Thermoelectrical and optical properties of double wall carbon nanotubes:polyaniline containing boron n‐type organic semiconductors

The electrical conductivity, thermoelectrical, and optical properties of the polyaniline containing boron/double wall carbon nanotubes (CNTs) composites have been investigated. The electrical conductivities of the composites prepared with 1%, 5%, and 8% CNT concentrations at 300 K were found to be 5.31 × 10^?6, 2.72 × 10^?4, and 1.12 × 10^?3 (S/cm), respectively. The thermoelectrical results indicate that all the samples exhibit n‐type electrical conductivity. The optical band gaps of the samples were found to be 3.71 eV for 0% DWNT, 3.32 eV for 1% DWNT, 3.15 eV for 5% DWNT, and 3.12 eV for 8% DWNT. The obtained results suggest that the electrical conductivity of PANI‐B polymer is improved by DWNT doping. Copyright © 2008 John Wiley & Sons, Ltd.     

The possible way to evaluate the purity of double-walled carbon nanotubes over single wall carbon nanotubes by chemical doping

Here, we carried out Raman study on chemically doped single wall carbon nanotube (SWNT)/double-walled carbon nanotube (DWNT) mixed bucky-papers. Their highly different Raman responses (e.g., a large upshift of tangential mode of SWNT and no large changes in the frequencies of tangential mode assigned to the outer tubes of the DWNT) upon doping with the sulfuric acid could be used as a qualitative indicator of the purity of the DWNT samples with the concentration of its SWNTs contents.     

Efficient H2 adsorption by nanopores of high-purity double-walled carbon nanotubes

DWNT buckypaper adsorbed much more hydrogen than did a SWNT bundle. XRD measurements and GCMC simulation results suggested that the DWNT bundle is loosely packed into an hexagonal array with interstitial pores which can efficiently adsorb H2 molecules.     

Synthesis of single- and double-walled carbon nanotube forests on conducting metal foils

Here, we report a highly efficient growth of single-walled carbon nanotubes (SWNTs) and double-walled carbon nanotubes (DWNTs) on conducting metal foils. We found that foils made of Ni-based alloys with Cr or Fe serve as excellent substrates for SWNT (DWNT) synthesis. In significant contrast, a CNT grown on Ni, Fe foils contains a significant ratio of MWNTs. This result opens up an economical route for the mass production of SWNT (DWNT) forests and also enables the straightforward integration of CNTs into nanoelectronic devices, such as field emission displays.     

Selective chemical vapor deposition synthesis of double-wall carbon nanotubes on mesoporous silica

Double-wall carbon nanotubes (DWNTs) have been selectively synthesized over Fe/Co loaded mesoporous silica by catalytic chemical vapor deposition of alcohol. Several silica materials with desired pore diameter and morphology have been investigated for the DWNT growth. The diameter distribution and selectivity of the DWNT are found to depend on the reaction temperature, pore size, and thermal stability of the support material. A high-yield synthesis of DWNTs has been achieved at 900 degrees C over high-temperature stable mesoporous silica. The outer diameter of DWNTs is found to be in the range of 1.5-5.4 nm with a "d" spacing of 0.38 +/- 0.02 nm between inner and outer layers, which is much larger than those of multiwall carbon nanotubes.     

Aligned double-walled carbon nanotube long ropes with a narrow diameter distribution

Aligned double-walled carbon nanotube (DWNT) long ropes with a narrow diameter distribution were directly synthesized by sulfur-assisted floating catalytic decomposition of methane. The DWNT ropes are typically up to several centimeters in length and possess good alignment and high purity. High-resolution transmission electron microscopy (HRTEM) images and resonant Raman spectra revealed that the outer and inner tube diameters of the DWNTs are narrowly distributed in the range of 1.7-2.0 and 1.0-1.3 nm, respectively. Moreover, based on the resonant Raman measurements, the electronic properties of the two constituent tubes of the DWNTs were identified. The successful synthesis of such DWNTs opens the possibility for their fundamental studies and further applications as nanomechanical, nanooptical, and nanoelectronic devices.     

