Electronic and Optical Properties of Size-Controlled ZnO Nanoparticles Synthesized by a Facile Chemical Approach

Facile low-temperature chemical route for the synthesis of ZnO nanoparticles is reported in this paper. Morphologically uniform and spherical shape with an average particle size of 8.8 nm and wurtzite phase with the crystalline structure of as-synthesized ZnO nanoparticles were confirmed by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The optical properties of ZnO nanoparticles were analyzed by UltraViolet Visible (UV-Vis) absorption and PhotoLuminescence (PL). The as-synthesized ZnO nanoparticles showed orange light-emitting properties when excited at 400 nm due to the well overlapping of electron and hole wave function across the compatible size of the particle of ZnO and the optical energy band gap of 3.5 eV due to quantum confinement. X-ray Photoelectron Spectroscopy (XPS) and Ultraviolet Photoelectron Spectroscopy (UPS) were used for the elemental, molecular and energetic information of ZnO nanoparticles. UPS analysis depicted the energy level position of ZnO nanoparticles whereas XPS spectra showed the presence of constitute elementals with the stoichiometric atomic % of Zn and O. The elemental composition was also confirmed by the EDS analysis. The significant Raman shifts for as-synthesized ZnO nanoparticles in the typical Raman-active modes of vibration assigned to the wurtzite crystal nanostructure of ZnO.