Low temperature preparation of CuO nanospheres and urchin-shaped structures via hydrothermal route

Abstract We demonstrated a simple one-step hydrothermal route for the preparation of cupric oxide (CuO) nanoparticles in the form of either nanospheres or urchin-shaped structures. The choice between these two types of structures was easily achieved by switching between NaOH or NaBH 4 during the nanoparticles synthesis. The first resulted in the production of nanospheres, the second gave rise to the urchin-like structures. Possible growth mechanisms for the formation of CuO nanospheres were discussed. Structural and optical properties of these nanospheres were investigated and their band-gap was found to be 1.54 eV. The higher band-gap value compared to the bulk CuO was attributed to the strong quantum confinement of charge carriers in the small nanoparticles comprising the nanospheres.