Keyan Bao

Sunlight-assisted fabrication of a hierarchical ZnO nanorod array structure

A ZnO hierarchical structure built up of a well ordered nanorod array was obtained by a simple treatment of zincate ion aqueous solution and a zinc foil mixture with sunlight irradiation. The as-prepared ZnO nanorods are all single crystalline with a uniform [0001] preferential growth direction and have an average diameter of approximately 40 nm and a length of approximately 300 nm. It is believed that sunlight gave rise to the driving force for the preformed ZnO nanorod to self-assemble into plates, which served as the substrate for secondary heterogeneous nucleation, and subsequently the crystal growth resulted into formation of a ZnO nanorod array. The formation mechanism of the ZnO hierarchical nanorod array structure was discussed, based on controlled experiment results. Raman spectroscopy, cathodoluminescence and UV-Vis absorbance spectra of the as-prepared ZnO product have been performed.

Controlled fabrication of SnO2 solid and hollow nanocubes with a simple hydrothermal route

SnO2 solid and hollow nanocubes have been fabricated by a one-step hydrothermal treatment of tin foil in aqueous alkaline solutions at 200°C. The obtained cubes have an average edge length of about 300nm, and the thickness of the hollow cubes’ shell is in the range of 30–50nm. Based on the time-dependent experiments, the evacuation behavior of Ostwald ripening is proposed to explain the formation mechanism of hollow cubes. Cathodoluminescence measurements disclose that the intensity for two peaks of hollow SnO2 nanocubes is enhanced significantly with respect to that of solid nanocubes.

Synthesis of GaN nanorods by a solid-state reaction

An atom-economical and eco-friendly chemical synthetic route was developed to synthesize wurtzite GaN nanorods by the reaction of NaNH2 and the as-synthesized orthorhombic GaOOH nanorods in a stainless steel autoclave at 600°C. The lengths of the GaN nanorods are in the range of 400-600nm and the diameters are about 80-150 nm. The process of orthorhombic GaOOH nanorods transformation into wurtzite GaN nanorods was investigated by powder X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM), indicating that the GaN product retained essentially the same basic topological morphology in contrast to that of the GaOOH precursor. It was found that rhombohedral Ga2O3 was the intermediate between the starting orthorhombic GaOOH precursor and the final wurtzite GaN product. The photoluminescence measurements reveal that the asprepared wurtzite GaN nanorods showed strong blue emission.

Controlled Growth of Carbon Spheres Through the Mg-Reduction Route

Hollow spheres, hollow capsules and solid spheres of carbon were selectively synthesized by Mg-reduction of hexachlorobutadiene at appropriate reaction conditions. X-ray powder diffraction and Raman spectra reveal that the as-prepared materials have a well-ordered structure. A possible formation mechanism has been proposed.

Growth and characterization of ZnS porous nanoribbon array constructed by connected nanocrystallities

Well-aligned ZnS porous nanoribbon array has been prepared with a simple one-step solvothermal approach. X-Ray diffraction, energy dispersive X-ray spectrometry and scanning electron microscopy indicate the formation of ZnS nanoribbon array. Transmission electron microscope measurements reveal that the porous nanoribbons are composed of a large amount of connected nanocrystallites with sizes of about 2–5 nm as the building blocks. These ZnS nanocrystallites are all found to adopt the same crystallographic direction. Uniform separated nanopores exist among these nanopraticles. A possible formation mechanism of the nanoribbon array and a porous structure are proposed. The room-temperature luminescence property of the as-prepared ZnS porous nanoribbon array is also studied.