碳源对碳纳米管形态的影响

以苯和甲苯为碳源,二茂铁为催化剂,含硫化合物为助催化剂,采用浮游催化裂解法制备了碳纳米管,并采用TEM对不同条件下所得碳纳米管进行了形态分析。结果发现,碳源中苯和甲苯的配比对碳纳米管的形态有着重要的影响。以纯苯为碳源时,产物主要为直线型碳纳米管,并存在极少量短的弯曲型碳纳米管。随着碳源中甲苯比例的增加,产物中折线型碳纳米管增加。以纯甲苯为碳源,产物中仍有少量直线型碳纳米管,而不完全是折线型碳纳米管;此外,产物中还发现了极少量分支型碳纳米管。根据所得结果讨论分析了甲苯的加入对碳纳米管形态的影响以及各种碳纳米管的形成机理,认为可能是由于甲苯在催化热解过程中产生的碳种不同于苯催化热解所产生的碳种,造成碳在催化剂颗粒各处浓度不同,从而在碳纳米管的不同部位引入五元环和七元环而形成各种形态的碳纳米管。     

Study of the photocatalytic degradation of toluene over CdS-TiO2 nanoparticles supported on multi-walled carbon nanotubes by back propagation neural network

To optimize the photocatalytic conditions for the degradation of volatile organic compounds (VOCs), this study focused on the application of a back propagation (BP) neural network to determine the photocatalytic performance of CdS-TiO₂ nanoparticles supported on multi-walled carbon nanotubes (MWCNTs) for toluene degradation. This was accomplished by first characterizing the photocatalyst using transmission electron microscopy (TEM), N₂ adsorption-desorption, X-ray diffraction (XRD) and UV-visible absorption spectrum (UV-vis). It was observed that TiO₂ and CdS particles were uniformly supported on the inner and outer walls of MWCNTs as a composite catalyst. Second, employing a test that included a training set and a prediction set, the results showed that the designed BP neural network exhibited a fast convergence speed and the system error was 0.0009702. Furthermore, the predictive values of the network were in good agreement with the experimental results, and the correlation coefficient was 0.9880. These results indicated that the network had an excellent training accuracy and generalization ability, which effectively reflected the performance of the system for the catalytic oxidation of toluene on a CdS-TiO₂/MWCNTs photocatalyst.     

Solvent Effects on Polymer Sorting of Carbon Nanotubes with Applications in Printed Electronics

Regioregular poly(3‐alkylthiophene) (P3AT) polymers have been previously reported for the selective, high‐yield dispersion of semiconducting single‐walled carbon nanotubes (SWCNTs) in toluene. Here, five alternative solvents are investigated, namely, tetrahydrofuran, decalin, tetralin, m‐xylene, and o‐xylene, for the dispersion of SWCNTs by poly(3‐dodecylthiophene) P3DDT. The dispersion yield could be increased to over 40% using decalin or o‐xylene as the solvents while maintaining high selectivity towards semiconducting SWCNTs. Molecular dynamics (MD) simulations in explicit solvents are used to explain the improved sorting yield. In addition, a general mechanism is proposed to explain the selective dispersion of semiconducting SWCNTs by conjugated polymers. The possibility to perform selective sorting of semiconducting SWCNTs using various solvents provides a greater diversity of semiconducting SWCNT ink properties, such as boiling point, viscosity, and surface tension as well as toxicity. The efficacy of these new semiconducting SWCNT inks is demonstrated by using the high boiling point and high viscosity solvent tetralin for inkjet‐printed transistors, where solvent properties are more compatible with the inkjet printing head and improved droplet formation.     

Synthesis and Superior Optical‐Limiting Properties of Fluorene‐Thiophene‐Benzothiadazole Polymer‐Functionalized Graphene Sheets

A polymer based on fluorene, thiophene, and benzothiadazole as the donor–spacer–acceptor triad is covalently coupled to reduced graphene oxide (rGO) sheets via diazonium coupling with phenyl bromide, followed by Suzuki coupling. These polymer–graphene hybrids show good solubility in organic solvents, such as chloroform, tetrahydrofuran (THF), toluene, dichlorobenzene, and N,N‐dimethylformamide (DMF), and exhibit an excellent optical‐limiting effect with a 532‐nm laser beam. The optical‐limiting threshold energy values (0.93 J cm^?2 for G–polymer 1 and 1.12 J cm^?2 for G–polymer 2) of these G–polymer hybrids are better than that of carbon nanotubes (3.6 J cm^?2).     

