Synthesis, characterization and photoconductivity behavior of inverted nanocrystalline titania and nanocrystalline titania-silica photonic crystals

The bottom-up template-directed synthesis approach, using a modified sol-gel process was used, to synthesize inverted nanocrystalline titania opal (i-ncTiO2-o) and nanocrystalline titania-silica opal (ncTiO 2/SiO2-o) on a substrate. Scanning electron microscopy and optical spectroscopy confirmed the high structural and optical quality of the i-ncTiO2-o and ncTiO2/SiO2-o films. The crystalline phase and size of the crystallites of the i-ncTiO2-o and ncTiO2/SiO2-o films were obtained from wide-angle X-ray Diffraction to be anatase in the range between 15 to 30 nm. Optical spectroscopy was used to investigate the effect of water on the optical characteristics of the i-ncTiO2-o and ncTiO2/SiO 2-o films. The photoconductivity behavior of the i-ncTiO2-o and ncTiO2/SiO2-o films in the range between 300 to 450 nm at the higher energy flat bands was investigated and compared with those of nanocrystalline titania (nc-TiO2) reference films.