Effect of concentration of hexamethylenetetramine in structure, microstructure and optical properties of CuO nanoparticles synthesized by hydrothermal route

Structural and optical studies on CuO nanoparticles prepared by hydrothermal route with different concentration of hexamethylenetetramine (HMTA) are reported. Evolution of structure, microstructure and optical properties were studied by X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR) analysis, and UV–visible spectrophotometer. The XRD analysis indicates the formation of CuO nanoparticles with a monoclinic structure. We also note the presence of a second phase Cu(OH)2 considered as impurity. FTIR technique confirms the presence of this phase. XRD analysis watches that the sample with less concentration of HMTA gives higher crystallite size with less strain. Optical absorption analysis indicated a blue shift in the direct band gap which is due to the quantum confinement effect, and a red shift in the indirect band gap which is attributed to the intra-gap defects states. The different optical parameters are calculated. Their values show a remarquable influence of the amine concentration in the properties of CuO nanoparticles.