High pressure is an important parameter for the study of C60 and doped fullerenes as these molecular crystals are very compressible. 13C-NMR experiments under pressure in K3C60 have given access to the determination of the 13C Knight shift and the chemical shift of this superconducting compound. These NMR data do not reveal significant effects of Coulomb correlations in K3C60 and support a pairing mechanism for superconductivity mediated by intramolecular vibrations. We report also a 13C-NMR investigation of Rb4C60 under pressure and temperature. The temperature dependence of the spin-lattice relaxation rate clearly shows, under pressure, the increase of a linear contribution which gradually substitutes to the exponential behaviour present at ambient pressure. The activated relaxation is attributed to intrinsic spin excitations through the direct Jahn-Teller gap whereas the closing of a small indirect gap under pressure gives rise to a semimetal and a Korringa like relaxation.

We have studied the evolution with temperature 30C K≤ T ≤ 500 K of the ESR charaeteristics, on Lithium doped cis-polyacetylene films (using metal complexes of Benzophenone or Naphthalene in THP). Asymmetric ESR lines were observed at R T for samples doped at ∼4% and ∼l6%. Annealing of the doped samples up to 500 K results in a significant irreversible increase of the peak to peak linewidth δpp at RT, while the asymmetry ratio A/B increases irreversiblyonly in the case of samples doped at-4%. Nevertheless for temperatures above 400 K a narrow ESR line (δpp < 1G) superposed on the asymmetric broader line was observed. In order to interpret these temperature behaviors, we suggest a model which takes into account the inhomogeneity of the dopant distribution and the solvent influence.

High resolution 13C NMR has been used to investigate the properties of solid C50 after intercalation of molecular oxygen, which does not induce charge transfer with the host molecules. We show that, via the magnetic characteristics of the intercalant, information can be gained on its position and movement in the structure. In particular, molecular oxygen is found to occupy the middle of the octahedral site in the fee structure of solid C60.

Carbon nanotubes systems have revealed large potentialities in terms of applications, especially at a nanometric scale. As a consequence, the different interactions which can take place can be of primary importance. In this paper, we report studies carried out on different carbon systems such as single-walled or multi-walled nanotubes and polymer/nanotubes composites. By using Raman spectroscopy, apart from the expected interactions between tubes in bundles which have initiated experiments on individual entities, we put in evidence strong chemical reactions at the interface metal/nanotubes when Ag or Au surfaces are used to carry out Surface Enhanced Raman Scattering experiments. We show in particular that a different behavior is observed for metallic and semiconducting tubes. Also, a high state of disorder is observed, together with the transformation of nanotubes to other carbon compounds. In the case of multi-walled nanotubes, theoretical calculations allow us to interpret the low frequency Raman modes by introducing interactions in concentric tubes, in rather good agreement with experiments. Finally, in polymer/nanotubes composites, an upshift of the radial breathing mode is observed and we show in this case that it originates from the dynamical stress applied by the polymer on the bundles in response to the breathing vibration.

In order to interpret adsorption results of hydrogen storage by adsorption in graphite nanofiber (GNF) materials at molecular scale and to propose optimized structures of graphitic materials, we have realized both experimental and numerical studies of gas adsorption in GNF. The porous materials have been synthesized by CVD method. The adsorption experiments were performed at 293K by a volumetric method at high pressure until 40 MPa. We completed the surface reactivity analysis by performing structural characterizations of the samples using different structural techniques and numerical modelling computed in the grand canonical Gibbs ensemble. Within the cell, stacks of plans of graphite are arranged periodically using boundary conditions. The present numerical approach enables to interpret the results based on the solid–gas molecular interactions reactivity analysis.

The charge transport properties of individual, metallic nitrogen doped, single-walled carbon nanotubes are investigated. It is demonstrated that n-type conduction can be achieved by nitrogen doping. Evidence was obtained by appealing to electric-field effect measurements at ambient condition. n-type conduction is attributed to the presence of graphite-type nitrogen. The observed temperature dependencies of the zero-bias conductance indicate a disordered electron system with electric-dipole scattering, caused mainly by pyridine-type nitrogen atoms in the honeycomb lattice.

Self-assembly formation of dense carbon nanotube (CNT) filaments is demonstrated with gas discharge breakdown. CNT filament formation is triggered by irradiation of ions generated by gas discharge breakdown on a CNT mat placed on a cathode. The ion irradiation causes detachment of CNTs from the CNT mat on the cathode. Those CNTs are collected on a counter electrode and reassembled into filaments from the effect of an electric field. We examined the CNT filament formation characteristics using the combination of a plate-shaped cathode covered with a CNT mat and a wire-shaped anode as the discharge electrodes. CNT filament formation strongly depended on the discharge gas (Ar) pressure. Low Ar gas pressure of 4–6 kPa resulted in dense tree-like CNT filament formation on the anode. Addition of a collection electrode to the anode and cathode resulted in drastic enhancement of CNT filament formation. Dense and long filaments, approximately 10 mm in length, formed on the collection electrode. These results indicate that CNT filament formation by discharge breakdown can be used as a versatile dry spinning method for various kinds of CNTs that are unspinnable by conventional methods.

We report a study of the effects of various sample purification and modification techniques on the band gaps and optical properties of bulk single walled carbon nanotubes (SWNTs). These include a variety of thermal and chemical oxidation treatments and a study of nitrogen and boron doping.

