Abstract:
Zinc oxide (ZnO) is one of the most promising semiconducting material in the field of photo-catalysis due to its optical and electrical properties. This work is based on synthesis of ZnO nanoparticles through modified coprecipitation technique. The growth conditions were controlled via carefully designed oil bath and reflux setup. The study explored the effect of acetate, sulfate and nitrate salt precursors along with synthesis temperature on physiochemical behavior of ZnO nanoparticles. XRD and SEM analysis confirmed phase pure hexagonal wurtzite zinc oxide nanoparticles of spherical morphology ranging from 30nm to 70nm in size. Moreover, TEM analysis revealed that nanoparticles contain high density of planar defects in the form of dislocations. Optical characterization was done using UV-Vis Spectroscopy, for band gap calculations. Further investigation of defects by Photoluminescence spectroscopy revealed highly defected nanoparticles, ultimately, offering possibility in visible range photoresponse of prepared ZnO nanoparticles. Hence, visible light photo-catalysis chamber was designed and developed at SCME to carry out the degradation studies of methylene blue dye. All of the synthesized nanoparticle catalysts exhibited excellent visible light photocatalytic activity ranging from 93.86% up to 99.39% degradation of methylene blue in 50 minutes. This enhanced photocatalytic activity has been attributed to the excessive defects, present in the form of dislocations, instigated via oxygen vacancies and surface hydroxyl group which effectively repress electron-hole recombination by taking care of charge carrier trapping and transferring. Nanoparticle showing highest photocatalytic activity was further tested for degradation of Rhodamine B dye and results concluded 98.85% degradation in an hour. Therefore, described synthesis procedure can be used for commercial scale production of visible active ZnO nanoparticle catalyst with controlled defects offering reproducible luminescence properties, opening possibilities in number applications via simple and cost-effective synthesis route.
Keywords: coprecipitation; ZnO; nanoparticles; methylene blue; rhodamine B; visible light photocatalysis.
