Yinong Lu

Extended vapor–liquid–solid growth and field emission properties of aluminium nitride nanowires

Hexagonal AlN (h-AlN) nanowires with an average diameter of around 15 nm have been prepared by an extended vapor–liquid–solid growth technique and characterized by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray analysis, Raman spectroscopy and field emission measurements. This preparation is a rather simple route for bulk fabrication of h-AlN nanowires. The promising field emission property observed for h-AlN nanowires points to the important application potential of this material.

Synthesis of single-crystalline α-Si3N4 nanobelts by extended vapour–liquid–solid growth

A simple chemical method for the production of single-crystalline alpha-Si(3)N(4) nanobelts has been developed, consisting of nitridation of a high-Si-content Fe-Si catalyst by ammonia at 1300 degrees C. The as-synthesized product was characterized by means of x-ray diffraction, electron microscopy and energy-dispersive x-ray spectroscopy. The alpha-Si(3)N(4) nanobelts have widths of 60-120 nm, thicknesses of 10-30 nm and lengths up to microns. Four intense green-blue luminescence bands at 398 nm (3.12 eV), 434 nm (2.86 eV), 492 nm (2.52 eV) and 540 nm (2.30 eV) were observed and analysed for the product, which indicates the potential applications in optoelectronics. The growth mechanism has also been speculated upon. The potential technological importance of the product, the simplicity of the preparation procedure, as well as the cheap commercial precursor of Fe-Si alloy particles makes this study both scientifically and technologically interesting.

Self-templated synthesis of polycrystalline hollow aluminium nitride nanospheres

Polycrystalline hollow AlN nanospheres with diameters ranging from 20 to 200 nm and shell thickness of about 10 nm were successfully synthesized through the reaction of irregular Al nanopowder with a CH4–NH3 mixture at around 1000 °C by the self-templated method. The products were well characterized by X-ray diffraction, high-resolution transmission electron microscopy, Raman spectroscopy and photoluminescence measurements. The photoluminescence properties of the hollow AlN nanospheres showed the routine blue emissions for AlN nanoparticles as well as an unusual green emission at around 533 nm, indicating the potential for luminescent devices. The synthesis mechanism was reasonably speculated and further supported by the similar synthesis of hollow AlN nanospheres from regular Al particles.

The synthesis of boron nitride nanotubes by an extended vapour?liquid?solid method

An extended vapour?liquid?solid (VLS) growth method, which is the reaction of a mixture of nitrogen and ammonia gas over nanoscale Fe?B catalyst particles at 1100??C, has been developed. With this method, BN nanotubes of diameter about 20?nm have been prepared and well characterized by high-resolution transmission electron microscopy and energy dispersive x-ray spectroscopy. In contrast to traditional VLS growth, the boron component in the BN nanotubes comes from the Fe?B catalyst itself, rather than from the vapour precursor. A growing mechanism has been discussed accordingly.

Synthesis of large-scale undoped and nitrogen-doped amorphous graphene on MgO substrate by chemical vapor deposition

Despite amorphous graphene (a-graphene) domains having been created and observed within crystalline graphene, large-area synthesis is still in its infancy. Here, using MgO single crystals as a catalytic substrate, large-area (10 × 5 mm) undoped and nitrogen-doped a-graphene were synthesized by chemical vapor deposition with benzene and pyridine as precursors, respectively. The dependence of the number of layers and the crystallinity of a-graphene on the growth temperature was observed by transmission electron microscopy, selected area electron diffraction and Raman spectroscopy. Few-layer (2–5 layers) a-graphene films are demonstrated to have high transmittance (>85% at 550 nm) and low conductivity (<1 × 10−3 S cm−1). When doped with nitrogen (N/C ratio = ∼0.09), the conductivity of the a-graphene film could be increased. The preparation of large-area a-graphene films not only extends to two-dimensional carbon materials but also might provide building blocks for future all-carbon devices.

Surfactant-free microwave-assisted hydrothermal synthesis of BaMoO4 hierarchical self-assemblies and enhanced photoluminescence properties

BaMoO(4) with 3D hierarchical multilayer disk-like and nest-like architectures self-assembled from 2D nanosheets was successfully synthesized via a microwave-assisted hydrothermal route without any surfactant. The as-prepared products were characterized by X-ray powder diffractometer (XRD), scanning electron microscope (SEM), field emission transmission electron microscope (FE-TEM), and photoluminescence (PL) spectrometer. The results show that the reaction parameters, including pH value, reactant concentration, and molar ratio of [Ba(2+)]/[MoO(4)(2-)], played important roles on the morphologies of the final products. And the formation mechanism of 3D hierarchical architectures is a stepwise oriented aggregation-based self-assembly process. The superstructure characteristic of 3D nest-like BaMoO(4) architecture was observed in HRTEM image and the corresponding fast Fourier transform (FFT) for the first time, and the superlattice reflections with non-integer indices occurred around the subcell reflections at ±1/6(2a*+2c*). Room temperature photoluminescence spectra of 3D BaMoO(4) architectures reveal a strong and broad blue emission, and the 3D nest-like architectures own the enhanced intensity than multilayer disks.

Chemical synthesis and characterization of boron/boron nitride core–shell nanostructures

A moderate chemical method [i.e., the reaction of diborane (B 2 H 6 ) and a mixture gas of ammonia and nitrogen (NH 3 /N 2 ) over nanoscale iron boride at 1100 °C] was developed to explore the boron nitride (BN) nanostructures. The products were well characterized by high-resolution electron microscopy and energy-dispersive x-ray spectroscopy. Two types of novel core-shell nanocapsules of amorphous boron core encapsulated in crystalline boron nitride shell were obtained. The first one looked like a peanut with an amorphous B core containing a trace of BN crystallites, a transition layer of BN nanofibers and amorphous B, and a thornlike shell of BN nanofibers. The second one looked like a perfect sphere consisting of a pure amorphous B core and a rather smooth crystalline BN shell. These results not only provided us a new chemical method for preparing BN nanostructures but also enriched the important BN nanostructures family. A growth mechanism is also briefly discussed.