3D flower- and 2D sheet-like CuO nanostructures: Microwave-assisted synthesis and application in gas sensors

3D flower- and 2D branching sheet-like CuO nanostructures have been synthesized by a microwave-assisted hydrothermal method. The samples were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared spectroscopy (IR), UV-vis diffuse reflectance spectroscopy (UV-DRS), and Brunauer-Emmett-Teller (BET) specific surface area analysis. The phase and morphology observations showed the formation of monoclinic CuO nanostructures with well-defined morphology. BET analysis displayed that the measured surface area was 15.0 m2 g−1 for CuO flowers, and 20.8 m2 g−1 for CuO nanosheets. Gas sensing properties of the as-synthesized CuO nanostructures were evaluated by the detection of volatile and toxic gases including ethanol, ethyl-acetate, acetone, xylene, and toluene. It was found that CuO flowers exhibited an enhanced gas response to the five gases at 260 °C, compared to CuO nanosheets. Furthermore, at 1000 ppm, the CuO flower sensor gave a higher response to ethyl-acetate (Rg/Ra = 4.6) and ethanol (Rg/Ra = 4.0), in comparison with toluene (Rg/Ra = 2.8). In addition, the CuO flowers displayed a rapid response and recovery as well as good reproducibility.