Cuiping Gu

Large-scale selective preparation of porous SnO2 3D architectures and their gas-sensing property

Porous SnO2 cubes and rods were obtained by a facile chemical solution route combined with subsequent calcination and an acid-washing process. Techniques of X-ray diffraction, scanning electron microscopy, thermogravimetric-differential thermalgravimetric analysis, transmission electron microscopy, and Brunauer–Emmett–Teller N2 adsorption–desorption analyses were used to characterize the structure and morphology of the products. The process of inducing porosity starts with a crystalline single-phase hydroxide precursor CuSn(OH)6 formed by the co-precipitation of the metal ions from aqueous solution. Thermal decomposition of the precursors leads to an intimate mixture of CuO and porous tetragonal SnO2. The porous SnO2 3D architectures are obtained after the CuO particles are removed by acid-washing. A decomposition–aggregation–dissolution process is proposed to demonstrate the formation of such a special structure. Furthermore, gas sensing properties of the as-prepared porous SnO2 3D architectures were investigated using toluene and formaldehyde as the representative target gases. The porous SnO2 3D architectures exhibit excellent sensing performances due to the high porosity and 3D morphology, which can significantly facilitate gas diffusion and mass transportation in sensing materials. This work further hints that this new facile and economical approach can be extended to synthesize other porous metal oxide materials with a unique morphology or shape.

Preparation of hollow porous Co-doped SnO2 microcubes and their enhanced gas sensing property

Hollow porous Co-doped SnO2 microcubes were achieved by a template-free chemical solution route combined with subsequent alkali-washing, calcination and acid-washing process. Spontaneous phase segregation yields such a special hollow porous structure. Several techniques, such as X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetric-differential thermal analysis, and Brunauer–Emmett–Teller N2 adsorption–desorption analyses, were used to characterize the structure and morphology of the products. During the process, alkali-washing in the first step is critical to the formation of the hollow structure. The process of inducing porosity starts with a crystalline single-phase hydroxide precursor CoSn(OH)6 formed by co-precipitation of the metal ions from aqueous solution. Thermal decomposition of the precursors leads to an intimate mixture of Co3O4 and porous tetragonal SnO2. The hollow porous Co-doped SnO2 microcubes are obtained after the Co3O4 phase has been removed by acid-washing. A decomposition–aggregation–dissolution process is proposed to demonstrate the formation of such a special structure. Furthermore, the gas sensing properties of the as-prepared hollow, porous, Co-doped SnO2 microcubes for some volatile organic vapors were tested, which exhibited a much better sensing performance than that of the porous Co-doped SnO2 microcubes, indicating that the special hollow porous Co-doped SnO2 structures are highly promising for applications as gas sensors.

Preparation of three-dimensional nanosheet-based molybdenum disulfide nanotubes as anode materials for lithium storage

Three-dimensional (3D) hierarchical nanosheet-based MoS2 nanotubes are synthesized via a self-sacrificial template method. The MoO3 nanorods as self-sacrificial templates are directly converted into MoS2 nanotubes through a solvothermal sulfidation reaction. The MoS2 nanotubes which are in a diameter range of 250–400 nm are systematically characterized by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photo electron spectroscopy, Raman spectroscopy, etc. The conversion mechanism of MoS2 nanotubes from MoO3 nanorods is also demonstrated. The as-prepared MoS2 hollow nanostructure anodes exhibit a high reversible capacity of 1035 mA h g−1 at 100 mA g−1 over 130 cycles. The excellent electrochemical performance suggests that the 3D hierarchical MoS2 nanotubes can be promising candidate anode materials for lithium-ion batteries.

Size-controlled synthesis and electrochemical performance of porous Fe2O3/SnO2 nanocubes as an anode material for lithium ion batteries

Uniform and monodisperse porous Fe2O3/SnO2 nanocubes with different particle sizes were synthesized by a template-free, economical aqueous solution method combined with subsequent calcination. The size of the precursor, FeSn(OH)6 cubes, was controlled carefully from 50–90 nm to 500–600 nm by adjusting the pH of the solution in the coprecipitation process. The structural and morphological evolution was characterized using a range of techniques. Thermal decomposition of the precursors led to an intimate mixture of hexagonal phase Fe2O3 and tetragonal phase SnO2. The as-prepared porous Fe2O3/SnO2 nanocubes with edge sizes in the range of 50–90 nm as anode materials for lithium storage achieved a very high reversible capacity of 620.8 mA h g−1 at 200 mA g−1 after 150 cycles. This paper reports a promising method for the design and preparation of porous nanocomposite electrodes for Li-ion batteries.

Synthesis, surface modification and ethanol sensing properties of Sb-doped SnO 2

Sb-doped SnO2 whiskers were prepared by thermal evaporation of mixture of SnO and Sb2O3 powders. And then the surface of the whisker was modified with the Au nanoparticles (Au NPs) by in situ reduction method. FE-SEM observations reveal that the synthesized products consist of a large number of whiskers. The Au NPs were homogeneously distributed on the surface of the whisker. The ethanol sensitive characteristics of single SnO2 whiskerbased sensors have been investigated. These sensors show good sensitivity, rapid response and recovery. The response and recovery time of the sensor is about 38-45 s and 125-150 s, respectively. It is found that the working temperature of the sensor decreases after the surface of Sb-doped whiskers modified with Au NPs. Compared to the unmodified Sbdoped SnO2 whisker, Au NPs modified Sb-doped SnO2 whisker exhibits greatly improvement of sensitivity which could be explained by the catalytic action of Au NPs. These results indicate that the Au NPs modifying the surface of SnO2 whiskers is important for improving its sensitivity and lowering the working temperature. This is the first step towards fundamental understanding of single-crystalline tin oxide whiskers for sensor applications, which could lead to integration in real devices.