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

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)center dot 2H(2)O 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.