Enhanced ethanol gas-sensing properties of flower-like p-CuO/n-ZnO heterojunction nanorods

A facile approach for synthesis of flower-like p-CuO/n-ZnO heterojunction nanorods was reported. The CuO/ZnO nanorods were prepared by co-precipitation of CuO nanoparticles on the hydrothermally grown ZnO nanorods. The obtained samples were characterized by X-ray diffraction and transmission electron microscopy, which confirms that the heterogeneous nanostructure of the CuO/ZnO nanorods was highly crystalline. The ethanol gas-sensing properties of CuO/ZnO nanorods were evaluated with different ethanol vapor concentrations at the working temperature of 300 °C. The response of 0.25:1 CuO/ZnO nanorod sensor to 100 ppm ethanol was 98.8, which is 2.5 times that of ZnO only sample, with a response and recovery time of 7 s and 9 s, respectively. Good selectivity and long-term stability can also be achieved and the response of low concentration as 1 ppm ethanol can reach the value of 9.68 using the flower-like p-CuO/n-ZnO heterojunction nanorods as sensing material. The enhanced ethanol response is mainly attributed to a wider depletion layer on the CuO/ZnO surface resulted from the formation of p–n heterojunctions between p-CuO nanoparticles and n-type ZnO nanorods.