Rapid synthesis of Zn2+ doped SnWO4 nanowires with the aim of exploring doping effects on highly enhanced visible photocatalytic activities

Abstract

In this work, we report on the rapid synthesis of Sn_1−xZn_xWO₄ nanocrystals with the aim of tailoring their structural, electronic, 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 the Barrett–Emmett–Teller technique. The effects of Zn²⁺ doping in SnWO₄ on the electronic structure and photogradation of methylene orange dye solution were investigated experimentally and theoretically. It was found that Zn²⁺ ions were homogeneously incorporated into the SnWO₄ host lattice with a solubility of x = 0.060, which led to a monotonous decrease in lattice volume. With Zn²⁺ doping, SnWO₄ nanocrystals showed a morphological alteration from irregular nanosheets to nanowires. Meanwhile, the BET surface areas were also greatly enlarged from 54 m² g⁻¹ to ∼100 m² g⁻¹. Contrary to the theoretical predictions of the quantum size effect, Zn²⁺ doped SnWO₄ nanocrystals showed an abnormal band gap narrowing, which can be well-defined as a consequence of the balance of quantum size effect, lattice contraction, electronegativity, and surface defect centers. With well-controlled morphology, surface area, and electronic structure via Zn²⁺ doping, the photocatalytic performance of Sn_1−xZn_xWO₄ nanocrystals was optimized at a Zn²⁺ doping level of x = 0.045.