Optical and magnetic properties of zinc vanadates: synthetic design of colloidal Zn3V2O7(OH)2(H2O)2, ZnV2O4 and Zn3V2O8 nanostructures

Abstract

Colloidal hierarchical self-assembled Zn3V2O7(OH)2(H2O)2 superstructures, were synthesized via a simple and large-scale production route and then was converted into ZnV2O4 and Zn3V2O8 by calcination with retaining Zn3V2O7(OH)2(H2O)2 original morphology and hydrophilicity. Prepared compounds were characterized by X-ray diffraction, energy dispersive X-ray analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The optical, magnetic and photoluminescence properties of Zn3V2O7(OH)2(H2O)2, ZnV2O4 and Zn3V2O8 were explored by ultraviolet–visible spectroscopy, vibrating sample magnetometer and emission/excitation spectroscopy, respectively. According to the scanning electron and transmission electron microscopy results, the as-prepared samples were crystallized with a flower-like morphology for the optimized materials. The hierarchical self-assembled flower-like particles were composed of a large number of similar nanosheets with a thickness of 10–70 nm. The photophysical properties investigation of Zn3V2O7(OH)2·2H2O demonstrated that this sample has a wide band gap with photoabsorption ability only in the UV region. The magnetic properties of the ZnV2O4 nanostructures were evaluated, and results showed sample has a ferromagnetic behavior at room temperature. Finally, the optical study of the Zn3V2O8 nanostructure showed a very pronounced red-shifted PL emission for the two excitation wavelengths of 237 and 340 nm in their photoluminescence spectra.