UV and visible light optimization of anatase TiO2 antimicrobial properties: Surface deposition of metal and oxide (Cu, Zn, Ag) species

Abstract

Presence of metallic Ag or oxidic Ag, Cu and Zn species on an anatase surface is shown to allow drastic modification of the disinfection capability of TiO2-based materials against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria and upon both ultraviolet and visible light excitations. While Cu shows non-positive influence in the photo-elimination of the microorganisms, Zn and Ag always displays an improved performance with respect to the bare titania reference. In particular, Zn has a positive effect with decreasing importance with increasing wavelength whereas Ag always display an optimum performance, irrespective of the initial oxidation state, excitation wavelength and microorganism nature. The physico-chemical analysis of the samples together with a spectro-kinetic combination based in a Langmuir-Hinshelwood-like kinetic model and the use of electron paramagnetic resonance were utilized to analyze the roots of the mentioned Cu, Zn, Ag dependent disinfection behavior. The approach allows the critical analysis of the effects that the metal-containing phases exert in anatase and provides evidence that two physical phenomena are of importance to justify the disinfection capability modification of the anatase phase. Both adhesion to bacteria and hole-radical derived attack to the microorganism appear critical to interpret disinfection although their relative contribution vary with the excitation light wavelength as well as the nature of the metal-containing phase present at the anatase surface.