Synthesis and characterization of highly ordered titania-alumina mixed oxide mesoporous films with high alumina content

Highly ordered mesoporous titania-alumina mixed oxide thin films are synthesized by using spin-coating method based on solvent evaporation process. The mole ratios of doped alumina are controlled in the range from 0 to 30 mol%. In order to achieve a highly ordered mesostructure, a low-temperature and low-humidity aging condition after the spin-coating is applied by means of controlling the hydrolysis and condensation reactions of metal species. During thermal treatment, the Im-3m mesostructure is unidirectionally contracted along the direction perpendicular to the substrates. The mesochannel walls are composed of periodically arranged cages with connecting necks between the neighboring cages. On the top-surface of the films, the uniformly-sized mesopores are observable. By doping alumina species in the pore walls, the thermal stability of the films is enhanced up to 450 °C. By finely tuning the amount of the doped alumina species, we can realize the successful anatase crystallization in the frameworks with the retention of the ordered mesoporous structures. The obtained mesoporous titania-alumina mixed oxide films are fully characterized by 2D-grazing-incidence small-angle X-ray scattering (2D-GISAXS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Raman spectroscopy.