Low temperature growth of CuO nanowires through direct oxidation

Abstract

CuO nanowires (NWs) are important for various applications, thus finding a low cost synthesis route is vital to best utilize this material. Herein, CuO NWs synthesized by direct oxidation of pure copper foil in a dry air environment at a low temperature regime between 100 and 400 °C were studied. Based on the results of our research, we have unprecedentedly identified (1) the threshold temperature and oxidation duration required to form CuO NWs; (2) an opposite trend in the NW lengths as function of temperature below 400 °C compared to that of above 400 °C; and (3) unambiguous evidences on the formation of Cu2O layer prior to the CuO NW formation. In particular, the threshold temperature and oxidation duration required to form CuO NWs are determined to be 250 °C and 2 h, respectively. The lengths and widths of the synthesized CuO NWs were found to be controllable with temperature (300 and 400 °C) and oxidation duration (1–3 h) ranging from 0.78 to 2.91 μm and 20 to 90 nm, respectively. The trend of the NW lengths was found to be increasing as the temperature increases and below 400 °C, which is opposite to that for oxidation temperature higher than 400 °C. Based on a combination of the Raman, X-ray diffraction, and scanning electron microscopy measurements, it was further concluded that a Cu2O layer is formed right before CuO NW growth.