FeOx-TiO(2) Film with Different Microstructures Leading to Femtosecond Transients with Different Properties: Biological Implications under Visible Light

This study presents the first report addressing the effect of FeOx-TiO(2) films microstructure on the transients detected by fast spectroscopy related to the long-range bacterial inactivation performance. The different fast kinetic femtosecond transient spectroscopy is reported for each FeOx+TiO(2) microstructure. The lifetime of the short transient-species and the oxidative intermediate radicals generated under light were identified. Co-sputtered FeOx-TiO(2) on polyethylene films presenting random distribution for both oxides were compared with sequentially sputtered FeOx/TiO(2) films made up only by FeOx in the topmost layers. The ratio FeOx:TiO(2) was optimized to attain the highest photo-conversion. By X-ray fluorescence, the Fe:Ti ration was found to be ~1.4 in the film bulk and by XPS-etching a ratio of 4:1 was found on the photocatalyst top-most layers. For co-sputtered FeOx-TiO(2)-PE films, the FeOx-TiO(2) heterojunction led to electron injection from the FeOx to lower-lying TiO(2) trapping states. The film optical properties, particle size, roughness, hydrophobic-hydrophilic shift and temporal evolution of the transient redox states were characterized in detail. Films with different microstructure led to different antibacterial activity. This suggests that the FeOx-TiO(2)-PE microstructure and not the position of the potential energy level of the semiconductors FeOx and TiO(2) control the charge transfer under light irradiation.