Résumé (à complèter)

In the present work, the non-resonant Raman-active modes are calculated for several diameters, chiralities and sizes for homogeneous and inhomogeneous bundles of single-walled carbon nanotubes (BWCNTs), using the spectral moment's method (SMM). Additional intense Raman-active modes are present in the breathing-like modes (BLM) spectra of these systems in comparison with a single fully symmetric A(1g) mode characteristic of isolated nanotubes (SWCNTs). The dependence of the wavenumber of these modes in terms of diameters, lengths and number of tubes was investigated. We found that, for a finite (in) homogeneous bundle, additional breathing-like modes appear as a specific signature.

The hydrolysis and condensation of a silylated derivative of ureidopyrimidinone led to nanostructured hybrid silica, such as that depicted, as clearly shown by powder XRD studies. The nanostructuring was directly related to molecular recognition through hydrogen bonding. By combining FTIR, solution and solid-state NMR spectroscopic data, the transcription of the hydrogen-bonding networks from the precursor to the final product was clearly evidenced.

We review the main information that we have obtained from Raman spectroscopy experiments combined with electron diffraction experiments on individual freestanding single-walled carbon nanotubes. This information concerns: the radial breathing mode vs diameter relationship; the dependence of the frequency and lineshape of the G-modes in semi conducting and metallic tubes; the evaluation of the optical transition energies for individual freestanding SWNTs. These experimental Raman results obtained on index-identified individual SWNTs are compared with other experimental data and theoretical predictions. The intrinsic lineshape of G-modes of the achiral and chiral semi conducting and metallic SWNTs are unambiguously established. The results also support the fact that non adiabatic effect should be taken into account to describe the diameter dependence of the LO modes of metallic SWNT. From these data, we can also define Raman criteria that allow identifying carbon nanotubes from their Raman features only. We show the efficiency of this approach: (i) to assign the (n,m) indices of individual freestanding single-walled carbon nanotubes, and (ii) to identify the (n,m) tubes organized in a small bundle.

New promising oligo(phenylenethienylene)s have been synthesized to realize suitable materials for improving electronic transport properties, particularly in organic field effect transistors (OFETs). Far-infrared and incoherent neutron scattering measurements have been performed to assign their phonon modes. The assignment of the main low-frequency phonon modes of these materials has been performed experimentally by using a filiation procedure. Assuming a small frequency dispersion of the high-frequency modes, the main intramolecular phonon modes of a model oligomer have been assigned by using first-principles calculations on its isolated molecule. These assignments constitute the preliminary work for a better understanding of these new promising materials in electronic and opto-electronics applications.