Study on the hydrophobized changes in wettability of sol-gel synthesized nano titanium dioxide films

The hydrophobized change in wettability of TiO2 films has been investigated for glass coated with acidic TiO2 nanosols containing varying concentrations of dispersed nanocrystalline titania, obtained by sol-gel method. The photo-induced change in wettability was evaluated by measuring the time dependent drop of water contact angle (WCA) after samples had been soaked in a decanoic acid (DA). TiO2 films treated in this way exhibit superhydrophobic behaviour, with WCA greater than 1600. After radiation with UV (black light), the superhydrophobic properties are transformed into superhydrophilic properties, with WCA of almost 08. As TiO2 content and layer thickness increase, high rates of photo-induced change are found. Use of a calcination temperature for the intermediate annealing of the single layers in multilayer coatings and a short final sintering step at a relatively high temperature (e.g. 500-700 degrees C for 10 min) allow the preparation of relatively thin TiO2 films on glass with a high photoactivity.