Wettability, Photoactivity, and Antimicrobial Activity of Glazed Ceramic Tiles Coated with Titania Films Containing Tungsten

Self-cleaning coatings are advanced materials for the removal of pollutants and microorganisms by combining wettability, photocatalytic degradation, and antimicrobial activity. In this work, we propose a rational design of self-cleaning films based on TiO₂ synthesized by sol–gel on commercial glazed ceramic tiles for building’s indoor applications. The synthesis strategy is based on hydrolysis and condensation of Ti-isopropoxide in the presence of W­(VI) precursors to tune defects and crystallinity of the resulting W–TiO₂ thin film. From the microstructure and surface composition analysis for different tungsten contents and annealing temperatures, we conclude that the film is composed by sintered TiO₂ particles with adsorbed polytungstates (WO_x) that inhibit anatase/rutile transformation. Polytungstates on TiO₂ also induce surface defects that enhance water contact angle and inactivation of Escherichia coli under visible light. The presence of W­(VI) has a negligible effect toward crystal violet degradation either under visible or under UV light. These results provide evidence on the existence of at least two different types of defects: (i) intrinsic defect from a sol–gel route and (ii) induced defect by tungsten species on the surface. Understanding the correlation between composition, structure, and self-cleaning properties provides a base for an efficient design of low-cost self-cleaning ceramic tiles that can be fully manufactured in an industrial plant.