Effect of the annealing temperature on crystalline phase of copper oxide nanoparticle by copper acetate precursor and sol–gel method

A sol–gel route to synthesize copper oxide nanoparticles with an average size of ca. 63 nm from copper acetate precursor and monoethanolamine as the capping agent is reported. Structural characterization showed the formation of a cubic phase for CuO. The effect of annealing temperature on formation of crystalline phases was investigated. Characterization of the products was performed using thermo-gravimetric analysis, X-ray diffraction, field emission scanning electron microscopy, and diffuse reflectance. The results showed that there are significant differences in the morphological, crystallographic, structural, and optical properties of the nanostructures prepared at different annealing temperatures. The optical properties and band gap of CuO nanoparticles were studied by UV–Vis spectroscopy. According to the results of the optical measurements, the band gap is estimated to be 1.41 eV. These results showed that the band gap energy changed with increase of annealing temperature, which can be attributed to the change in grain size of the samples.