund, Mversity of Florida
Nanoscale Biopolymers With Tunable Properties for
Improved Decontamination and Recycling of Heavy
Metals
Wilfred Chen, Mversity of CaliforniaRiverside
Use ofOzonation in Combination With Nanocrystalline
Ceramic Membranes for Controlling Disinfection
By-Products
Simon Davies, Michigan State Mversity
Fate, Transport, and Transformation
Kevin Dreher, Chair
10:30-10:40 a.m.
10:40-10:50 a.m.
10:50-11:00 a.m.
11:00-11:10 a.m.
Absorption and Release of Contaminants Onto
Engineered Nanoparticles
Mason Tomson, Rice Mversity
Impacts of Manufactured Nanomaterials on Human
Health and the Environment: A Focus on
Nanoparticulate Aerosol and Atmospherically
Processed Nanoparticulate Aeorosol
Vicki Grassian, Mversity of Iowa
Chemical and Biological Behavior of Carbon Nanotubes
in Estuarine Sedimentary Systems
P. Lee Ferguson, Mversity of South Carolina
Transformations of Biologically Conjugated CdSe
Quantum Dots Released Into Water and Biofilms
Patricia Holden, Mversity of CaliforniaSanta Barbara
The Office of Research and Development's National Center for Environmental Research 135
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
11:10 - 11:20 a.m. Repercussion of Carbon-Based Manufactured
Nanoparticles on Microbial Processes in Environmental
Systems
Ronald Turco, Purdue Mversity
11:20 — 11:30 a.m. The Fate, Transport, Transformation, and Toxicity of
Manufactured Nanomaterials in Drinking Water
Yongsheng Chen, Arizona State Mversity
Toxicology
Kevin Dreher, Chair
11:30 — 11:40 a.m. Short-Term Chronic Toxicity of Photocatalytic
Nanoparticles to Bacteria, Algae, and Zooplankton
Chin-Pao Huang, Mversity of Delaware
11:40 - 11:50 a.m. Evaluation of Nanoparticles Interactions With Skin
Nancy Monteiro-Reviere, North Carolina State Mversity
11:50 a.m. — 12:00 noon Physical and Chemical Determinants ofNanofiber/
Nanotube Toxicity
Robert Hurt, Brown Mversity
12:00-12:30 p.m. Closing Remarks
Barbara Karn and Nora Savage, BEPA, ORD, NCER,
Washington, DC
12:30 p.m. Adjourn
136 The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR)
Progress Review Workshop — Nanotechnology and the Environment II
Loews Philadelphia Hotel
1200 Market Street
Philadelphia, PA 19107
August 18 - 20, 2004
Participants List
Anne Anderson
tali Sta te University
Logan, UT
Larry Andrews
Rohm and Haas Company
Spring House, PA
Lajos Balogh
Mversi ty of Michigan
Ann Arbor, MI
Earl Beaver
Practical Sustainability, LLC
Chesterfield, MO
Georges Belfort
Rensselaer Polytechnic Institute
Troy, NY
Dibakar Bhattacharyya
University of Kentucky
Lexington, KY
Eli Casdin
Cooper Hill Partners
New York, NY
Thomas Chandler
University of South Carolina
Columbia, SC
Wilfred Chen
Mversi ty of CaliforniaR iverside
Riverside, CA
Yongsheng Chen
Arizona State Mversi
Tempe, AZ
ty
Shuk Han Cheng
City University of Hong Kong
Kowloon, Hong Kong
Huang Chihpin
National Chiao Tung M versity
Hsinchu, Taiwan
George Chumanov
Clemson Mv ersity
Clemson, SC
Simon Davies
Michigan State M versity
East Lansing, MI
Sudeep Debnath
Temple M versity
Philadelphia, PA
Mamadou Diallo
California Institute of Technology
Pasadena, CA
Kevin Dreher
IS. Environm ental Protection Agency
Research Triangle Park, NC
Lawrence Drzal
Michigan State M versity
East Lansing, MI
Ayca Erdem
Mversi ty of Delaware
Newark, DE
Lee Ferguson
University of South Carolina
Columbia, SC
The Office of Research and Development's National Center for Environmental Research
137
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Kristen Fichthorn
The Pennsylvania State M versity
Mversi ty Park, PA
Henry Fogle
Chester, VA
Robert Gawley
Mversi ty of Miami
Coral Gables, FL
Kevin Geiss
Air Force Research Laboratory
Wright-Patterson AFB, OH
Vicki Grassian
Mversi ty of Iowa
Iowa City, IA
Carolyn Green
National Advisory Council on Environmental
Policy and Technology
Philadelphia, PA
Sally Hamlin
IS. Environm ental Protection Agency
Washington, DC
Alan Hecht
IS. Environm ental Protection Agency
Washington, DC
Robert Hillger
IS. Environm ental Protection Agency
Boston, MA
Patricia Holden
Mversi ty of CaliforniaSa nta Barbara
Santa Barbara, CA
Hazel-Ann Hosein
Temple M versity
Philadelphia, PA
Chin Pao Huang
Mversi ty of Delaware
Newark, DE
Matthew Hull
Luna Innovations, Inc.
