Eco-friendly Green Synthesis of stable ZnO nanoparticles using citrus limon: X-Ray Diffraction Analysis and Optical Properties

Eco-friendly stable ZnO nanoparticles (NPs) were synthesized by sol-gel method using citrus limon as a chelating agent. The structural analysis and optical properties of ZnO NPs annealed in air ambient at different temperatures ranging from 600 to 900 degrees C are reported. A detailed x-ray diffraction (XRD) analysis of ZnO NPs has been discussed. Morphological and optical properties of the NPs were investigated using Field Emission Scanning Electron Microscopy (FE-SEM), XRD, Diffuse Reflectance Spectroscopy (DRS), Photoluminescence (PL), Fourier Transform Infrared spectroscopy (FTIR) and Raman Spectroscopy techniques. The FE-SEM reveals that the average particle size of ZnO NPs increased from 62 to 77 nm due to agglomeration of particles or Ostwald ripening which usually happens at high temperature. Physical and microstructural properties such as crystallite size, strain, stress and dislocation density of ZnO NPs were obtained from XRD spectra studies and compared the estimated parameters by various models. It is observed that, the crystallite size increased after annealing and the strain present in NPs is due to defects. Kubelka-Munk function is used to obtain bandgap of NPs from DRS spectra. A slight decrease in the bandgap of ZnO NPs is due to the increase in particle size. PL spectra reveals that the emission around 402 nm near the UV region is attributed to the near band edge emission (NBE) and emission peaks in a visible region is due to the transition of electrons from traps in bandgap to the valence band.