ZnO–Fe3O4–Au Hybrid Composites for Thioanisole Oxidation Under Visible Light: Experimental and Theoretical Studies

Abstract

Organic sulfides are present in many materials such as coal, organic polymers, and xenobiotics and cause severe pollution problems during disposal, and their oxidation is essential from the environmental point of view. ZnO and ZnO–Fe3O4–Au NPs were prepared, and characterized by analytical methods (XRD, TEM, HRTEM, XPS and Confocal Microscope Analysis) for employment as photo-catalysts for the oxidation of thioanisole under visible light. A considerable visible light photo-oxidation of sulfur compound was observed in the presence of ZnO–Fe3O4–Au NPs, where the content Fe3O4 facilitates its isolation and recovery from the reaction medium by an external magnet for reuse in the oxidation. The oxidation of thioanisole was monitored spectroscopically, and was found to follow first order kinetics in the substrate, for which a possible mechanism is proposed. Density functional theory was used to analyze the oxidation pathway in order to predict the rate limiting step in the reaction since the sulfoxidation through sulfide radical cation >S+· → >S=O is important biotechnologically and environmentally.