Encapsulating molecules inside nanotubes (called hybrid nanotubes in the following) is a common strategy to add new functionalities to the nanocontainer. The one-dimensional nature of single-walled carbon nanotubes (SWCNT) internal channels is exploited here to induce a molecular order and specific interactions which are dependent of the size of the nano container (figure 1). I present here the study of the relation between structural, vibrational and electronic properties of hybrid nanotubes encapsulating dyes. Dimethyl-quarterthiophene (4TCH3) encapsulated inside single-walled carbon nanotubes is studied by inelastic neutron scattering. The results reveal specific dynamics of the 4TCH3 modes characterized in particular by a large sensitivity in the low frequency domain of the methyl libration to the confinement. DFT based calculations consistently describe the observed phenomena and give insights on the structure of the hybrid nanotubes at low temperature where molecules preferentially interact with the nanotube wall. We evidence also by means of Raman spectroscopy and transmission electron microscopy that the supramolecular organizations of the confined oligothiophenes depend on the nanocontainer size. Charge transfer between the dyes and the nanocontainer is shown. A strong dependence on the infrared response of the hybrid nanotube due to confinement effect is finally investigated. The results are compared to experiments performed on nanotubes where dyes are π-stacked at the outer surface. Surprisingly, the confinement properties lead to an exaltation of the infrared absorption response in the carbon nanotubes from dye molecule interactions. Thanks to the comparison between the experimental investigations and DFT calculations, we elucidate the origin of the large enhancement of this infrared absorption.

Le contrôle de la structure et de la morphologie de solides hybrides organiques-inorganiques est un élément clef pour la conception de matériaux fonctionnels. En particulier, pour les silsexquioxanes pontants (SP) auxquels nous nous intéressons, il a été montré que structure et morphologie pouvaient être contrôlées à travers la maitrise des conditions de synthèses (PH, Solvant, …) : à partir d’une même molécule précurseur, des matériaux lamellaires, amorphes, tubulaires, ou de morphologies spongieuses ont pu être obtenus. Les SP présentent l’avantage d’être fonctionnalisés soit en incluant des groupes fonctionnels au sein des molécules précurseurs, soit par l’association de ces précurseurs à des ions/molécules fonctionnelles au cours de la synthèse. A travers un travail centré sur les spectroscopies vibrationnelles, nous nous intéressons aux mécanismes de structurations de ces matériaux, afin d’optimiser leur contrôle et leur impact sur les propriétés de ces matériaux fonctionnels. Ces mécanismes intervenant au cours la réaction sol-gel sont fortement impactés par la compétition entre l’auto-assemblage par liaisons non covalentes (formation de ponts intermoléculaires par liaisons hydrogènes entre amides) et la condensation de la sous structure inorganiques (formation de liaisons covalentes Si-O-Si). Les conditions de synthèse jouent un rôle important dans la maîtrise de cette compétition, nous montrons également qu’il est également possible de jouer sur les liaisons hydrogène en jouant sur la substitution amide/thioamide (conformation/force de liaisons…). La maitrise de la structure et de la substitution amide/thioamide jouent un rôle sur les propriétés d’absorption de la lumière des SP. Ces matériaux, si on maitrise gamme et efficacité d’absorption de la lumière présentent un potentiel pour l’incorporation d’ions luminescents lanthanides, favorisant un effet d’antenne par les sous structures du SP jouant le rôle de ligands pour les ions Ln3+. A travers les spectroscopies vibrationnelles nous montrons un fort impact du choix des précurseurs jouant le rôle de ligands, et de la présence de ces ligands sur les propriétés d’assemblages des précurseurs. La compréhension de ces mécanismes a permis d’élaborer des films de rendements quantiques absolus de l’ordre de 0.60±0.02 (excitation 345 nm) permettant l’élaboration de concentrateurs solaires de rendement de conversion de l’ordre de 12.3% lorsqu’ils sont excités dans la gamme (300-380nm).Dans un deuxième temps, nous nous intéressons au comportement de ces matériaux SP sous haute pression et nous montrons que les liaisons hydrogènes confèrent à ces matériaux une élasticité, jouant le rôle de nano-ressorts. A travers une étude in-situ en IR, nous étudions l’impact de la structuration et de la modulation de la liaison hydrogène sur la limite de ce domaine élastique.

