Acetone sensing of ZnO nanosheets synthesized using room-temperature precipitation

Abstract

Zinc oxide (ZnO) nanosheets were directly synthesized using a facile precipitation method at room temperature without any template, surfactant or organic solvent. X-ray diffraction (XRD) confirms that the ZnO nanosheets belong to hexagonal wurtzite structure. Scanning electron microscope (SEM) and transmission electron microscope (TEM) reveals the morphology and structure of the ZnO nanosheets, showing the predominantly exposed non-polar {100} planes and an average thickness of about 20nm. In order to regulate and control the intrinsic surface defect contents, improving the thermal stability, the samples were calcined at different temperatures (200°C, 400°C and 600°C respectively), showing that the sheet-like structures can be maintained below 400°C. Photoluminescence (PL) analysis shows that abundant intrinsic surface defects exist on the ZnO crystal surfaces. Gas sensors based on ZnO nanosheets calcinated at 200°C exhibits high response, fast response-recovery and good selectivity to 5–1000ppm acetone vapor at 300°C. The response value to acetone vapor is correlated with the surface defect contents, namely, the more defects, the higher sensor response. Thus, it is considered that the improved acetone sensing property, especially enhanced response value, is mainly originated from the increased intrinsic defect content on the surface of ZnO nanosheets. Developed precipitation method is facile for synthesis of ZnO nanosheets, which demonstrate an effective strategy for surface defect engineering to improve the metal oxide semiconductor gas sensing performance.