Synthesis of diamagnetic ZnO nano-crystallites via sol-gel method and their photocatalytic activity

The diamagnetic zinc oxide (ZnO) nano-crystallites were synthesized via the sol-gel method. The X-ray diffraction(XRD) and field emission scanning electron microscope (FESEM) were used for structural characterization. The XRDpattern demonstrates that the ZnO nanoparticles (NPs) have a wurtzite structure with an average crystallite size of ~20 nm.TheFESEM and EDAX (energy- dispersive x-ray analysis) confirm the particles are in granular, spherical, and rod-likemixed-phase. The absorption spectra show a red shift and observed bandgap energy of about 3.17 eV, which might attributebecause of the oxygen vacancies. Further, photoluminescence (PL) exhibits dual peaks at wavelengths 430 and550 nm, which maybe due to defects induced at the surface of the NPs. The vibrating sample magnetometer (VSM) studydemonstrates the diamagnetic behavior of zinc oxide nanoparticles at 300 K. The photocatalytic effectiveness of the ZnONPs was examined by decomposing a congo red (CR) dye as an organic water pollutant under UV irradiation. The leadingabsorption peak of CR dye decreases with the UV irradiation time. The complete decolorization of the CR dye was observedafter 150 min with the reaction rate constant of 0.018 min-1.