Example Research Projects for REU Fellows

Duke #1:  Nanoparticle Exposure, Transport and Transformation

Faculty Mentor: Mark Wiesner, Professor, Civil & Environmental Engineering, Duke

Nanoparticles have extremely high surface to volume ratios so processes that affect nanoparticle surface chemistry will affect their transport, biouptake, and reactivity. Our project researches how surface chemistry of nanoparticles affects their fate in the environment and how quickly these particles reach eco-receptors. This information is then used to populate a modeling framework for assessing the risks posed by nanomaterials to the environment based on likely exposures (concentrations and availability) and long-term persistence of nanomaterials. Key physical-chemical pathways such as aggregation, deposition, and dissolution are examined. Additional transformations to nanoparticles and their surfaces resulting from oxidation, reduction, and adsorption are studied. Students will be fully involved in the execution of research investigating a wide range of materials including metal nanoparticles, metal oxides, fullerenes, carbon nanotubes and composites of these and other materials. We will examine the relative affinity of these materials for various environmentally relevant solid phases as a basis for predicting where nanoparticles will likely reside in the environment, and how nanoparticle transformation may affect bio-uptake and availability. The role of aggregation and adsorption in altering nanoparticle reactivity, particularly as measured by the production of reactive oxygen species, will be quantified.

Duke #2: Quantitative Analysis of Carbon Nanomaterials in the Aquatic Environment

Faculty Mentor: P. Lee Ferguson, Associate Professor, Civil & Environmental Engineering, Duke

Assessment of the fate, transport, and effects of nanomaterials in environmental systems requires sensitive and selective analytical methods for determining the concentrations and physicochemical characteristics of these materials in complex mixtures. Such trace analytical methods are generally very challenging in the environment, as typical environmental analytical chemistry techniques (e.g. GC-MS, atomic spectroscopy, and HPLC) are often of limited utility for detection and quantitation of nanoparticles in complex mixtures, and method development activity has lagged behind laboratory fate & transport studies. The objective of work in the Ferguson laboratory is to utilize sensitive and selective spectroscopies (e.g. near-infrared fluorescence, NIRF) as well as inorganic mass spectrometry methods that can resolve single nanoparticles, in combination with high-resolution particle separation methods (e.g. asymmetric field flow fractionation and density gradient ultracentrifugation) to provide both quantitative and qualitative information about carbon-based nanoparticles (including carbon nanotubes) in estuarine sediment, water, and aquatic organisms. The REU undergraduate researchers participating in this project will learn fundamental analytical chemistry principles (e.g. calibration of instruments, quantitative analysis, evaluation of analytical data) and gain experience in trace quantitative method development for environmental samples.

Duke #3: Environmental Impacts of Nanomaterials in the Real World: Measuring the Fate, Transport and Impact of NPs in Wetland Ecosystems

Faculty Mentor:  Emily S. Bernhardt, Associate Professor, Department of Biology, Duke

Work in the Bernhardt lab primarily deals with understanding the cycling of carbon and nutrients in natural ecosystems. Through research in a variety of degraded ecosystems (agricultural fields and urban streams) the research group has recently grown interested in understanding how environmental contaminants affect the community composition and activity of the microbes and plants that drive many ecosystem processes (nutrient and carbon cycling). This laboratory is currently examining how manufactured nanomaterials alter the biomass, composition and activity of microbes and plants, and how the complexity of environmental media (pure culture, lab microcosms, or field conditions) alter these responses. Environmental conditions can dramatically alter particle behavior, fate, and transportation and thus a key interest is examination of mechanisms by which nanomaterial toxicity may change among various environmental media and under differing chemical conditions. Students will assist in efforts to explore the fate, transport and impact of nanomaterials through food webs and between ecosystem compartments. Students will gain experience with quantitative field sampling techniques, analytical chemistry and a suite of field and lab assays aimed at measuring organismal biomass and activity and the rates of microbially mediated ecosystem processes (e.g. nitrification, methanogenesis, denitrification).

