Fabrication of titania films by sol-gel method using transparent colloidal aqueous solutions of anatase nanocrystals

The fabrication of dense or porous titania films by the sol-gel method using anatase colloidal solutions was examined. When anatase colloidal solutions without surfactants were deposited on a substrate, the anatase films thus obtained had a relatively high refractive index (~ 2.0). Porous films were fabricated using the anatase colloidal solutions with surfactants. Some films had phase separation structures on the submicron scale, such as spinodal decomposition, which consisted of anatase nanocrystal agglomerate regions and surfactant regions. When the dispersion of the anatase colloids was improved, mesoporous films could also be fabricated, although mesopores were irregular in size, shape, and arrangement.