This thesis reports the investigation of molecular materials for hydrogen storage applications with a particular emphasis on alkali-metal amidoboranes. I have developed new routes for the synthesis of $alpha$-LiNH$_{2}$BH$_{3}$ and NaNH$_{2}$BH$_{3}$, and have studied their hydrogen storage properties by thermogravimetric analysis, variable temperature X-ray and neutron diffraction and inelastic neutron scattering. I report the synthesis and full structural characterization of two new materials, KNH$_{2}$BH$_{3}$ and $beta$-LiNH$_{2}$BH$_{3}$, and have performed initial studies on a tetragonal phase of a variant of LiNH$_{2}$BH$_{3}$ with a preliminary structure solution. I have also performed variable temperature neutron diffraction on ammonium borodeuteride, ND$_{4}$BD$_{4}$, and report the full structural characterisation of the three phases identified as a result of these measurements. Furthermore, variable temperature inelastic neutron scatting (INS) measurements were performed on ammonia borane, NH$_{3}$BH$_{3}$, and the results are discussed in terms of crystallographic phase changes.

Spectroscopic measurements are detailed within this thesis, utilising incoherent neutron scattering to examine the dynamics of various condensed-matter systems, from nanosecond to sub-femtosecond timescales. The body of this work is divided into two distinct areas of research. I. Nuclear Momentum Measurements of Multiple Masses Deep inelastic neutron scattering (DINS) is used to probe the nuclear momentum distributions and kinetic energies of individual atomic species in sodium hydride (both in bulk and as nanoparticulates within a silica matrix), enriched lithium-7 fluoride and lithium tetra-ammoniate. Extension of DINS to examine heavier (M>4amu) nuclei is detailed, accomplished by the application of a simple stoichiometric fixing technique within the standard DINS theory and analysis protocols. The validity and accuracy of such simultaneous measurements are discussed. II. The Dynamics of Coordinated Ammonia in Zeolite A Inelastic neutron scattering (INS) and quasielastic neutron scattering (QENS) are utilised in the examination of vibrational and stochastic dynamics of the ammonia molecule, as coordinated to the internal surface of a zeolite host. Both sodium and copper-exchanged forms of zeolite-A are studied, with proton-weighted, low energy phonon-modes and rotational processes being observed and assigned.

Le traitement des effluents aqueux issus des usines de retraitement de La Hague est un enjeu important pour l'environnement. Ces effluents sont contaminés par des substances organiques et des éléments possédant une radioactivité résiduelle. Ce travail porte donc sur le développement et l'optimisation du procédé de dépollution avec pour objectifs d'exempter l'effluent de toute pollution et de former un déchet final compatible avec les matrices de conditionnement classiques dans le milieu nucléaire. Le procédé de séparation se décompose en deux étapes : l'étape de solubilisation de la pollution dans des micelles de tensioactifs et l'étape de précipitation d'une phase minérale par transition sol-gel.Dans la cadre de la thèse, seule la pollution due aux radionucléides a été étudiée. Lors de la première étape, la stratégie a consisté à utiliser des molécules complexantes capable d'interagir avec les ions et de former des complexes préférentiellement solubles dans le cœur des micelles de tensioactifs. Par la suite, la deuxième étape a consisté à ajouter un précurseur de silice qui après hydrolyse et polycondensation permet d'agréger les micelles contenant les complexes entre elles et de former une phase silice qui précipite de façon in-situ. L'objectif de dépollution de l'effluent a été atteint et le déchet final formé est une poudre de silice contenant les micelles et la pollution qui après calcination est compatible avec les matrices de conditionnement telles que le verre ou le ciment. Différentes études ont permis de définir un système de référence pour lequel le procédé de séparation est optimal. Ce système comprend un tensioactif non-ionique (P123), un ion simulant les radionucléides (néodyme), une molécule complexante (HDEHP) et un précurseur de silice (TEOS). Ainsi, ce système a fait l'objet d'études approfondies pour élargir le champ d'action du procédé de séparation et pour comprendre les mécanismes en jeu lors de la complexation des ions et de la solubilisation micellaire, puis lors de la formation de la poudre de silice avec des techniques de diffusion, d'imagerie, de spectrométrie et d'analyses de surface.En conclusion, le procédé alternatif de dépollution développé dans cette thèse a permis d'atteindre les objectifs de dépollution et d'expliquer les différents mécanismes qui régissent chaque étape du procédé.Mots-clés : Tensioactifs, Lanthanides, Ligands organophosphorés, Procédé sol-gel, Diffusion des neutrons, wet-STEM / Treatment of aqueous outflows by complexation in micellar media and precipitation with sol-gel processAbstract Being able to deal with aqueous outflows from treatment sites in the Hague is a major environmental issue. These outflows are contaminated with organic substances and elements with residual radioactivity.This work deals with the development and optimization of the process of depolluting, and we aim at removing all pollution from the outflow, and produce a final waste compatible with traditional conditioning matrices in the nuclear area. The separation process consists of two steps: dissolving the pollution in the surfactants micelles, and precipitating a mineral phase via sol-gel transition. Within this thesis, only pollution originating from radionuclides is studied. During the first step, our strategy is to use complexing molecules able to interact with ions and to form mainly solvable complexes at the core of surfactant micelles. Thereafter, the second step consisted to add silica precursor which, after hydrolyse and polycondensation, makes it possible to aggregate those micelles that contain complexes together, and to form a silica phase which precipitates in an in-situ fashion.The goal to depollute the outflow was achieved, and the final waste thus produced is a silica powder that contains the micelles and the pollution which, after calcination, is compatible with conditioning matrices such as glass or concrete. A reference system for which the separation process is optimal was defined throughout various studies. This system contains a non-ionic surfactant (P123), an ion that surrogates radionucleides (neodymium), a complexing agent (HDEHP) and a silica precursor (TEOS). Hence, this system was further studied in order to broaden the application scope of the separation process, as well as to understand the mechanisms involved, during the complexation of the ions and the micellar solubilization and during the formation of the silica powder. This study was performed using diffusion, imaging and spectrometry techniques.To conclude, the alternative depolluting process developed as part of this thesis allowed to achieve the depolluting goals and to explain the different mechanisms that govern each step of the process.Keywords: Surfactants, Lanthanides, Organophosphorous ligands, Sol-gel process, Neutrons scattering, wet-STEM

