Intellectual Merits: The objective of the project is to establish a correlation among physicochemical properties, photochemical fate, and toxicity of TiO2 nanoparticles (NPs). We will synthesize and characterize three forms of NPs: bare TiO2 nanospheres, bare TiO2 nanowires and amine-coated TiO2 nanowires. We will use in vitro cultures of primary murine alveolar macrophages to study the direct immunomodulatory effects of NPs, and an in vivo mouse model to investigate the pulmonary and central nervous system (CNS) toxicity after lung deposition. We will determine how the shape and/or the surface coating affect the aggregation status, solubility, chemical stability, surface chemistry, reactive oxygen species (ROS) generation and reactivity (photocatalytic activity) of TiO2 NPs, and determine the impact of these parameters on NP toxicity. We will also observe the photochemical fate of TiO2 in the aqueous environment upon irradiation of solar-simulated light in the drinking water and synthetic wastewater, including the transformation of the aggregation status, solubility, chemical stability, surface chemistry, ROS and reactivity of TiO2 NPs. Finally, we will study how these environmental transformations will, in turn, influence the toxicity of TiO2 NPs. Broader Impacts: Implementation of the project will promote the fusion of different disciplines and the collaborative partnership among two universities and one federal lab. The research will identify the environmental fate and the transformation process of engineered TiO2 nanoparticles in the aqueous environment under the solar-simulated light irradiation. The research will provide new insight into the toxicological responses to both the "as-produced" TiO2 NPs and after environmental transformation. Broad data dissemination will directly impact the risk analysis for human health and environmental impacts and will provide mechanisms for improved planning for commercialization of NPs. The educational objectives of this effort are to train graduate and undergraduate students, to recruit underrepresented students to participate in the proposed research, and to outreach to high school teacher training. In addition, the experimental results will provide a valuable resource for case study in class. The education and learning activities will attract young talents into the multidisciplinary field interfacing environmental engineering with nanotechnology and biology, and thus helping U.S. stay in a leading position in this strategic field not only today but also in the future.
