CuO/ZnO Heterojunction Nanograins: Methanol Vapour Detection

Polyvinyl alcohol (PVA)-based CuO/ZnO beads-free nanofibers were prepared by electrospinning with the precursor containing PVA, zinc acetate dihydrate and copper acetate monohydrate salts. Through the scanning electron microscopy characterization studies, it was observed that the obtained nanofibers are crosslinked and have a higher surface area-to-volume ratio with smooth edges. These nanofibers were calcined at 450°C for 24 h to obtain polycrystalline CuO/ZnO nanograins with an average grain diameter of 32 nm. The calcined CuO/ZnO nanograins exhibited polycrystalline nature, which was confirmed by the x-ray diffraction pattern. X-ray photoelectron spectroscopy studies confirm the presence of Zn and Cu in the synthesized CuO/ZnO nanograins in Zn +2 and Cu +2 elemental forms. The vapour sensing properties of CuO/ZnO nanograins were observed as neck control mode of charge transport and shows better response towards methanol vapour concentration, ranging from 21 ppm to 2094 ppm at an operating temperature of 350°C. For 167 ppm concentration of methanol, CuO/ZnO nanograins showed quick response and recovery time of 13 s and 36 s, respectively. The methanol vapour sensing mechanism was proposed for the charge transport between p-CuO/n-ZnO heterojunction at 350°C for the electrospun nanograins.