There is currently very little known about the environmental implications of rigid highly anisotropic nanostructures. Nanorods possessing high aspect ratios (AR = length:diameter) are an exciting nanomaterial class with many potential applications. To date, however, only a limited number of studies have examined the environmental fate of these elongated nanomaterials. The lack of work in this area is particularly surprising given that it has been definitively shown that anisotropy affects how nanorods interact with biological systems. The underlying hypothesis driving the present effort is that changes in AR and surface chemistry will alter the mechanisms and kinetics dictating nanorod fate in riverine systems. To test this hypothesis the PIs have developed a research plan that consists of four highly inter-related project tasks: In Task 1 we will synthesize gold nanorods with varying AR and we will then functionalize them using a range of environmentally relevant metal oxides (e.g., SiO2, gamma-Fe2O3, CeO2) to obtain a suite of nanomaterials that exhibit both shape and surface chemical heterogeneity. These nanorods will then be used in studies to evaluate nanorod aggregation (Task 2), nanorod deposition (Task 3), and uptake by the filter feeding bivalve Corbicula fluminea (Task 4). Completion of each of these tasks is an important undertaking in its own right; however, we have developed a cohesive research plan in which the knowledge gained in any one task is used to help refine the overall research plan. Intellectual Merit : Anisotropic nanoparticles are being produced in an ever-expanding variety of shapes and sizes in ever-increasing quantities. Presently ery little is known about the environmental implications of these highly complex nanomaterials. The effort proposed herein will provide a fundamental basis for the description of how material anisotropy dictates nanomaterial fate in environmental matrices. The expected intellectual outcomes of this effort are i) systematic examination of nanorod aggregation kinetics and fractal dimension as a function of aspect ratio and solution chemistry (ii) delineation of deposition mechanisms by the systematic variation of particle properties (AR, surface chemistry) and collector parameters (e.g., collector size and surface roughness) in column studies; and (iii) quantification of the effects of AR on nanomaterial uptake by the ubiquitous filter feeder C. fluminea. Although our focus is on gold and gold-core nanorods, the results obtained are expected to be translatable to other anisotropic materials. Broader Impacts : A multi-dimensional approach to broader impacts has been developed. This approach leverages existing programs at the three collaborating institutions while working to integrate efforts across the groups. Research dissemination and outreach. The PIs will collectively promote and disseminate the research results through existing community programs in Virginia, South Carolina, and Illinois. In addition, the results of this project will be broadcast to a broad technical audience through the traditional pathways of peer-reviewed publications and presentations at relevant conferences. Outreach efforts will target minority students in local high schools. Undergraduate research. Undergraduate research opportunities will be made available at all three collaborating institutions. Over the course of their careers, the PIs have collectively supported over 90 undergraduate researchersin their laboratories (a significant percentage of whom are members of historically under-represented groups in science and engineering) and this effort will provide additional undergraduate research opportunities. Undergraduate and graduate education. The research proposed in this effort combines nanomaterial synthesis and characterization techniques with colloidal physical principles in a manner that is not routinely found in undergraduate chemistry or environmental engineering curricula. Given this fact, all three PIs will take part in the development and production of classroom material (e.g., lectures, demonstrations) based upon this research that will be incorporated into courses at all three institutions.
