Assemblies of carbon and boron-nitrogen nanotubes and fullerenes: Structure and properties

This review concerns assemblies of the main carbon nanostructures (fullerenes and nanotubes) generated by interactions between similar and dissimilar species. The two major families of these nanomaterials are reviewed: (1) assemblies with weak (van der Waals) bonds between fullerenes and/or nanotubes (fullerites, nanopeapods, nanotube bundles, and nanotubular crystals) and (2) assemblies formed by covalently bonded (polymerized) fullerenes and/or nanotubes (covalent crystals of small fullerenes C _{n < 60} , nanobuds, ropes of polymerized nanotubes, and covalent networks built of nanotubes). Data are systematized on their atomic structures, stability factors, electronic structures, chemical bonding, physical and chemical properties, and potential fields of application. Related heteronanomaterials (assemblies of boron-nitrogen fullerene-like molecules and/or nanotubes) are reviewed briefly.     

Structural and electronic characteristics of perhydrogenated carbon nanotubes

The structural and electronic characteristics of fully hydrogenated armchair and zigzag carbon nanotubes have been determined by quantum chemical methods. With use of line group symmetries, the structures of nanotubes up to 10 nm in diameter could be optimized by periodic B3LYP calculations. “In–out” isomerism is shown to significantly stabilize perhydrogenated carbon nanotubes, the energetically most favorable structures being those with 1/3–1/2 of the carbon atoms endo-hydrogenated. In favored nanotubes the ratio of endo- to exo-hydrogens is 1:1, the stabilities increasing as a function of the diameter of the nanotube. The calculated band gaps indicate that the perhydrogenated carbon nanotubes are insulators.     

Effect of oxyfluorination on electromagnetic interference shielding of polyaniline-coated multi-walled carbon nanotubes

Highly conducting polyaniline (PANi)-coated multi-walled carbon nanotubes (MWCNTs) were prepared by in situ polymerization method for electromagnetic interference shielding. The thickness of the PANi coatings was controlled by the oxyfluorination treatment on the multi-walled carbon nanotubes and analyzed with both SEM and TEM. The oxyfluorination with higher oxygen content produced more hydrophilic functional groups on the surface of multi-walled carbon nanotubes. The functional groups led to the well distribution and coating of PANi on the multi-walled carbon nanotubes resulting in the higher interfacial affinity between them. The uniform coating of PANi on MWCNTs by controlling the oxyfluorination conditions also played a crucial role in increasing the electrical conductivity of nanocomposites. The improved interfacial affinity resulted in the higher electromagnetic interference (EMI) SE of 47.03?dB based on the synergistic combination of the conductive components. The EMI shielding mechanism of PANi on MWCNTs suggested that EMI was mainly shielded by adsorption to avoid secondary EMI.     

129Xe and 131Xe NMR of gas adsorption on single- and multi-walled carbon nanotubes

129Xe and 131Xe nuclear magnetic resonance (NMR) spectroscopy was used to study the adsorption of xenon gas on as-produced single-walled and multi-walled carbon nanotubes. Overall, the adsorption was weak, with slightly stronger interaction between xenon and multi-walled nanotubes. Temperature-dependent spectra, relaxation times, line widths, and signal intensities provide evidence that xenon forms a multilayer bulk phase rather than a homogeneous surface coating. The estimated adsorption energy of 1.6 kJ/mol is significantly lower than 23 kJ/mol predicted for monolayer adsorption but is in keeping with the Xe-Xe attractive potential. Xenon preferentially adsorbs on metallic particles in single-walled tubes, while defects are the nucleation sites for the stronger adsorption on multi-walled tubes.     

Nitrogen-doped carbon nanotubes: growth, mechanism and structure

Nitrogen-doped bamboo-structured carbon nanotubes have been successfully grown using a series of cobalt/molybdenum catalysts. The morphology and structure of the nanotubes were analysed by transmission electron microscopy and Raman spectroscopy. The level of nitrogen doping, as determined by X-ray photoelectron spectroscopy, was found to range between 0.5 to 2.5 at.%. The growth of bamboo-structured nanotubes in the presence of nitrogen, in preference to single-walled and multi-walled nanotubes, was due to the greater binding energy of nitrogen for cobalt in the catalyst compared to the binding strength of carbon to cobalt, as determined by density functional theory.     

In situ ethylene copolymerization with an olefin-type monomer for one-pot synthesis of polyethylene tethered on multi-walled carbon nanotubes

A one-pot procedure for the synthesis of polyethylene tethered on multi-walled carbon nanotubes by in situ ethylene copolymerization with an olefin-type comonomer, α-alkene functionalized multi-walled carbon nanotubes (MW - CH = CH₂) is reported. The covalent linkage between polyethylene and multi-walled carbon nanotubes is demonstrated. The MWCNTs are chemically oxidized first by a strong oxidizing agent and then functionalized with chlorocarbonyl groups (MW-COCl) via reacting with thionyl chloride. The MW-CH=CH₂ are obtained by esterification of ω-undecylenyl alcohol with MW-COCl. The MW-CH=CH₂ may serve as olefin-type comonomers to further synthesize core-shell structured copolymers with a multi-walled carbon nanotubes core grafted with side chains of polyethylene via rac-(en)(THInd)₂ZrCl₂ copolymerization catalyst. The core-shell structured nanocomposites were characterized by means of ¹H-NMR, SEM, FTIR and TGA. The results confirmed the formation of polyethylene chains growing from the surface of multi-walled carbon nanotubes.     

