One pot direct hydrothermal growth of photoactive TiO₂ films on glass

We demonstrate that titanium (IV) oxide films may be deposited on Corning glass by a simple, one-pot, low temperature (95 °C) hydrothermal growth technique and that providing the correct conditions are employed, the films produced show clear photoactivity under UV illumination as evidenced by changes in water contact angle and the progressive photo-oxidation of stearic acid. It is further demonstrated that the growth, structure and photoactivity of the films depends critically upon the H₂O concentration employed during growth. For H₂O concentrations below 0.1 M, little or no growth was observed, while above 0.3 M, precipitation or even gelation rapidly occurred. Only at H₂O concentrations of 0.1 M and 0.2 M was appreciable film growth observed, while photoactive titania was formed only via growth using a water concentration of 0.1 M, the films grown using the higher concentration of water (0.2 M) being essentially photo-inactive. The method developed is discussed in terms of the possible chemical steps involved and is proposed as a low-cost alternative to higher temperature, less environmentally friendly approaches to TiO₂ film production.