Particle Size and Structural Control of ZnWO4 Nanocrystals via Sn2+ Doping for Tunable Optical and Visible Photocatalytic Properties

In this work, we report on the microwave-assisted hydrothermal synthesis of Sn2+-doped ZnWO4 nanocrystals with controlled particle sizes and lattice structures for tunable optical and photocatalytic properties. The samples were carefully characterized by X-ray diffraction, transmission electron microscopy, inductive coupled plasma optical emission spectroscopy, UV–vis diffuse reflectance spectroscopy, and Barrett–Emmett–Teller technique. The effects of Sn2+ doping in ZnWO4 lattice on the crystal structure, electronic structure, and photodegradation of methylene orange dye solution were investigated both experimentally and theoretically. It is found that part of the Sn2+ ions were homogeneously incorporated in the ZnWO4 host lattice, leading to a monotonous lattice expansion, and part of Sn2+ ions were expelled at surface sites for decreased crystallinity and particle size reduction. By Sn2+ doping, ZnWO4 nanocrystals showed a significant XPS binding energy shift of Zn 2p, W 4f, and O 1s, which is attribut...