Zinc oxide (ZnO) nanoparticles were synthesized by precipitation and sol-gel methods. The aim of this study was to understand how different synthetic methods can affect the photocatalytic activity of ZnO nanoparticles. As-synthesized ZnO nanoparticles were characterized by X-ray diffraction (XRD) and UV-Visible spectroscopic techniques. XRD patterns of ZnO powders synthesized by precipitation and sol-gel methods revealed their hexagonal wurtzite structure with crystallite sizes of 30 and 28 nm, respectively. Their photocatalytic activities were evaluated by photocatalytic degradation of methylene blue, a common water pollutant, under UV radiation. The effects of operational parameters such as photocatalyst load and initial concentration of the dye on photocatalytic degradation of methylene blue were investigated. While the degradation of dye decreased over the studied dye concentration range of 20 to 100 mg/L, an optimum photocatalyst load of 250 mg/L was needed to achieve dye degradation as high as 81 and 92.5 % for ZnO prepared by precipitation and sol-gel methods, respectively. Assuming pseudo first-order reaction kinetics, this corresponded to rate constants of 8.4 × 10 and 12.4 × 10 min, respectively. Hence, sol-gel method is preferred over precipitation method in order to achieve higher photocatalytic activity of ZnO nanostructures. Photocatalytic activity is further augmented by better choice of capping ligand for colloidal stabilization, starch being more effective than polyethylene glycol (PEG).
ABSTRACT. Ag-N-codoped zinc oxide nanoparticles were synthesized by a one-step impregnation of Ag in N-doped ZnO nanoparticles. The morphologies and structures of the as-synthesized nanomaterials were investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-Vis spectrophotometric techniques. Photocatalytic degradation of methyl red dye using synthesized photocatalysts was studied under solar as well as UV irradiations. Modified zinc oxide photocatalysts showed higher photocatalytic activity compared to pure zinc oxide both under solar as well as UV irradiations. Calcined zinc oxide shows better photocatalytic activity than commercial zinc oxide under both solar and UV irradiations. Highest catalytic activity of Ag-N co-doped zinc oxide (ANZ) among the undoped, Ag-doped and N-doped photocatalysts was attributed to the lower rate of recombination of the photogenerated electrons and holes as well as its lower band gap energy. Photocatalytic degradation of methyl red dye follows pseudo first order kinetics for all the nanoparticles so-obtained.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.