Guo-Feng Cheng

Large-scale synthesis of single crystalline gallium nitride nanowires

Large-scale synthesis of single crystalline GaN nanowires in anodic alumina membrane was achieved through a gas reaction of Ga2O vapor with a constant flowing ammonia atmosphere at 1273 K. X-ray diffraction, Raman backscattering spectroscopy, scanning electron microscopy, and transmission electron microscopy indicated that those GaN nanowires with hexagonal wurtzite structure were about 14 nm in diameter and up to several hundreds of micrometers in length. The growth mechanism of the single crystalline GaN nanowires is discussed.

ZnFe2O4 nanoparticles: microwave-hydrothermal ionic liquid synthesis and photocatalytic property over phenol.

We report the microwave-hydrothermal ionic liquid (MHIL) synthesis and photocatalytic property over phenol of ZnFe(2)O(4) nanoparticles. Zn(CH(3)COO)(2).2H(2)O and Fe(NO(3))(3).9H(2)O were used as the zinc and iron sources, respectively, in the presence of CO(NH(2))(2) and the ionic liquid 1-n-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM][BF(4)]). Deionized water was used as a solvent. The ionic liquid [BMIM][BF(4)] and microwave heating temperature have significant influences on the crystal phase of the product. Different dosages of [BMIM][BF(4)] or microwave heating temperature could lead to the formation of different products such as ZnFe(2)O(4) and beta-FeOOH. The MHIL method has the advantages such as simplicity, rapidness and energy saving. The ZnFe(2)O(4) nanoparticles prepared by the MHIL method exhibit high photocatalytic activity for the degradation of phenol, which was up to 73% within 360 min. The TOC measurement confirmed the good photocatalytic efficiency of ZnFe(2)O(4) nanoparticles.

Sonochemical synthesis of single-crystalline CeOHCO3 rods and their thermal conversion to CeO2 rods

Single-crystalline CeOHCO3 rods with an orthorhombic structure have been successfully synthesized by the sonochemical method from aqueous solution containing CeCl3 and urea. Polycrystalline CeO2 rods have been prepared by thermal conversion of single-crystalline CeOHCO3 rods at 500 °C in air. CeOHCO3 and CeO2 rods were characterized by x-ray powder diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TG) and differential scanning calorimetric analysis (DSC).

Highly ordered nanostructures of single crystalline GaN nanowires in anodic alumina membranes

Abstract Synthesis of highly ordered nanostructures of single crystalline GaN nanowires in anodic alumina membranes was achieved through a gas reaction of Ga 2 O vapor with a constant ammonia atmosphere at 1000°C in the presence of nano-sized metallic indium catalysis. Atomic force microscopy, X-ray diffraction, Raman backscattering spectrum, scanning electron microscopy, and transmission electron microscopy indicate that the ordered nanostructure consists of the single crystalline hexagonal wurtzite GaN nanowires with about 20 nm in diameter and 40∼50 μm in length in the uniform nanochannels of the anodic alumina membrane. The vapor–liquid–solid (VLS) growth mechanism of the ordered nanostructure was discussed in detail.

Synthesis of orderly nanostructure of crystalline GaN nanoparticles on anodic porous alumina membrane

Synthesis of an orderly nanostructure of crystalline GaN nanoparticles on anodic porous alumina membrane through a gas reaction of Ga2O vapor with a constant ammonia atmosphere at 900°C was achieved. The investigation using atomic force microscopy, x-ray diffraction, transmission electron microscopy and high resolution electron microscopy indicated that the orderly nanostructure consisted of polycrystalline GaN nanoparticles with a hexagonal wurtzite structure and about 10–20 nm in diameter. The growth mechanism of the orderly nanostructure of the GaN nanoparticles was discussed. The photoluminescence spectrum of the orderly nanostructure was also reported.

Microwave-assisted preparation of Ca{sub 6}Si{sub 6}O{sub 17}(OH){sub 2} and {beta}-CaSiO{sub 3} nanobelts

Xonotlite (Ca6Si6O17(OH)2) nanobelts were synthesized by a microwave-assisted hydrothermal method at 180 8C for 90 min independent of the feeding molar ratio of Ca(NO3)24H2 Ot o Na 2SiO39H2O in the range of 0.8–3.0. Crystalline wollastonite (b-CaSiO3) nanobelts were obtained by microwave thermal transformation of Ca6Si6O17(OH)2 nanobelts at 800 8C for 2 h. Ca6Si6O17(OH)2 nanobelts were used as both the precursor and the template for the preparation of b-CaSiO3 nanobelts. The morphology and size of Ca6Si6O17(OH)2 nanobelts could be well preserved during the microwave thermal transformation process. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED).Xonotlite (Ca{sub 6}Si{sub 6}O{sub 17}(OH){sub 2}) nanobelts were synthesized by a microwave-assisted hydrothermal method at 180 {sup o}C for 90 min independent of the feeding molar ratio of Ca(NO{sub 3}){sub 2}.4H{sub 2}O to Na{sub 2}SiO{sub 3}.9H{sub 2}O in the range of 0.8-3.0. Crystalline wollastonite ({beta}-CaSiO{sub 3}) nanobelts were obtained by microwave thermal transformation of Ca{sub 6}Si{sub 6}O{sub 17}(OH){sub 2} nanobelts at 800 {sup o}C for 2 h. Ca{sub 6}Si{sub 6}O{sub 17}(OH){sub 2} nanobelts were used as both the precursor and the template for the preparation of {beta}-CaSiO{sub 3} nanobelts. The morphology and size of Ca{sub 6}Si{sub 6}O{sub 17}(OH){sub 2} nanobelts could be well preserved during the microwave thermal transformation process. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED).