Search

Your search keyword '"Bruneel, Jean-Luc"' showing total 39 results
Start Over Author "Bruneel, Jean-Luc"
39 results on '"Bruneel, Jean-Luc"'

12. Raman micro spectrometry as a new approach to the investigation of molecular recognition in solids: chlorofornm-cryptophane complexes

Author

Cavagnat, Dominique ; Brotin, Thierry, Bruneel, Jean-Luc ; Dutasta, Jean-Pierre, Thozet, Alain, Perrin, Monique, and Guillaume, Francois

Subjects
Molecular structure -- Research, Raman spectroscopy -- Analysis, Chloroform -- Research, Chemicals, plastics and rubber industries
Abstract

A polarized Raman micro spectrometry study of micro crystals of cryptophane-A, selectively deuterated cryptophane-A, bis-cryptophane, and cryptophane-E encapsulating chloroform molecules is presented. By x-ray diffraction analysis, the crystallographic structures of these different molecular entities are isolated.

Published
2004

13. Guest Partitioning and Metastability of the Nitrogen Gas Hydrate

Author

Petuya, Claire, Damay, Françoise, Chazallon, Bertrand, Bruneel, Jean-Luc, and Desmedt, Arnaud

Abstract

Gas clathrate hydrates or gas hydrates are made of H-bonded water molecules forming cages, within which gaseous (guest) molecules are encapsulated. The formed clathrate structures, which may be metastable, depend on the nature and on the partitioning of the guest molecules in the water cage. This work focuses on the structural and vibrational properties of nitrogen hydrate in its two clathrate forms (namely, SI and SII) in the thermodynamic ranges 50–200 bar and 150–270 K, together with a comprehensive analysis of the transformation from SI to SII of this gas hydrate. The thermal expansion of both structures has been measured at 1 bar, and the melting of the nitrogen hydrate has been measured at ca. 210 K at 1 bar. Moreover, the SI structure is metastable in the studied pressure region: from time-dependent neutron powder diffraction analysis, it is shown that the SI structure transforms over time to the SII structure with a rate of (1.37 ± 0.17) × 105s–1at 100 K and at 1 bar. The transformation is also characterized by an induction time (i.e., the lifetime of the pure SI structure) of 0.49 day. We have also investigated the guest partitioning of the nitrogen hydrate using high-resolution Raman scattering. Vibrational bands of nitrogen molecules encapsulated in large cages are measured at lower wavenumbers than the one associated with encapsulation in small cages (by 1.1 cm–1in SI and 0.8 cm–1in SII). In the case of the thermodynamically stable SII phase, the dependence of the guest partitioning has been characterized as a function of the pressure–temperature conditions. Variation of the relative cage filling is demonstrated. While the small cages remain singly occupied according to previous neutron diffraction analysis, this variation is attributed to large cages of the nitrogen hydrate that easily catch or release nitrogen guest molecules. This study thus provides new opportunities for preparing nitrogen gas hydrates with a “targeted” structure and relative cage filling not only by varying the pressure and temperature but also by playing with the structural metastability.

Published
2024
Full Text
View/download PDF

15. Raman spectroscopy of white wines

Author

Martin, Coralie, primary, Bruneel, Jean-Luc, additional, Guyon, François, additional, Médina, Bernard, additional, Jourdes, Michael, additional, Teissedre, Pierre-Louis, additional, and Guillaume, François, additional

Published
2015
Full Text
View/download PDF

37. Photoinduced orientations of azobenzene chromophores in two distinct holographic diffraction gratings as studied by polarized Raman confocal microspectrometry

Author

Labarthet, François Lagugne´, Bruneel, Jean-Luc, Buffeteau, Thierry, Sourisseau, Claude, Huber, Marco R., Zilker, Stephan J., and Bieringer, Thomas

