Chemical Pathways for Controlling Polymorphism in Nanoscale Metal Chalcogenides

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This award by the Solid State and Materials Chemistry (SSMC) program supports work by Professor Raymond Schaak at the Pennsylvania State University to identify and understand the chemical factors that lead to the formation of nanoparticulate non-equilibrium phases of transition metal sulfides and selenides, including ZnS, ZnSe, and several sulfides and selenides of Co, Ni, and Mn. The targeted materials exhibit a variety of interesting and useful electronic, magnetic, and optical properties, and their crystal structures directly impact their properties. This research builds on emerging capabilities for synthesizing non-equilibrium phases using chemical routes that form nanoparticulate solids in solution from soluble precursors. Such discoveries are usually serendipitous, involving a large number of variables and complex in-situ chemistry. In this project, Prof. Schaak's group investigates the reaction pathways by which these new solids form to reveal important insights that can help lead to a predictive framework for selectively targeting desired non-equilibrium phases based on fundamental chemical principles.The crystal structure that an extended solid adopts plays a key role in defining its properties. At the same time, the techniques and conditions used to synthesize a solid can help to influence the crystal structure that it forms. This project seeks to identify and understand the chemical factors that selectively lead to the formation of one crystal structure instead of others in a system where multiple structures may be accessible. These insights will help researchers to more predictably synthesize desired materials with targeted properties. This project provides multi-disciplinary training to a diverse group of graduate and undergraduate students. Emphasis is placed on integrating teams of undergraduate researchers directly into the technical goals of the project through specially designed undergraduate research projects.