Visible-light-responsive bicrystalline (anatase/brookite) nanoporous nitrogen-doped TiO2 photocatalysts by plasma treatment

Abstract The plasma treatment method was employed to characterize nitrogen (N)-doped nanoporous TiO 2 photocatalysts (N-nTiO 2 ) of ∼18 nm diameter. With respect to the organic dye degradation efficiencies and antibacterial properties after exposure to visible-light irradiation, N-nTiO 2 showed better performance than the alternative commercial 5 nm anatase TiO 2 (TiO 2 ), as-grown nanoporous TiO 2 (as-grown nTiO 2 ), and Ar-plasma-treated nanoporous TiO 2 (nTiO 2 ) photocatalysts. This was attributed mainly to N-nTiO 2 ’s higher anatase/brookite phase crystallinity and large surface area (375.9 m 2  g − 1 ). The N doping of N-nTiO 2 was confirmed by a shift of ∼0.25° toward the higher angles in the XRD patterns and high-resolution X-ray photoelectron spectroscopy (HR-XPS) surface analysis results. Additionally, N-nTiO 2 ’s total surface energy was significantly increased. Its photoluminescence (PL) response and apparent quantum yield inhibited the recombination of holes and electrons and decreased the band-gap energy (Eg  − 1 for N-nTiO 2 , respectively. In contrast, under exposure to visible light, the value for nTiO 2 was 0.395 h − 1 . Moreover, the antibacterial activity indicated that ∼100% of both Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ) were destroyed after 30 min visible-light irradiation while photostability was maintained. Considering all of these results, it was concluded that N-nTiO 2 is an excellent solar-light-activated photocatalyst candidate for water/waste treatment and medical applications.