Grantee Research Project Results
Final 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 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: 1) fully characterize a variety of manufactured metal and metal oxide nanoparticles in terms of their size, shape, bulk and surface physicochemical properties; 2) 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; 3) 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 4) 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.
Summary/Accomplishments (Outputs/Outcomes):
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 – over a range of sizes. 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 are 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 Behavior in Acidic Media in the Presence and Absence of Coordinating Ligands
- TiO2 Nanoparticle Behavior in Water Systems as a f(pH)
- ZnO in in Aqueous Systems as Function of Particle Size in the Presence and Absence of humic and citric acid
Conclusions:
Thus far, we found 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 will focus on determining the impact of aggregation on dissolution, the importance of coordinating organic ligands and dissolved organic matter on the dissolution of metal and metal oxide nanomaterials. Careful size dependent studies are continuing and are important for these studies as nanoscience is “a science all about size." These size dependent studies are important if we are to gain an understanding of how size will impact the physicochemical properties of nanomaterials as it relates to the transformation and fate of these materials in the environment. Additionally, we are looking at copper nanoparticles, which often have a thin surface oxide layer, how these particles can age in the ambient environment and become even more oxidized over time. These aged nanoparticles will then have different properties compared to the original nanoparticle. Recently, we have characterized three different types of copper-based nanoparticle (NP) samples designated as Cu(new) NPs, Cu(aged) NPs and CuO NPs that differ in the level of oxidation. The behavior of these three copper-based NP types shows interesting differences in solution and in fact Cu(aged) NPs exhibit unique chemistry including oxide phases that form and surface adsorption properties. Besides TiO2, ZnO, Ag and Cu, we also investigated CeO2 and Fe2O3 nanomaterials. Overall, our studies provide some insights into the impacts of nanoparticle aging and how the physicochemical characteristics and reactivity of nanomaterials can change upon aging.
Journal Articles on this Report : 9 Displayed | Download in RIS Format
Other project views: | All 29 publications | 9 publications in selected types | All 9 journal articles |
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Bian S-W, Baltrusaitis J, Galhotra P, Grassian VH. A template-free, thermal decomposition method to synthesize mesoporous MgO with a nanocrystalline framework and its application in carbon dioxide adsorption. Journal of Materials Chemistry 2010;20(39):8705-8710. |
R833891 (2010) R833891 (Final) |
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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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Elzey S, Baltrusaitis J, Bian SW, Grassian VH. Formation of paratacamite nanomaterials via the conversion of aged and oxidized copper nanoparticles in hydrochloric acidic media. Journal of Materials Chemistry 2011;21(9):3162-3169. |
R833891 (2010) R833891 (Final) |
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Mudunkotuwa IA, Grassian VH. Citric acid adsorption on TiO2 nanoparticles in aqueous suspensions at acidic and circumneutral pH: surface coverage, surface speciation, and its impact on nanoparticle-nanoparticle interactions. Journal of the American Chemical Society 2010;132(42):14986-14994. |
R833891 (2010) R833891 (Final) |
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Mudunkotuwa IA, Grassian VH. The devil is in the details (or the surface): impact of surface structure and surface energetics on understanding the behavior of nanomaterials in the environment. Journal of Environmental Monitoring 2011;13(5):1135-1144. |
R833891 (2010) R833891 (Final) |
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Mudunkotuwa IA, Rupasinghe T, Wu C-M, Grassian VH. Dissolution of ZnO nanoparticles at circumneutral pH: a study of size effects in the presence and absence of citric acid. Langmuir 2012;28(1):396-403. |
R833891 (2010) R833891 (Final) |
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Mudunkotuwa IA, Pettibone JM, Grassian VH. Environmental implications of nanoparticle aging in the processing and fate of copper-based nanomaterials. Environmental Science & Technology 2012;46(13):7001-7010. |
R833891 (2010) R833891 (Final) |
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Mudunkotuwa IA, Minshid AA, Grassian VH. ATR-FTIR spectroscopy as a tool to probe surface adsorption on nanoparticles at the liquid-solid interface in environmentally and biologically relevant media. Analyst 2014;139(5):870-881. |
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.