Structural transformation of Ag3PO4 and Ag3PO4/TiO2 induced by visible light and Cl− ions: its impact on their photocatalytic, antimicrobial, and antifungal performance

In this work, synthesis of Ag 3 PO 4 and its composite with TiO 2 (Ag 3 PO 4 /TiO 2 ) toward study of two phenomena naturally occurring in Ag 3 PO 4 is reported, specifically a visible light-driven (i.e., photocorrosion) and chloride ion-driven transformation of Ag 3 PO 4 to AgCl in chloride-free and chloride-present aqueous solution. A deeper insight on this transformation via study of their structural and morphological changes using X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) is performed. Substantial amount of AgCl is detected in both Ag 3 PO 4 -based materials after visible light irradiation in chloride-present environment. This led to an increase in optical band gap of Ag 3 PO 4 and Ag 3 PO 4 /TiO 2 from 2.52 to 2.99 eV and 2.48 to 3.02 eV, respectively. Impact of these structural changes in Ag 3 PO 4 and Ag 3 PO 4 /TiO 2 on their photocatalytic activity is evaluated from the photoinduced catalytic, antibacterial, and antifungal performance under visible light irradiation. The photocatalytic activity of pristine and photocorroded Ag 3 PO 4 is increased by ~ 10 times compared to that of pristine and photocorroded Ag 3 PO 4 /TiO 2 . Photocorroded Ag 3 PO 4 and Ag 3 PO 4 /TiO 2 possess minor antibacterial and antifungal activities (cell survival ~ 90%), whereas using pristine Ag 3 PO 4 and Ag 3 PO 4 /TiO 2 the cell survival is reduced by 100% after 60 and 120 min, respectively. Graphic abstract