Photo-active molecules are confined into single-wall carbon nanotubes to create 1D hybrid systems with new and original opto-electronic properties. This work deals with the encapsulation of quaterthiophene derivative and phthalocyanine molecules. They display strong optical absorption in the visible range, respectively around 400 and 670 nm. Encapsulation efficiency is investigated through Transmission Electron Microscopy. The physical interactions are mainly investigated by optical spectroscopies. The Raman spectra of the oligothiophene hybrid systems exhibit a striking dependence with the excitation energy which is correlated to the optical absorption energy of the photo-active molecule. Close to the molecule resonance, the results suggest a significant photo-induced charge transfer between the photo-active molecules and the nanotubes. In addition, the resonance window of the confined molecules depends on the nanotube diameter. The Raman spectra of the phthalocyanine based systems depend on the optical resonance conditions of the encapsulated molecules and on the structural properties of the hybrid system.

In this paper, we compare the Raman responses obtained on individual suspended Single-Walled Carbon Nanotubes (SWNTs) and Double-Walled Carbon Nanotubes (DWNTs). We focus on the comparison of the frequencies, line widths, intensities and resonance conditions of the main Raman active modes measured on an index-identified DWNT with those measured on SWNTs having atomic structures close to the inner and outer tubes of the DWNT. By this way, we state that the relation between the radial breathing mode frequencies and the diameters established for SWNTs do not work in DWNTs. We found that resonance of only one tube can be sufficient to observe the response of the coupled layers in DWNTs. These results are understood in terms of mechanical coupling between the layers in DWNTs. We evidence that the spectral line widths of the Raman active modes are systematically narrower for DWNTs compared to the corresponding SWNTs. Finally, we present the measurements of the G modes of two different DWNTs which behave in a different way. For the first one, the frequencies of the G modes are not significantly affected by the interaction between the layers, while for the second one we evidence a downward shift of the LO and TO bands arising from the inner layer.

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.

The combination of transmission electron microscopy, electron diffraction and resonant Raman spectroscopy on individual suspended nanostructures is the ultimate method to relate unambiguously theirs structural parameters [1], optical transitions [2, 3], and Raman-active phonons [1, 3, 4]. This approach has been successfully used to study the main Raman-active modes of individual double-walled carbon nanotubes [5] (DWCNT). In this contribution, we will show, in particular, that low-frequency features in the Raman spectra cannot be connected to the layer diameters d by means of the 1/d power law, widely used for the diameter dependence of the radial-breathing mode of single-walled nanotubes. We discuss this disagreement in terms of mechanical coupling between the layers of the DWCNT, which results in collective vibrational modes. The mechanical coupling qualitatively explains the observation of Raman lines of breathing-like modes, whenever only one of the layers is in resonance with the laser energy. [1] J. C. Meyer, M. Paillet, M. ; Michel, T. ; Moréac, A. ; Neumann, A. ; Duesberg, G. S. ; Roth, S.; Sauvajol, J.-L., Phys. Rev. Lett., 95, 217401 (2005). [2] T. Michel, M. Paillet, J.C. Meyer, V.N. Popov, L. Henrard, J.L. Sauvajol, Phys. Rev. B, 75, 155432 (2007). [3] M. Paillet, T. Michel, J.C. Meyer, V.N. Popov, L. Henrard, S. Roth, J.L. Sauvajol, Phys. Rev. Lett., 96, 257401 (2006). [4] T. Michel, M. Paillet, D. Nakabayashi, M. Picher, V. Jourdain, J.C. Meyer, A.A. Zahab, J.L. Sauvajol, Phys. Rev. B, 80, 245416 (2009). [5] D. Levshov, T. X. Than, R. Arenal, V. N. Popov, R. Parret, M. Paillet, V. Jourdain, A. A. Zahab, T. Michel, Yu. I. Yuzyuk, and J.-L. Sauvajol, Nano Lett., 11, pp 4800–4804 (2011).

In this paper, we discuss the low-frequency range of the Raman spectrum of individual suspended index-identified single-walled (SWCNTs) and double-walled carbon nanotubes (DWCNTs). In SWCNTs, the role of environment on the radial breathing mode (RBM) frequency is discussed. We show that the interaction between the surrounding air and the nanotube does not induce a RBM upshift. In several DWCNTs, we evidence that the low-frequency modes cannot be connected to the RBM of each related layer. We discuss this result in terms of mechanical coupling between the layers which results in collective radial breathing-like modes. The mechanical coupling qualitatively explains the observation of Raman lines of radial breathing-like modes, whenever only one of the layers is in resonance with the incident laser energy.

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.