Effect of the structure on biological and photocatalytic activity of transparent titania thin-film coatings

In this work, the effect of titanium dioxide (TiO2) thin film microstructure on photocatalytic and biological activity was described. The films were prepared by low-pressure and high-energy magnetron sputtering processes. The structural investigations performed by X-ray diffraction revealed that the films from both the processes were nanocrystalline. It was found that TiO2 prepared by low-pressure process had the anatase structure with crystallites in size of 20 nm, while the film deposited in high-energy process had the rutile form with crystallites in size of 5 nm. The analysis of surface topography with the aid of optical profiler showed that all prepared films were homogenous and their roughness was lower than 1 nm. The wettability studies revealed hydrophilic nature of both films. The values of water contact angle obtained for anatase and rutile films were equal to 40° and 49°, respectively. Both types of the thin films were photocatalitycally active, but rutile exhibited higher decomposition rate as compared to anatase. During the photocatalytic reaction in the presence of TiO2-rutile film after 12 hours of UV-Vis irradiation 30 % of phenol was decomposed, whereas in case of TiO2-anatase it was only 10 %. Moreover, the influence of as-deposited coatings on the growth of selected microbes (Staphylococcus aureus, Escherichia coli, Candida albicans) was examined. It was found that the structural properties of TiO2 had an effect on biological activity of these films