Photo-active pi-conjugated molecules (quaterthiophene and phthalocyanine) are either encapsulated into the hollow core of single-walled carbon nanotubes or non-covalently stacked at their outer surface in order to elaborate hybrid nano-systems with new physical properties, providing practical routes to fit different requirements for potential applications. In this study, we are interested in the relationship between the structure and the opto-electronic properties. The structural properties are investigated mainly by x-ray diffraction and/or Transmission Electron Microscopy and Raman spectroscopy. We evidence that the supramolecular organizations of confined quaterthiophenes depend on the nanocontainer size whereas phthalocyanine encapsulation leads the formation of a 1D-phase for which the angle between the molecule ring and the nanotube axis is close to 32°. Confined phthalocyanine molecules display Raman spectra hardly altered with respect to the bulk phase, suggesting a rather weak interaction with the tubes. In contrast, the vibrational properties of the molecules stacked at the outer surface of tubes display important modifications. We assume a significant curvature of the phthalocyanine induced by the interaction with the tube walls and a change of the central atom position within the molecular ring, in good agreement with our DFT calculations.

The sol−gel preparation of a bridged silsesquioxane containingeuropium(III) salts and 2-thenoyltrifluoroacetone has been achieved from a newethane tetracarboxamide-based organosilane. Free-standing films with thicknessesup to 440 μm and maximum absolute quantum yield (q) of 0.34 ± 0.03(excitation at 320 nm) were prepared by the drop cast method, while thin films(∼200−400 nm) spin-coated on glass substrates led to highly luminescentcoatings with q = 0.60 ± 0.02 (excitation at 345 nm). The thin films were testedas planar luminescent solar concentrators and the optimized device displays anoptical conversion efficiency of 12.3% in the absorbing spectral region of theactive layer (300−380 nm).

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.

Nanostructuring and control over morphology in hybrid solids are of great interest for the design of polyfunctional materials. For appropriately designed bridged silsesquioxanes, the bridging organic unit is able to self-direct the structure of the solid network independently of any external structure-directing agent. Indeed anisotropic organization due to interactions between organic substructure units was demonstrated with urea functional groups capable of self-assembly via H-bonding (1). We previously showed that H-bonding interactions between precursor molecules during the hydrolysis–condensation of trialkoxysilanes can deeply influence kinetic parameters of the gelation and modify the texture and morphology of the resulting silsesquioxane (2).Considering that the bridging unit plays a key role on controlling the arrangement of the material over a long-range, we developed new hybrid precursors (fig 1) liable to exhibit modulated hydrogen-bonding properties via organic substructures with either two urea groups (UU) or two thiourea groups (TT). It is expected that the strength of the H bonding decreases from urea to thiourea links.We here report our studies on the influence of H-bonding strength on the self-organization properties of the organic substructures and corresponding hybrid solids using vibrational spectroscopies (Raman, Far and Middle Infrared spectroscopies coupled with DFT calculations). Far infrared domain probing directly the intermolecular H-bonding vibrations is shown to be very sensitive to long range arrangement of organic substructure. Besides, as amide vibrations are very sensitive to intermolecular H bonding strength and dispersion, temperature dependence studies of the vibrational dynamic of the internal modes, likely to give insights into the supramolecular interactions, were performed. Additionally, in-situ high pressure infrared studies of intra- and intermolecular interactions demonstrate the role of supramolecular interactions on the mechanical response of hybrid materials towards compression.Following these studies, we propose a mechanistic model for the self-assembling process in H-bonded bridged silsesquioxanes.

In this work, we develop the concept of evaporation-induced self-structuring as a novel approach forproducing organised films by exploiting cooperative physical and chemical interactions under far-fromequilibriumconditions (spin-coating), using sol–gel precursors with multiple functional groups. Thin filmsof self-structured silsesquioxane nanohybrids have been deposited by spin coating through the sol–gelhydrolysis and condensation of a bridged organosilane bearing self-assembling urea groups. The resultingnanostructure, investigated by FTIR, AFM and SEM, is shown to be highly dependent on the catalyst used(nucleophilic or acidic), and can be further modulated by varying the spinning rate. FTIR studies revealed thepresence of highly organised structures under acidic catalysis due to strong hydrogen bonding between ureagroups and hydrophobic interactions between long alkylene chains. The preferential orientation of the ureacross-links parallel to the substrate is shown using polarized FTIR experiments.