Synthesis, Characterization and Photocatalytic Activity of Mg-Impregnated ZnO-SnO2 Coupled Nanoparticles.

ZnO-SnO2 nanoparticles were prepared by coprecipitation method; then Mg, with different molar ratios and calcination temperatures, was loaded on the coupled nanoparticles by impregnation method. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), and Brunauer-Emmett-Teller (BET) techniques. Based on XRD results, the ZnO-SnO2 and Mg/ZnO-SnO2 nanoparticles were made of ZnO and SnO2 nanocrystallites. According to DRS spectra, the band gap energy value of 3.13 and 3.18 eV were obtained for ZnO-SnO2 and Mg/ZnO-SnO2 nanoparticles, respectively. BET analysis revealed a Type III isotherm with a microporous structure and surface area of 32.051 and 49.065 m(2)  g(-1) for ZnO-SnO2 and Mg/ZnO-SnO2 , respectively. Also, the spherical shape of nanocrystallites was deduced from TEM and FESEM images. The photocatalytic performance of pure ZnO-SnO2 and Mg/ZnO-SnO2 was analyzed in the photocatalytic removal of methyl orange (MO). The results indicated that Mg/ZnO-SnO2 exhibited superior photocatalytic activity to bare ZnO-SnO2 photocatalyst due to high surface area, increased MO adsorption and larger band gap energy. Maximum photocatalytic activity of Mg/ZnO-SnO2 nanoparticles was obtained with 0.8 mol% Mg and calcination temperature of 350°C.