Duke #4: Environmental Nanogeochemistry: Fate, Mobility and Bioavailability of Nanoscale Mercury and Other Metal Pollutants

Faculty Advisor:  Helen Hsu-Kim, Associate Professor, Civil & Environment Engineering, Duke

The Hsu-Kim research group studies chemical processes that govern the fate of contaminant metals in natural and engineered ecosystems. This research primarily focuses on mercury, a toxic metal that can bioaccumulate in the food chain, and thus, impose health risks to people who eat contaminated fish. The current project examines the ability of mercury and other metals to persist as sulfide particles, the most stable form of mercury in aquatic and sediment ecosystems. In particular, this research group is investigating interfacial surface reactions that enable mercury nanoparticles to persist naturally in polluted sediments. Research goals are to understand the implications of this process for controlling bioavailability of mercury to sediment microorganisms and, ultimately, to develop models that can predict ecosystem 'hotspots' that are vulnerable to mercury bioaccumulation. Students working on this research project will gain experience in conducting environmental biogeochemistry research in laboratory and the field setting.

Duke #5: Nanoparticle Ecotoxicology: Effects of Transformations and Environmental Conditions on Particle Toxicity in Fish

Faculty Mentor: Richard Di Giulio, Professor, Nicholas School of the Environment, Duke

Although limited experimentation has resulted in a basic understanding of the toxicity of a small number of nanomaterials to fish, very little research has been done under environmentally realistic conditions. Research in the DiGiulio laboratory is focused on understanding the mechanisms of nanoparticle toxicity and how the environment may alter this toxicity. Surface transformations may significantly increase or (more likely) decrease nanoparticle toxicity. Environmental conditions may also dramatically alter nanoparticle behavior, fate, and transport. Changes in particle behavior can subsequently affect bioavailability and toxicity. Students will investigate patterns and mechanisms of nanoparticle toxicity in standard fish models (e.g. zebrafish and killifish). The research will involve standard toxicity tests and more advanced genetic techniques. Also, interactions among nanomaterials and other environmental contaminants such as hydrocarbons will be investigated. By investigating how various conditions and transformations affect nanoparticle toxicity, students will gain a better understanding of potential environmental and human health risks.

Duke #6: Nanoparticle Toxicity in Caenorhabditis elegans

Faculty Mentor: Joel Meyer, Associate Professor, Nicholas School of the Environment, Duke

The nematode worm Caenorhabditis elegans is a versatile model organism for research, as it is characterized by a well-annotated genome, powerful genetic and molecular tools, and straightforward laboratory culturing. Although traditionally used for genetics and developmental biology, the Meyer lab is using this small nematode to test the toxicity of a range of nanoparticles. The research objective is to examine uptake and toxicity (measured as growth inhibition, reproduction, lethality, DNA damage, oxidative damage, and other responses) in wild-type as well as a variety of stress-sensitive and transgenic strains of C. elegans. Students working on this project will gain experience in understanding mechanisms of impacts of nanoparticles on C. elegans, basic principles of toxicology, C. elegans biology, and lab skills including microscopy, autoclaving, preparation of media and solutions, maintenance and culture of C. elegans, basic toxicological procedures, and basic genetics and molecular biology skills (or more advanced methods if students arrive with basic skills in hand). We have recently found that silver nanoparticles cause mitochondrial toxicity, and this REU experience may have the opportunity to further explore mitochondrial outcomes.

Duke #7: Toxicity Studies of Nanomaterials in Water: Using Small Aquarium Model Fish to Detect Uptake, Distribution and Response

Faculty Mentor: David E. Hinton, Professor, Nicholas School of the Environment, Duke

Embryos and eleutheroembryos (free swimming forms with yolk sac attached) are sensitive life stages of fish. Using the aquarium model fish, medaka (Oryzias latipes) the Hinton lab images uptake, tissue distribution, and response of host cells and tissues to nanomaterials. The research group coordinates with other teams to make sure that exposures to real world nanomaterials are adequately evaluated for potential unwanted effects. If students are interested in visualizing toxic reactions of these model fish, they will learn cutting-edge approaches to evaluate toxicity that include: in vivo morphological assessments, high resolution microscopy, Cytoviva hyperspectral imaging, gene expression, histology, selective electron microscopy and immuno-histochemical lab techniques. The results of these assays can be used to understand structural and functional alterations in a dynamic lab setting and provide exposure to biomedical type research approaches in environmentally relevant life forms.