The use of phosphorus as a co‐catalyst enabling modification of the kinetic equilibrium between the elementary growth steps of multiwalled carbon nanotubes and induction of a mechanism of sequential catalytic growth is reported. The mechanism produces nanotube‐based filaments periodically inserted with catalyst nanoparticles, which resemble nanoscale matches (see Figure).

Using the nitrene reaction, two individual single-walled carbon nanotubes can be covalently connected inducing only few defects to the nanotube sidewall. With this functionalization method nanotubes can be linked within a bundle as well as between bundles. For systematic investigations, a series of linker molecules of different lengths were synthesized. By filtering and drying, a buckypaper of linked nanotubes was obtained. The paper of modified nanotubes shows a higher stability than a buckypaper of pristine material. After the impurities and unreacted nanotubes have been washed out, the remaining connected SWCNTs are insoluble in any solvent. This report represents the first results of linking nanotubes using this method. Characterization on a molecular scale was carried out using SEM, TEM, AFM, XPS, XRD and Raman spectroscopy. Spectroscopic methods and X-ray diffraction give clear evidence for the reaction of nitrenes with the nanotube sidewall. With microscopic methods the linkage of the nanotubes can be observed.

Intercalation of single wall carbon nanotube (SWNT) bundles with alkali metals is expected to modify the electronic band structure and to raise the Fermi level. We report results from temperature dependent 13C‐ and 133Cs‐NMR measurements on Cs intercalated SWNT. Cs was reversibly intercalated with different stoichiometries. NMR lineshapes as well as relaxation effects are studied and discussed in context of dynamics of alkali ions in SWNT bundles. The results are compared with structural simulations of Cs‐ions intercalated in SWNT.

We present 13C NMR results on the intercalated 2D C60-polymers Li4-xNaxC60 (x=0-4 with half integer steps) showing that while Li4C60 forms a tetragonal polymer with double polymer bonds between the ...

The main issue in the research field of NT composites is the load transfer and homogeneity of the composites. Our investigations open a route to reach this homogeneity by functionalizing these nanotubes. We have tested several functionalisation methods and here, we want to focus on the addition of amines to the oxidized nanotube sidewalls. Using bi-functionalities, a chemical link between the nanotubes and polymer should result in more stable and homogeneously dispersed composites. The chemistry behind the modification of the nanotubes and the process in lab scale will be discussed in detail.

Using a novel, low-cost approach based an aerosol technique, highly branched, Y-junction nanotubes were synthesised. A catalyst-precursor solution composed of metal salts in water was sprayed into a furnace. A heated mixture of carbon reactant gas and hydrogen creates an atmosphere in which the catalyst particles are formed in situ and nanotube growth occurs. Controlled by several parameters, the catalyst induces the growth of different carbon nano-structures. This is the first time that Y-branched nanotubes have been synthesised in high quality and purity. A mechanism involving a one catalyst particle process is proposed to rationalise the formation of junction tubes.

Single-walled nitrogen doped nanotubes were prepared using two novel approaches in an arc-discharge process. In both cases a nitrogen-rich precursor was introduced into the anode rods together with graphite and the catalysts. The nitrogen rich precursors were organic and inorganic, respectively. Both synthesis routes gave nanotubes with a nitrogen concentration of a maximum of 1%, determined using electron energy loss spectroscopy (EELS) coupled with transmission electron microscopy (TEM). All samples were characterized with scanning electron microscopy (SEM), TEM, and high-resolution transmission electron microscopy (HRTEM).

Lithium intercalted carbon nanotubes have attracted considerable interest as perspective components for energy storage devices. We performed 13C Nuclear Magnetic Resonance spin lattice relaxation measurements in a temperature range from 4 K up to 300 on alkali intercalated Single Walled Carbon Nanotubes in order to investigate the modifications of the electronic properties. The density of states at the Fermi level were determined for pristine, lithium and cesium intercalated carbon nanotubes and are discussed in terms of intercalation and charge transfer effects.

13C Nuclear Magnetic Resonance measurements were performed on pristine and lithium intercalated single wall carbon nanotubes (SWNT). We investigated the NMR signatures by means of static and high resolution Magic Angle Spinning experiments. This allows us to measure in detail the modifications of the lineshape with the Li concentration. Our results can be explained in terms of charge transfer and changes of the metallic state with an increasing density of states at the Fermi level compared to the pristine SWNT.

Multi walled nitrogen doped nanotubes were synthesized using two different methods. The growth mechanism and nitrogen concentration of the nanotubes synthesized by both methods are discussed and studied. The morphology and nitrogen concentration of the nanotubes are seen to strongly depend on the synthesis methods. The results are based on detailed high resolution transmission electron microscopy (HRTEM) data coupled with electron energy loss spectroscopy (EELS).

Adsorption isotherms of krypton between 77 and 93 K and xenon between 110 and 120 K on mechanically-opened single-walled carbon nanotubes (SWNTs) have been measured. The comparison of the results with those obtained under the same conditions on closed nanotubes is discussed. Evidence of adsorption inside the tubes is given through the appearance of an additional adsorbed amount at very low relative pressure on the isotherms. Different orderings are predicted for xenon and krypton, based on their respective adsorbed amounts inside the nanotubes, and on geometrical considerations. Finally, the fraction of opened nanotubes accessible to xenon and krypton was estimated, as well as the impurity content originating from the cutting process.

We present a new synthesis route for nitrogen doped carbon nanotubes (CNx) based on the aerosol method. Tubes with a record high concentration of nitrogen (approximately 20 atom%) have been synthesized, confirmed by electron energy loss spectroscopy (EELS). A strong correlation between the N/C ratio and morphology of the tubes is observed and discussed.