Xiaohua Jia

Solid state synthesis of tin-doped ZnO at room temperature: Characterization and its enhanced gas sensing and photocatalytic properties

A room temperature solid-state reaction has been used to prepare crystalline tin-doped ZnO. Zinc nitrate hexahydrate, cetyltrimethyl ammonium bromide, stannic chloride pentahydrate and sodium hydroxide with proper ratios were ground together. As-synthesized samples were characterized by inductively coupled plasma analysis (ICP), scanning electron microscopy (SEM) and X-ray powder diffraction (XRD); The products were of different morphologies, well dispersed and exhibited good crystallinity, it is also found that the growth direction and morphology of ZnO depend on the amount of Sn doped, which is mainly caused by the difference in sizes between Zn and Sn atoms as well as the change of pH value. Moreover, gas sensing and photocatalytic properties of the obtained products were studied. The materials showed a high gas response to ethanol vapor, and the gas response can reach a maximum of R(a)/R(g) = 124. In addition, tin-doped ZnO materials exhibited improved photocatalytic performance toward methyl orange (MO) solution under a current density of 0.03 mg L(-1) comparison with undoped ZnO.

Using sonochemistry for the fabrication of hollow ZnO microspheres.

Hollow ZnO microspheres assembled by nanoparticles have been prepared by a sonochemical synthesis at room temperature using carbon spheres as template. The growth process of the precursor was investigated. The prepared hollow spheres were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM). The diameter of the obtained hollow spheres is about 500nm, and the walls are composed of numerous ZnO aggregate nanocrystallines with diameters of 90nm. A possible growth mechanism for the formation of ZnO microspheres has been proposed, in which carbon spheres play a crucial role in the formation of the wurtzite hollow ZnO microspheres. The specific structure of the hollow spheres may find applications in nanoelectronics, nanophotonics and nanomedicine.

Hierarchically Structure SnO2/ZnO Nanocomposites: Preparation, Growth Mechanism and Gas Sensing Property

SnO2/ZnO nanocomposite was synthesized from mixed ethanol and water systems and the ethanol-sensing properties of sensors based on SnO2/ZnO were investigated. The structure and morphology of the products was characterized by x-ray diffraction (XRD) and a field emission scanning electron microscope (FE-SEM). The results showed that the diameter of the liked pine needle SnO2 was about 40 nm with a length about 300 nm, which are uniformly dispersed on the surface of the ZnO nanosheets. The growth process of the SnO2/ZnO nanocomposite was discussed. The results of gas sensing properties of SnO2/ZnO nanocomposite sensor showed high and quick response to ethanol vapor at 5.0 v. This sensor showed the advantages of high selectivity, strong stability, and prompt response/recovery characteristics in detecting ethanol vapor at 5.0 v.

Ultraviolet photovoltage characteristics in ZnO/La0.7Sr0.3MnO3 heterostructure

Ultraviolet photovoltage characteristics have been observed in a ZnO/La0.7Sr0.3MnO3 heterostructure, which exhibits reproducible rectifying characteristics. The peak photovoltage is about 0.704 V and the rise time is about 10 ns for the photovoltaic pulse at T = 78 K when the heterostructure is irradiated by a 248 nm laser pulse of 25 ns duration. The peak photovoltages and the full widths at half-maximum decrease with increasing temperature. These might be attributed to the change in the fractions of the ferromagnetic insulating phases in the depletion layer.

Hydrothermal Synthesis and Primary Gas Sensing Properties of CuO Nanosheets

Uniformity nanosheets of CuO were prepared by a mild hydrothermal synthesis method. Phase analysis was carried out using x-ray diffraction (XRD) and the result confirmed the CuO nanosheets as a single phase. The field-emission scanning electron microscopy (FE-SEM) was used to observe the morphology of CuO nanosheets while the gas sensing properties of these unique CuO nanosheets were tested at a static state system. The results show that the CuO has uniformity nanosheets, and the gas sensing property show that the CuO nanosheets gas sensor has a stable gas response and the same gas sensitivity trend to tested gases. This method may be suitable for larger-scale production of these CuO nanosheets for practical applications.