ZrNO-Ag co-sputtered surfaces leading to E. coli inactivation under actinic light: Evidence for the oligodynamic effect

This study reports visible light sensitive ZrNO and ZrNO-Ag polyester samples prepared by sputtering in an Ar/N-2/O-2 atmosphere leading to Escherichia coli bacterial inactivation. The bacterial inactivation by ZrNO avoids the increasing environmental concern involving the fate of Ag-leaching of many disinfectants. The simultaneous co-sputtering of ZrNO and Ag2O enhanced the E. coli bacterial inactivation kinetics compared to the sequential sputtering of ZrNO and Ag. A reaction mechanism is suggested triggered by photoinduced interfacial charge transfer (IFCT) suggesting electron injection form the Ag2Ocb, to the ZrO2cb. The sizes of the ZrO2 and Ag nanoparticles in the co-sputtered ZrNO-Ag were 80-130 nm and 8-15 nm respectively as determined by high angular annular dark field (HAADF) microscopy. Evidence is presented by X-ray photoelectron spectroscopy (XPS) for the self-cleaning of the photocatalysts after bacterial inactivation. This enabled a stable catalyst reuse. The XPS experimental spectra of ZrNO and ZrNO-Ag were deconvoluted into their ZrN, ZrNO and ZrO2 components. The amounts of Ag-ions released during bacterial inactivation were <5 ppb/cm(2) and well below the Ag cytotoxic levels. Since no cytotoxicity was introduced during the bacterial inactivation process, the ZrNO-Ag disinfection proceeds through an oligodynamic effect. (C) 2013 Elsevier B.V. All rights reserved.