Morphological and size effects of NiO nanoparticles via solvothermal process and their optical properties

Different morphologies of NiO nanoparticles have been achieved controllably by the solvents-assisted facile solvothermal method. The size of the NiO nanoparticles was estimated by X-ray powder diffraction (XRD) pattern, which was in good agreement with the particle size calculated by transmission electron microscopy (TEM) analysis. The chemical structure information of the products was studied by Fourier transform infrared (FT-IR) spectroscopy. Spherical, elliptical, sheet- or snowflake-like, rod-like and rod morphologies were obtained by scanning electron microscopy (SEM) analysis. The band gap value of the NiO nanoparticles is about 3.74–3.99 eV calculated by ultraviolet–vis (UV–vis) spectroscopy. The very prominent strong UV emission peak was observed at 346 nm (3.58 eV) in the luminescence spectra, which was studied by photoluminescence (PL) spectroscopy. The magnetic property was studied using the vibrating sample magnetometer (VSM). The possible formation mechanisms also have been phenomenologically proposed for the as-synthesized NiO nanoparticles with different morphologies.