Anatase type titania nanotube arrays direct fabricated by anodization without annealing

In this paper, anatase type titania nanotube arrays were direct fabricated by anodization in dimethyl sulfoxide electrolyte containing 1 wt% HF solution at above 50 °C without subsequently annealing. The length of the nanotubes decreases with increasing anodization temperature from about approximately 15 μm at 40 °C to approximately 4.5 μm at 60 °C. High resolution transmission electron microscope images and selected area electron diffraction pattern confirm the polycrystalline anatase specimen consisting of many nanocrystals with a random orientation.     

Nonlinear Deformation Processes and Damage Modes of Super Carbon Nanotubes with Armchair-Armchair Topology

The tensile deformations and fractures of super carbon nanotubes （SCNTs） with armchair-armchair topology are investigated by using the atomic-scale finite element method. SCNTs generated from carbon nanotubes （CNTs） with different characteristic aspect ratios are found to have different nonlinear behaviours under uniaxial tensions. Specifically, an SCNT wi~h higher aspect ratio has three distinct stages： rotation, stretch and rupture, while an SCNT with lower aspect ratio has only two stages. This information may compensate for previous work and enrich our knowledge about Y-branched CNTs and SCNTs.     

Effect of doping on electronic properties of double-walled carbon and boron nitride hetero-nanotubes

The effect of boron nitride (BN) doping on electronic properties of armchair double-walled carbon and hetero-nanotubes is studied using ab initio molecular dynamics method. The armchair double-walled hetero-nanotubes are predicted to be semiconductor and their electronic structures depend strongly on the electronic properties of the single-walled carbon nanotube. It is found that electronic structures of BN-doped double-walled hetero-nanotubes are intermediate between those of double-walled boron nitride nanotubes and double-walled carbon and boron nitride hetero-nanotubes. Increasing the amount of doping leads to a stronger intertube interaction and also increases the energy gap.     

Electrocatalytic oxidation of formaldehyde on platinum well-dispersed into single-wall carbon nanotube/polyaniline composite film

Single-walled carbon nanotubes (SWNTs)/polyaniline (PANI) composite films with good uniformity and dispersion were prepared by electrochemical polymerization of aniline containing well-dissolved SWNTs. The composite films were dispersed Pt by electrodeposition technique. The presence of SWNTs and platinum in the composite film was confirmed by XRD analysis and scanning electron microscopy (SEM). Four-point probe investigation and electrochemical impedance spectroscopy (EIS) revealed that the well arrangement of PANI coated SWNTs in these films enhanced electric conductivity and facilitated the charge-transfer of the composite films. Cyclic voltammogram (CV) and chronoamperogram showed that Pt-modified SWNT/PANI composite film performs higher electrocatalytic activity and better long-term stability than Pt-modified pure PANI film toward formaldehyde oxidation. The results imply that the SWNT/PANI composite film as a promising support material improves the electrocatalytic activity for formaldehyde oxidation greatly.     

Functional multi-walled carbon nanotube/polyaniline composite films as supports of platinum for formic acid electrooxidation

Embedding of carbon nanotubes in conducting polymeric matrices for various nanocomposites material is now a popular area. In this article, a concise chemical method has been described for the preparation of homogeneous nanocomposite of multi-walled carbon nanotube (MWNT)/polyaniline (PANI) by electrochemical codeposition. For this we functionalized the MWNTs via the diazotization reaction. This helped to disperse the nanotubes in aniline. The composite films were dispersed Pt by electrodeposition technique. The presence of MWNTs and platinum in the composite films was confirmed by XRD analysis and transmission electron microscopy (TEM). Four-point probe investigations revealed that the MWNT/PANI composite films exhibited a good conductivity. Cyclic voltammograms (CV) showed that Pt-modified MWNT/PANI composite films perform higher electrocatalytic activity and better long-term stability than Pt-modified pure PANI film toward formic acid oxidation. The results imply that the MWNT/PANI composite films as a promising support material improves the electrocatalytic activity for formic acid oxidation greatly.     

