Facile microwave-assisted hydrothermal synthesis of varied-shaped CuO nanoparticles and their gas sensing properties

In this work, CuO nanoparticles of varying shape (tadpole-shaped, spindly, leaf/sphere-like and fusiform) have been prepared by a facile microwave-assisted hydrothermal (MH) method. The products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy FTIR and transmission electron microscopy (TEM). XRD and TEM results revealed pure phase monoclinic CuO nanoparticles with uniform shapes and sizes. FTIR and UV–vis measurements of these nanoparticles with varying shape showed a highly shape-dependent nature. The gas sensing performance of the obtained nanoparticles was analyzed by detection of target gases, including methanol, ethanol and acetone at 220 °C. The tadpole-shaped CuO nanoparticles displayed the best response of ∼5 toward 1000 ppm methanol, ∼7 toward 1000 ppm ethanol, and ∼8 toward 800 ppm acetone, respectively. All these CuO-based sensors exhibited a relatively higher response to acetone when compared to their response toward methanol and ethanol. The enhanced sensing performance of the tadpole-shaped CuO sensor may be attributed to their unique shape and small size, which is more favorable in rapid and efficient diffusion of organic vapors than the other shaped CuO nanoparticles.