Reactivity and antimicrobial properties of nanostructured titanium dioxide

The photo-induced reactivity of three nanostructured titanium dioxides including TiO2 nanoparticles (i.e., nano-TiO2), titania–silica aerogel and nanotextured TiO2 film, were investigated for gas phase photocatalytic oxidation of trichloroethylene and inactivation of Bacillus subtilis and Escherichia coli microbial cells. A correlation was observed between photoreactivity for TCE conversion and bactericidal activity within TiO2 of similar nanostructures and composition (i.e., elemental and phase). This indicates that the photogenerated radical species from UV-irradiated TiO2 responsible for TCE photo-oxidation also play a major role in the inactivation of microbial cells. The superb bactericidal activities of titania–silica aerogels (i.e., up to 6log reductions in viable B. subtilis) and nanotextured TiO2 film (3.4log reduction) compared to commercial Degussa P25 TiO2 (0.64log reduction) and optimum nano-TiO2 (1.3log reduction) far exceeds the observed activity enhancement for TCE photo-oxidation. This implies that nanoscale chemical and structural environment also contribute towards the bactericidal activities.