Synthesis and Raman scattering study of double-walled carbon nanotube peapods

Double-walled carbon nanotubes (DWNTs) encapsulating C₆₀ fullerenes were successfully synthesized by gas phase diffusion method. The obtained peapods were examined using high-resolution transmission electron microscopy (HRTEM). The HRTEM images indicate that the ordered packing phases of fullerene molecules inside are sensitively related to the inner-tube radius of DWNTs. Also, Raman measurements were carried out for the first time to characterize DWNTs peapods. There are obvious differences between the Raman spectrum of DWNTs peapods and that of SWNTs peapods. The intensities of resonances from C₆₀ in the former are much stronger than those in the latter. In addition, changes of tangential mode (TM) and radial breathing mode (RBM) of DWNTs after C₆₀ doping were observed. The possible reasons are discussed in the text.     

Formation of Y-junction carbon nanotubes by catalytic CVD of methane

Y-junction carbon nanotubes were grown by catalytic CVD of methane at 700 ^°C on NiO-CuO-MoO(7:2:1) (w/w/w)/SiO₂ catalyst. For comparison, NiO-CuO(8:2) (w/w)/SiO₂ and NiO-MoO(8:2) (w/w)/SiO₂ catalysts were tested for carbon nanotube formation. TEM analysis indicates that no Y-junction structures were formed with the latter two catalysts. This finding elucidates why the addition of a small amount of MoO to NiO-CuO/SiO₂ catalyst is crucial for enhancing the formation of Y-junction carbon nanotubes.     

Amine-functionalized boron nitride nanotubes

The surface of boron nitride nanotubes (BNNTs) has been functionalized with amine groups via ammonia plasma irradiation. The functionalized tubes were characterized by Fourier transform infrared spectroscopy and electron energy loss spectroscopy. Amine-functionalized BNNTs were found to be highly dispersible in chloroform, and are predicted to form the basis of a new class of chemically reactive nanostructures.     

ZnSe‐based conductive nanotemplates for nanofabrication

We show that anodic etching of n‐type ZnSe crystalline substrates leads to the formation of pores which, after nucleation at surface defects, prove to follow the current lines, exhibiting multiplication until the front of the porous network covers the whole available space. No growth of crystallographically oriented pores has been observed in ZnSe. The formation of multilayer porous structures is realized, including layers subjected to successive porosification at two different length scales. The electrochemical pulsed deposition of arrays of Pt nanotubes in the porous ZnSe matrix is demonstrated. The obtained results show that porous ZnSe structures are promising for use as conductive and optically transparent nanotemplates for nanofabrication, in particular for the important application of metal nanotubes. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Free standing double walled boron nanotubes

Based on density functional calculations we propose stable structures of free standing double walled boron nanotubes in the form of two single walled boron nanotubes (SWBNTs) inside one another. Puckering of the boron sheets allows the inner atoms of the outer wall and outer atoms of the inner wall to be matched giving sp-type hybrid σ bonding between the walls. The structural stability, in the case of double walled tubes, increases as the bond interaction between the walls strengthens. All the optimized structures reported in this study are electronically conducting in good agreement with the previously calculated metallic behavior of the experimentally observed SWBNTs.     

Synthesis of single crystalline layered lithium manganese oxide nanorods

Single-crystalline layered lithium manganese oxide nanorods were prepared via a low-temperature molten salt synthesis method. The material was investigated by a variety of techniques, including X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS).     

Hydrothermal synthesis and electrochemical characterization of VO2 (B) with controlled crystal structures

Three different VO₂ (B) nanostructures, including urchin-like VO₂ (B), VO₂ (B) honeycombs and VO₂ (B) nanorods have been successfully fabricated through hydrothermal process by adjusting the concentrations of the oxalic acid. The microstructure and morphology of the VO₂ nanostructures were evaluated by using X-ray diffraction and scanning and transmission electron microscopies. Electrochemical properties measurements of urchin-like VO₂ (B) and VO₂ (B) honeycombs showed excellent cycling performance, especially the urchin-like VO₂ (B) exhibited higher discharge capacity and better capacity retention.