Organic nanowire-templated fabrication of alumina nanotubes by atomic layer deposition

Alumina nanotubes were fabricated by a template method. Tris-(8-hydroxyquinoline) gallium (GaQ3) organic nanowires were used as a soft template for coating with alumina using an atomic layer deposition technique. The deposition was conducted at 25 degrees C by using trimethylaluminum and distilled water as the precursors of Al2O3. Amorphous alumina nanotubes were obtained after removing the GaQ3 by dissolving in toluene or by heat treatment at 350 degrees C. The amorphous nanotubes could be crystallized by heating at 900 degrees C for 1 h in vacuum.     

Crystallographic order in multi-walled carbon nanotubes synthesized in the presence of nitrogen

Multi-walled carbon nanotubes were synthesized by chemical vapor deposition from pure toluene and toluene/diazine mixtures using ferrocene as a catalyst precursor at 760 degrees C. As recently announced, characterization of the resulting nanotube films showed that, unlike pure carbon nanotubes, those grown in the presence of nitrogen have an extremely high degree of internal order, both in terms of the uniform chirality in the nanotube walls and of the crystallographic register between them. Here, the structure, defects, and morphology of the nanotubes were analyzed in depth using advanced electron microscopy techniques, and compared with existing models and observations. Nitrogen, which seems to be responsible for the dramatic structural order, was found to segregate preferentially within the core of the nanotubes.     

Metal Chelation Assisted In Situ Migration and Functionalization of Catalysts on Peapod‐Like Hollow SnO2 toward a Superior Chemical Sensor

Rational design of nanostructures and efficient catalyst functionalization methods are critical to the realization of highly sensitive gas sensors. In order to solve these issues, two types of strategies are reported, i.e., (i) synthesis of peapod‐like hollow SnO₂ nanostructures (hollow 0D‐1D SnO₂) by using fluid dynamics of liquid Sn metal and (ii) metal–protein chelate driven uniform catalyst functionalization. The hollow 0D‐1D SnO₂ nanostructures have advantages in enhanced gas accessibility and higher surface areas. In addition to structural benefits, protein encapsulated catalytic nanoparticles result in the uniform catalyst functionalization on both hollow SnO₂ spheres and SnO₂ nanotubes due to their dynamic migration properties. The migration of catalysts with liquid Sn metal is induced by selective location of catalysts around Sn. On the basis of these structural and uniform functionalization of catalyst benefits, biomarker chemical sensors are developed, which deliver highly selective detection capability toward acetone and toluene, respectively. Pt or Pd loaded multidimensional SnO₂ nanostructures exhibit outstanding acetone (R _air/R _gas = 93.55 @ 350 °C, 5 ppm) and toluene (R _air/R _gas = 9.25 @ 350 °C, 5 ppm) sensing properties, respectively. These results demonstrate that unique nanostructuring and novel catalyst loading method enable sensors to selectively detect biomarkers for exhaled breath sensors.     

Sidewall Functionalization of Single-Walled Carbon Nanotubes by Organometallic Chromium-Centered Free Radicals

The interaction of organometallic chromium-centered free radicals generated by the homolytic dissociation of (pentamethylcyclopentadienyl)chromiumtricarbonyl dimer in toluene with single-walled carbon nanotubes (SWNT) was investigated using ESR spectroscopy. Low values of g-factors of the radical species formed from chromium-centered free radicals and SWNT as well as invariability of disorder mode (D band) intensity in Raman spectra of pristine and functionalized SWNT after this reaction indicated that chromium-centered free radicals added to the surface of nanotubes through rather oxygen atoms than to sidewall carbon atoms. This is the first chromium-derivatization of carbon nanotubes.     

Fracture and progressive failure of defective graphene sheets and carbon nanotubes

An atomistic based finite bond element model for the prediction of fracture and progressive failure of graphene sheets and carbon nanotubes is developed by incorporating the modified Morse potential. The element formulation includes eight degrees of freedom reducing computational cost compared to the 12 degrees of freedom used in other FE type models. The coefficients of the elements are determined based on the analytical molecular structural mechanics model developed by the authors. The model is capable of predicting the mechanical properties (Young’s moduli, Poisson’s ratios and force–strain relationships) of both defect-free and defective carbon nanotubes under different loading conditions. In particular our approach is shown to more accurately predict Poisson’s ratio. The numerical prediction of nonlinear stress–strain relationships for defect-free nanotubes including ultimate strength and strain to failure of nanotubes is identical to our analytical molecular structural mechanics solution. An interaction based mechanics approach is introduced to model the formation of Stone–Wales (5-7-7-5) topological defect. The predicted formation energy is compared with ab initio calculations. The progressive failure of defective graphene sheets and nanotubes containing a 5-7-7-5 defect is studied, and the degradation of Young’s moduli, ultimate strength and failure strains of defective nanotubes is predicted.     

