Optical bandgap tuning, photocatalysis, and reduction performance of Ag-loaded ZnO/SiO 2 nanostructure

Abstract In this work, we have synthesised ZnO nanoparticles (Nps) with an average diameter of 9.5 nm via a soft chemical route. These ZnO Nps were encapsulated within a mesoporous SiO 2 matrix through a microemulsion-assisted sol–gel procedure to form ZnO@SiO 2 (ZS) composite. Then, silver Nps were successfully impregnated onto the SiO 2 matrix surface to form ZnO@SiO 2 @Ag (ZSAg) nanocomposite. Transmission electron micrographs and scanning electron microscope analysis confirmed that nano-sized Ag of size about 5 nm is homogeneously incorporated into the SiO 2 matrix, which formed a Schottky barrier in the structure and narrowed the band gap energy from 3.1 to 2.58 eV. The samples have been evaluated for photocatalytic degradation of methylene blue (MB) under irradiation of UV and sunlight. ZnO demonstrated excellent photocatalytic performance for the degradation of MB under both UV and sunlight irradiation with degradation rates of 0.04 and 0.03 min −1 , respectively and swiftly degraded the MB within 90 min. On the other hand, ZSAg degraded the MB dye faster with a rate of 4.5 × 10 −3 under sunlight as compared to UV light with a rate of 3.5 × 10 −3 . In addition, ZSAg with NaBH 4 exhibited superior catalytic activity for the reduction of Rhodamine B and 2-nitrophenol. These research findings highlight that the ZSAg composite is a promising potential catalyst, providing stability, reduction capability and utilising sunlight for the catalysis process.