Influence of temperature on green synthesis of cobalt oxide nanoparticles by sol-gel method and investigation of its structural and optical properties

There is a growing interest in the synthesis and applications of cobalt oxide nanoparticles due to their unique properties. Current methods in nanotechnology focus on developing a new technique for the synthesis of nanoparticles using biological methods such as using plant extracts, mucilage, essential oils, fungi, or bacteria that can minimize the use of hazardous substances. Therefore, in this study, the synthesis of cobalt oxide nanoparticles is provided in a simple green and environmental friendly method using Cydonia oblonga seed mucilage as a reducing and stabilizing agent and cobalt (II) nitrate hexahydrate as a precursor of cobalt at different temperatures of 500, 600, 700 and 800°. Prepared nanoparticles were investigated using X-ray diffraction (XRD) techniques, Fourier transforms infrared spectroscopy (FT-IR), Ultraviolet-Visible (UV-Visible) spectroscopy, and field emission scanning electron microscopy (FESEM). XRD showed the formation of the cubic phase cobalt oxide nanoparticles with an average particle size of 31 to 63 nm, and the size of cobalt oxide nanoparticles increased with the calcination temperature. The FT-IR showed a strong absorption band related to the stretching vibration of Co3+-O and Co2+-O bond and confirmed the formation of Co3O4 structure in all samples. The results of the UV-Visible spectrum of the samples showed the band gap value of the nanoparticles in the range of 3.64 – 3.93 eV. Using FESEM images, it can be seen that the particles have a spherical shape.