Effect of tungsten (W⁶⁺) metal ion dopant on structural, optical and photocatalytic activity of SnO₂ nanoparticles by a novel microwave method

In this report, we have successfully synthesized pristine and tungsten (W) doped SnO₂ nanoparticles by using novel and one-step microwave irradiation method for the first time. Powder X-ray diffraction results suggest that both pure and W doped SnO₂ nanoparticles are crystalline with tetragonal rutile type structure (space group of P42/mnm) formed directly during the microwave irradiation process. The morphology of the nanoparticles are in spherical shaped and the average particle sizes were around 23–32 nm was observed for pure and W doped SnO₂ nanoparticles as investigated by transmission electron microscopy analysis. UV–Vis transmission spectra analysis revealed that optical transmission is decreases with the increase of W concentrations (0–10 wt%) and the red shift was observed. The calculated band gap energy of pure SnO₂ was found to be 3.61 eV and further it was decreases to 3.47 eV for W (10 wt%) doped SnO₂. The photocatalytic properties of the pure and W doped SnO₂ samples were evaluated by the degradation of methylene blue rhodamine B in an aqueous solution under visible light irradiation. The photocatalytic activity and reusability of W (10 wt%) doped SnO₂ was much higher than that of the pristine SnO₂. The improvement mechanism by W doping was also discussed. The samples were further characterized by photoluminescence and Fourier transforms infra- red spectra analysis.