We have investigated the experimental x-ray and far-infrared responses of three polythiophenes synthesized from a thiophene, alpha-bithiophene and alpha-quaterthiophene monomer. The x-ray data show that the crystallinity of the different polythiophene samples depends on the synthesis conditions. An excellent correlation between the crystallinity of polythiophenes and their far-infrared signatures is demonstrated. In addition, the assignment of the far-infrared phonon modes in polythiophenes is given by a direct comparison with its oligomers. In particular, the ring libration inside the polymeric chain, directly involved in the electron-phonon coupling, is assigned.

A long-range ordered organic/inorganic material is synthesized from a bissilane, (EtO)3Si–(CH2)3–NHCONH–C6H4–NHCONH–(CH2)3–Si(OEt)3. This crosslinked sol–gel solid exhibits a supramolecular organization via intermolecular hydrogen bonding interactions between urea groups (–NHCONH–) and covalent siloxane bonding, Si–O–Si . Time-resolved in situ X-ray measurements (coupling small- and wide-angle X-ray scattering techniques) are performed to follow the different steps involved in the synthetic process. A new mechanism based on the crystallization of the hydrolyzed species followed by their polycondensation in solid state is proposed.

The electrochemical properties of â-type nickel (oxy)hydroxides Ni(OH)2 and NiO(OH) are known to depend significantly on their structural features. In this work, these features are investigated by means of inelastic neutron scattering and infrared and Raman spectroscopies. Our experiments probe both inter- and intramolecular (40-4000 cm-1) vibrational ranges and particular attention is paid to the low-frequency (40-300 cm-1) domain, where new features are observed. Namely, the presence of an IR active mode at around 130 cm-1, characteristic of the oxidized â-NiO(OH) phase, is observed for the first time. The effects of temperature (10-300 K) and deuteration are also measured in order to provide deeper insight into the nature of the vibrational states. A detailed comparison of all of the collected data allows us to propose a new assignment of the vibrational features observed in both â-Ni(OH)2 and â-NiO(OH) and to quantify the proton dynamic relevance on the vibrational modes. We show that the interlayer interactions are mostly electrostatic and, hence, do not involve hydrogen bonding. We also point out that, in the oxidized â-phase, protons cannot be localized so that they can be considered as fully labile. To sum up, this investigation emphasizes that proton delocalization and crystalline disorder, which arise concomitantly upon oxidation, are the key factors that explain the evolution of the vibrational features observed between the oxidized and reduced â-type forms.

Herein, we report the experimental investigation of the vibrational properties of corannulene using Raman spectroscopy. The temperature dependences of the Raman spectra between 300 and 20 K reveal a very high sensitivity of the low frequency domain between 40 and 200 cm(-1) compared to the intramolecular domain. The behavior of the Raman modes of the corannulene under pressure, between 0.53 GPa and 8 GPa, is also studied. Under pressure, in the intermolecular vibrational domain (<150 cm(-1)), two transitions occur suggesting metastable intermediate stages under pressure. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

By combining, on the same freestanding single-walled carbon nanotubes, electron diffraction and Raman experiments, we were able to obtain the resonance energy of unambiguously (n,m)-identified single-walled carbon nanotubes. We focus on the analysis of the first optical transition of metallic tubes (E-11(M)) and the third and fourth transitions of semiconducting tubes (E-33(S) and E-44(S), respectively) in comparison with calculated values using a nonorthogonal tight-binding approach. For semiconducting tubes, we find that the calculated energies E-33(S) and E-44(S) have to be corrected by non-diameter-dependent (rigid) shifts of about 0.43 eV and 0.44 eV, respectively, for tubes in the 1.4-2.4-nm-diameter range. For metallic tubes in the 1.2-1.7-nm-diameter range, we show that a rigid shift (0.32 eV) of the calculated transition energy also leads to a good estimation of E-11(M). The rather large and non-diameter-dependent shifts for the third and fourth transitions in semiconducting tubes question a recent theoretical study, which relates the shifts to electron-electron correlation and exciton binding energy and suggest that the exciton binding is very small or missing for the higher transitions E-33(S) and E-44(S), contrary to the lower transitions E-11(S) and E-22(S).