Plasmon-Induced Inactivation of Enteric Pathogenic Microorganisms with Ag−AgI/Al2O3 under Visible-Light Irradiation

The plasmon-induced photocatalytic inactivation of enteric pathogenic microorganisms in water using Ag−AgI/Al2O3 under visible-light irradiation was investigated. The catalyst was found to be highly effective at killing Shigella dysenteriae (S. dysenteriae), Escherichia coli (E. coli), and human rotavirus type 2 Wa (HRV-Wa). Its bactericidal efficiency was significantly enhanced by HCO3 − and SO4 2− ions, which are common in water, while phosphate had a slightly positive effect on the disinfection. Meanwhile, more inactivation of E. coli was observed at neutral and alkaline pH than at acid pH in Ag−AgI/Al2O3 suspension. Furthermore, the effects of inorganic anions and pH on the transfer of plasmon-induced charges were investigated using cyclic voltammetry analyses. Two electron-transfer processes occurred, from bacteria to Ag nanoparticles (NPs) and from inorganic anions to Ag NPs to form anionic radicals. These inorganic anions including OH− in water not only enhanced electron transfer from plasmon-excited Ag NPs to AgI and from E. coli to Ag NPs, but their anionic radicals also increased bactericidal efficiency due to their absorbability by cells. The plasmon-induced electron holes (h+) on Ag NPs, O2 •−, and anionic radicals were involved in the reaction. The enhanced electron transfer is more crucial than the electrostatic force interaction of bacteria and catalyst for the plasmon-induced inactivation of bacteria using Ag−AgI/Al2O3.