Doping ZnO nanoparticles with rare-earth element and investigating its photocatalytic activity

Abstract

In this study, pristine and rare-earth elements doped ZnO nanoparticles were successfullysynthesized as potential photocatalystsby modified sol-gel method. Synthesized nanoparticles were characterized usingX-ray diffraction, field emission scanning electron microscopy, energy dispersion X-ray spectrum analysis, UV-visible diffuse reflectance spectroscopy, photoluminescence spectroscopy and simultaneous thermogravimetry-differential scanning calorimetry. ZnO nanoparticles were doped to enhance the photocatalytic degradation efficiency of the nanoparticles. Optimized process parameters were used to synthesize Zn1-xHoxO and Zn1-xSmxO nanoparticles (x = 0.01, 0.03 and 0.05). Rare earth elements were added to utilize their ability of introducing sideway band to reduce optical band gap and shift its photocatalytic activation towards visible range of the solar spectra. Also, the elements were added because of their electron scavenger nature to reduce photogenerated electron-hole recombination rate for better photocatalytic properties of the nanoparticles.

In the current exploration, modified sol-gel derived ZnO nanoparticles were effectively doped with rare earth elements i.e. Ho and Sm. Prior to doping, synthesis and annealing parameters were optimized to have pristine ZnO nanoparticles with enhanced photocatalytic properties. Effect of process parameters, chelating agent and dopants on the surface morphology of ZnO nanoparticles, along with particle size distribution (uniform size and bimodal), were studied steadily. Crystallization of the nanoparticles and successful doping were confirmed prior to their usage for photocatalytic degradation. Effect of doping on absorption edge shifting, to use visible spectra to a greater extent for photocatalytic degradation, was investigated thoroughly. Finally, doping concentrations were optimized for both Ho and Sm to maximize photocatalytic efficiency and all the findings were analyzed for understanding the fundamental mechanisms i. e. structure-property relationship and kinetics.