SusChEM: Unjamming the Growth of Metal Pnictide Synthesis

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Nanoscaled crystals are atomically-ordered microscopic particles that are approximately 100,000 smaller in diameter than a human hair. At these dimensions, the nanoparticles take on interesting chemical and physical properties not seen in larger dimensioned particles. The chemical synthesis of nanostructures is tricky, and the quality of the nanocrystal depends heavily on perfecting a good synthetic methodology, which is often specific to the chemical composition and morphology of the nanoparticle of interest. Dr. Jonathan Owen of Columbia University is researching new methods to synthesize indium and zinc phosphides with novel synthesis reagents that provide greater flexibility, safety, and control of the nanocrystal properties. To analyze their structural characteristics, Prof. Owen uses a novel and cutting edge technique called pair distribution function analysis of x-ray scattering. This approach allows Dr. Owen to select for conditions that lead to nanocrystals with greater purity and crystalline order. This program is shedding light on how the syntheses take place mechanistically and results of the project readily transfer to synthesis of other nanoparticle compositions. Broader societal impacts of the research are the development of new materials with reduced toxicity, earth abundance, and improved performance in energy technologies from luminescent displays, to solid state lighting, and photovoltaics. Prof. Owen involves high school, undergraduate, and graduate students in this research project and maintains a quantum dot synthesis laboratory module for undergraduate courses that clearly illustrates the principles of quantum confinement and the mechanisms of crystal nucleation and growth.The synthesis of III-V and II-V semiconductor quantum dots (QDs) has lagged behind that of the canonical II-VI QDs, which can be presently fabricated with outstanding monodispersity and bright photoluminescence. While there are many fewer examples of III-V nanocrystals (NCs) in the literature, these "pnictides" represent a rapidly developing field. Prof. Jonathan Owen of Columbia University is researching synthesis methods of metal pnictide nanoparticles by designing pnictogen precursors with tunable conversion reactivity. Additional control is achieved by speeding the crystallization kinetics using high temperature compatible surfactants and crystallization catalysts to facilitate rapid and reversible bond formation. Methodology for the synthesis of III-V and II-V QDs, with an emphasis on phosphides and arsenides of zinc and indium, are the initial pnictide target compositions, but the information obtained is generally transferable to other pnitide materials. The broader impacts of this proposed research result from the development of new materials with reduced toxicity, earth abundance, and improved efficiencies in energy technologies with applications ranging from luminescent displays to solid state lighting and photovoltaics. Prof. Owen involves high school, undergraduate, and graduate students in this research project. He also works to bring an improved understanding of QD properties into the undergraduate laboratory in developing a QD synthesis lab module that clearly illustrates the principles of quantum confinement and the mechanisms of crystal nucleation and growth.