Duke #8: Phytotoxicity of Carbonaceous Nanomaterials: How Structure Affects Physical and Chemical Properties

Faculty Mentor: Jie Liu, Professor, Department of Chemistry, Duke

The fate and transport of nanomaterials after release into the environment is a complex process. The majority of released nanomaterials will be accumulated in soil where they can directly affect the growth of plants. Recently, many new carbonaceous nanomaterials have been synthesized including C dots, C onions, and nanodiamonds. While they are similar in size they have different physical properties. Understanding how these nanomaterials cause toxicity in plants will provide important information on how physical and chemical properties relate to toxicity when the base nanomaterial is the same. This will allow researchers to better understand what properties cause phytotoxicity and allow them to synthesize nanomaterials with a a smaller environmental impact. The students involved in this project will synthesize complex nanostructures composed of carbon and subsequently characterize them using surface analytical and microscopy instrumentation. They will learn how to perform complex nanomaterial syntheses and nanomaterial metrology, and insight into how physical and chemical properties relate to nanomaterial toxicity.

Duke #9: Nanomaterial Exposure Assessment: Trends in Nanomaterial Production Life Cycle Use, Disposal and Recovery

Faculty Mentor:  Mark Wiesner, Professor, Civil & Environmental Engineering, Duke

Our risk assessment work addresses both hazard and exposure, with an accent on exposure assessment. We consider exposure at consecutive stages in the value chain of nanomaterial production and incorporation into products, and the potential “leakage” from each stage. This bottom-up additive approach to estimating exposure based on separate releases requires considerable amounts of (currently unavailable) information concerning practices over a wide range of activities. As an alternative, we are developing upper bound “inventories” of nanomaterials production for key materials and predictions of nanomaterial production based on indices of commercialization/innovation that we published for the case of nano TiO2. Based on an estimated “reservoir” of nanomaterial production, first-order estimates can be obtained that employ easily understood transparent assumptions regarding the quantities of nanomaterials entering the environment across the value chain. In addition, a key question we are examining concerns potential for “collateral damage” i.e. environmental impacts that arise from nanomaterial production processes, as opposed to those from nanomaterials themselves. Students working on this project will work in an interdisciplinary context between basic sciences, business, and policy as they examine methods for forecasting nanomaterial production and use. They will learn elements of risk assessment under uncertainty and become familiar with trends in nanomaterial fabrication, use, disposal, and reuse.

Duke #10: Membrane fabrication for water treatment and desalination using nanomaterial composites and the release of nanomaterials from these composites

Faculty Mentor: Mark Wiesner, Professor, Civil & Environmental Engineering, Duke.

Membrane separations, including ultrafiltration membranes (UF), reverse osmosis membranes (RO), forward osmosis (FO), and membrane distillation (MD) can provide highly scalable technologies for water and wastewater treatment to meet the world’s increasing water demands. Existing membrane systems are currently limited by the properties of the polymeric/ceramic membranes used, which readily foul or require large pressure drops thereby increasing energy and operating costs (references). As a result, one of the grand challenges of membrane science is to enhance or maintain water flux without sacrificing salt rejection over a long period in order to increase efficiency and reduce the cost of operation. There are several approaches to overcoming this challenge. First is to design thin, strong membranes to decrease the diffusion path length across the membrane. This will reduce the necessary operating pressures and decrease the energy requirements for the system. The second is to modify membrane surfaces to make them resistant to biofouling. Nanotechnology can provide strong membranes that are both thin and resistant to biofouling. Polymer nanocomposites (PNCs) are polymers with NMs incorporated into their structures to enhance their performance (e.g., mechanical strength, thermal conductance, or electrical conductivity). PNCs such as NM-amended thermoplastics, adhesives, and membranes for water filtration, flat panel displays, membranes for fuel cells, food packaging, plastic water bottles, electrostatic dissipative plastics, and a host of ‘smart materials’ that utilize multiple Biological exposure to NMs occurs if the incorporated NMs are released from the PNC during their use or at the end of life. NM release rates will be a function of the environmental parameters to which they are subject, including physical abrasion, UV exposure, chemical insult (e.g., high/low pH or reduction/oxidation), and thermal extremes. However, studies of NP release from PNCs are extremely limited in number and fragmentary. The current lack of fundamental parametric studies prohibits forecasting NP releases and subsequently mitigating unacceptable discharges through tailored chemistries to minimize release. This project considers on one hand the potential release of nanomaterials from PNCs. We also seek to fabricate novel nanomaterial composites as the basis for membranes showing improved water flux, reduced biofouling and lower energy consumption. These will include membranes for conventional pressure driven membrane processes as well as membrane distillation and forward osmosis- two emerging membrane processes for desalination.

