Influence of dispersion of various proportions of metallic gold nanoparticles on the optical and photocatalytic properties of titania

Abstract

In this research work, metallic gold nanoparticles with optimal concentration 6.7 × 1017 atom/m2 illustrates an exceptional photocatalytic reactivity in removal of methylene blue and indigo carmine dyes on titania surface. Titania nanoparticles were fabricated by sol-gel method and Au nanoparticles were incorporated by incipient wetness route on titania surface without using reducing agent. Various developed techniques as XRD, N2-adsorption-desorption isotherm, DRS, PL and HRTEM are selected for studying the physicochemical properties of the hybrid nanoparticles. The photocatalytic efficiency of the as-synthesized nanoparticles was estimated and the results reflect that the photocatalytic activity in removal of MB and IC dyes increases with increasing Au concentration and maximizes at 1 wt% followed by remarkable reduction in the photoreactivity monotonically. The photocatalytic rate constant in removal of MB dye is 0.069 min−1 which is fifty times than that of titania single phase (0.0014 min−1). The point of zero charge of Au/TiO2 estimated from zeta potential measurement is 8.4 reflecting the facility of removal of IC dye compared with MB dye. The electron transfer from titania conduction band to Au Fermi level is primary cause for enhancing the quantum efficiency of the photogenerated charge carriers. Hydroxyl radical and positive hole are the main reactive species in removal of MB dye on gold doped titania. The photocatalytic stability implies the strong catalytic performance of the prepared nanoparticles after five consecutive cycles.