Entity

Time filter

Source Type


Le Caer S.,Institute Rayonnement Matiere Of Saclay | Klein G.,Institute Rayonnement Matiere Of Saclay | Ortiz D.,Institute Rayonnement Matiere Of Saclay | Lima M.,University of Florence | And 8 more authors.
Physical Chemistry Chemical Physics | Year: 2014

Solutions containing 8 and 32 wt% myoglobin are studied by means of infrared spectroscopy, as a function of temperature (290 K and lower temperatures), in the mid- and far-infrared spectral range. Moreover, ultrafast time-resolved infrared measurements are performed at ambient temperature in the O-D stretching region. The results evidence that the vibrational properties of water remain the same in these myoglobin solutions (anharmonicity, vibrational relaxation lifetime...) and in neat water. However, the collective properties of the water molecules are significantly affected by the presence of the protein: the orientational time increases, the solid-liquid transition is affected in the most concentrated solution and the dynamical transition of the protein is observed, from the point of view of water, even in the least concentrated solution, proving that the water and myoglobin dynamics are coupled. © the Partner Organisations 2014. Source


Fourdrin C.,Ecole Polytechnique - Palaiseau | Aarrachi H.,CNRS Center for Research on Divided Matter | Latrille C.,Institute Rayonnement Matiere Of Saclay | Esnouf S.,CNRS Center for Research on Divided Matter | And 2 more authors.
Environmental Science and Technology | Year: 2013

The radiolysis of water confined in montmorillonites is studied as a function of the composition of the montmorillonite, the nature of the exchangeable cation, and the relative humidity by following the H2 production under electron irradiation. It is shown that the main factor influencing this H2 production is the water amount in the interlayer space. The effect of the exchangeable cation is linked to its hydration enthalpy. When the water amount is high enough to get a basal distance higher than 1.3 nm, then a total energy transfer from the montmorillonite sheets to the interlayer space occurs, and the H2 production measured is very similar to the one obtained in bulk water. For a basal distance smaller than 1.3 nm, the H2 production increases with the relative humidity and thus with the water amount. Lastly, electron paramagnetic resonance measurements evidence the formation of a new defect induced by ionizing radiation. It consists of a hydrogen radical (H2 precursor) trapped in the structure. This implies that structural hydroxyl bonds can be broken under irradiation, potentially accounting for the observed H2 production. © 2013 American Chemical Society. Source


Le Caer S.,Institute Rayonnement Matiere Of Saclay | Lima M.,University of Florence | Gosset D.,CEA Saclay Nuclear Research Center | Simeone D.,CEA Saclay Nuclear Research Center | And 4 more authors.
Journal of Physical Chemistry C | Year: 2012

Ultrafast infrared spectroscopy of the O-D stretching mode of dilute HOD in H 2O probes the local environment and the hydrogen bond network of confined water. The dynamics of water molecules confined in the interlayer space of montmorillonites (Mt) and in interaction with two types of cations (Li + and Ca 2+) but also with the negatively charged siloxane surface are studied. The results evidence that the OD vibrational dynamics is significantly slowed down in confined media: it goes from 1.7 ps in neat water to 2.6 ps in the case of Li + cations with two water pseudolayers (2.2-2.3 ps in the case of Ca 2+ cations) and to 4.7 ps in the case of Li + cations with one water pseudolayer. No significant difference between the two cations is noticed. In this 2D confined geometry (the interlayer space being about 0.6 nm for two water pseudolayers), the relaxation time constants obtained are comparable to the ones measured in analogous concentrated salt solutions. Nevertheless, and in strong opposition to the observations performed in the liquid phase, anisotropy experiments evidence the absence of rotational motions on a 5 ps time scale, proving that the hydrogen bond network in the interlayer space of the clay mineral is locked at this time scale. © 2012 American Chemical Society. Source


Le Caer S.,Institute Rayonnement Matiere Of Saclay | Brunet F.,Institute Rayonnement Matiere Of Saclay | Chatelain C.,Institute Rayonnement Matiere Of Saclay | Ladevie L.,Institute Rayonnement Matiere Of Saclay | And 4 more authors.
Journal of Physical Chemistry C | Year: 2013

The behavior of different nanoporous grafted silicas (-Si(CH 3)2R) under ionizing radiation is investigated as a function of the chemical nature of the grafting. The structure and reactivity of the grafting after irradiation is characterized by solid-state NMR spectroscopy. The chemical reactivity is also investigated by mass spectrometry gas analysis. The major gases detected after irradiation are H2 and/or CH4. Different types of behaviors under ionizing radiation are depicted as a function of R. When R contains an aromatic ring or is the cyclopentadienyl moiety, then the overall measured radiolytic yields are low and CH4 is the major gas detected. The aromatic ring acts as an efficient energy trap. When R contains an alkyl chain with a-CN ending, the major gas detected is dihydrogen due to the lysis of the-CH(H) bond, but it is also shown that the-CN group acts as an energy trap, even if it is of course less efficient than an aromatic ring. When R consists of a long alkyl chain, an efficient energy transfer occurs at the interface and leads to a significant H2 production due to the lysis of the-CH(H)-bond. Lastly, when R is small (a methyl or an ethyl group), the situation is different and the Si-C bond is preferentially cleaved over the C-H bond. © 2013 American Chemical Society. Source


Le Caer S.,Institute Rayonnement Matiere Of Saclay | Brunet F.,Institute Rayonnement Matiere Of Saclay | Chatelain C.,Institute Rayonnement Matiere Of Saclay | Durand D.,CEA Saclay Nuclear Research Center | And 3 more authors.
Journal of Physical Chemistry C | Year: 2012

Controlled pore glasses with a pore size of 8 nm are grafted with chlorodimethylsilane (ClSi(CH 3) 2H). The surface of the glass is carefully characterized before and after irradiation with 10 MeV electrons by solid-state NMR measurements. 1H MAS NMR experiments in one and two dimensions (2D double quantum and 2D exchange) have been used to reveal the grafting of the chlorodimethylsilane at the silica surface and evidence the formation of a homogeneous layer on the surface. Irradiation leads to a high H 2 yield (3.3 × 10 -7 mol/J) due to the efficient cleavage of the Si-H bond. Methane is detected in smaller quantities (5.5 × 10 -8 mol/J), indicating that the Si-H bond is preferentially cleaved over the Si-C bond. The H 2 production arising from -OH groups on the surface is very minor in comparison to the Si-H and Si-C radiolysis. © 2012 American Chemical Society. Source

Discover hidden collaborations