Synthesis and characterization of noble metal nanocomposites: Ag/Fe3O4/ZnO and Ag/Fe3O4/CuO/ZnO for better photocatalytic activity under visible light irradiation

Nobel metal such as silver (Ag) nanoparticles have been proven could enhance photocatalytic activity under visible light irradiation and prevent recombination of electron and hole. Fe3O4/ZnO and Fe3O4/CuO/ZnO has been investigated in our previous study. So in this work, a magnetic Ag/Fe3O4/ZnO and Ag/Fe3O4/CuO/ZnO nanocomposites were successfully synthesized using sol-gel method. The as-synthesized products were characterized by X-ray diffraction and ultraviolet-visible (UV-Vis) spectroscopy. The results showed that the nanocomposites were the combination of the desired nanoparticles. From the UV-Vis absorption spectra, we found the surface plasmon resonance (SPR) to be around similar to 440 nm. Under visible light irradiation, the Ag/Fe3O4/ZnO and Ag/Fe3O4/CuO/ZnO nanocomposites exhibited much higher photocatalytic activity than the Fe3O4/ZnO and Fe3O4/CuO/ZnO. The effect of catalyst dosage and initial concentration of methylene blue (MB) were also tested. To understand the mechanism in photocatalytic activity, several scavengers were tested. The reusability study suggested that the prepared nanocomposites can still maintain the degradation efficiency after four cycles, showing great potential for water purification.