X-ray diffraction as a tool for the determination of the structure of double-walled carbon nanotube batches

The average structure of double-walled carbon nanotube DWCNT samples can be determined by x-ray diffraction XRD. We present a formalism that allows XRD patterns of DWCNTs to be simulated and we give researchers the tools needed to perform these calculations themselves. Simulations of XRD patterns within this formalism are compared to experimental data obtained on two different DWCNT samples, produced by chemical vapor deposition or by peapod conversion i.e., high-temperature peapod annealing. For each sample, we are able to determine structural aspects such as the number of walls, the diameter distribution of inner and outer tubes, the intertube spacing, and the bundled structure

Structural selective charge transfer in iodine-doped carbon nanotubes

We have investigated iodine intercalated carbon nanostructures by extended X-ray absorption fine structure (EXAFS) and Raman spectroscopies. We discuss here the charge transfer and the iodine–carbon interaction as a function of the carbon nanostructures (graphite, multi-walled, double-walled and single walled nanotubes). The results show that iodine is weakly adsorbed on the surface of all multi-walled nanotubes. By contrast, a charge transfer between iodine and single walled nanotubes is evidenced

EXAFS investigations of iodine-doped carbon nanotubes

International audienceWe report an x-ray absorption fine structure study at the iodine-K edge of the local structure in iodine-doped carbon nanotubes. The iodine-carbon host interaction is shown to be weaker in multiwalled carbon nanotubes (MWNTs) than in single-walled carbon nanotubes (SWNTs). Iodine species are only localized at the surface of the external tube for MWNTs, whereas iodine species enter inside SWNTs. For doped SWNTs, both the experimental and the theoretical EXAFS spectra allow us to establish the structure of the iodine chain as disordered pentaiodide at the saturation level

EXAFS study of rubidium-doped single-wall carbon nanotube bundles

International audienceThe local structure around the rubidium ions inserted in single-wall carbon nanotube bundles (Rb-doped SWCNT) is studied by Rb K-edge extended x-ray-absorption fine structure (EXAFS). The dependence of the local order around the rubidium ions is investigated as a function of the time of doping (i.e., as a function of the stoichiometry of the sample). The first coordination shell of the rubidium ions, related to the distance between rubidium and the first nearest-neighboring carbon atoms, has a clear time doping dependence. Comparison between ab initio simulations of the EXAFS spectra and experimental data questions the interstitial site (between three tubes) as the preferential insertion site in SWCNT bundles. The results indicate that the rubidium ions are mainly located inside the tubes and around the bundles. The results are in good agreement with combined x-ray and neutron diffraction experiments performed on the same samples

Structure of Doped Single Wall Carbon Nanotubes

A review of the structure of carbon nanotubes doped either by electron donors or electron acceptors is presented. The structure of doped carbon nanotubes probed by X-ray and neutron diffraction and the short range atomic arrangement by TEM and EXAFS spectroscopy were found to depend on the cristallinity and purification treatment of host SWCNTs. The modifications of 2D lattice of SWCNTs ropes induced by doping reactions are examined. The sites of insertion at the surface of bundles, in between the individual tubes or inside the tubes are discussed as a function of the type of dopant and the mode of doping, electrochemical, vapour or liquid phase. Finally, some Raman studies of alkali-doped bundled SWCNTs are reported. The striking dependence of the Raman modes under doping are explained on the basis of structural information

Correlations between structure and far-infrared active modes in polythiophenes

International audienceWe have investigated the experimental x-ray and far-infrared responses of three polythiophenes synthesized from a thiophene, alpha-bithiophene and alpha-quaterthiophene monomer. The x-ray data show that the crystallinity of the different polythiophene samples depends on the synthesis conditions. An excellent correlation between the crystallinity of polythiophenes and their far-infrared signatures is demonstrated. In addition, the assignment of the far-infrared phonon modes in polythiophenes is given by a direct comparison with its oligomers. In particular, the ring libration inside the polymeric chain, directly involved in the electron-phonon coupling, is assigned

Polymerization of conducting polymers inside carbon nanotubes

Supercritical carbon dioxide is an universal tool to impregnate carbon nanotubes with a wide range of organic molecules. In this Letter, we present our results of carbon nanotubes filled with the photo-conducting polymer poly(N-vinyl carbazole) and the conducting polymer polypyrrole which were prepared by polymerizing the monomers inside the nanotubes. The endohedral nanotubes were characterized by HRTEM and H-1 NMR which confirmed that the encapsulated material was indeed the conducting polymer. (c) 2006 Elsevier B.V. All rights reserved

A comprehensive scenario for commonly used purification procedures of arc-discharge as-produced single-walled carbon nanotubes

International audienceThe purification of single-walled carbon nanotube (SWCNT) samples was analysed using a multi-technique approach, with structural as well as spectroscopic probes, in order to characterize the samples and to identify important factors for improvement of SWCNT sample quality. The first dry oxidation step (air at 365 degrees C) is shown to have only a weak selectivity for the removal of the amorphous carbon or weakly organized graphitic species as well as resulting in a partial consumption of the SWCNTs. The functionalization of the SWCNTs is highly specific with formation of carboxyl, hydroxyl and carbonyl groups. On the other hand this oxidation step is highly efficient for the oxidation of the catalytic impurities (Ni, Y) which can be easily removed by subsequent acid treatment. A final high temperature treatment indicates some incomplete restoration of the quality of the SWCNT surface. (C) 2009 Elsevier Ltd. All rights reserved