Ref HAL: hal-00785831_v1
PMID 23194077
DOI: 10.1021/nn3048878
WoS: 000314082800020
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29 Citations
Résumé:

We report in situ Raman scattering experiments on single-layer graphene (SLG) and Bernal bilayer graphene (BLG) during exposure to rubidium vapor. The G- and 2D-band evolutions with doping time are presented and analyzed. On SLG, the extended doping range scanned (up to about 1014 electrons/cm2) allows the observation of three regimes in the evolution of the G-band frequency: a continuous upshift followed by a plateau and a downshift. Overall the measured evolution is interpreted as the signature of the competition between dynamic and adiabatic effects upon n-doping. Comparison of the obtained results with theoretical predictions indicates however that a substrate pinning effect occurs and inhibits charge-induced lattice expansion of SLG. At low doping, a direct link between electrostatic gating and Rb doping results is presented. For BLG, the added electrons are shown to be first confined in the top layer, but the system evolves with time toward a more symmetric repartition of the added electrons in both layers. The results obtained on BLG also confirm that the slope of the phonon dispersion close to the K point tends to be slightly reduced at low doping but suggest the occurrence of an unexpected increase of the phonon dispersion slope at higher electron concentration.

Ref HAL: hal-00715023_v1
DOI: 10.1016/j.cplett.2012.03.067
WoS: 000303437900022
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3 Citations

Ref HAL: hal-00811653_v1
DOI: 10.1021/jp307536d
WoS: 000311650400029
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11 Citations
Résumé:

Vibrational dynamics in the corannulene crystal is exhaustively studied through Raman scattering, infrared spectroscopy, and inelastic neutron scattering. Experimental data are coupled to simulations of the phonon modes performed in the framework of first principle calculations. Intermolecular vibrations (libration and translation) are assigned in the low frequency domain (10-200 cm-1). These modes exhibit specific temperature dependence in the far-infrared.

Ref HAL: hal-00753011_v1
PMID 22836107
DOI: 10.1088/0953-8984/24/33/335304
WoS: 000306997300005
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6 Citations
Résumé:

In this work, the infrared active modes are computed for homogeneous bundles of single-walled boron nitride nanotubes (BBNNTs), using the so-called spectral moments method. The dependence of the wavenumber on these modes in terms of diameters, lengths, and numbers of tubes, is investigated. To this end, use is made of a Lennard-Jones potential for describing the van der Waals interactions between tubes in a bundle. We find that, for a finite homogeneous bundle, additional modes appear as a specific signature. Finally, these results are useful for the interpretation of the experimental infrared spectra of BBNNTs.

Ref HAL: hal-00718101_v1
DOI: 10.1166/jno.2012.1221
WoS: 000303279800016
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1 Citation
Résumé:

We report the temperature dependence of the Raman spectra of a gelatine-based composite material doped with single-walled carbon nanotubes (SWNT@gelatin). On decreasing the temperature from 290 to 20 K a significant up-shift of the G-mode and no changes in the radial breathing modes are observed. This behaviour cannot be understood by pure thermal effects. We explain these results in terms of an uniaxial strain of the nanotubes induced by the thermal expansion mismatch between the nanotubes and the surrounding matrix.

Ref HAL: hal-00711335_v3
Ref Arxiv: 1206.5464
DOI: 10.1016/j.carbon.2012.06.007
WoS: 000308898900001
Ref. & Cit.: NASA ADS
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31 Citations
Résumé:

A spectroscopic study of the amino functionalization of double-walled carbon nanotube (DWCNT) is performed. Original experimental investigations by near edge X-ray absorption fine structure spectroscopy at the C and O K-edges allow one to follow the efficiency of the chemistry during the different steps of covalent functionalization. Combined with Raman spectroscopy, the characterization gives a direct evidence of the grafting of amino-terminated molecules on the structural defects of the DWCNT external wall, whereas the internal wall does not undergo any change. Structural and mechanical investigation of the amino functionalized DWCNT / epoxy composites show coupling between epoxy molecules and the DWCNTs. Functionalization improves the interface between amino-functionalized DWCNT and the epoxy molecules. The electrical transport measurements indicate a percolating network formed only by inner metallic tubes of the DWCNTs. The activation energy of the barriers between connected metallic tubes is determined around 20 meV.

Ref HAL: hal-00691320_v1
DOI: 10.1103/PhysRevB.85.115437
WoS: 000301916100007
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18 Citations
Résumé:

Using the spectral moment's method, the infrared spectra of single-walled boron nitride nanotubes are calculated. The dependence of these modes has been calculated as a function of the nanotube chirality, diameter (from 0.7 to 5 nm), and length. These predictions are useful for understanding the experimental infrared spectra of boron nitride nanotubes.