ZnO/Ag multilayer for enhancing the catalytic activity against 4-nitrophenol

A multilayer thin film from zinc oxide and silver (ZnO/Ag multilayer thin film) has been synthesized via the technique of pulsed infrared laser deposition at 600 °C to be used as a portable catalyst for the degradation of 4-nitrophenol. The multilayer thin film was formed by two steps; the first one was making a thin film with a 300 nm thickness, followed by a 100 nm thin film from Ag, which was characterized by different characterization techniques. The XRD data demonstrated the presence of hexagonal Ag on ZnO in the formation of ZnO thin films and ZnO/Ag thin films. Also, it showed that crystallite size is decreasing as the Ag concentration rises because of the difference in atomic radius between Zn and Ag atoms in the crystal structure formation of ZnO coated with Ag. The crystal quality of ZnO and Ag was evaluated using photoluminescence (PL). The optical investigation showed the decrease in transmittance after coating ZnO film with Ag was due to ZnO films including more voids than ZnO/Ag films. From SEM images, the morphology of ZnO films was modified by the appearance of brilliant spots, which was related to the coating of the Ag layer as confirmed by elemental analysis. Then, based on the findings of catalytic experiments against 4-nitrophenol, the ZnO/Ag multilayer thin film shows an exceptional potential enhancement in compared to that of ZnO thin film.