EAGER: Development of a Mechanistic Framework Correlating Quantum Dot Surface Chemistry and Subsurface Environmental Fate and Transport

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1505718Goldfarb, JillianThe interfacial interactions between quantum dots (QD) surface coatings and ecological surfaces are critical determinants of the environmental fate and transport of these materials. However, currently there is no foundational understanding of the mechanisms by which such interactions occur. Therefore it is necessary to examine and test every nanomaterial using a battery of tests to predict resulting subsurface behavior. This proposal will lay a foundation for a mechanistic understanding of the interplay between QD surface coatings and their subsurface reactions. Multivariate statistical analysis tools will be used to analyze data in a framework that reduces the experimental burden by correlating the composition of QD coatings with the environmental factors that influence nanoparticle behavior. By laying a mechanistic foundation for understanding of how QDs with varying structures respond to different environmental stimuli, the project may transform our approach to evaluating the environmental impacts of emerging nanomaterials from the test-and-observe approach to one of predict-and-verify. The long-term goal is to enable assessment of environmental impacts of manufactured nanomaterials in a combined computational and experimental framework. This is a radically different approach from the existing strategy of thoroughly test every new nanomaterial and involves an innovative methodology for developing a novel predictive tool.Core/shell semiconductor quantum dots (QDs) are heterogeneous nanomaterials with seemingly infinite applications and unknown potential effects on human health and the environment. As QDs transition from specialized research laboratories to components in consumer and biological devices, there is a need to develop an understanding of how they will interact, persist, and degrade in the environment. The objective of this proposal is to develop an experimental framework to enable a mechanistic understanding of the relationships between QD surface characteristics and the physico-chemical properties of the subsurface environment on the agglomeration, adsorption, and partitioning of core/shell QDs. This objective will be met by synthesizing QDs with four organic coating combinations (hydrophobic interactions or dative bonding, paired with electrostatic repulsions or steric hindrance). The nanoparticles will be fully characterized to assess their size, morphology, monodispersity, concentration, quantum yield and photoluminescence, crystalline structure, ratio of core and shell atoms, and ratio of coating to particle. To develop this mechanistic understanding, the agglomeration kinetics of QDs with common soil colloids, their partitioning behavior between octanol and water, and their adsorption to saturated porous media, all as a function of ionic strength and pH, will be measured. An initial framework using multivariate statistical analysis will enable the modeling and quantification of relationships between pH and ionic strength and the partitioning, agglomeration, and adsorption for each of the four coating possibilities.