Blacksburg, VA
Robert Hurt
Brown University
Providence, RI
Sulay Jhaveri
American Association for the Advancement
of Science
Alexandria, VA
Murray Johnston
Mversi ty of Delaware
Newark, DE
Mark Joyce
IS. Environm ental Protection Agency
Washington, DC
Edwin Kan
Cornell 61 iversity
Ithaca, NY
Agnes Kane
Brown University
Providence, RI
Barbara Karn
IS. Environm ental Protection Agency
Washington, DC
Barbara Klieforth
IS. Environm ental Protection Agency
Washington, DC
Albert Koenig
The Nanotechnology Institute
Philadelphia, PA
Kuo-Liang Lai
IS. Environm ental Protection Agency
Philadelphia, PA
Ron Landy
IS. Environm ental Protection Agency
Fort Mead, MD
Sarah Larsen
Mversi ty of Iowa
Iowa City, IA
Barry Lavine
Oklahoma State M versity
Stillwater, OK
138
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Hong-Ying Lin
Mversi ty of Delaware
Newark, DE
Ming-Yu Lin
Mversi ty of Delaware
Newark, DE
Steve Lingle
IS. Environm ental Protection Agency
Washington, DC
Shannon Lloyd
Carnegie Mellon 6J iversity
Pittsburgh, PA
Gregory Lowry
Carnegie Mellon 61 iversity
Pittsburgh, PA
Rovshan Mahmudov
Mversi ty of Delaware
Newark, DE
Terry Mclntyre
Environment Canada
Gatineau, Canada
Peter McMurry
Mversi ty of Minnesota
Minneapolis, MN
Somenath Mitra
New Jersey Institute of Technology
Newark, NJ
Nancy Monteiro-Riviere
North Carolina State M versity
Raleigh, NC
Vladimir Murashov
Centers for Disease Control and Prevention
Washington, DC
Sean Murdock
NanoBusiness Alliance
Glencoe, IL
Madeleine Nawar
IS. Environm ental Protection Agency
Washington, DC
Raymond Oliver
Cenamps
Newcastle upon Tyne, United Kingdom
Laurie Osher
Mversi ty of Maine
Orono, ME
Martha Otto
IS. Environm ental Protection Agency
Washington, DC
Charlie Pennington
Luna Innovations
Blacksburg, VA
Pat Phibbs
BNA, Inc.
Washington, DC
Stephen Ritchie
Mversi ty of Alabama
Tuscaloosa, AL
Victor Robinson
Centers for Disease Control and Prevention
Morgantown, WV
Mihail Roco
National Science Foundation
Arlington, VA
Abiodun Sadik
Clear Channel TV
Binghamton, NY
Omowunmi Sadik
State University of New YorkB inghamton
Binghamton, NY
Nora Savage
IS. Environm ental Protection Agency
Washington, DC
Philip Sayre
IS. Environm ental Protection Agency
Washington, DC
S. IsmatShah
Mversi ty of Delaware
Newark, DE
The Office of Research and Development's National Center for Environmental Research
139
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Wan Shih
Drexel Mver sity
Philadelphia, PA
Wei-Heng Shih
Drexel Mver sity
Philadelphia, PA
Wolfgang Sigmund
Mversi ty of Florida
Gainesville, FL
Anita Street
IS. Environm ental Protection Agency
Washington, DC
Daniel Strongin
Temple M versity
Philadelphia, PA
Vivek Subramanian
Mversi ty of CaliforniaB erkeley
Berkeley, CA
Nongjian Tao
Arizona State Mversi
Tempe, AZ
ty
Thomas Theis
Mversi ty of Illinois-Chicago
Chicago, IL
Mason Tomson
Rice M versity
Houston, TX
William Trogler
University of CaliforniaSa n Diego
La Jolla, CA
