The effect of nanoparticles size on photocatalytic and antimicrobial properties of Ag-Pt/TiO2 photocatalysts

Abstract

Ag-Pt-modified TiO2 nanocomposites were synthesized using the sol–gel method. Bimetallic modified TiO2 nanoparticles exhibited improved photocatalytic activity under visible-light irradiation, better than monometallic Ag/TiO2 and Pt/TiO2 nanoparticles (NPs). All modified powders showed localized surface plasmon resonance (LSPR) in visible region. The photocatalysts’ characteristics by X-ray diffractometry (XRD), scanning transmission electron microscopy (STEM), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption (BET method for specific surface area) showed that sample with the highest photocatalytic activity had anatase structure, about 93m2/g specific surface area, maximum plasmon absorption at ca. 420nm and contained small NPs of silver of 6nm and very fine platinum NPs of 3nm. The photocatalytic activity was estimated by measuring the decomposition rate of phenol in 0.2mM aqueous solution under Vis and UV/vis light irradiation. It was found that size of platinum was decisive for the photocatalytic activity under visible light irradiation, i.e., the smaller Pt NPs were, the higher was photocatalytic activity. While, antimicrobial activities, estimated for bacteria Escherichia coli and Staphylococcus aureus, and pathogenic fungi belonging to Candida family, were only observed for photocatalysts containing silver, i.e., Ag/TiO2 and Ag-Pt/TiO2 nanocomposites.