Conversion of toluene into carbon nanotubes using arc discharge plasmas in solution

In order to form nanocarbon materials, an arc discharge plasma method in hydrocarbon solvent is developed. In the case that the arc discharge is performed in toluene with nickel electrodes, tube-like nanocarbons were formed from toluene. The catalysis of the metal electrodes is found to be an important factor for the formation of the nanocarbons by the arc discharge in toluene. This method has a possibility of forming carbon nanotubes from liquid state solvents as a new carbon source by using catalyst ingredient as discharge electrodes.     

THE INFLUENCE OF SYNTHESIS PARAMETERS ON THE PRODUCTION OF MULTIWALLED CARBON NANOTUBES BY THE FERROCENE CATALYZED PYROLYSIS OF TOLUENE

A high yield (∼32 wt.%) of multiwalled carbon nanotubes was obtained in an iron catalyzed reaction. This was achieved in the temperature range 800-1000°C under an atmosphere of H₂/Ar by an improved solution injection method in a horizontal reactor using toluene as carbon source and ferrocene as catalyst precursor. The pyrolysis temperature, ferrocene concentration, solution feeding rate and carrier gas flow rate all influenced the yield of carbon nanotubes and the thickness of the aligned carbon nanotube films. The carbon nanotubes was prepared in high purity using optimized pyrolysis conditions.     

THE INFLUENCE OF SYNTHESIS PARAMETERS ON THE PRODUCTION OF MULTIWALLED CARBON NANOTUBES BY THE FERROCENE CATALYZED PYROLYSIS OF TOLUENE

ABSTRACT

A high yield (～32?wt.%) of multiwalled carbon nanotubes was obtained in an iron catalyzed reaction. This was achieved in the temperature range 800–1000°C under an atmosphere of H₂/Ar by an improved solution injection method in a horizontal reactor using toluene as carbon source and ferrocene as catalyst precursor. The pyrolysis temperature, ferrocene concentration, solution feeding rate and carrier gas flow rate all influenced the yield of carbon nanotubes and the thickness of the aligned carbon nanotube films. The carbon nanotubes was prepared in high purity using optimized pyrolysis conditions.     

Effect of Temperature on the Change of Refractive Index on Mixing for Butyl Acetate + Aromatic Hydrocarbons

In this work experimental data for the refractive index on mixing for butyl acetate + (toluene, ethylbenzene, p-xylene, isopropylbenzene, butylbenzene, isobutylbenzene, mesitylene, or t-butylbenzene) binary mixtures, and some computed derived properties, as a function of temperature, are presented. The mixtures show a clear expansive trend for the highest molar mass compounds. Values of measured properties were compared with results obtained by semiempirical relations and equations of state with simple mixing rules. Accurate results were obtained with the latter, and such parameters could be used in the prediction of multicomponent refractive indices or other thermodynamic properties using standard thermodynamic expressions     

Prediction of the Viscosity of Liquid Mixtures: An Improved Approach1

A recently developed theoretically based scheme for the prediction of the viscosity of gas mixtures is modified by making use of the hard-sphere theory and applied to the prediction of the viscosity of liquid mixtures. Preliminary results are compared with viscosity measurements of mixtures of n-hexane with toluene and with cyclohexane, and demonstrate the predictive power of this scheme.     

Nitrogen doping of CVD multiwalled carbon nanotubes: Observation of a large g-factor shift

Nitrogen doped multi-walled carbon nanotubes (N-CNTs) and undoped multi-walled carbon nanotubes (MWCNTs) were synthesized by a chemical vapour deposition (CVD) floating catalyst method. The N-CNTs were synthesized by the decomposition of a ferrocene/N-source/toluene (N-source = triethylamine, dimethylamine, acetonitrile) mixture at 900 °C. The undoped MWCNTs were synthesized using a ferrocene–toluene mixture without a nitrogen source under similar reaction conditions. The structure of the N-CNTs and MWCNTs was ascertained using HRTEM, SEM and Raman spectroscopy. Systematic ESR measurements of the carbon products produced, in the temperature range of 293–400 K showed line widths that were in general very large ∼ kOe. Most importantly, a large g-factor shift in samples of N-CNTs from that of the free electron g-factor was observed. Further, the shift increased with increasing temperature. The large g shift has been analysed in terms of Elliott-Wagoner and Bottleneck models. The temperature dependence of the g shift in the N-CNT samples rules out the Elliott-Wagoner type spin–orbit coupling scenario. The large g shift and temperature dependence can be qualitatively explained in terms of the Bottleneck model.     