The conversion of polyaniline nanotubes to nitrogen-containing carbon nanotubes and their comparison with multi-walled carbon nanotubes

Polyaniline (PANI) nanotubes were prepared by the oxidation of aniline in solutions of acetic or succinic acid, and subsequently carbonized in a nitrogen atmosphere during thermogravimetric analysis running up to 830 °C. The nanotubular morphology of PANI was preserved after carbonization. The molecular structure of the original PANI and of the carbonized products has been analyzed by FTIR and Raman spectroscopies. Carbonized PANI nanotubes contained about 8 wt.% of nitrogen. The molecular structure, thermal stability, and morphology of carbonized PANI nanotubes were compared with the properties of commercial multi-walled carbon nanotubes.     

Electrocatalytic oxidation of hydrazine at a glassy carbon electrode modified with nickel ferrite and multi-walled carbon nanotubes

A hydrothermal technique was used to synthesize nickel ferrite nanoparticles (NF-NPs) deposited on multi-walled carbon nanotubes (MWCNTs). The material was characterized by scanning electron microscopy, energy dispersive spectrometry, and X-ray powder diffraction which showed that the NF-NPs are located on the surface of the carboxylated MWCNTs. The material was used to modify a glassy carbon electrode which then was characterized via cyclic voltammetry, electrochemical impedance spectroscopy, and amperometry. The electrode displays strong electrochemical response to hydrazine. A potential hydrazine sensing scheme is suggested.

Decorating catalytic palladium nanoparticles on carbon nanotubes in supercritical carbon dioxide

Hydrogen reduction of a Pd(II)-beta-diketone precursor in supercritical carbon dioxide produces palladium nanoparticles on multi-walled carbon nanotubes that exhibit promising catalytic properties for hydrogenation of olefins in carbon dioxide as well as electro-reduction of oxygen in fuel cell applications.     

Electrochemical synthesis of gold nanoparticles on the surface of multi-walled carbon nanotubes with glassy carbon electrode and their application

Gold nanoparticles on the surface of multi-walled carbon nanotubes with glassy carbon electrode were prepared using electrochemical synthesis method. The thin films of gold Nanoparticles/multi-walled carbon nanotubes were characterized by scanning electron microscopy, powder X-ray diffraction, and cyclic voltammetry. Electrochemical behavior of adrenaline hydrochloride at gold nanoparticles/multi-walled carbon nanotube modified glassy carbon electrode was investigated. A simple, sensitive, and inexpensive method for determination of adrenaline hydrochloride was proposed.     

Electrochemical properties of thin-layered composites formed by carbon nanotubes and polybithiophene

Redox behavior of thin films of polybithiophene deposited on substrates of conducting glass and single- or multi-walled carbon nanotubes is studied at positive potentials in a 0.1 M (C₄H₉)₄NBF₄ solution in acetonitrile. The polymers formal doping-undoping potentials are nearly the same for all substrates, which points to the absence of any marked donor-acceptor interaction between nanotubes and polybithiophene. Some polybithiophene electrochemical characteristics (reversibility, doping degree) are improved when deposited onto nanotubes, probably due to the developed surface of the electrode based on carbon nanotubes.__________Translated from Elektrokhimiya, Vol. 41, No. 4, 2005, pp. 501–509.Original Russian Text Copyright © 2005 by Ovsyannikova, Efimov, Moravsky, Loutfy, Krinichnaya, Alpatova.     

Self-catalytic behavior of carbon nanotubes

Self-catalytic behavior of multi-walled carbon nanotubes is proposed and validated experimentally under the conditions in which metal catalysis was previously figured to work only. The self-catalysis could support the nanotube nucleation and radial and axial developing processes. This result should lead to a new and better understanding of the growth mechanism of carbon nanotubes in a metal catalytic process.     

Functionalised endohedral fullerenes in single-walled carbon nanotubes

Atomically thin carbon nanotubes serve as transparent-test tubes for individual molecules of functionalised endohedral fullerenes. Aberration-corrected transmission electron microscopy reveals the complex dynamic behaviour of these molecules at the atomic level, and it sheds light on the mechanism of their encapsulation into nanotubes.     

Magnetic assembled electrochemical platform using Fe2O3 filled carbon nanotubes and enzyme

A novel electrochemical nanostructured biosensor based on carbon nanotubes (CNTs) has been constructed by magnetic assembly method. The magnetic multi-walled carbon nanotubes (M-MWNTs) were prepared by introducing Fe₂O₃ nanoparticles into the nanotubes. Thus the multilayered functional platform could be assembled with the aid of magnetic field. The horseradish peroxidase (HRP) was employed as a model enzyme to demonstrate the final performance of the nanostructured biosensor. SEM, UV–vis spectroscopy and electrochemical techniques were used for characterization of assembly process. The resulting three-dimensional M-MWNTs/HRP multilayer films have showed satisfactory stability, biocompatibility and electrochemical properties.     