Thermal and spectroscopic characterization of polypropylene-carbon nanotube composites

Thermogravimetric (TG) and varied temperature Raman spectroscopic measurements of melt-blended polypropylene composites (PP) with double wall (DWNT) and multi-wall carbon nanotubes (MWNT) revealed that the incorporation of carbon nanotubes into polymer matrix increased the thermal stability comparing to the virgin polypropylene. The characterization of reference nanotubes was also done by Raman microscopy and TG measurements. Varied temperature rheological analysis provided further information about the thermal decomposition of the composites indicating the formation of high strength char in case of MWNT and limited applicability of DWNT at high temperature. The residue of the decomposition of PP-MWNT nanocomposites consists of nanotubes of spectroscopically higher purity comparing to the original one indicating the thermally induced chemical changes in the solid phase.     

Double-walled carbon nanotubes as a solid phase extractor for separation-preconcentration of traces of gold from geological and water samples

In this work, a solid phase extraction method has been developed using a column filled with double-walled carbon nanotubes (DWNT) for preconcentration-separation of gold(III) ions prior to their flame atomic absorption spectrometric determination. Gold(III) ions were quantitatively recovered on DWNT in 1.0?mol?L^?1 HCl. The influences of the analytical conditions including eluent type, sample volume, etc. on the recoveries of gold(III) ions were examined. The effects of concomitant ions were also investigated. The detection limits for gold(III) based on 3σ was calculated as 1.5?µg?L^?1. The procedure presented in this paper was applied to the gold content of a number of water, geological and anodic slime samples with successful results.     

Highly transparent and conductive thin films fabricated with nano-silver/double-walled carbon nanotube composites

This study develops a technique for enhancing the electrical conductivity and optical transmittance of transparent double-walled carbon nanotube (DWNT) film. Silver nanoparticles were modified with a NH(2)(CH(2))(2)SH self-assembled monolayer terminated by amino groups and subsequent surface condensation that reacted with functionalized DWNTs. Ag nanoparticles were grafted on the surface of the DWNTs. The low sheet resistance of the resulting thin conductive film on a polyethylene terephthalate (PET) substrate was due to the increased contact areas between DWNTs and work function by grafting Ag nanoparticles on the DWNT surfaces. Increasing the contact area between DWNTs and work function improved the conductivity of the DWNT-Ag thin films. The prepared DWNT-Ag thin films had a sheet resistance of 53.4 Ω/sq with 90.5% optical transmittance at a 550 nm wavelength. After treatment with HNO(3) and annealing at 150 °C for 30 min, a lower sheet resistance of 45.8 Ω/sq and a higher transmittance of 90.4% could be attained. The value of the DC conductivity to optical conductivity (σ(DC)/σ(OP)) ratio is 121.3.     

Synthesis and characterization of monolithic carbon aerogel nanocomposites containing double-walled carbon nanotubes

We report the synthesis and characterization for the first examples of monolithic low-density carbon aerogel (CA) nanocomposites containing double-walled carbon nanotubes. The CA nancomposites were prepared by the sol-gel polymerization of resorcinol and formaldehyde in an aqueous surfactant-stabilized suspension of double-walled carbon nanotubes (DWNTs). The composite hydrogels were then dried with supercritical CO 2 and subsequently carbonized under an inert atmosphere to yield monolithic CA structures containing uniform dispersions of DWNTs. The microstructures and electrical conductivities of these CA nanocomposites were evaluated for different DWNT loadings. These materials exhibited high BET surface areas (>500 m (2)/g) and enhanced electrical conductivities relative to pristine CAs. The details of these results are discussed in comparison with theory and literature.     

Surfactant-free nanofluids containing double- and single-walled carbon nanotubes functionalized by a wet-mechanochemical reaction

Single-walled carbon nanotubes (SWNTs) and double-walled carbon nanotubes (DWNTs) have been functionalized through the wet-mechanochemical reaction method. Results from the infrared spectrum and zeta potential measurements show that the hydroxyl groups have been introduced onto the treated SWNT and DWNT surfaces. Transmission electron microscope observations revealed that the SWNTs and DWNTs were cut short after being milled. SWNTs and DWNTs with optimized aspect ratio can be obtained by adjusting the ball milling parameters. Thermal conductivity enhancement of water-based nanofluids containing treated carbon nanotubes (CNTs) shows augmentation with the increase of temperature mainly due to the effects of an ordering liquid layer forming around the chemical surfaces of CNTs. Moreover, the thicker interfacial layer of water molecules on the surfaces of CNTs with smaller diameter, such as SWNTs, is in favor of greater thermal conductivity enhancement compared with the thinner one on the surfaces of DWNTs or MWNTs with larger diameter.     

