UNS: Role of dopant concentration and distribution in the environmental behavior of indium tin oxide nanoparticles

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#1511826Saleh, Navid Nano-scale metal oxides are one of the most prepared and used engineered nanomaterials with applications in electronics, optical devices, and medical processes and devices. Nano-scale indium tin oxide (nITO) is one such doped metal oxide particle that is used heavily in electronic display modules such as touch screens, electronic inks, and organic light-emitting diodes. Manufacturing processes and end-of-life disposal events for these products might serve as exposure pathways of nITO to humans and the natural environment and thus raise concerns for eco- and nano-toxicity. This project systematically assesses the influence of crystal properties (at the atomic scale) on the environmental health and safety of nITO. The purpose of this project is to determine key physicochemical properties and band gap energetics of nITO as a function of the concentration and distribution of tin doping and to elucidate mechanisms for fate, transport, transformation, and toxicity of these nano-scale bimetallics. This study will address the following aims: (1) synthesize nITO with tunable band structure via control over dopant concentration and distribution; (2) sample preparation and characterization of nITO for a range of tin doping to gain detailed understanding of crystal structure, bimetallic morphology, and colloidal properties; (3) examination of aggregation kinetics, fractal dimension, and porous media transport as a function of ionic strength and organic matter composition; (4) evaluation of microbial toxicity (to planktonic and biofilm cells) and toxicity mechanisms using band gap energetics and ROS measurements; (5) assessment of chemical transformation of nITO and evaluation of fate and toxicity of the transformed materials. This study will be the first of its kind, using changes in fundamental electronic and physicochemical properties of nITO caused by controlled variations in tin doping distribution and concentration at the atomistic level to elucidate mechanisms of fate, transport, and toxicity in aquatic environments. The proposed work will generate critical and fundamental knowledge to better understand the environmental implications of a highly concerning and commercially important next- generation nanomaterial, nITO. nITO, that are utilized as transparent catalysts in touch-screen devices with higher recycling rate and relatively short lifetime, necessitate understanding their environmental safety. The results obtained from this project will result in direct societal benefit by providing better understanding of nTO environmental health and safety. In outreach and education aspects, the PIs will continue their strong track records of recruiting students from underrepresented groups. At least one graduate student from an underrepresented group will be attracted via the University of Texas at Austin?s Diversity Mentoring Fellowship, while undergraduate women and minority students will be brought into this cutting-edge nanomaterial and microbiology research utilizing the University's Graduates Linked with Undergraduates in Engineering (GLUE) and the Texas Research Experience (TREX) programs. Multi-pronged outreach activities at San Juan Diego High School (which has 85% Hispanic students) will have profound educational impact on the high school students through seminars and hands-on experiments.