Effect of crystallization on the formation of mesostructured TiO2 thin films

Strict control of the crystallization of TiO2 is one of the most important factors in forming mesoporous structured TiO2 thin films. Effects of the crystallization of TiO2 on the formation of mesoporous structures have been studied by transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) observation and X-ray diffractometry (XRD) analysis. The obtained well-ordered mesoporous TiO2 thin films, calcined at 450degreesC to remove the template, are composed of a continuous non-crystalline TiO2 matrix containing TiO2 nanocrystals, whose mean size is sufficiently small to support the mesostructure. In the mean time, the mesoporous TiO2 materials that almost lose their ordered structure after calcination consist of large TiO2 crystallites (over 6 nm), and the overgrowth of TiO2 crystallites cause a collapse of the mesoporous structure.