Effects of addition of supramolecular assembly on the anatase nanocrystalline precipitation of sol-gel derived SiO2-TiO2 coating films by hot-water treatment.

Effects of the addition of a supramolecular assembly of cetyltrimethylammonium bromide in SiO 2 -TiO 2 gel films on the formation of anatase type TiO 2 nanocrystals with hot-water treatment were investigated. Anatase nanocrystals were formed in the whole SiO 2 -TiO 2 gel films with the addition of cetyltrimethylammonium bromide by the treatment, whereas the nanocrystals were formed only on the film surface in the case of gel films without cetyltrimethylammonium bromide. Cetyltrimethylammonium bromide molecules in the SiO 2 -TiO 2 gel films were completely removed by the hot-water treatment and the following UV irradiation. In the usual procedure for preparation of porous materials, the removal of template molecular assemblies required high temperature treatment over 400 °C. In this system, all the processes were performed at temperatures less than 100 °C. Additionally, the porous structure produced by the removal of micellar assembly allowed anatase nanocrystals to be formed inside the films. Therefore, the method presented in this work provides us with the novel photocatalyst coatings of porous membrane with highly-dispersed TiO 2 nanocrystals via low temperature process.