Insight on the photocatalytic bacterial inactivation by co-sputtered TiO2-Cu in aerobic and anaerobic conditions
Co-sputtered TiO2-Cu polyester (TiO2-Cu-PES) under actinic light induced bacterial reduction of E. coli in the presence of O2 (air) and under anaerobic conditions. The bacterial inactivation/oxidation proceeds in the absence of O2 (air) probably due to the highly oxidative TiO2vb(h+) species and the toxic Cu present. By the choice of suitable scavengers, the presence of highly oxidative radicals was confirmed in aerobic media. The E. coli inactivation in aerobic media proceeds on TiO2-Cu-PES within 30 min and with a slower kinetics of 90 min in anaerobic media. Malondialdehyde generation a product of bacterial inactivation, was observed on the TiO2-Cu-PES in air and in lesser amounts under anaerobic conditions. Repetitive bacterial inactivation cycles show a Cu-release of 2 ppb/cm2 by the TiO2-Cu-PES surface as determined by inductively coupled plasma mass spectrometry (IPC-MS). The Cu released is far below the values reported for the Cu released by TiO2-Cu-PES samples by sputtering Ti and Cu in sequential order from two targets. By X-ray photoelectron spectroscopy (XPS), redox catalysis by the Cu and TiO2-species was observed under anaerobic conditions providing further evidence for processes leading to bacterial inactivation in anaerobic media. A mechanism for the TiO2-Cu-PES bacterial inactivation is suggested consistent with the results reported in this study.