Optical properties of Zn3(OH)2V2O7·nH2O nanosheets

Strong green photoluminescence (PL) was observed for hydrothermal synthesized Zn3(OH)2V2O7·nH2O nanosheets. The energy band structure of the material was theoretically computed using first principle method and experimentally obtained by linear extrapolating from UV–vis reflection spectrum. It is shown that the material is an indirect bandgap semiconductor with a direct bandgap of 3.03 eV at Γ and an indirect gap of 2.8 eV from R to Γ. UV–vis reflection spectrum changes regularly along with doping of cobalt, showing clearly reflection peaks of Co2+. The bandgap of Zn3(OH)2V2O7·nH2O decreases significantly along with doping of cobalt, indicating the substitution of Co2+ with Zn2+. The intensity of the PL spectrum of Zn3(OH)2V2O7·nH2O that annealed in vacuum remains almost unchanged, whereas it distinctly decreases with doping of cobalt. The results indicate that it is zinc vacancies that cause the green emitting, which is in accordance with Zn deficiency that deduced from energy dispersion spectroscopy characterization.