O. Chauvet

Sensitivity of single wall carbon nanotubes to oxidative processing: structural modification, intercalation and functionalisation

Abstract The effect of oxidation on modification of single wall carbon nanotubes (SWCNTs) through successive purification steps has been studied. The efficient elimination of metal impurities has been followed by induced coupled plasma spectroscopy. Upon acid treatment, Raman spectroscopy clearly proofed that HNO3 molecules were intercalated into the bundles of SWCNTs. At the same time, SWCNTs also have suffered a high degree of degradation and defects were introduced. The subsequent thermal processes led to the removal of further defect carbon materials and to the almost complete de-intercalation of the HNO3 molecules. Changes in the structure of the SWCNT bundles have been observed by transmission electron microscopy. While bundles tend to separate upon acid treatment, after the complete purification process, the remaining SWCNTs tend to form thick bundles again. The existence of functional groups in the raw single wall carbon nanotubes material and their modification and almost complete removal after the final annealing step has been studied by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and temperature programmed desorption. Nitrogen adsorption isotherms analysed according to Brunauer–Emmet–Teller showed important changes in the pore volume and surface area through the purification steps.

Synthesis of a new polyaniline/nanotube composite: “in-situ” polymerisation and charge transfer through site-selective interaction

A new polyaniline/multi-wall carbon nanotube (PANI/MWNT) composite has been successfully synthesized by an “in-situ” polymerisation process; Raman studies indicate a site-selective interaction between the quinoid ring of the polymer and the MWNTs opening the way for charge transfer processes; transport measurements clearly reveal drastic changes in the electronic behaviour confirming the formation of a true composite material with enhanced electronic properties.

Transport properties of PMMA-Carbon Nanotubes Composites

We report transport measurements on PMMA-singlewalled carbon nanotubes composites films. The films are characterized by Raman spectroscopy, optical absorption and electron microscopy. At room temperature, classical percolation theory applies. It shows that the composites resistivity is indeed controlled by the nanotubes. Decreasing the temperature shows a unusual behavior which suggests that a distribution of intertube/interbundle barriers of some 10 of Kelvin is superposed to the topological percolation problem.

Synthesis and characterization of new polyaniline/nanotube composites

Abstract New polyaniline/nanotube (PANI/NT) composites have been synthesized by “in situ” polymerization processes using both multi-wall carbon nanotubes (MWNTs) and single-wall carbon nanotubes (SWNTs) in concentrations ranging from 2 to 50 wt.%. Although no structural changes are observed using MWNTs above a concentration of 20 wt.%, the in situ synthesis results in electronic interactions between nanotubes and the quinoid ring of PANI leading to enhanced electronic properties and thus to the formation of a genuine PANI/MWNT composite material. On the other hand, using SWNTs favors the formation of inhomogeneous mixtures rather than of a homogeneous composite materials, independent of the SWNT concentration. X-ray diffraction, Raman and transport measurements show the different behavior of both classes of nanotubes in PANI/NT materials. The difficulties in the formation of a true PANI/SWNT composite are related to the far more complex structure of the SWNT material itself, i.e. to the presence of entangled bundles of SWNTs, amorphous carbon and even catalytic metal particles.

Modifications of single-wall carbon nanotubes upon oxidative purification treatments

A systematic characterization of single-wall carbon nanotube (SWCNT) material after successive purification steps, including reflux treatment with nitric acid, air oxidation, and annealing, has been performed. Inductively coupled plasma–optical emission spectroscopy shows that a considerable reduction of the metal impurities by up to 95% can be obtained by the nitric acid reflux treatment. During this process, Raman spectroscopy clearly proves that HNO3 molecules are intercalated into the bundles of SWCNTs. At the same time, SWCNTs have suffered a high degree of degradation and defects are being introduced. The subsequent thermal processes lead to the removal of further defect carbon materials and to the almost complete de-intercalation of the HNO3 molecules. Transmission electron microscopy reveals that the remaining SWCNT bundles tend to form thick bundles. Thus the applied purification process results in a high-purity SWCNT material with a drastically reduced content of metal nanoparticles and composed of large bundles of SWCNTs.

Low-frequency Raman studies of multiwalled carbon nanotubes: Experiments and theory

In this paper, we investigate the low frequency Raman spectra of multiwalled carbon nanotubes (MWNTs) prepared by the electric arc method. Low frequency Raman modes are unambiguously identified on purified samples thanks to the small internal diameter of the MWNTs. We propose a model to describe these modes. They originate from the radial breathing vibrations of the individual walls coupled through the van der Waals interaction between adjacent concentric walls. The intensity of the modes is described in the framework of bond polarization theory. Using this model and the structural characteristics of the nanotubes obtained from transmission electron microscopy, we simulated the experimental low frequency Raman spectra with excellent agreement. Therefore Raman spectroscopy can be as useful in the characterization of MWNTs as it is for single-wall nanotubes.

Localization, Coulomb interactions, and electrical heating in single-wall carbon nanotubes/polymer composites

Low-field and high-field transport properties of carbon nanotubes/polymer composites are investigated for different tube fractions. Above the percolation threshold

A soluble and highly functional polyaniline–carbon nanotube composite

{f}_{c}\ensuremath{\sim}0.33%,

Raman spectroscopy and conductivity measurements on polymer-multiwalled carbon nanotubes composites

transport is due to hopping of localized charge carriers with a localization length

Cellulose Nanocrystal-Assisted Dispersion of Luminescent Single- Walled Carbon Nanotubes for Layer-by-Layer Assembled Hybrid Thin Films

\ensuremath{\xi}\ensuremath{\sim}10\ensuremath{-}30 \mathrm{nm}.