Synthesis of TiO2 sol in a neutral solution using TiCl4 as a precursor and H2O2 as an oxidizing agent

Nanosize TiO2 thin film on glass substrate was obtained through dip-coating method using TiO2 sol. Suspended nanosize TiO2 sols with anatase structure in aqueous solution were synthesized by sol–gel method using TiCl4 as a precursor. TiCl4 was reacted with an aqueous solution of NH4OH to form Ti(OH)4, and H2O2 was then added to form peroxo titanic acid. It was further heated in water and converted to TiO2. The effects of the preparation parameters, viz., pH value of the Ti(OH)4 gel, concentration of H2O2, and heating temperature and time, on the properties of the TiO2 sol were investigated. The materials were characterized by X-ray diffraction, Fourier transform-infrared spectroscopy, and transmission electron microscopy. The results showed that the primary TiO2 particles were rhombus with the major axis ca. 10 nm and minor axis ca. 4 nm, and were in anatase structure. The sol was excellent in dispersibility and was stable in neutral and even slight basic conditions for at least 2 years without causing agglomeration. The best preparation condition was optimized with the pH value of Ti(OH)4 gel at 8, H2O2/TiO2 mole ratio of 2, and heating at 97 °C for 8 h. The transparent adherent TiO2 film on glass substrates exhibits strong hydrophilicity after illuminating with ultraviolet light and it can be used as an efficient photocatalyst.