Nanoporous silica and carbon thin films: Synthesis and characterizations.

摘要

Mesoporous carbons with different symmetries and mesoporous carbon-silica composites with hexagonal symmetry have been studied previously through polymer templating; however, those studies were only limited to powder materials. Here, by using polymer as a versatile platform, multiple routes including vapor infiltration of preformed templates and cooperative self-assembly were utilized to create nanoporous silica, carbon and carbon-silica composite films with the desired morphologies. Materials of different characteristics were developed and the potential applications were discussed. First, a facile method was investigated for patterning nanoporous silica, polymer and carbon films with structures on the order of ten nanometer, hundred nanometer and micron sizes from self assembly, phase separation and lithographic patterning, respectively. The methodology developed provides a simple, etch-free route to patterning nanoporous films utilizing commercially available materials.;To improve the ordering of mesoporous carbon films, mesoporous polymer/carbon films with different symmetries were explored through the evaporation induced self-assembly (EISA) approach with water soluble resol as a carbon precursor and triblock copolymers as templates. Films exhibited well-defined orthorhombic and well-ordered rectangular symmetries after template removal by using two different block copolymers, respectively. The predominant difficulties in fabricating cylindrical mesopores were proposed, and a new composition window for obtaining ordered cylindrical mesopores in carbon films was obtained.;A facile approach to improve the robustness of mesoporous polymer/carbon films by the addition of silica to a carbon matrix through the reactive co-assembly of resol and tetraorthosilicate with triblock copolymer template was then explored. The pyrolysis of the resol-silica-triblock copolymer film yielded a porous film with well defined pore size. The addition of silica to the matrix impacted the pore size, porosity, modulus and conductivity. For films with higher silica concentration, the conductivity was decreased by approximately an order of magnitude in comparison to a pure carbon mesoporous film, but the conductivity is comparable to typical printed carbon inks used in electrochemical sensing. The mechanical properties of these mesoporous silica-carbon hybrid films were improved in comparison to pure carbon analogs. These silica-carbon composite mesoporous films hold significant promise for sensing applications.