(36d) Templated Engineering of Ultra-Thin Mesoporous and Hierarchically Porous Films

Ultra-thin ordered mesoporous and mesopore-supported microporous inorganic films on the order of tens of nanometers in thickness bearing ordered pore topology hold exciting technological implications spanning, among others, membrane separations, devices for integrated reaction-separations, and chemical sensing.  Yet control over film thickness and quality (i.e., minimizing defects like cracks and grain boundaries) has been a persistent challenge in the fabrication of inorganic films supported on porous and non-porous substrates.  This talk will highlight two hierarchical synthesis strategies in which near-monolayer to multilayer colloidal crystal films composed of size-tunable silica nanoparticles (ca. 5-50 nm in size) template replica films through interstice infiltration by a wide range of carbon sources (e.g., furfural, phenol resin, vinyl alcohol, sucrose).  In a first proof-of-concept, pre-assembled colloidal crystal films are employed as a robust framework for liquid and/or vapor-phase infiltration, polymerization and pyrolysis of various carbon sources without pore contraction and/or collapse upon template sacrifice.  An alternative approach employs careful control over the zeta potential of silica particles in sols containing monomeric and oligomeric carbon precursors such that co-assembly of colloidal template particles and replica material into ordered thin films can be achieved in a single step.  The wide range of carbon sources accommodated by this templating strategy can be employed as a handle for tuning final film properties including microporosity, mechanical stability, and graphitic composition, among others.  It also underscores the versatility of this approach, and the extension to other classes of materials such as ordered porous metal oxide films (e.g., ZrO₂) will be presented.  The size tunability of the primary silica particles and ability to control the thickness of multi-layer colloidal crystal films translates into respective control over the resulting mesopore structure and film thickness scalability.  The result is robust, flexible mesoporous or mesopore-supported microporous films that can be transferred by stamp techniques to various substrates (i.e. porous stainless steel support, FTO glass, conductive polymer sheets) for applications as high-sensitivity, high flux membranes and promising counter-electrodes for dye-sensitized solar cell.