Ronald Turco
Purdue University
West Lafayette, IN
Courtney Usher
Temple M versity
Philadelphia, PA
Dennis Utterback
IS. Environm ental Protection Agency
Washington, DC
Darrell Velegol
The Pennsylvania State M versity
Mversi ty Park, PA
Kevin Walkush
Nanobusiness Alliance
Glencoe, IL
Joseph Wang
New Mexico State Mversi ty
Las Cruces, NM
David Warheit
DuPont Haskell Laboratory
Newark, DE
Iddo Wernick
Center for Responsible Environmental Strategies
Passaic, NJ
Caitlin Wilson
IS. Environm ental Protection Agency
Washington, DC
Gregory Wilson
American Association for the Advancement
of Science
Arlington, VA
William Winter
The State 61 iversity of New York
Syracuse, NY
Brooke Yamakoshi
IS. Environm ental Protection Agency
Washington, DC
Wei-Xian Zhang
Lehigh University
Bethlehem, PA
140
The Office of Research and Development's National Center for Environmental Research
-------
U.S. EPA 2004 Nanotechnology Science To Achieve Results (STAR) Progress Review Workshop
Index of Speakers, Authors, and Co-Authors
Anderson, A.J., 7, 56, 58
Andreescu, D., 51, 54
Applegate, B.M., 112, 113
Bachas, L., 75
Balogh, L.P., 10, 77, 79
Beaver, E.R., 11,125, 126
Belfort, G., 9, 32, 33
Bhattacharyya, D., 10, 75, 76
Capco, D., 114
Chen, W., 3, 98, 99
Chen, Y., 14,114
Chumanov, G., 5, 29, 30
Crittenden, J., 114
Davies, S.H., 13, 100
Diallo,M, 10, 77, 78
Dreher, K., 13, 15
Drzal, L.T., 3, 5, 23, 25
Eisele, F., 41
Ferguson, P.L., 13, 107, 108
Fichthorn, K.,4, 21,22
Filley,!., 112, 113
Gawley, R.E., 7, 47, 48
Goddard, W.A., 77
Grassian, V.H., 13,105, 106
Holden, P.A., 14, 109, 111
Huang, C.P., 15, 117, 118
Hurt, R.H., 15, 121, 122
Iida,K.,41
Johnson, J.H., 77
Johnston, M, 6, 39, 40
Kan, E.C., 9, 67, 68
Kane,A.B., 122
Karn, B., 2, 4, 6, 15
Larsen, S., 5, 26, 27
Lave, L.B., 127, 128
Lavine, B.K., 8, 59, 60
Lingle, S.A., 1
Liu, Y., 83
Lloyd, S.M.,11,127, 128
Loi, A., 12
Lowry, G.V., 11,83, 86
Majetich, S.A., 83, 86
Matyjaszewski, K., 83, 86
Mazyck, D., 96
McLean, J.E., 56, 58
McMurry, P., 6, 41, 42
Meyer, D., 75
Miller, C.D., 56, 58
Minch, B.A., 67, 68
Misra, M., 23, 25
Mitra, S., 7, 49, 50
Mohanty, A.K., 23, 25
Monteiro-Riviere, N.A., 15, 119, 120
Nadeau,J.L., Ill
Oliver, R., 16
Otto, M., 6
Phillips, D.C., 117
Ritchie, S., 75
Roco, M., 1
Sadik, O.A., 7, 51, 54
Saleh,N., 83
Sarbu, T., 83
Savage, N., 4
Sayre, P.,9, 11
Shah, S.I., 12, 93, 95
Shi, X., 79
Shih, W-H., 61
Shih,W.Y., 8,61,62
Sholl,D.S., 83
Sigmund, W.M., 12, 96, 97
Sirk, K., 83
Street, A., 12
Strongin, D.R., 11,87,90
Subramanian, V., 8, 65, 66
Tao, N., 2, 9, 69, 71
Tilton, R.D., 83, 86
Tomson, M.B., 13, 103, 104
Trogler, W.C., 6, 45, 46
Turco,R.F., 14, 112, 113
Velegol, D., 22
Wanekaya, A.K., 51,54
Wang, J., 8, 51,54, 63, 64
Westerhoff, P., 114
Wilson, G, 3
Winter, W.T., 5, 34, 35
Wu, C.Y., 96
Wu, L., 75
Xu, J., 75
Zhang, W.-x., 10,82
The Office of Research and Development's National Center for Environmental Research
141
-------
-------
&
EPA
No,
of
(8101R)
DC
for
www.epa.gov
------- |