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

•Controlled sol–gel synthesis of hydroxyl defect-laden sub-5 nm anatase TiO2•Clarification of the surface and sub-surface hydroxyl defects•Hydroxyl defects rendered the sub-5 nm anatase TiO2 visible light-active.•Effective visible-light-driven degradation of organic pollutants in water and in air•Effective photocatalytic bacterial disinfection under visible light irradiation

Visible-light-sensitive sub-5 nm anatase titanium dioxide (TiO2) 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.

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