Ce travail de cette thèse porte sur la dynamique des protéines, accompagnées de leur eau d'hydratation, une couche de solvant autour des protéines vitale pour leur fonction biologique. Chacune de ces deux composantes s'accompagne d'une dynamique qui lui est propre et dont la réunion reforme le paysage énergétique du système biologiquement actif. La mise en application conjointe de la deutération sélective, de la diffusion incohérente de neutrons ainsi que la spectroscopie terahertz a permis d'explorer de manière indépendante la dynamique des protéines et de celles des couches d'hydratation. L'influence de l'état de repliement de la protéine sur sa dynamique a été étudié par diffusion élastique de neutrons. Les protéines globulaires se sont montrées moins dynamiques que ses analogues intrinsèquement désordonnées. Eux même semblent être plus rigides que les protéines dépliées non physiologiques. L'état d'oligomérisation et les conséquences sur la dynamique de ces protéines ont été développés. Les agrégats d'une protéine globulaire se sont avérés être plus flexibles que la forme soluble. A l'inverse, les agrégats d'une protéine désordonnée voient leur dynamique moyenne baisser par rapport à la forme soluble. Ces observations témoignent de la grande diversité de dynamiques à travers le protéome. Les expériences de diffusion incohérente de neutrons sur les couches d'hydratation des protéines globulaires et désordonnées ont permis d'obtenir des informations sur la nature des mouvements de l'eau autour des protéines. Les mesures ont mis en évidence la présence de mouvements translationnels concomitants à l'apparition de la transition dynamique dans les couches d'hydratations, vers 220 K. Les mesures ont de même montré un couplage plus fort entre une protéine désordonnée et son eau d'hydratation que celui entre une protéine globulaire et son eau d'hydratation. La nature de la couche d'hydratation et son influence sur sa dynamique ont été explorés, avec l'utilisation de polymères qui miment le comportement de l'eau et agissent comme source de flexibilité pour la protéine. Pour terminer, la dynamique des groupements méthyles, impliqués dans les modifications dynamiques observées à 150 et 220 K, a été étudiée. / This thesis work focused on the dynamics of proteins, surrounded by their hydration layer, a water shell around the protein vital for its biological function. Each of these components is accompanied by a specific dynamics which union reforms the complex energy landscape of the system. The joint implementation of selective deuteration, incoherent neutron scattering and terahertz spectroscopy allowed to explore the dynamics of proteins and that of the hydration shell. The influence of the folding state of protein on its dynamics has been studied by elastic neutron scattering. Globular proteins were less dynamic than its intrinsically disordered analogues. Themselves appear to be stiffer than non physiological unfolded proteins. The oligomerization state and the consequences on the dynamics were investigated. Aggregates of a globular protein proved to be more flexible than the soluble form. In contrast, aggregates of a disordered protein showed lower average dynamics compared to the soluble form. These observations demonstrate the wide range of dynamics among the proteome. Incoherent neutron scattering experiences on the hydration layer of globular and disordered proteins have yielded information on the nature of water motion around these proteins. The measurements revealed the presence of translational motions concomitant with the onset of the transition dynamics of hydration layers, at 220 K. Measurements have also shown a stronger coupling between a disordered protein and its hydration water, compared to a globular protein and its hydration shell. The nature of the hydration layer and its influence on its dynamics has been explored with the use of polymers that mimic the water behavior and that act as a source of flexibility for the protein. Eventually, the dynamics of methyl groups involved in the dynamical changes observed at 150 and 220 K, was investigated.

