Cu-Doped TiO₂ Nanoparticle-Based Thin Films Obtained via the Mist-Deposition Method and Their Photocatalytic Antibacterial Properties

We successfully obtained Cu-doped TiO2 nanoparticles (CT NPs) using an ambient hydrothermal method and proposed a mist-deposition method to prepare CT NP-based transparent thin films. The resulting films exhibited 100% transmittance under visible light. Transmission electron microscopy (TEM) observations and X-ray diffraction (XRD) measurements were conducted to investigate the morphology and crystallinity of CT NPs. To clarify the relationship between the doping state of Cu and photocatalytic activity, we examined the effects of pH and the type of complexing agent to control the doping state of anatase-type TiO2 NPs. The thin film composed of these CT NPs exhibited superior photocatalytic antibacterial properties against E. coli compared to pristine anatase-type TiO2 NPs films. X-ray absorption fine structure (XAFS) spectroscopy was used to examine the active sites of the CT NPs, revealing that defects derived from Cu doping in TiO2 NPs play an important role in enhanced photocatalytic activity.