Formation of carbon nanotubes in water by the electric-arc technique

A simplified arc discharge apparatus was used for growing carbon nanotubes, required only water (solution) in a glass container with no need for vacuum, water-cooled chamber. Carbon nanotubes with highest purity (20%) and highest yield (7 mg/min) were obtained when using salt solution as the medium. Resonance Raman spectrum of multi-walled carbon nanotubes (MWNTs) presented in as-grown materials was measured and RBM peaks originating from very thin core nanotubes were observed. The results show that high-quality MWNTs can be effectively prepared in water-arcing process.     

A density functional theory study of shake-up satellites in photoemission of carbon fullerenes and nanotubes

Carbon 1s shake-up spectra of fullerenes C(60), C(70), and C(82) and single-walled carbon nanotubes (SWCNTs) of (5,5), (6,5), and (7,6) have been investigated by using equivalent core hole Kohn-Sham density functional theory approach, in which only one-electron transition between molecular orbitals within core-hole potential is considered. The calculated spectra are generally in good agreement with results of equivalent core-hole time-dependent density functional theory calculations and available experiments, and reliable assignments for the complicated shake-up spectra of such large systems are provided. Calculations have also been performed for endohedral metallofullerene Gd@C(82) to demonstrate the possible use of shake-up processes to identify the charge transfer between the metal ion and the carbon cage. It is found that the exciton binding energy of all systems under investigation is around 0.5 eV.     

Evaluation of carbon nanotubes as a solid-phase extraction adsorbent for the extraction of cephalosporins antibiotics, sulfonamides and phenolic compounds from aqueous solution

The adsorptive potential of carbon nanotubes (single-walled carbon nanotubes and multi-walled carbon nanotubes) for solid-phase extraction of three groups of highly polar compounds (namely cephalosporins antibiotics, sulfonamides and phenolic compounds) was tested in this article. The analytes were strongly retained by the carbon nanotubes. And acceptable recoveries were obtained with the addition of ammonium acetate into eluents. The effects of solution pH on the recoveries of the antibiotics and phenolic compounds were examined. To check the retention abilities of three groups of compounds on carbon nanotubes, fixed amount of each analyte was added to different volumes (up to 500 mL) of aqueous solution, and then extracted by the sorbents. Comparative studies showed that the carbon nanotubes were much superior to C₁₈ for the extraction of the highly polar analytes. For the cephalosporins antibiotics and sulfonamides, the carbon nanotubes showed stronger retention capability than graphitized carbon blacks, but for some of the phenolic compounds graphitized carbon blacks seemed to be more suitable, indicating different retention mechanisms of these analytes. To further assess the enrichment ability of carbon nanotubes for highly polar compounds, the solid-phase extraction method of multi-walled carbon nanotubes packed cartridge was well developed, and the sulfonamides were used as model compounds. Under the optimal procedures, the detection limits of sulfonamides were in the range of 27-38 ng L⁻¹. The spiked recoveries from several real water samples obtained for sulfathiazole and sulfadiazine ranged from 55% to 79% and 72% to 92%, respectively, while the recoveries of sulfapyridine and sulfamethazine were in the range of 85-102%.     

Electrochemical properties and the determination of nicotine at a multi-walled carbon nanotubes modified glassy carbon electrode

Electrochemical properties of nicotine at the glassy carbon electrode modified with multi-walled carbon nanotubes were explored. Nicotine underwent irreversible reduction at the modified electrode, which was an adsorption-controlled process with two protons and two electrons. The reductive peak current of nicotine significantly increased at the modified electrode compared with the bare glassy carbon electrode, suggesting that the multi-walled carbon nanotubes can enhance the electron transfer rate. The current was proportional to the concentration of nicotine over two line ranges, and the detection limit was 9.3 µM (at S/N?=?3). For ten parallel detections of 0.62 mM nicotine, the relative standard deviation was 2.67%, suggesting that the film modified electrode had excellent reproducibility. The modified electrode was applied to the direct determination of nicotine in tobacco samples with good sensitivity, selectivity and stability.     

Polystyrene grafted multi-walled carbon nanotubes

Oxidised, multi-walled, carbon nanotubes can be grafted with polystyrene molecules using an situ radical polymerisation reaction, thereby dramatically modifying their solubility and their suitability for nanocomposite applications.     

普鲁士蓝/多壁碳纳米管修饰电极测定维生素C

利用电化学方法在多壁碳纳米管修饰的玻碳电极表面聚合一层普鲁士蓝,制备普鲁士蓝/多壁碳纳米管修饰玻碳电极,运用循环伏安法研究了维生素C(vc)在该修饰电极上的电化学行为.该修饰电极对Vc显示出快速的电化学响应和较好的电催化活性,在pH为4.0的磷酸盐溶液中,Ve浓度与其氧化峰电流在8.0×10-4～1.0×10-2 mol/L范围内呈现良好的线性关系,相关系数为0.9993,检测限为6.4×10-5mol/L.该电极具有较好的稳定性和重现性.