CuO nanobelts synthesized by a template-free hydrothermal approach with optical and magnetic characteristics

The present study reports a simple hydrothermal approach for conveniently synthesizing cupric oxide (CuO) nanobelts without a templating agent. Electron microscopic studies indicate that these nanobelts have a wide stem (300–500 nm) and sharp tip (80–150 nm), with lengths up to 6 µm. X-ray diffraction patterns confirm the formation of a single monoclinic phase of CuO. A possible reaction mechanism was proposed to account for the growth of nanobelts. The optical properties of the products were investigated using UV–vis spectroscopy and photoluminescence (PL) measurement. The direct band gap energy for CuO nanobelts was estimated to be 3.2 eV, which is larger than the value of bulk CuO and likely related to quantum size effects. The magnetic properties of CuO nanobelts measured at room temperature exhibited a ferromagnetic behavior with a coercive force (Hc) of 93.35 Oe, whereas a paramagnetic behavior was observed in liquid nitrogen. The magnetic behavior was discussed in terms of CuO morphology effects.