Grantee Research Project Results
2009 Progress Report: Transformation and Fate of Manufactured Metal Oxide and Metal Nanoparticles in Aqueous Environments
EPA Grant Number: R833891Title: Transformation and Fate of Manufactured Metal Oxide and Metal Nanoparticles in Aqueous Environments
Investigators: Grassian, Vicki H.
Institution: University of Iowa
EPA Project Officer: Aja, Hayley
Project Period: January 15, 2009 through January 14, 2012
Project Period Covered by this Report: January 15, 2009 through January 14,2010
Project Amount: $389,303
RFA: Exploratory Research: Nanotechnology Research Grants Investigating Fate, Transport, Transformation, and Exposure of Engineered Nanomaterials: A Joint Research Solicitation - EPA, NSF, & DOE (2007) RFA Text | Recipients Lists
Research Category: Nanotechnology , Safer Chemicals
Objective:
In this proposal, an experimental study designed to provide the data needed to predict the environmental fate of commercially manufactured metal and metal oxide nanoparticles is discussed. The study will be conducted to satisfy four main objectives. These objectives are to:
- Fully characterize a variety of manufactured metal and metal oxide nanoparticles in terms of their size, shape, bulk and surface physicochemical properties;
- Determine under what environmental conditions (pH, ligands, organic matter, surface adsorption and nanoparticle concentration) do manufactured metal oxide and metal nanoparticles of different size and composition aggregate in aqueous solution and measure the size of the aggregates as a function of these environmentally important variables;
- Determine under what environmental conditions (pH, ligands, surface adsorption and solar irradiation) do manufactured metal oxide and metal nanoparticles of different size and composition dissolve in aqueous solutions and;
- Investigate fundamental aspects of the surface properties and surface chemistry of metal oxide and metal nanoparticles as surface properties and surface chemistry will control both nanoparticle aggregation and nanoparticle dissolution as well as impact nanoparticle-biological interactions.
Progress Summary:
The focus of the research is on some of the most widely used metal and metal oxide nanomaterials in consumer products as well as nanomaterials that may be particularly problematic to the environment or human health. The nanomaterials that have been investigated or are currently under investigation include Ag, Cu, TiO2 and ZnO. For our studies we use a combination of commercially available powdered materials as well as synthesized materials. These materials while either purchased or synthesized are fully characterized in terms of their bulk and surface properties using a wide range of techniques that include X-ray diffraction, transmission and scanning electron microscopy, surface area measurements, ATR-FTIR spectroscopy and X-ray photoelectron spectroscopy. Commercially available materials are often of low quality with different shapes and sizes present in the sample making it difficult to study nanoscale behavior in aqueous phase. Therefore we have begun to synthesize a number of metal and metal oxide nanoparticles and in some cases nanorods for this research. One additional focus of this research that is worth noting is that we very interested in the behavior of some of the smallest nanoparticles available, preferably with a particle size below 10 nm, as these particles have unique nanoscale size-dependent behavior including quantum-size effects and high energy corner and edge sites present on the nanoparticle surface that render them particularly chemically reactive and thus need to be studies for their potential unique behavior in the environment.
As discussed in the objectives, in this EPA-funded research we are interested in understanding the state of nanoparticles in aqueous phase so as to better predict their behavior in the environment and ultimately be able to model the fate and transport of these particles if they were to get into the environment sometime during the life cycle of the material. The state of the nanoparticle includes whether these particles are found as isolated particles or as larger aggregates or as dissolved ions. Additionally, we are interested whether aggregates alter the chemical behavior of the nanoparticles. These different phenomena are studied using several methods including particle sizing instruments, such as dynamic light scattering and scanning mobility particle sizer, inductively coupled plasma optical emission spectroscopy. The proposed studies are going in a number of fruitful directions. Several particular systems are being explored as part of this grant and include:
- Silver Nanoparticle Behavior in Water Systems as a f(pH)
- Copper Nanoparticle Behavor in Acidic Media in the Presence and Absence of Coordinating Ligands
- TiO2 Nanoparticle Behavior in Water Systems as a f(pH)
- ZnO in Aqueous Systems as function of particle size
Thus far we find that TiO2 nanoparticles undergo aggregation but no dissolution in aqueous phase over a wide range of pHs. Aggregation depends on a number of important environmental variables including the presence of organic ligands. We have determined that silver nanoparticles dissolve more readily compared to larger micrometer sized particles in very low pH environments. Several studies are now focused on comparing these results to copper nanoparticles. Copper nanoparticle behavior is complex due to the ease at which it oxidizes and undergoes dissolution under a wide range of conditions. ZnO nanoparticles and nanorods, which have been synthesized, also show rather complex behavior and can dissolve under circumneutral pH. We are investigating ZnO behavior for some of the smaller nanoparticles. It is expected that the results form these studies will provide important information on the properties of nanoscale materials and their transformations in the environment.
Future Activities:
The research is currently going in a number of important directions. Future activities will focus on determining the impact of aggregation on dissolution, the importance of coordinating organic ligands on the dissolution of metal and metal oxide nanomaterials.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 29 publications | 9 publications in selected types | All 9 journal articles |
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Elzey S, Grassian VH. Nanoparticle dissolution from the particle perspective: insights from particle sizing measurements. Langmuir 2010;26(15):12505-12508. |
R833891 (2009) R833891 (2010) R833891 (Final) |
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Elzey S, Grassian VH. Agglomeration, isolation and dissolution of commercially manufactured silver nanoparticles in aqueous environments. Journal of Nanoparticle Research 2010;12(5):1945-1958. |
R833891 (2009) R833891 (2010) R833891 (Final) |
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Supplemental Keywords:
Health, Scientific Discipline, Health Risk Assessment, Risk Assessments, Biochemistry, Biology, biological pathways, aquatic ecosystem, bioavailability, genetic analysis, nanotechnology, carbon fullerene, human exposure, nanomaterials, toxicologic assessment, nanoparticle toxicity, carcinogenicProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.