Long-lasting photocatalytic activity of trace phosphorus-doped g-C3N4/SMSO and its application in antibacterial ceramics

Conventional photocatalysts generate numerous active species-primarily hydroxyl radicals (•OH)-under solar light excitation to exert photocatalytic activity for especially antibacterial effects. However, the light dependence limits their competitiveness against other antimicrobial materials since they do not work at night. Herein, a P-g-C₃N₄/Sr₂MgSi₂O₇:Eu²⁺,Dy³⁺ (P-g-C₃N₄/SMSO) composite day-night photocatalyst is synthesized, using a model methyl orange (MO) substrate, and the impacts of trace P doping and the SMSO composite on the activity of the photocatalyst in MO degradation is investigated; Its antibacterial effect against Escherichia coli and Staphylococcus aureus on ceramic surfaces is further examined. The morphology, structure, and composition of the photocatalyst are characterized by SEM, TEM, XRD, FT-IR, and UV-vis DRS. Finally, the photocatalytic mechanism is elucidated through active species capture experiments and ESR testing. P doping and the SMSO heterojunction structure reduce the width of the forbidden band of g-C₃N₄ and broaden its visible-light-response range. Moreover, SMSO acts as a light source to realize long-lasting photocatalytic performance of the composite, even in the dark. The photocatalytic process produces •O₂^-, ¹O₂, and h⁺ active species, with •O₂^- and ¹O₂ playing the dominant role-instead of •OH as previously thought.