CMU #1: Microbial Interactions with Nanoparticles

Faculty Mentor: Kelvin B. Gregory, Associate Professor of Civil & Environmental Engineering, Carnegie Mellon

Bacteria have the ability to interact with and transform particles in a way that alters their fate, transport, and toxicity in the environment. Professor Gregory’s research group studies the interactions between bacteria and nanoparticles at the ecological, cellular, and subcellular level. Work on this project will involve laboratory experiments with common, non-pathogenic, soil bacteria. Student(s) will use biological reactors and various analytical biology and chemistry techniques to determine the impact of nanomaterials on microorganisms. Student(s) will gain novel insights into the ecology and biology of nanoparticle fate and transport as well as exposure to cutting-edge environmental science and engineering research techniques.

CMU #2: Environmental Nanobiogeochemistry: Influence of soil and water biogeochemistry on the transformation rate of Zn- and Cu-based agriculturally relevant nanomaterials

Faculty Mentor: Greg Lowry, Professor, Civil & Environmental Engineering, Carnegie Mellon

This research project will investigate the role of pH, organic matter, and water saturation on the dissolution and transformation of Zn- and Cu-based nanoscale fungicides, pesticides, and micronutrients in standard soils and in water from a freshwater wetland mesocosm. The fundamental knowledge gained in these studies will be used to create appropriate conceptual and numerical models for nanomaterial fate under various environmental conditions, and to develop functional assays/test guidelines for CEINT/OECD. The student will conduct laboratory research investigating the effect of soil and solution conditions (e.g. pH, redox potential, ionic strength, and ionic composition) on the dissolution rate and transformation of Cu, CuO, and ZnO nanoparticles. Participating students will learn physicochemical characterization techniques for nanomaterials in water (such as ICP-MS for metals analysis, dynamic light scattering for particle sizing and aggregation state), as well as develop simple tests (functional assays) to measure the transformation rate of these nanomaterials in soil and water.

CMU #3: Physicochemistry of Nanomaterials: Effect of Adsorbed Natural Organic Matter on Nanoparticle Interactions with Mineral and Biological Surfaces in the Environment

Faculty Mentor: Robert Tilton, Professor, Chemical Engineering, Carnegie Mellon

Natural organic matter (NOM), especially humic substances, polysaccharides and proteins adsorb readily to nearly any nanoparticle, such that the fate of virtually any nanomaterial that enters the environment will be strongly influenced by the properties of the adsorbed layers that form on their surfaces. Of particular importance are the effects of adsorbed NOM layers on nanoparticle aggregation and adhesion to mineral surfaces, biological matrices associated with biofilms or plant roots, air/water interfaces and oil/water interfaces that can be associated with complex contaminant mixtures. Nanoparticle aggregation and adhesion limit their transport and must be understood in order to predict how far nanoparticles are likely to migrate in environmental systems. Students working in the Tilton laboratory will perform adsorption and adhesion experiments with carbon and metal oxide nanoparticles, various organic macromolecules, oxide mineral surfaces, biofilms and mucilage matrices. Students will learn fundamental colloid and interface science principles and their manifestations in environmental materials systems and become practiced in one or more experimental tools including UV-VIS spectrophotometry, fluorescence spectroscopy, dark field and fluorescence microscopy and image analysis, ellipsometry, quartz crystal microbalance with dissipation, total organic carbon analysis, contact angle goniometry, interfacial tensiometry, and static, dynamic light or electrophoretic light scattering.

