Low-temperature deposition of TiO2 thin films with photocatalytic activity from colloidal anatase aqueous solutions

Crystalline TiO2 films have been deposited on several substrates (glass, F-doped SnO2-covered glass, and silicon wafers) by a drain-coating method from a colloidal anatase aqueous solution. The process is performed at low-temperature, 333 K, in open atmosphere. The colloidal TiO2 consists on anatase nanoparticles of about 9 x 5 nm size, stabilized by tetrabutylammonium cations (TBA(+)). This colloid has also been obtained under mild conditions (i.e., low temperature and ambient pressure) by hydrolysis of tetraisopropyl. orthotitanate (TIP) in the presence of (TBA)OH and subsequent treatment by microwave radiation to enhance crystallization. Different film thicknesses have been obtained by consecutive deposition processes. Titania films thus obtained were transparent and showed good adherence, FT-IR analysis of the films reveal that TBA cations were not trapped in the film during the deposition process. No further thermal posttreatment was required to eliminate organics from the films or to induce titania crystallization. The photocatalytic activity of as-deposited titania has been assessed by the photodegradation of salicylic acid in aqueous solution under aerated conditions.