Preparation of periodically organized mesoporous bicomponent TiO2 and SnO2-based thin films by controlling the hydrolytic kinetics of inorganic precursors during EISA process

Highly organized cubic mesoporous TiO2 and SnO2 nanocrystalline thin films were reproducibly synthesized via an evaporation-induced self-assembly (EISA) process with a triblock copolymer (Pluronic F127) as the template, by precisely controlling the water content and chelating agent in the initial sol solution as well as by controlling the external relative humidity during the aging step. It has been found that the mesoscopic regularity of the fabricated mesoporous films critically depends on the hydrolytic reactions of inorganic precursors. That is, suppressing the hydrolysis reaction in the initial sol and providing the long-term stability for the sol in the coated film during the aging step are key factors in the formation of highly organized structure. The synthetic strategy was also extended to obtain various TiO2- and SnO2-based mixed oxide thin films with tunable composition, including WO3/TiO2, SiO2/TiO2, Nb2O5/SnO2, by selectively controlling the kinetics of hydrolytic reaction for the additional inorganic precursors. The prepared composite films were crack-free, ultra-highly transparent, and thermally stable.