Calcium germanate nanowires by vanadium doping with improved photocatalytic activity

<div><p>Vanadium-doped calcium germanate nanowires were prepared by a simple hydrothermal method. The samples were analysed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and solid UV–Vis diffuse reflectance spectrum. The photocatalytic activity of the vanadium-doped calcium germanate nanowires was investigated by the degradation of methylene blue (MB) under solar light irradiation. The results show that the vanadium-doped calcium germanate nanowires are composed of rhombohedral Ca<sub>3</sub>GeO<sub>5</sub> and orthorhombic CaV<sub>3</sub>O<sub>7</sub> phases. The nanowires have the diameter and length of 50–200 nm and several dozens of micrometres, respectively. The band gap of the vanadium-doped calcium germanate nanowires strongly depends on the vanadium doping mass percentage. The absorption spectrum can be broadened to visible light region. The photocatalytic activity of the vanadium-doped calcium germanate nanowires is remarkably improved. Vanadium-doped calcium germanate nanowires with the vanadium doping mass percentage of 10% have the highest photocatalytic activity for MB degradation under solar light irradiation.</p></div>