Synthesis of Au–ZnO and Pt–ZnO nanocomposites by one-step flame spray pyrolysis and its application for photocatalytic degradation of dyes

Au–ZnO and Pt–ZnO nanocomposites have been synthesized by one-step flame spray pyrolysis (FSP) and characterized by X-ray diffraction (XRD), nitrogen adsorption, UV–vis spectroscopy, photoluminescence (PL), and transmission electron microscopy (TEM). The XRD and TEM results revealed that Au and Pt metallic phase were formed late during flame synthesis after ZnO was formed. Their average particle/cluster sizes were ranged between 3 and 7 nm depending on the amount loading (1 and 3 wt%). Although both of the FSP-derived Au–ZnO and Pt–ZnO possessed similar physical properties (i.e., crystallite size and specific surface area), an improvement in photocatalytic degradation of methylene blue in comparison to pure ZnO and commercial titania photocatalysts (JRC-TiO2 and P-25) was observed only for the Au–ZnO and not for the Pt–ZnO due probably to the different type of Fermi-level equilibration between Au and Pt.