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Deposition of Polymer- and NOM-Coated Nanoparticles to Environmental Surfaces: Conceptual Model Development and ValidationEPA Grant Number: FP917141
Title: Deposition of Polymer- and NOM-Coated Nanoparticles to Environmental Surfaces: Conceptual Model Development and Validation
Investigators: Louie, Stacey Marie
Institution: Carnegie Mellon University
EPA Project Officer: Cobbs-Green, Gladys M.
Project Period: September 1, 2010 through August 31, 2013
Project Amount: $111,000
RFA: STAR Graduate Fellowships (2010) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Fellowship - Pesticides and Toxic Substances
Nanoparticles are typically engineered with polymer coatings and can become further coated with natural organic matter (NOM) upon release to the environment. These coatings control nanoparticle fate and transport and hence bioavailability and exposure risk; therefore, a comprehensive model to predict nanoparticle transport (as controlled by deposition) must consider the properties of the coating. This project will determine the effect of the morphology of the coated nanoparticles on their deposition to environmental surfaces.
The use of nanoparticles (NPs) in consumer products is increasing, but their environmental impact remains to be fully characterized. NPs are typically coated with polymers (engineered or incidental), which control their distribution in the environment. This project focuses on determining the role of the coated NP structure on fate and transport. This work will contribute to environmental modeling and exposure risk assessments, thus helping to advise regulatory guidelines for nanotechnology.
The overall approach is to systematically create a model set of polyelectrolyte-coated nanoparticles over a range of morphologies and to measure their deposition onto silica surfaces on laboratory scale columns and Quartz Crystal Microbalance (QCM). The morphologies will range from individual polymer-decorated nanoparticles where the radius of gyration of the polymer is less than 0.1 times the diameter of the NP, to a nanoparticle-decorated polymer (two or more particles) where the radius of gyration of the polymer is 10 to 50 times the NP diameter. First, titanium dioxide nanoparticles will be coated using poly(acrylic acid) (PAA) of various molecular weights. These coated nanoparticle systems will be characterized by several methods, including transmission electron microscopy and atomic force microscopy, to determine their morphologies. Then, deposition of the coated nanoparticles will be measured in column and QCM studies to quantitatively determine the impact of morphology on deposition. After testing these model synthetic macromolecule coatings, various NOM coatings will be similarly tested to extend the study to natural environmental systems.
The two end member morphologies (polymer-decorated nanoparticles and nanoparticle-decorated polymers) are expected to show significantly different deposition behavior. Deposition of the polymer-decorated nanoparticle is expected to follow the extended DLVO model, which accounts for electrosteric interactions between the nanoparticle and the surface. Conversely, the nanoparticle-decorated polymer structure is expected to show deposition behavior more similar to that of the macromolecule itself. The effect of NOM coatings on morphology and deposition are expected to depend on the properties of the NOM (e.g. molecular weight and rigidity). The results of this research will contribute to models used to predict nanoparticle transport and partitioning in the environment.
Potential to Further Environmental/Human Health Protection:
Risk assessments for environmental and human health protection must account for both toxicity and exposure risks. The deposition behavior of nanoparticles, which is controlled by their macromolecule coatings, will determine their partitioning among environmental media and the risk of potential exposure and bioavailability to humans and ecological communities. Therefore, a thorough, quantitative understanding of the role of polymer and NOM coatings on nanoparticle deposition will contribute to exposure risk assessments for nanoparticles, which will provide guidance for environmental regulations.