Intrinsic sensing properties of the flower-like ZnO nanostructures

The flower-like ZnO nanostructures were successfully synthesized by a simple hydrothermal method without surfactant or organic solvent. The structure and morphology of the ZnO crystals were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The sensing test results show that the ZnO based sensor exhibits high response to NO₂ and high selectivity to CO and CH₄, respectively, at lower operating temperature of 150 C. The intrinsic sensing characteristic results from native defects in ZnO crystals (i.e. nonstoichiometry) due to the relative content of donors is more than that of the acceptors, which have been confirmed by the X-ray photoelectron spectroscopy (XPS) and room temperature photoluminescence (PL) analysis. The transient responses for different gas concentrations were measured and modeled using Langmuir-Hinshelwood reaction mechanism. This work can give rise to interesting option for researching other metal oxides.