Insight into the catalyst/photocatalyst microstructure presenting the same composition but leading to a variance in bacterial reduction under indoor visible light

Abstract

a b s t r a c tInsight into two different uniform atomic-scale microstructures of Cu-and Ti-oxides sputtered on polyethylene (PET) presenting different redox properties and a distinct bacterial inactivation dynamics. Co-sputtered (CuOx-TiO 2 -PET) consists mainly of CuO. It leads to bacterial inactivation kinetics within 20 min under very low intensity actinic light (0.5 mW/cm 2 ). The sequential sputtered (CuOx/TiO 2 -PET) consist mainly of Cu 2 O and led to bacterial inactivation within 90 min. Evidence for redox catalysis is present leading to bacterial inactivation by X-ray photoelectron spectroscopy (XPS). The Cu and Ti uniform distribution on the catalyst surface was mapped along the coating thickness by wavelength dispersive spectrometry (WDS). The inactivation time of E. coli determined by fluorescence stereomicroscopy was in agreement with the time found by agar plating. The short-lived transient intermediates on the cosputtered catalyst were followed by laser spectroscopy in the femto/picosecond region (fs-ps). By atomic force microscopy (AFM) the roughness of the co-sputtered (CuO) and sequentially sputtered samples (Cu 2 O) were found respectively as 1.63 nm and 22.92 nm. The magnitude of the roughness was correlated with the bacterial inactivation times for both types of catalysts. The differentiated mechanisms for the vectorial charge transfer on co-sputtered and sequential sputtered CuOx/TiO 2 catalysts and it is suggested as one of the factors leading to a distinct bacterial inactivation kinetics.

Abatement of ammonia and butyraldehyde under non-thermal plasma and photocatalysis: Oxidation processes for the removal of mixture pollutants at pilot scale

“…The carbon C1s line with position at 284.6 eV was used as a reference to correct the charging effects. The surface atomic concentration of elements was determined from peak areas using known sensitivity factors [33]. Spectrum background was subtracted according to Shirley [34].…”

Self-Sterilizing Sputtered Films for Applications in Hospital Facilities

“…Figure 2 , trace 6) shows complete bacterial reduction in the dark. Bacterial inactivation takes place in the dark possibly through an oligodynamic effect as recently reported by S. Rtimi [ 41 , 52 , 53 ]. The effect of Cu on bacteria has been associated to reactions blocking the of proteins/enzymes regulating the respiratory chain [ 32 , 41 , 52 ].…”

“…During the last years, we investigated the bactericidal activity on Ag, Cu, and other metal oxides sputtered on polymers and textile fabrics. The antibacterial kinetics, microstructure and surface properties have been reported in details [ 40 , 41 , 42 , 50 , 51 , 52 , 53 ].…”

“…This is due to the inward charge diffusion of the generated charges in the TiO 2 under band–gap irradiation [ 29 , 51 ]. In addition, longer sputtering times facilitate the TiO 2 inter-particle growth decreasing the TiO 2 contact surface with bacteria [ 52 ]. Figure 2 , trace 6) shows complete bacterial reduction in the dark.…”

“…In addition, the semiconductor space charge layer in both the TiO 2 and CuO further decreases the potential depth available for the charge injection at the TiO 2 -Cu hetero-junction. This in turn, decreases the energy difference between TiO 2 and Cu, which is not favorable for the charge injection [ 29 , 52 ]. The conduction band of CuO at −0.30 V vs. SCE (pH 7) is at a more negative potential than the potential required for one electron oxygen reduction [ 52 ].…”