The growing application of III-V materials (e.g., gallium indium arsenide) in semiconductor and electronics manufacturing is expected to lead to generation of large volumes of wastewaters containing III-V metals (arsenic (As), gallium (Ga) and indium (In)) and metal oxide nanoparticles (SiO₂, Al₂O₃ and CeO₂). The potential that these engineered nanoparticles (NPs) may act as carriers of toxic III-V species and modify the reactivity of the NPs themselves is a concern. This project aims to quantify the adsorption of III-V materials by NPs and explore how these interactions impact the environmental fate, biological uptake, and aquatic toxicity of III-V species and NPs. This research will be conducted in collaboration with the semiconductor industry, a major user of SiO₂, Al₂O₃, and CeO2 NPs, that is launching extensive R&D efforts to develop a new class of integrated circuit devices that will employ III-V semiconductors.

Research work will be conducted to: i) determine new equilibrium aqueous complexation constants for In, Ga, and As with NPs and simulate the speciation and distribution of III-V elements in the presence of NPs; ii) demonstrate experimentally and through quantum calculations that sorption of III-V ions on NPs alters their surface reactivity and potential to produce reactive oxygen species, a marker commonly associated with increased cytotoxicity; and iii) understand the impact of III-V species?NP interactions on the toxicity and uptake of these emerging contaminants by model aquatic organisms. Work supported by industry will assess the fate and impact of a binary mixture of NPs and III-V ions during on-site water treatment and downstream municipal wastewater treatment. The primary intellectual merit of this project is the exploration of the central hypothesis that NPs can act as a ?Trojan Horse? of adsorbed III-V species, and thereby affect the surface reactivity and toxicity of NPs, as well as the biological uptake, fate and toxicity of the dissolved III-V metals in the aquatic environment. Whereas the concept of using NPs as Trojan Horse delivery systems for biomedical applications has attracted wide research attention, there are few realistic studies of this concept using environmentally relevant ions and NPs. Also it is well established that some NP can adsorb environmental contaminants, but the notion that adsorbed metals can alter the reactivity of NPs is novel. The study will also improve our understanding about the environmental chemistry, fate and ecotoxicity of Ga and In, two poorly characterized metals which have increasing risk to enter water systems because of their expanding industrial uses. This project will be among the first to conduct in depth experimental and modeling work of NPs in industrial waste streams.

Safe development of nanotechnology is a major theme on both UA and ASU campuses and this research will contribute to expand the broader impacts associated with nanotechnology development at both institutions. The project will have benefits in education by supporting graduate student research and providing scientific results to develop modules in environmental engineering courses. Other key impacts include the development of best practice guidelines that can be used by industry to reduce the potential environmental impact of semiconductor effluents containing NPs, including effluents from planarization of III-V films. Overall, the research could benefit society by providing new knowledge and tools to facilitate assessment of potential hazards of NPs and III-V metals in the aquatic environment. Findings from this study will be made publicly available in scientific publications and presentations at scientific conferences, and they will be presented at professional meetings organized by the semiconductor industry.