Collaborative Research: Guiding synthesis of nanoparticles with nanometric phase diagram and in situ X-ray diffraction

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Non-technical SummaryMetallic nanostructures are widely used in many important applications, such as catalysts, energy storage and biomedical engineering. The synthesis of metallic nanostructures is more difficult than that of bulk metals and alloys. Conventional phase diagrams are used as road maps to guide the synthesis and processing of bulk metals and alloys, but they are not suitable for nanoparticles, which have drastically increased surface area and surface energy. Nanometric phase diagrams as the counterpart of conventional phase diagram is highly desired. This project aims to establish nanometric phase diagrams for guiding synthesis of nanoparticles using advanced experimental characterizations and atomistic modeling. Experiments are conducted to observe the formation and growth of metal/alloy nanoparticles in real time, and atomistic modeling provides theoretical understanding of these processes. The synthesis of new forms of metal and alloy nanoparticles is guided by the novel nanometric phase diagrams. This project adds to the fundamental knowledge about the formation process of nanoparticles, and provides a new avenue of synthesizing novel nanoparticles for a range of applications. The scientific findings from this project are integrated as education components into undergraduate and graduate courses. Students at different stages of education participate through a variety of research, education, and outreach activities. Technical SummaryMany metallic nanostructures show unique physical and chemical properties that are different from their bulk forms. Previous researches have demonstrated that these metallic nanomaterials often form phases that are not stable in conventional phase diagram. However, it is not yet fully understood why this can happen and in what condition this would happen. This project aims to answer these fundamental questions via a novel approach combining computational and experimental research efforts. State-of-the-art in situ X-ray characterization techniques are developed and employed to monitor the nucleation and growth processes of metallic nanoparticles in solutions, both qualitatively and quantitatively. First principles computations are used to evaluate the bulk, surface and total energies of nanoparticles in different synthesis conditions and at different length scales. By coupling computational and experimental investigations, the formation mechanisms of metallic nanostructures are revealed and the nanometric phase diagrams are established to predict and guide the syntheses of metallic nanomaterials. The findings and outcome of this project have impacts and implications in multiple fields, such as solid state chemistry, metallurgy, and nanotechnology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.