Electronic structures and three-dimensional effects of boron-doped carbon nanotubes

Abstract

We study boron-doped carbon nanotubes by first-principles methods based on the density functional theory. To discuss the possibility of superconductivity, we calculate the electronic band structure and the density of states (DOS) of boron-doped (10,0) nanotubes by changing the boron density. It is found that the Fermi level density of states D(?_F) increases upon lowering the boron density. This can be understood in terms of the rigid band picture where the one-dimensional van Hove singularity lies at the edge of the valence band in the DOS of the pristine nanotube. The effect of three-dimensionality is also considered by performing the calculations for bundled (10,0) nanotubes and boron-doped double-walled carbon nanotubes (10,0)@(19,0). From the calculation of the bundled nanotubes, it is found that interwall dispersion is sufficiently large to broaden the peaks of the van Hove singularity in the DOS. Thus, to achieve the high D(?_F) using the bundle of nanotubes with single chirality, we should take into account the distance from each nanotube. In the case of double-walled carbon nanotubes, we find that the holes introduced to the inner tube by boron doping spread also on the outer tube, while the band structure of each tube remains almost unchanged.     

Effect of solvent type on the formation of tubular fullerene nanofibers

1D Fullerene C₆₀ nanofibers (FNFs) were prepared via liquid-liquid interfacial precipitation (LLIP) using toluene, m-xylene, pyridine and/or N-methyl-2-pyrrolidone (NMP) as solvents and isopropyl alcohol as the precipitation agent at 8 °C. C₆₀-saturated solutions were exposed to visible light to promote the growth of FNFs. When the solvents were toluene and m-xylene, it was difficult to synthesize hollow C₆₀ fullerene nanotubes (FNTs). By contrast, the hollow FNTs were easily grown in the C₆₀-pyridine solution or C₆₀-NMP solution upon exposure to visible light. It is found that there is a critical correlation between the adducts of the solvents with C₆₀ molecules and the tubular structure of FNFs.     

Composites of polyvinyl alcohol and carbon (coils, undoped and nitrogen doped multiwalled carbon nanotubes) as ethanol, methanol and toluene vapor sensors

We investigate the chemical sensing behavior of composites prepared with polyvinyl alcohol and carbon materials (undoped multiwalled carbon nanotubes, nitrogen-doped multiwalled carbon nanotubes and carbon nanocoils). We determine the sensitivity of thin films of these composites for ethanol, methanol and toluene vapor, comparing their conductance and capacitance responses. The composite that exhibits highest sensitivity depends on specific vapor, vapor concentration and measured electrical response, showing that the interactivity of the carbon structure with chemical species depend on structural specificities of the carbon structure and doping.     

Temperature dependence of electrical conductivity in double-wall and multi-wall carbon nanotube/polyester nanocomposites

The aim of this study is to investigate temperature dependence of electrical conductivity of carbon nanotube (CNT)/polyester nanocomposites from room temperature to 77 K using four-point probe test method. To produce nanocomposites, various types and amounts of CNTs (0.1, 0.3 and 0.5 wt.%) were dispersed via 3-roll mill technique within a specially formulized resin blend of thermoset polyesters. CNTs used in the study include multi walled carbon nanotubes (MWCNT) and double-walled carbon nanotubes (DWCNT) with and without amine functional groups (–NH₂). It was observed that the incorporation of carbon nanotubes into resin blend yields electrically percolating networks and electrical conductivity of the resulting nanocomposites increases with increasing amount of nanotubes. However, nanocomposites containing amino functionalized carbon nanotubes exhibit relatively lower electrical conductivity compared to those with non-functionalized carbon nanotubes. To get better interpretation of the mechanism leading to conductive network via CNTs with and without amine functional groups, the experimental results were fitted to fluctuation-induced tunneling through the barriers between the metallic regions model. It was found that the results are in good agreement with prediction of proposed model.     

Functionalization of single- and multi-walled carbon nanotubes with cationic amphiphiles for plasmid DNA complexation and transfection

The possibility of delivering DNA efficiently to cells represents a crucial issue for the treatment of both genetic and acquired diseases. However, even although the efficiency of non-viral transfection systems has improved in the last decade, none have yet proven to be sufficiently effective in vivo. We report herein our results on the functionalization of single-walled carbon nanotubes (SWNT) and multi-walled carbon nanotubes (MWNT) by two cationic amphiphiles (lipid RPR120535 and pyrenyl polyamine), their use for the complexation of plasmid DNA, and their efficiency in transfecting cells in vitro. The experiments have shown that the efficiency of transfection is higher when using SWNT instead of MWNT, and that transfection efficiency is similar or slightly higher when using nanoplexes (SWNT/lipid RPR120535/DNA) instead of lipoplexes (lipid RPR120535/DNA) and several orders of magnitude higher than that of naked DNA. This study therefore shows both that the transfection is better when using SWNTs and that it is dependent on the nature of the amphiphilic molecules adsorbed on the nanotubes.