CAREER: Synthesis and Characterization of Metal/Silica Multicomponent Classes by the Sol-Gel Process

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Abstract 9623570 Stiegman The two principal goals of this research are to advance study of the chemical parameters that effect the synthesis and processing of multicomponent glasses by the sol-gel process, and to fabricate and characterize entirely new metal/silica multicomponent glasses. Three primary activities will be conducted: 1. The synthesis of new metal/silica xerogels. Several metal and metal-centered functional groups will be incorporated into the silica xerogel matrix using the synthetic protocol established for the oxovanadium materials. Central to this effort is the optimization of conditions to insure homogeneity for each metal. The metals chosen for incorporation will be based on their anticipated reactivity and on their position as part of a series of systematically varying materials for the elucidation of structure-property relationships. 2. Elucidation of the chemistry of the sol-gel process under multicomponent conditions. This will involve determining the effects of the metal on the kinetics and mechanism of gelation, the processes of aging, drying and stabilization. This will provide a fundamental understanding of the chemical processes that occur in the solgel process when many kinetically different components are present. 3. Characterization of the properties and reactivity of the new multicomponent glasses. The characterization of the hybrid materials will entail two primary activities: (1) characterization of the coordination geometry and electronic structure of the metal center as it is found in the silica matrix; and (2) characterization of the physical and morphological properties of the bulk xerogel. %%% Homogeneous multicomponent glasses, comprised of differing ratios of metal and semimetal oxides, have attracted considerable attention due to their diverse and potentially useful properties and reactivities. Among the applications predicted for these materials are as heterogeneous catalysts, chemical sensors and environmental monitors, and optical and electronics components. While the sol-gel process has been used successfully to prepare specific materials, problems have precluded its general employment as a method for preparing homogeneous hybrid glasses. These problems arise from the widely differing gelation kinetics of the various constituents and by the many variables associated with aging and drying these materials; all of which can lead to heterogeneity in the final product. The aim of this work is to optimize the conditions needed to produce a homogeneous glass, and provide a detailed and comprehensive picture of the formation and properties of hybrid metal/silica glasses to contribute significantly to bringing this class of materials into the sphere of real applications.