Sulfur-doped titanium dioxide exhibits a strong visible-light-induced antibacterial effect. The new photocatalyst can effectively kill Micrococcus lylae, a common Gram-positive bacterium. The relationship between sulfur concentration and the bactericidal activity of S-doped TiO2 was investigated. Results from DMPO spin-trapping electron spin resonance measurements confirm the formation of hydroxyl radicals, which is the origin of the considerable bactericidal activity under visible light irradiation.
Constructing a TiO based heterostructure is a very effective strategy for enhancing photocatalytic performance. The details of the electronic structure, interfacial interaction, and photogenerated carrier separation are important for explaining the photocatalytic properties of a heterostructure. Herein, the density of states, charge distribution, and the band offset of the monolayer g-CN/TiO heterojunction are systematically investigated through the hybrid DFT method. Results indicated that the valence band offset and the conduction band offset of the g-CN/TiO heterostructure were 0.40 and 0.18 eV, respectively. Interfacial interaction made the TiO surface with negative charge, whereas the g-CN surface with positive charge, which led to the formation of a built-in electric field at the interface. Under illumination, the built-in electric field accelerates the transfer of photoexcited electrons in the CB of TiO into the VB of g-CN, thus resulting in the photoexcited electrons and holes naturally accumulating in the CB of g-CN and the VB of TiO, respectively. The photoexcited electrons and holes gathering in different surface regions efficiently prolonged the lifetime of photogenerated carriers. Meanwhile, electrons in the CB of g-CN and holes in the VB of TiO had a stronger redox ability. Therefore, g-CN/TiO is a direct Z-scheme photocatalyst, and the Z-scheme heterostructure mechanism can well explain the improved photocatalytic activity of the g-CN/TiO heterostructure.
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