Materials for bio-sensors and renewable energy applications: Fabrication of mesoporous metal oxide films by the three-dimensional replication of block copolymers
Since their discovery in the early 1990's, mesoporous materials have been a field of vast growth and widely studied for various potential applications. The inherent well-defined pore structure is one attractive characteristic of these materials. Desirable functional materials may be infiltrated into these pores to generate a responsive device for specified applications. Likewise, the desired application of these materials dictates the domain size ( d-spacing) and morphology of these materials.
The use of two novel methods for mesoporous material fabrication will be introduced. First, the fabrication of mesoporous titania by the 3-D replication of block copolymers using supercritical carbon dioxide as a delivery medium will be implemented. Catalyst-doped block copolymer templates were spin-coated onto suitable substates and exposed to a solution of supercritical carbon dioxide and titania precursor. The precursor readily diffused into the swollen template and reacted with the catalyst, thus selectively condensing in a single domain. This method was extended for the fabrication of well ordered mesoporous titania thin films for sensor and renewable energy applications. The final well-ordered structures were analyzed with XRD, TEM, and GISAXS.
The second method introduced involves an aqueous method to fabricate mesoporous silica at neutral pH and ambient conditions through the incorporation of a bifunctional catalyst into an amphiphilic surfactant template. Highly condensed porous silica nanoparticles were formed at these conditions providing for excellent materials for sensor-type applications. These materials exhibited unusually high linking leading to low thermal shrinkage. NMR, TEM, and SAXS were utilized to characterize these particles.