Bactericide effects of transparent polyethylene photocatalytic films coated by oxides under visible light

This review addresses catalytic/photocatalytic films under visible light inducing fast bacterial inactivation. These films present uniform, stable and adhesive surfaces able to inactivate bacteria within minutes. Uniform sputtered polyethylene-TiO2 (PE-TiO2) films absorbing mainly in the UV-region were later followed by studies on PE-FeOx and PE-FeOx-TiO2 absorbing light in the visible region. The amount of TiO2 sputtered on PE was significantly increased by RF-plasma pre-treatment due to the additional polar binding sites introduced on the PE-film. The hydrophobic to hydrophilic conversion of the PE-TiO2 films under light irradiation was observed to be concomitant with the bacterial inactivation time. The TiO2 diffuse reflectance spectra (DRS) of TiO2-PE-films were extensively modified by the sputtering of FeOx. The structure of the sputtered layers revealed a random deposition of FeOx-TiO2 on PE. The oxidative radical species generated on semiconductor surfaces were identified by appropriate scavenging experiments. By photoelectron spectroscopy (XPS), the redox processes occurring on the photocatalysts were evaluated. Repetitive bactericide cycling was possible for the three films discussed in this review. Bacterial inactivation mechanisms were suggested for the different films presented in this review.