Low-Temperature Deposition of TiO₂ Thin Films with Photocatalytic Activity from Colloidal Anatase Aqueous Solutions

Crystalline TiO 2 films have been deposited on several substrates (glass, F-doped SnO 2 -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 TiO 2 consists on anatase nanoparticles of about 9 × 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.