Synthesis of transparent mesoporous and mesostructured thin silica films

A novel method for obtaining crack-free transparent periodic mesoporous thin films is described. Such films are prepared by a simple sol-gel process using surfactants as templates, with a pre-treatment of the glass substrate. The silicate precursor (tetraethoxysilane) is pre-hydrolyzed under acidic conditions before dissolving directly cetyltrimethylammonium bromide (CTAB). The solution is then spin-coated on pre-treated glass substrate. After the film has been deposited, it is calcined in air. X-ray Diffraction (XRD) has been used to characterize the film before and after thermal treatment. The film consists of a nanocomposite material with a periodic structure. Before calcination the XRD pattern has a sharp peak at d = 3.8 nm, which is broadened and shifted by about 3.0 nm after calcination. Infrared transmission spectra have been performed on the films. Analysis of the free OH group stretching vibration indicates the removal of the surfactant after calcination in addition to an enhancement of the specific surface area.