Supercritical fluid processing of thermally stable mesoporous titania thin films with enhanced photocatalytic activity

Employing triblock copolymers as structural directing agents, high-quality mesostructured titania thin films have been prepared on silicon substrates by spin coating. Post-treatment of the films in supercritical carbon dioxide, in the presence of small amounts of either tetraisopropoxide, tetramethoxysilane, or other precursors, greatly improved the thermal stability of the mesoporous coatings without affecting their optical transparency or integrity. Nanosized anatase crystallites formed within the mesostructured walls, during the supercritical fluid treatment and calcination, prevented unidirectional contraction of the films and collapse of the pore walls at the high temperatures employed. In addition, the post-treated mesoporous titania films exhibited high photocatalytic efficiency in the degradation of waste organic compounds.