“…Copper oxide is a well-known p-type semiconductor with a narrow band gap of 1.2 eV and has been extensively studied because of its versatile applications, such as catalysts [1], magnetic storage media [2], gas sensors [3][4][5], lithium batteries [6], amperometric sensors [7][8][9], etc. Because the practical performances of CuO nanomaterials are close related to its morphology and size, which ultimately depends on the preparation methods and reaction conditions [10,11], various methods have been developed to synthesize CuO nanostructures, for example, thermal oxidation of copper foil, hydrothermal route, vapor-liquid-solid synthesis, ultrasound irradiation, thermal decomposition of precursors, electron beam lithography, etc.…”