Cu Doped TiO2: Visible Light Assisted Photocatalytic Antimicrobial Activity and High Temperature Anatase Stability

Indoor surface contamination by microbes is a major public health concern. A damp environment is one potential sources for microbe proliferation. Smart photocatalytic coatings on building surfaces using semiconductors like titania (TiO2) can effectively curb this growing threat. Metal-doped titania in anatase phase has been proved as a promising candidate for energy and environmental applications. In this present work, the antimicrobial efficacy of copper (Cu) doped TiO2 (Cu-TiO2) was evaluated against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) under visible light irradiation. Doping of a minute fraction of Cu (0.5 mol %) in TiO2 was carried out via sol-gel technique. Cu-TiO2 further calcined at various temperatures (in the range of 500 °C – 700 °C) to evaluate the thermal stability of TiO2 anatase phase. The physico-chemical properties of the samples were characterised through X-ray diffraction (XRD), Raman spectroscopy, X-ray photo-electron spectroscopy (XPS) and UV-visible spectroscopy techniques. XRD results revealed that the anatase phase of TiO2 was maintained well, up to 650 °C, by the Cu dopant. UV-DRS results suggested that the visible light absorption property of Cu-TiO2 was enhanced and the band gap is reduced to 2.8 eV. Density functional theory (DFT) studies emphasises the introduction of Cu+ and Cu2+ ions by replacing Ti4+ ions in the TiO2 lattice, creating oxygen vacancies. These further promoted the photocatalytic efficiency. A significantly high bacterial inactivation (99.9%) was attained in 30 mins of visible light irradiation by Cu-TiO2.