VT #1: Nanoparticle Stability in the Presence of Filter Feeding Clams

Faculty Mentor: Peter Vikesland, Professor, Civil & Environmental Engineering, Virginia Tech

The Vikesland research group examines the interfacial chemistry of environmental surfaces, with a current theme of improving the understanding of how nanoparticle surface chemistry affects their uptake by the common filter feeding clam Corbicula fluminea. The overall goal of the research is to gain fundamental insights into nanoparticle stability by altering the identity of nanoparticles in terms of size, shape, surface functionality, and surrounding solution chemistry. Work on this project will involve small and large scale experiments to examine how these parameters affect nanoparticle uptake rates. Upon completion of this internship, the student(s) will have gain an appreciation of how environmental chemistry affects nanoparticle interactions with aquatic organisms. Specific skills learned include: nanoparticle synthesis, field collection of aquatic organisms, assay design, and nanoparticle characterization strategies.

CEREGE #1: Aging of Nano-enabled Products Across a Salinity Gradient

Faculty Mentor:  Melanie Auffan, Junior Scientist, InterfasT Group, the CEREGE, Aix-en-Provence, France

In most industrial applications, pristine nanoparticles are surface-modified and embedded into final products. Therefore it is unlikely that aquatic organisms will be in direct contact with these nanoparticles in their unmodified form. So, in parallel with studies concerning the impacts of pristine nanoparticles, there is an urgent need to assess the environmental fate of more environmentally relevant materials such as degradation byproducts released from currently commercialized nano-products; no data exist on this important question as of yet. For this assessment, several nano-enabled products will be selected based on relevance criteria (textiles, paint, etc. containing nano-Ag, nano-CeO2). Nano-CeO2 and nano-Ag are increasingly integrated into household and consumer products. Subsequent weathering/leaching is anticipated to occur with time, resulting in some degree of environmental discharge. For each nano-enabled product, we will implement accelerated aging protocols that reproduce conditions of use or degradation as realistically as possible in order to reflect environmental conditions encountered by the products across their value chains. Then the physico-chemical behavior of the nano-enabled products will be studied across a salinity gradient mimicking the marine-continental interface. The recovered residues of these aged materials will then be thoroughly characterized to understand their fate and impacts. The surface properties (e.g. surface functionalization, chemical stability, crystalline structure) will be analyzed using a set of physico-chemical characterization techniques (DLS, TEM, SEM, 2D and 3D x-ray-based imaging, XRD, FTIR, ICP MS, ICP, AES).

CEREGE #2: Imogolite:  A Natural Analogue of Carbonaceous Nanoparticles Dispersed in Ecosystems

Faculty Mentor: Jerome Rose, Director, InterfasT Group, the CEREGE, Aix-en-Provence, France

There are naturally occurring mineral materials that represent interesting structural analogs for manufactured nanomaterials and/or carbon-based materials. Research at the CEREGE has considered the environmental fate of natural Al-Si nanotubes (imogolite) from volcanic soils. Indeed nanotubes (carbon or inorganic) are promising systems with many potential applications from gas storage to micro-electronic application and composite reinforcement among others. Research on this topic will address the synthesis and effects of imogolites as they may be produced in mass production through self-assembling methods. These nanotubes have the same structure as the natural imogolite encountered in volcanic soils. In natural soil they are strongly related to organic matter and trace metals. Student researchers will be involved with research comparing imogolite extracted from natural system to synthetic ones in terms of surface reactivity and biological effects. In addition to learning methods for characterization of nanomaterials, students will study methods for large scale nanomaterial fabrication.