Rare earth (RE: La and Ce) elements doped ZnWO4 nanoparticles for enhanced photocatalytic removal of methylene blue dye from aquatic environment

In the present study, the enhanced photocatalytic behaviour of La:ZnWO4 and Ce:ZnWO4 nanoparticles produced by a simple co-precipitation technique is reported. The X-ray diffraction study suggested that La and Ce ions are harmoniously incorporated into the Zn2+ sites or interstitial sites within the ZnWO4 lattice without altering the monoclinic wolframite phase. The field emission scanning electron microscopic study showed the formation of spherical particles and nanorod-like morphology for La:ZnWO4 and Ce:ZnWO4 samples. The shrinkage in optical band gap energy of La and Ce doped ZnWO4 nanoparticles was realized owing to the effect of dopant concentration induced microstructural defects. The broad blue-green emission peak perceived at 350-600 nm regions is ascribed to the electronic transition from O2p to W5d orbitals. The highest surface area of 283.272 m(2)/g was obtained for 2% La doped ZnWO4 sample. The elemental composition of samples was ascertained by x-ray photoelectron spectroscopic study. La:ZnWO4 and Ce:ZnWO4 nanophotocatalysts showed an excellent dye removal efficiency towards the degradation of methylene blue than the pure ZnWO4 catalyst. This may be due to the fact that the RE ions (La and Ce) endorse the separation of photo-induced electron-hole pairs in ZnWO4.