Hydrothermal synthesis, characterization, and optical properties of wolframite ZnWO4nanorods

Abstract

In this research, the effects of pH, reaction temperature and holding reaction time on the synthesis of one-dimensional ZnWO₄ nanostructures by a hydrothermal method were studied. Phase, morphology and atomic vibration were characterized by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and Fourier transform infrared (FTIR) and Raman spectroscopy. The pure monoclinic ZnWO₄ structure was synthesized at the pH solutions of 7 and 8. By varying the pH values, the mixtures of monoclinic ZnWO₄ and hexagonal ZnO as major and minor phases were detected at the pH 9 and 10 solutions, and the pure hexagonal ZnO phase at the pH 11 and 12. SEM and TEM images proved that ZnWO₄ nanorods grew along the [021] direction, with the reaction temperature and time to control their morphologies. The Zn–O, Zn–O–W, and W–O stretching vibrations were detected at 474, 888, and 726 cm⁻¹, and their corresponding bending vibrations at 430, 826, and 582 cm⁻¹, respectively. The optical properties of ZnWO₄ nanorods were also investigated by UV-visible (UV-vis) and photoluminescence (PL) spectroscopy. The above analyses proved that the appropriate condition for synthesizing of ZnWO₄ nanorods is at pH 8 by the 200 °C and 24 h hydrothermal treatment.