The crystalline structure of ureidopyrimidinone-based silane (UPY) has been determined. The local and long range order structuring of the bridged silsesquioxane (MUPY) resulting from the sol-gel hydrolysis-condensation of the former precursor has been investigated by MFTIR (Mid Fourier Transform InfraRed) combined with DFT (Density Functional Theory) and XRD (X-ray diffraction) studies. These studies showed that a long range structuring exists within the organic fragments with the transcription of the DDAA (Donor-Donor-Acceptor-Acceptor) H-bonding array from UPY to MUPY whereas a disordered siloxane network was revealed in the hybrid material.

This study deals with a hybrid system consisting in quaterthiophene derivative encapsulated inside single-walled and multi-walled carbon nanotubes. Investigations of the encapsulation step are performed by transmission electron microscopy. Raman spectroscopy data point out different behaviors depending on the laser excitation energy with respect to the optical absorption of quaterthiophene. At low excitation energy (far from the oligomer resonance window) there is no significant modification of the Raman spectra before and after encapsulation. By contrast, at high excitation energy (close to the oligomer resonance window), Raman spectra exhibit a G-band shift together with an important RBM intensity loss, suggesting a significant charge transfer between the inserted molecule and the host nanotubes. Those results suggest a photo induced process leading to a significant charge transfer.

A hybrid system consisting of quaterthiophene derivative inserted into carbon nanotubes is studied. Encapsulation efficiency of the conjugated oligomers in the hollow core of nanotubes is investigated by transmission electron microscopy and spatial-resolved electron energy loss spectroscopy. Infrared spectroscopy showed evidence of a significant positive charge transfer on the inserted oligothiophene. Raman spectra display different behaviors depending on the excitation energy and correlated to the quaterthiophene optical absorption energy. At high excitation wavelength (far from the oligomer resonance), radial breathing modes exhibit a significant upshift consistent with an encapsulation effect. At low excitation wavelength (close to the oligomer resonance), both the G-band shift and the low-frequency modes vanishing suggest a significant charge transfer between the quaterthiophene and the nanotubes

résumé

Two hydrothermally synthesised allophanes (Si/Al = 0.5 and 1) were modified by heating at 400 degrees C. N-methyl-D-glucamine, a specific boron complexant, was grafted on the allophane material with Si/Al = 0.5. The surface and structural properties of the different materials were characterised by infrared spectroscopy and Si-29 CP MAS NMR spectroscopy. The porous characteristics of the different allophanes (specific surface area, pore size distribution) were determined by nitrogen adsorption at 77 K using the BET equation and the BJH model. The adsorption of boron, i.e. boric acid/borate, by the modified allophanes was studied in aqueous solutions with boron contents of 1 to 100 mg L-1. The pH-dependence of boron adsorption of all the sorbents showed a maximum at a pH value close to the pKa value of boric acid (pKa H3BO3/B (OH)(4)(-) = 9.26). The adsorption isotherms of boron by raw and modified allophanes were fitted with a double Langmuir equation, assuming the presence of two sets of adsorption sites. The grafting of N-methyl-D-glucamine did not improve the boron adsorption of the allophanes but the structural changes by heating at 400 degrees C increased the adsorption. (C) 2011 Elsevier B.V. All rights reserved.

We carried out a complete study (magnetic, electronic, dielectric, dynamic, and elastic properties) of the nickel hydroxide [Ni(OH)2] from first-principles calculations based on density functional theory. No theoretical investigations of these physical properties have been previously reported in literature. Our work supports that Ni(OH)2 is an A-type antiferromagnetic material. In addition, it is negative uniaxial and semiconducting with a direct band gap at the Γ point around 3 eV. By contrast to its electronic dielectric tensor, its static tensor is strongly anisotropic in the plane orthogonal to its optical axis. This anisotropy is mainly governed by a highly polar phonon centered around 510 cm−1 and assigned as a rotational Eu mode. Both Raman and infrared spectra have been computed to clarify the longstanding debate on the assignment of the Ni(OH)2 phonon modes reported in literature. All these theoretical results are fruitfully compared to the experimental ones obtained on large Ni(OH)2 "pseudosingle" crystals when available.

The Hybrid system consisting in quaterthiophene derivative inserted into single and multi-walled carbon nanotubes is studied. Encapsulation efficiency of the conjugated oligomers in the hollow core of nanotube is investigated by Transmission Electron Microscopy and spatial resolved electron energy loss spectroscopy. We clearly show from Raman spectroscopy that the interaction between nanotubes and oligomers deeply depends on the metallic or semiconducting character of nanotubes. The charge transfer is shown to be significantly stronger for semiconducting tubes than for metallic ones. In addition, the shift of the Raman-active G band together and the appearance of a new peak in the 2D band of the semiconducting nanotubes state a ntype doping of the nanotubes. Complementary, the infrared spectra evidence a p-type doping of the oligomer.