Photocatalytic TiO2 thin films and coatings prepared by sol-gel processing: a brief review

The use of nanostructured coatings is crucial to maintain clean surfaces in public transport, shopping malls, parks, and hospitals. Megacities produce large amounts of pollutants in water and air, making it necessary to develop strategies to prevent diseases caused by accumulation of organic compounds, bacteria, viruses, and other harmful microorganisms on surfaces. This concise review analyzes the fundamental deposition techniques based on the sol-gel process for the preparation of TiO2 films and coatings. In this regard, methodologies such as dip-coating, spin coating, spray pyrolysis, and electrophoretic sol-gel deposition are reviewed in detail. Outstanding properties such as chemical stability, reusability, hydrophilicity, and activation by sunlight or simulated solar radiation position these TiO2 thin films and coatings as a suitable technology for commercial devices that keep public surfaces clean. Environmental and energy applications including water and air purification, gas sensing, production of renewable fuels from water splitting and CO2 photoreduction, as well as antimicrobial features of the sol-gel-based TiO2 coatings can be considered as potential and valuable strategies to control pollution in the actual worldwide societies.