Local structure of titania decorated double-walled carbon nanotube characterized by scanning transmission X-ray microscopy

Scanning transmission X-ray microscopy was demonstrated to deliver detailed local structure and chemical composition of a complicated system with titania nanoparticles dispersed inside and outside the double-walled carbon nanotube (DWNT) channels. Areas with inhomogeneous distribution of titania and the associated water were particularly investigated at the C K-edge, Ti L-edge, and O K-edge. The results show that titania nanoparticles located inside DWNTs are present as amorphous, while those unsuccessfully introduced into the channels behave more like bulk materials in forms of anatase and rutile. Strong interaction was detected between the confined titania and DWNTs, as evidenced by up to 0.6 eV energy shift at the Ti L-edge. Strong hydration was observed for the as-prepared samples. Functionalization due to reduction and oxidation between titania and carbon layer is observed upon heat-treatment. This detailed structural information of specific areas cannot be provided by other techniques such as HRTEM, XRD, and XANES.     

Theoretical Study of α‐V2O5‐Based Double‐Wall Nanotubes

First‐principles calculations of the atomic and electronic structure of double‐wall nanotubes (DWNTs) of α‐V₂O₅ are performed. Relaxation of the DWNT structure leads to the formation of two types of local regions: 1) bulk‐type regions and 2) puckering regions. Calculated total density of states (DOS) of DWNTs considerably differ from that of single‐wall nanotubes and the single layer, as well as from the DOS of the bulk and double layer. Small shoulders that appear on edges of valence and conduction bands result in a considerable decrease in the band gaps of the DWNTs (up to 1 eV relative to the single‐layer gaps). The main reason for this effect is the shift of the inner‐ and outer‐wall DOS in opposite directions on the energetic scale. The electron density corresponding to shoulders at the conduction‐band edges is localized on vanadium atoms of the bulk‐type regions, whereas the electron density corresponding to shoulders at the valence‐band edges belongs to oxygen atoms of both regions.     

Advanced Catalytic Performance of Au–Pt Double‐Walled Nanotubes and Their Fabrication through Galvanic Replacement Reaction

Bimetallic tubular nanostructures have been the focus of intensive research as they have very interesting potential applications in various fields including catalysis and electronics. In this paper, we demonstrate a facile method for the fabrication of Au–Pt double‐walled nanotubes (Au–Pt DWNTs). The DWNTs are fabricated through the galvanic displacement reaction between Ag nanowires and various metal ions, and the Au–Pt DWNT catalysts exhibit high active catalytic performances toward both methanol electro‐oxidation and 4‐nitrophenol (4‐NP) reduction. First, they have a high electrochemically active surface area of 61.66 m² g^?1, which is close to the value of commercial Pt/C catalysts (64.76 m² g^?1), and the peak current density of Au–Pt DWNTs in methanol oxidation is recorded as 138.25 mA mg^?1, whereas those of Pt nanotubes, Au/Pt nanotubes (simple mixture), and commercial Pt/C are 24.12, 40.95, and120.65 mA mg^?1, respectively. The Au–Pt DWNTs show a markedly enhanced electrocatalytic activity for methanol oxidation compared with the other three catalysts. They also show an excellent catalytic performance in comparison with common Au nanotubes for 4‐nitrophenol (4‐NP) reduction. The attractive performance exhibited by these prepared Au–Pt DWNTs can be attributed to their unique structures, which make them promising candidates as high‐performance catalysts.     

Aryl- and alkenyllithium preparations and copper-catalyzed reaction between the derived magnesium reagents and the monoacetate of 4-cyclopentene-1,3-diol

[reaction: see text] Aryl- and alkenyllithiums, prepared by halogen-lithium exchange with lithium, exchange with n-(or t-)BuLi, stannane-lithium exchange with n-BuLi, and direct lithiation with n-BuLi, were transformed into magnesium reagents with MgCl2 and subjected to CuCN-catalyzed reaction with the title monoacetate. Except for the halogen-lithium exchange with n-BuLi, the other preparations of the lithium anions were found to be compatible with the CuCN-catalyzed reaction to afford S(N)2-type products efficiently.     

