Direct growth of Al-doped ZnO ultrathin nanosheets on electrode for ethanol gas sensor application

Highlights: • Al-doped ZnO ultrathin nanosheets were synthesized directly onto Al₂O₃ ceramic tubes. • The nanosheets possess abundant defects and exposed planes perpendicular to [121] crystal orientation. • The maximum response is 90.2 to 100 ppm ethanol for the ZnO nanosheets sensor at 370 °C. • The response and recovery times are 1.6 s and 1.8 s, respectively, to 100 ppm ethanol at 370 °C. ZnO nanosheets were synthesized directly onto the sensing measurement element by introducing an Al nano-interlayer. The morphology, structure, element content, and surface defects of the prepared ZnO nanosheets were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopic (TEM), energy-dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The ZnO nanosheets possess ultrathin thickness of about 15 nm and abundant intrinsic defects. Al elements were observed in the ZnO nanosheets and the predominantly exposed planes of the ZnO nanosheets were perpendicular to [121] crystal orientation. The sensor based on the Al-doped ZnO ultrathin nanosheets showed excellent ethanol sensing properties, including high response, fast response/recovery, good selectivity, long-term stability and well repeatability. The excellent sensing properties of the ZnO nanosheets are attributed to their large specific surface area, the doping of Al elements, abundant intrinsic defects and high surface energy of the exposed planes.