Nanochemical Control of Polymorphism in Transition Metal Chalcogenides

NON-TECHNICAL ABSTRACT Many useful and important technologies rely on materials that contain compounds formed by combining transition metals with sulfur, selenium, or tellurium. The properties of these so-called metal chalcogenides depend on their crystal structures, or the arrangements of the atoms that comprise them. Some useful metal chalcogenide systems can form several closely related crystal structures, and even small differences in how the atoms are arranged can dramatically influence their properties. Therefore, in order to control and tune the properties of metal chalcogenides, it is important to understand how to control their crystal structures. With the support of the Solid State and Materials Chemistry program, the research team is investigating chemical methods that precisely target the formation of one particular crystal structure in metal chalcogenide systems where multiple crystal structures are known. Nanoscale crystals of metal chalcogenides have unique characteristics that enable these studies, including the ability to facilitate chemical reactions that manipulate important features of their crystal structures. The knowledge gained from this project is useful for producing new materials that are relevant for applications in catalysis, electronics, and magnetism. This project is providing a diverse group of graduate and undergraduate students with multi-disciplinary training in research, communication, project management, and outreach. A formal collaboration with an undergraduate research group further expands both training and research opportunities. In addition, the entire research team is engaged in the development of news clips and social media content for showcasing to the general public the diversity of materials-focused research and researchers. TECHNICAL ABSTRACT Transition metal chalcogenides comprise an important class of inorganic solids that enable a wide range of applications, particularly as nanoscale materials. Underpinning their applications is the ability to synthetically achieve precisely controlled features, including crystal structure and morphology, that directly impact properties. In this project, the research team is identifying and understanding the reaction parameters, reaction pathways, and materials characteristics that lead to the predictable and selective formation of stable and metastable metal chalcogenide polymorphs. The primary materials systems being studied include cobalt, iron, and manganese sulfides and molybdenum tellurides made using both direct synthesis methods and nanoparticle chemical transformation reactions. This new knowledge is being used to overcome significant chemical bottlenecks in the formation of several high-value materials targets for emerging applications. This project is providing a diverse group of graduate and undergraduate students with multi-disciplinary training in research, communication, project management, and outreach. The project includes a formal collaboration with an undergraduate research group and also engages students in the development of news clips and social media content for showcasing to the general public the diversity of materials-focused research and researchers.