Coordination Polymer Heterostructures

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TECHNICAL SUMMARYThe project will undertake a series of systematic investigations of the structural aspects of nanometer scale and mesoscale coordination polymer heterostructures. The goals are to better understand how coordination polymer networks accommodate the presence of an interface and, therefore, how interfaces can be used to control properties. Specific studies will elucidate the nature of structural changes induced by an interface, for example biaxial or isotropic, and how the structural changes differ if the strain is compressive vs tensile. The depth away from the interface that strain or structural reorganization persists and the limits of structural parameters that allow epitaxial relationships between the heterostructure components will also be explored. After comparing static structures, elastic processes and how a light- or thermally-induced structural event in one component is manifested in the other component via the interface will be investigated. Studies will focus on cyanometallate coordination polymers of the Prussian blue analogue family, taking advantage of more than twenty easily accessible and air-stable analogues based on first-row transition metals. A wide range of heterostructures are known, allowing for systematic variation of the parameters to be studied via control of particle size, structure, composition and component thickness. The principal method of analysis will be X-ray diffraction, using both laboratory and synchrotron sources. Data from X-ray scattering will be complemented by electron microscopy and electron diffraction. NONTECHNICAL SUMMARYThe simple promise of composite particles, or "heterostructures", is combining more than one property in a single material. However, beyond simply adding properties, synergy between components can lead to new behavior and new function. When heterostructures lead to "more than the sum of the parts", it is the interface between the constituents that causes the new properties. The goals of the project are to learn how interfaces change the structures of a new class of materials, called coordination polymer heterostructures, and to then develop insights into how these heterostructures can be used to control properties. Generalized results can inform many areas of current materials science, including magnetism, battery technology, thermal properties of materials, gas storage and separations, catalysis, as well as applications in bioanalysis and biomaterials. The research tasks are designed to be platforms for graduate and undergraduate student education, preparing them with the "21st-Century Skills" needed to contribute to a high-technology workforce. The research activities emphasize collaboration between disciplines, both among US institutions and with international partners, and will make significant use of the Advanced Photon Source, a major US multi-user facility where students receive training.