Abstract

Optically isotropic thin films (0.5 μm) of an amorphous side-chain copolymer containing 10% azobenzene moieties and 90% meso-azobenzene groups (K1-10 sample) were irradiated by two interfering orthogonal (±45°) or parallel (p+p) linearly polarized laser beams; permanent holographic diffraction gratings were thus inscribed. From atomic force microscopy (AFM) measurements, relatively weak amplitudes (about 50–60 nm) in the surface relief modulation (SRM) are detected but strong perturbations in the profiles and new substructures are evidenced at half-period positions. Using a confocal microspectrometric technique we have recorded various pre-resonance enhanced polarized Raman spectra from a large grating area and obtained spatially resolved Raman images of the intensity variations. This yields new insight into the photoinduced orientation effects, the angular distributions of the chromophore species, and finally the grating formation mechanisms. Different theoretical equations of the polarized Raman scattering intensities, taking account of the pump polarization directions and the high numerical aperture objective used, are derived. Then, an analysis of the experimental results allows us to extract values of the second 〈P2〉 and fourth 〈P4〉 coefficients in the chromophore orientation functions at several positions of the SRM, in particular at the top and bottom regions, and to calculate the corresponding normalized distribution functions via information entropy theory. In both gratings, somewhat broader distributions are found in the bottom regions, regions of greater polymer removal. Thus, mass-transport phenomena have perturbed, to a weak extent in the (±45°) first case and to a larger extent in the (p+p) second case, the primary photoinduced orientations. So, two simultaneous and superimposed mechanisms appear to be responsible for the observed complex SRM in the highly birefringent K1-10 copolymer under study and significant second-order contributions are suggested. The grating surface profiles are thus reproduced by fitting the SRM amplitudes at the fundamental and doubled frequency and the corresponding phase constant parameters: a good agreement between the observed (AFM) and simulated profiles is obtained.

Published
2000

38. Vibrational and theoretical study of the complexation of LiPF6 and LiClO4 by di(ethylene glycol) dimethyl ether

Author

Grondin, Joseph, Ducasse, Laurent, Bruneel, Jean-Luc, Servant, Laurent, and Lassègues, Jean-Claude

Subjects
*OXYGEN, *FLUIDS, *ETHERS, *GLYCOLS
Abstract

Solid [(diglyme)2Li+]PF6− and [(diglyme)2Li+]ClO4− salts melting at 132 and 66 °C, respectively, have been isolated. They involve two diglyme molecules wrapping the six-coordinated cation and a “spectroscopically free” anion in a similar local structure of complexation as in the P(EO)6,LiPF6 and P(EO)6,LiClO4 systems. The structures and vibrational assignments of the [(diglyme)2Li+]X− salts have been established by comparison with the corresponding IR and Raman spectra of liquid and solid diglyme and by using ab initio calculations. In particular, the atomic motions involved in the so-called “rattling”, D-LAM or “breathing” modes have been described in terms of a distorted octahedral cage of oxygen coordinating the lithium. Various (diglyme)n,LiClO4 samples (n=12–2) could be melted without decomposition and the Raman profile of the symmetric stretching vibration ν1 of the anion has been studied as a function of the temperature. An equilibrium is evidenced between two kinds of 2/1 complexes: in the first one, the anions are “spectroscopically free” (ν1=933 cm−1) and the cation is coordinated to six ether oxygen as in the solid state, while in the second, less stable by ∼14 kJ mol−1, the cation is coordinated to five ether oxygen and one perchlorate oxygen to form contact ion-pairs (ν1=938 cm−1). [Copyright &y& Elsevier]

Published
2004
Full Text
View/download PDF

39. Raman spectroscopy probing of self-assembled monolayers inside the pores of gold nanotube membranes

Author

Jean-Luc Bruneel, Joseph G. Shapter, Leonora Velleman, François Guillaume, Dusan Losic, Velleman, Leonora, Bruneel, Jean-Luc, Guillaume, Francois, Losic, Dusan, and Shapter, Joe George

Subjects
Nanotube, separation, Materials science, templates, General Physics and Astronomy, Nanotechnology, fabrication, Physics, Atomic, Molecular & Chemical, symbols.namesake, alumina membranes, silver, Physical and Theoretical Chemistry, Porosity, Deposition (law), Chemistry, Physical, Physics, electroless gold, technology, industry, and agriculture, silicon, Self-assembled monolayer, equipment and supplies, 4-mercaptobenzoic acid, Chemistry, Template, Membrane, nanowires, transport, symbols, Raman spectroscopy, Raman scattering
Abstract

Electroless deposition was used to coat porous alumina membranes with gold. This process reduced the pore diameters and provided a platform suitable for surface modifications with self assembled monolayers (SAMs). The surface enhanced Raman scattering (SERS) effect was employed in order to confirm and characterise the formation of SAMs of 3-mercaptobenzoic acid (mMBA) inside the pores of gold nanotube membranes prepared using porous alumina (PA) templates. The investigation of the coverage and reproducibility of SAMs within porous matrices is of utmost importance in the design of filtration membranes and sensing platforms. Raman spectroscopy is capable of spatially resolved techniques such as mapping which was used to characterise the distribution of mMBA assembly within the pores. Due to the highly ordered structure of porous alumina and well controlled electroless gold deposition, these gold coated membranes have the potential to develop into SERS active substrates for ultrasensitive sensing technologies. Refereed/Peer-reviewed

Published
2011

Catalog

Books, media, physical & digital resources
See catalog results