Innovative photocatalyst (FeOx–TiO2): transients induced by femtosecond laser pulse leading to bacterial inactivation under visible light

Abstract

This study reports the photosensitizing effect/mechanism of FeO_x under visible light irradiation and charge transfer to TiO₂ on FeO_x–TiO₂ cosputtered film. The transients which were photo-induced by femto-second laser pulses at 545 nm (25 fs) were identified, in addition to the concomitant bleaching bands at <440 nm. Electron trapping at 150 fs was observed to compete with electron–hole recombination. A regularized inverse Laplace transform of the transient decay kinetics was worked out to determine the lifetime of the transients. About 50% of the charge carriers recombined within 500 fs, less than 50% of the charges recombined within 25 ps and a small percentage remained trapped. The transient decay within 500 ps did not decay to zero. This is the evidence for the photo-induced charges in FeO_x–TiO₂ leading subsequently to bacterial inactivation in the minute range. The second part of this study addresses the details of the FeO_x–TiO₂–PE photocatalyst performance during E. coli inactivation under solar light irradiation. The bacterial inactivation kinetics was similar under solar or visible light irradiation (>400 nm). This observation unexpectedly confirms the role of FeO_x absorbing light in the visible region. The important role of TiO₂ is reported, leading to bacterial inactivation in the FeO_x–TiO₂ co-sputtered films.