Baisong Geng

Morphology-controlled synthesis, growth mechanism, optical and microwave absorption properties of ZnO nanocombs

ZnO nanocombs and nanorods with different morphologies have been successfully synthesized through a simple metal vapour deposition route at 600-750 degrees C using pure zinc powder or zinc and graphite powders as source materials. The structures and morphologies of the products were characterized in detail by using x-ray diffraction, scanning electron microscopy, transmission electron microscopy and laser Raman spectrometer. The morphologies of the products can be easily controlled by tuning the following four factors: reaction temperature, the distance between the source and the substrates, the kinds of substrates and the kinds of precursors. Possible growth mechanisms for the formation of ZnO nanostructures with different morphologies are discussed. Photoluminescence studies show that there are sharp UV and broad defect-related green emissions for all products. Relative intensity of the UV to defect-related green emissions decreases from ZnO nanorods to nanocombs. Microwave absorption properties of these nanocombs are also investigated. The value of the minimum reflection loss is -12 dB at 11 GHz for the ZnO nanocomb composite with a thickness of 2.5 mm.

Morphology and thermal stability of Ti-doped copper nitride films

A weakly Ti-doped copper nitride (Cu3N) film was prepared by cylindrical magnetron sputtering. The XPS results indicate that Ti atoms do not substitute for the Cu atoms but probably locate at the grain boundaries. The columnar grains size is about half of that of the undoped Cu3N film and the surface is smoother. For weakly Ti-doped Cu3N films, a dense layer appears on top of the columnar crystals. The RMS of the Cu film formed by annealing of the weakly Ti-doped Cu3N film is more than twice larger than that of the film before annealing. Compared with the undoped Cu3N film, it possesses fine thermal stability both in vacuum and in atmosphere.

3D flower-like hierarchitectures constructed by SnS/SnS 2 heterostructure nanosheets for high-performance anode material in lithium-ion batteries

Sn chalcogenides, including SnS, Sn2S3, and SnS2, have been extensively studied as anode materials for lithium batteries. In order to obtain one kind of high capacity, long cycle life lithium batteries anode materials, three-dimensional (3D) flowerlike hierarchitectures constructed by SnS/SnS2 heterostructure nanosheets with thickness of ∼20nm have been synthesized via a simple one-pot solvothermal method. The obtained samples exhibit excellent electrochemical performance as anode for Li-ion batteries (LIBs), which deliver a first discharge capacity of 1277 mAhg-1 and remain a reversible capacity up to 500 mAhg-1 after 50 cycles at a current of 100 mAhg-1.

Structure and optical investigation of faceted hexagonal aluminum nitride nanotube arrays

Arrays of single-crystalline aluminum nitride nanotubes (AlNNTs) were successfully synthesized at 780 °C by a facile CVD method without templates or catalysts. Faceted hexagonal AlNNTs with diameters from tens to hundreds of nanometers were observed. 264 nm deep-ultraviolet emission associated with Al vacancies was detected by photoluminescence. Raman characterization indicates that the lattice of the AlNNTs is notably defective, and disorder-activated silent B1 (low) and B1 (high) were detected at 583.0 and 730.0 cm−1 respectively, which were allowed by the breakdown of the translational crystal symmetry. The redshift of E2 (high) Raman modes indicates that biaxial tensile stress exists in the samples.

High rate performance SnO2 based three-dimensional graphene composite electrode for lithium-ion battery applications

In order to improve the rate performance and cycling stability at high current densities of lithium-ion batteries (LIBs), a sample composite of SnO2 and three-dimensional graphene (SnO2/3DG) was fabricated using a hydrothermal method, with polystyrene balls (PS) as templates. The reversible capacity is 720.8 mA h g−1 at a current density of 100 mA g−1, after 100 cycles. The rate performance is also excellent, with a reversible capacity of about 800 mA h g−1 at 1000 mA g−1. The excellent electrochemical performance is attributed to its 3D structure, which possesses a large specific surface area and abundant reaction active positions, leading to fast kinetics and short pathways for both Li-ions and electrons.

Large-size and high performance visible-light photodetectors based on two-dimensional hybrid materials SnS/RGO

We report a facile solvothermal method to synthesize two-dimensional hybrid materials consisting of layered SnS nanosheets and reduced graphene oxide (SnS/RGO). Large-size photodetectors with a channel length/width = 2 mm/7 mm are fabricated on Si/SiO2 substrates, showing an excellent photoresponsivity of 0.18 A W−1 under visible-light illumination with a detectivity of 4.18 × 1010 Jones, as well as fast rise and decay times (τrise = τdecay = 0.4 s). SnS/RGO hybrids are therefore promising candidates for potential applications in optoelectronics and low cost, high performance, and reliable photodetectors.