Synthesis of titanium oxide layers on glass substrates with aqueous refluxed sols (RS) and photocatalytic activities

Nanocrystalline anatase films were prepared on glass substrates by the dip-coating method from aqueous refluxed sols and calcined at 100, 300 and 500 C. FT-IR, TEM, SEM, XRD, UV–VIS and XPS analysis were used to characterize the microstructure, phase evolution and chemical composition of the refluxed sols (RS) sols and TiO2 films. The photocatalytic activities of the TiO2 films were evaluated by photocatalytic degradation of aqueous methyl orange solutions. It was found that the RS sols were flavescent, alkalescent and contained anatase crystals. The TiO2 thin films contained not only Ti and O elements, but also a small amount of N and Na elements. The TiO2 films were transparent and its maximal light transmittance exceeded 80% under visible light region. Calcined at 300 C, the TiO2 thin film showed the highest photocatalytic activity, when the calcination temperature is higher than 300 C, the decrease in photocatalytic activity is due to sintering and growth of TiO2 crystallites resulting in the decrease of surface area. The results suggested that RS sols are promising novel precursors for synthesizing TiO2 films, and refluxing technique is quite efficient in preparing titania nanocrystalline films.