合成聚芳酯树状分子的新方法

以３，５－二羟基 苯甲酸为起始原料，经甲醇酯化保护羧基，与苯甲酰氯反应，得到３，５－二苯甲酰氧基苯甲酸甲酯用ＡｌＣｌ３．ＮａＩ去掉保护基甲基，以高收率得到３，５－二苯甲酰氧基苯甲酸。其结构均是由ＩＲ，＾１ＨＮＭＲ，ＥＡ等方法证实。     

N-去甲万古霉素的亲和吸附

通过交联聚丙烯酸甲酯与乙醇胺反应,形成聚(N-羟乙基丙烯酰胺)树脂,在酸催化作用下与环氧氯丙烷反应,形成含有α-羟基氯乙基的树脂.含α-羟基氯乙基的树脂与D-丙氨酸、L-丙氨酸或甘氨酸反应,分别得到含有这3种氨基酸的吸附剂.这3种吸附剂吸附N-去甲万古霉素的结果表明,含D-丙氨酸的吸附剂的吸附量最大,含甘氨酸的吸附剂的吸附量次之,而含L-丙氨酸的吸附剂不吸附N-去万古霉素.说明前两种吸附剂对N-去甲万古霉素存在亲和吸附作用.含D-丙氨酸吸附剂的最佳吸附pH值为5.8,当吸附液中的盐(NaCl)浓度增加时,吸附量降低.用0.4mol/LNa₂CO₃/CH₃CN(摩尔比7∶3,pH=9.5)作为洗脱剂可完全脱附被吸附的N-去甲万古霉素.     

Electrochemical Characterization of the Interaction of Multiwalled Carbon Nanotubes with Doxorubicin

It has been suggested that multiwalled carbon nanotubes (MWCNTs) interacting with pharmaceutics may be introduced into the body as nanocarriers. To deliver the anticancer drugs, covalent or noncovalent functionalization of MWCNTs is required. In this study, the influence of oxidation on MWCNTs in the interaction with chemotherapeutic drug, doxorubicin, was characterized. The binding of doxorubicin with MWCNTs decreased rapidly with the increasing oxidation period with sulfuric acid. However, with nitric acid, the interaction increased initially and slowly decreased with time. The best results were obtained for sulfuric and nitric acid following 1 and 3?h of oxidation, respectively. The results show that sulfuric acid provided more favorable interaction for MWCNTs with doxorubicin than nitric acid.     

Geometry optimised ab initio calculations on cyclopropenone and dimethylcyclopropenone

Geometry optimised ab initio calculations are reported for cyclopropenone (I) and its dimethyl derivative (II). The effect of the methyl substituents in this strained ring system with an exocyclic heteroatom is to increase the bond lengths and the electronic delocalisation. For cyclopropenone the results are compared, firstly, with previous ab initio calculations, without geometry optimisation, secondly, with a semi-empirical calculation with partial optimisation, and finally, with experimental results. The calculated geometry for this molecule agrees with the experimental results.     

分子动力学模拟研究纳米碳管中甲醇-水混合溶液的结构与输运性质

利用分子动力学模拟方法,对比考察了平衡条件、外压作用、梯度电场作用下,摩尔比为1:1的甲醇-水混合溶液在纳米碳管(CNT)中的静态结构以及输运行为.研究发现:在平衡体系与外压作用下,纳米碳管内甲醇与水呈现出明显的不混溶现象,甲醇主要分布于管壁附近,水分子主要分布于纳米碳管轴心附近;而在梯度电场作用下,纳米碳管由疏水性向亲水性转变,更多的水分子分布于管壁,导致纳米碳管内甲醇-水的不混溶现象消失.另一方面,在外压作用下,纳米碳管内甲醇与水呈现单向移动;而在梯度电场下,甲醇与水呈现快速的双向移动,其流通量较相应外压作用体系高出近一个数量级,但由于双向的流通量大小相近,导致净流通量与外压作用下的净流通量差异不大.