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

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 NaBH4 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.