Different antibacterial effect of Ag3PO4/TiO2 heterojunctions and the TiO2 polymorphs

Abstract Herein, we analyzed the antibacterial effect of the TiO2 polymorphs and Ag3PO4/TiO2 heterojunctions. The sol-gel-derived TiO2 was calcined at 400 °C, 550 °C and 700 °C to get different polymorphs. Subsequently, Ag3PO4/TiO2 composites were synthesized by the in-situ precipitation method. These photocatalysts were characterized by XRD, TEM, UV–VIS–NIR, XPS, FP, AAS, and SEM. Photocatalytic sterilization was employed by the transferring and spreading tests with Gram-positive S. aureus (ATCC 25933) and Gram-negative E. coli (ATCC 25922) bacteria. It was noted that the anatase TiO2 has better antibacterial effect than rutile. And there was an existing synergetic effect between these two polymorphs. Besides partially preventing the photo corrosion, the Ag3PO4/TiO2 heterojunctions exhibit a remarkable bactericidal activity and almost completely collapse the high concentration bacterial cells. Moreover, The Ag3PO4/TiO2 heterojunctions show more pronounced in E. coli than S. aureus for their different cellular structure. The sterilization of the tolerant Gram-positive bacteria often needs the assistance of Ag-ion, while Gram-negative E. coli is more sensitive to •O2− radicals, and h+ during the photocatalytic sterilization.