Due to their hollow space, nanotubes NT can host molecules giving rise to new hybrid molecule@NT systems. A possible class of molecules that can be hosted by nanotubes are π-conjugated oligomers which are attractive due to their electronic and optoelectronic properties[3]. Its drawback are brittleness and low electric conductivity[4]. Encapsulation of dimethyl-quaterthiophene (4TCH3) inside SWCNTs gives rise to a hybrid material, expected to combine the protection of the confining matrix to the photo-physical properties of the encapsulated unit. This hybrid material will be referred hereafter as 4TCH3@NTφ(where φ is the nanotube diameter in Å).The first recent experimental study, based on Raman spectroscopy, brought the proof that the number of encapsulated molecules depend on the size of the confining matrix[5]. Some influence of the diameter of the nanotube on the confinement state of the molecule as well as their interaction with the nanotube is expected. Inelastic neutron scattering, mostly sensitive to the confined molecule, due to the strong cross-section of hydrogen atoms, probes wide Q vector range, which is a very interesting tool in order to obtain a complete picture of the vibrational properties of such system.We are interested on the confinement properties of two hybrid systems: 4TCH3@NT09 and 4TCH3@NT14. Those materials were studied by means of inelastic neutron scattering (INS) at two instruments at the Institute Laue-Langevin, time-of-flight IN4C and Triple Axis IN1-Lagrange spectrometers. The resulting experimental HPDOS can be compared to the DFT-simulated HPDOS, allowing thus the assignment of main vibrational modes. We show that specific vibrational modes undergo to modifications upon a change of the size of the confining matrix, evidencing the influence of encapsulation in such molecules.

1D hybrid nano-systems are elaborated with photo-active pi-conjugated molecules (quathertiophene and phathlocyanine) encapsulated into the hollow core of single-walled carbon nanotubes. We evidence that the supramolecular organizations of confined oligothiophenes (from 1 to 3 chains into a nanotube section) depend on the nanocontainer size. The physical interactions can switch from molecule-molecule to molecule-nanotube interactions depending on the tube diameter. In addition, permanent and photo-induced electron transfers are evidenced from the confined molecules to the nanotubes. The supramolecular organization of MPc molecules is shown to be a 1D-phase for which the angle between the molecule ring and the nanotubes axis is close to 32°. Confined MPc molecules display Raman spectra hardly altered with respect to the bulk phase, suggesting a rather weak interaction with the tubes.

New one-dimensional (1D) hybrid nanosystems are elaborated with metalated or metal free phthalocyanine molecules encapsulated into the hollow core of single-walled carbon nanotubes. The X-ray diffraction experiments coupled to simulation allow evidencing the 1D structural organization of the molecules inside the nanotubes. The angle between the molecule ring and the nanotube axis is close to 32° as determined from our density functional theory calculations. Confined molecules display Raman spectra hardly altered with respect to the bulk phase, suggesting a rather weak interaction with the tubes. For comparison, noncovalent functionalization at the outer surface of the tube is also investigated. The vibrational properties of the molecules functionalized at the outer surface of tubes display important modifications. A significant curvature of the phthalocyanine is induced by the interaction with the tube walls, leading to change of the central atom position within the molecular ring, in good agreement with our first-principles calculations.

Un nanotube de carbone (NT) peut être envisagé comme un enroulement spécifique d’un plan de graphène sur lui-même. La géométrie hélicoïdale ainsi obtenue détermine sa structure moléculaire et par conséquent ses propriétés physiques. En particulier, les NTs sont soit métalliques soit semi-conducteurs selon leur angle d’enroulement et ils présentent des propriétés optiques qui dépendent de leur diamètre. Cependant, ces propriétés ne sont pas modulables.Une méthode élégante pour contrôler et ajuster les propriétés opto-électroniques consiste à élaborer des nano-matériaux hybrides 1D par confinement de molécules dans la cavité des nanotubes. Nous présenterons ici les principaux résultats obtenus après insertion de molécules d’iode [1], d’oligothiophène [2] et de phthalocyanine [3]. Nous montrerons qu’il est possible, essentiellement par spectroscopie Raman, d’étudier les propriétés structurales des molécules encapsulées (organisation supramoléculaire et effets de confinement), la nature des interactions physiques permanentes (dispersive ou avec transfert de charge, entre molécules ou avec les NTs) et de mettre en évidence d’éventuels effets photo-induits.

Confinement of conducting oligomers inside single-walled carbon nanotubes : simulation of the vibrational dynamics

Simulation of the encapsulation of photoactive molecules inside carbon nanotubes

Simulation of hybrid systems : nanotubes-photoactive molecules