We study the intrinsic optical spectroscopy (UV-vis-NIR absorption, Raman and photoluminescence) signatures of single wall carbon nanotubes (SWNT) dispersed in degassed water without additives, so called ‘‘eau de nanotubes” (EdN). They are found to be very close to those of SWNT dispersed in aqueous suspensions stabilized with surfactants. Absorption peaks appear to be even slightly better resolved for EdN, suggesting sharper excitonic resonances, which is also supported by the Raman data. On the other hand, the photoluminescence signal is significantly weaker. These signatures suggest that SWNT are dispersed as individuals in degassed water, in a similar way single layer graphene was recently shown to be readily dispersable in degassed water [1-3].References[1]G. Bepete et al, Nat. Chem. 2016, DOI 10.1038/NCHEM2669[2]G. Bepete et al, J. Phys. Chem. C 2016, 120 (49), 28204–28214.[3]G. Bepte et al, Phys. Stat. Solidi 2016, 10 (12), 895-899.

The aim of the present work is to study by means of thermodynamic measurements, i.e. isotherms of adsorption and desorption of water and Infrared (IR) spectroscopy, the effect of the interlayer cations on the mechanism of adsorption-desorption of water in the case of a montmorillonite exchanged with alkaline-earth metals. For the first time, the net isosteric heat of water adsorption and desorption is determined from isotherms recorded at three temperatures. The net isosteric heat is a very useful parameter for getting more insights into the sorption mechanism since it provides information about the sorption energy evolution which can be complementary to that obtained from structural or gravimetric measurements. The homoionic montmorillonite samples are prepared from purification and cationic exchanged in aqueous solution of the raw material, i.e the reference SWy-2 Wyoming material. XRD at the dry state and elemental chemical analysis confirm that the treatment does not deteriorate the clay structure and yield the expected homoionic composition. The adsorption and desorption isotherms measured at various temperatures show that the nature of the interlayer, i.e. exchangeable, cation changes the adsorbed/desorbed amount of water molecules for a given water relative pressure. The total amount of water adsorbed at = 0.5 follows the cation sequence Ca>Mg>Ba. Although the adsorption isosteric heat also follows the cation sequence Ca>Mg>Ba, that of desorption obeys a slightly different sequence Ca~Mg>Ba. This discrepancy between the adsorption and desorption heat is due to the higher irreversibility of water sorption process in the Ca exchanged montmorillonite. Finally, analysis of the IR spectra recorded at room temperature and under a primary vacuum reveals that the amount of adsorbed water follows the same sequence as that of the isosteric heat of adsorption and shows the coexistence of liquid-like and solid-like water confined in the interlayer space.

The main hurdle preventing the widespread useof single-walled carbon nanotubes remains the lack ofmethods with which to produce formulations of pristine,unshortened, unfunctionalized, individualized single-walledcarbon nanotubes, thus preserving their extraordinary properties.In particular, sonication leads to shortening, which isdetrimental to percolation properties (electrical, thermal,mechanical, etc.). Using reductive dissolution and transfer intodegassed water, open-ended, water-filled nanotubes can bedispersed as individualized nanotubes in water−dimethylsulfoxide mixtures, avoiding the use of sonication andsurfactant. Closed nanotubes, however, aggregate immediately upon contact with water. Photoluminescence andabsorption spectroscopy both point out a very high degree of individualization while retaining lengths of several microns.The resulting transparent conducting films are 1 order of magnitude more conductive than surfactant-based blanks atequal transmittance.

Some countries with rich textile industries are nowadays facing water quality issues as a consequence of impacting dye pollution. In addition to their inherent toxicity, dyes induce modification in water acidity or salinity which has harmful consequences on the photosynthesis of aquatic plants. As dye are hardly biodegradable, water treatment is necessary to get ride of them [1], and adsorption treatment appears as a good candidate with efficient low-cost adsorbents, such as clays [2]. As a matter of fact, lamellar materials are widely used for sorbtion of ions and molecules harmful for health and environment. In order to gain in efficiency in the use of such materials, it is essential to get a deeper understanding of the retention mechanisms at the interface solid/liquid. In this work, anionic clays, namely layered double hydroxides (LDH) have been chosen as model compounds in order to study sorption mechanism. The presence of charged layer induce strong anionic exchange capacity in these materials, moreover their composition and structual parameters are easily controled through mastered synthesis process [3]. This study work has been focused on the the mechanisms that can lead to the capture of polluting molecules. Several model dyes have been chosen (MethylOrange - MO, Carmen Indigo - CI et Orange G - OG) for their charge, symmetry and hydrophobicity. Parameters such as the solution concentration and the activity of the solvant, playing with the nature of ions, have also been explored.The work presented here rely on vibrational spectroscopies (Infrared and Raman spectroscopies) sensitive to the intermolecular interaction of the dye with its environment particularly at the interface solid/dye. In parallel, X-Ray Diffraction probes the structural modification in the clay during sorption.The experimental results interpreted though the help of simulations (Monte-Carlo, DFT), lead a fine description of ions sorption at the interfaces with these models lamellar materials.