Synthesis and Properties of Mesostructured Thin Films

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This project concerns the synthesis and properties of mesostructured thin films of metal oxides based on surfactant and block copolymers as the structure-directing agents. A central concept involves the chemically different and spatially separated regions of the mesostructure. On the molecular level, the mesostructures consist of two distinct regions: the "framework" that is formed by the sol-gel metal oxide, and the "organic" region that is formed by the template. The project contains two complementary objectives. The first objective is to deliberately place dopants in specified regions of transparent mesostructured silica. The location of specific molecules will be characterized by optical spectroscopy, and the spatial relationships between multiple dopants will be probed by energy transfer. The second objective is to synthesize semiconductor frameworks in mesostructured films and to characterize their formation processes. Mesostructured films of tin dioxide will be synthesized and optical probes will be used to monitor and interpret the dynamics of both micelle and metal oxide framework formation. The optical methods to be used provide 50 nm resolution of the dynamic transformations taking place in a time frame of a few seconds over film dimensions of several centimeters. The experiments are directed at determining the evolution that occurs from the dissolved "unimer" (individual dissolved copolymer molecules) to the micelle to the mesostructured metal oxide film. These dynamic measurements will correlate the chemical changes and structural development occurring as the film is deposited. The second set of experiments will monitor the development of the semiconductor framework. Electron transport in mesostructured films will be measured and interpreted. %%%The prospects for creating mesostructured films with unique electrical and optical properties. The development of these novel materials will have a significant impact on the fields of optical physics, and device areas such as sensors for medical applicatons (e.g., implants and in vivo and in vitro biosensors). Students trained in these areas will compete very favorably in the job market. This project is to be funded jointly by the Chemistry Division and the Division of Materials Research.