Visible light-active sub-5 nm anatase TiO2 for photocatalytic organic pollutant degradation in water and air, and for bacterial disinfection

Abstract Visible-light-sensitive sub-5 nm anatase titanium dioxide (TiO 2 ) nanoparticles (NPs) were fabricated without any doping and calcination treatments. The energy band gap was effectively narrowed to ~ 2.98 eV. The surface and subsurface hydroxyl defects were ascertained as the origin for the band gap narrowing and for the efficient azo-based dye degradation in water and formaldehyde decomposition in air, as well as disinfection of Staphylococcus aureus bacteria, under visible light irradiation.