Das Peptid Amyloid-beta wird seit vielen Jahren mit der Alzheimer''schen Demenz in Verbindung gebracht, aber die Verbindung zwischen dem Peptid und der Herkunft der Symptome bleibt unklar. Eine neue Hypothese besagt, dass Wechselwirkungen von Mono- oder Oligomeren des Amyloid-beta mit neuronalen Zellmembranen zu Veränderungen der Membran-Doppelschichtsruktur führen und Störungen dynamischer Prozesse in den Membranen verursachen können. Mit Methoden der Röntgen- und Neutronenstreuung wurden die Struktur und Dynamik von Modellmembranen und Änderungen durch den Einfluss des Peptids Amyloid-beta auf die Modellmembranen untersucht. Es konnte gezeigt werden, dass Monomere des Peptidfragments Amyloid-beta 22-40 in anionische Lipidmembranen eingebaut werden. Mittels quasielastischer-inkohärenter Neutronenstreuung wurde die Dynamik von Lipidmembran untersucht. Ein Anteil von 1,5 mol % Amyloid-beta 22-40 in einer Lipidmembran bei 30°C verursacht eine Verringerung der Diffusionskoeffizienten sowohl der Schwerpunktbewegung der Lipide im ns-Bereich als auch der Dynamik der Fettsäurereste im ps-Bereich. Andererseits wird in der Gelphase der Lipidmembran bei 15°C ein Anstieg der Diffusionskoeffizienten beider Prozesse beobachtet. Eine Serie von Lipidproben mit unterschiedlichem Cholesteringehalt und eingelagerten Peptiden Amyloid-beta 1-42 und Amyloid-beta 22-40 wurde Mittels Röntgendiffraktion charakterisiert. Für das Peptid Amyloid-beta 22-40 wurden zwei Positionen gefunden, eine auf der Oberfläche der Membran, eine zweite in der Membran eingelagert. Das Peptid Amyloid-beta 1-42 ist teilweise in die Membran eingelagert und ist in einer 40 mol % Cholesteringehaltige Membrane durch eine einzelne Position modelliert. Zusätzlich wird der Entwurf und die Inbetriebnahme der BerILL Feuchtekammer beschrieben. / The peptide amyloid-beta has long been associated with Alzheimer’s disease; however the link between the peptide and the origin of symptoms is poorly understood. An emerging hypothesis is that monomeric and oligomeric forms of the peptide interact with neuronal membranes, resulting in perturbations in the bilayer structure and in the dynamic processes which take place in the bilayer. Using X-ray and neutron scattering techniques, the structure and dynamics of model lipid membranes and the changes which arise in the presence of amyloid-beta peptide fragments have been studied. Monomers of the peptide fragment amyloid-beta 22-40 were found to intercalate into an anionic lipid bilayer. Through quasi-elastic neutron scattering, dynamics of bilayer lipids were observed. The presence of 1.5 mol % of the peptide results in a decrease in the diffusion coefficients for lipid centre of mass motion on the nanosecond time-scale, as well as for the lipid tail dynamics on the picosecond scale at 30°C. On the other hand, in the gel-phase of the lipid, at 15°C, an increase in the diffusion coefficients for both of these processes was observed. A series of samples with various cholesterol content and either the amyloid-beta 22-40 peptide fragment or the amyloid-beta 1-42 full length peptide was characterized using X-ray diffraction. The amyloid-beta 22-40 peptide was found to populate two positions, on the surface and embedded in the bilayer. The amyloid-beta 1-42 peptide embeds itself into the membrane, and is modelled by a single population for high cholesterol levels (40 mol % cholesterol). In addition, the design and commissioning of the BerILL humidity chamber, a sample environment with precise temperature and humidity control compatible with neutron scattering experiments is presented.

No description available.

Ce manuscrit présente l’étude de transitions de phase quantiques dans l’oxyde BaCo2V2O8, un système antiferromagnétique quasi-unidimensionnel constitué de chaînes d’ions cobalt portant un spin effectif S = 1/2 caractérisé par une forte anisotropie de type Ising. Lors de ce travail, nous avons étudié les propriétés statiques et dynamiques de BaCo2V2O8 sous l’effet de différents paramètres physiques.Notre première étude a porté sur l’effet d’un champ magnétique transverse, i.e. appliqué perpendiculairement à l’axe Ising. Il a été proposé que lors de l’application d’un tel champ, un champ magnétique alterné effectif est induit perpendiculairement à l’axe d’anisotropie et au champ uniforme appliqué. La comparaison d'expériences de diffusion (élastique et inélastique) de neutrons et de calculs numériques nous a permis de montrer que ce champ alterné entre en compétition avec l’anisotropie. Ceci aboutit à une transition de phase originale, dite topologique, que l'on peut modéliser par une théorie quantique des champs nommée « modèle de double sine-Gordon » qui décrit la compétition entre deux excitations topologiques duales. Nous avons pu montrer que BaCo2V2O8 sous champ magnétique transverse était la première réalisation d'une telle théorie.La seconde étude était consacrée à BaCo2V2O8 sous champ magnétique longitudinal, i.e. un champ appliqué parallèlement à l’axe Ising. La dynamique de spins a été sondée grâce à la diffusion inélastique de neutrons et nous avons montré qu’au-dessus d’un champ critique de 4 T, celle-ci semble en accord avec le spectre des fluctuations de spin attendu pour un liquide de Tomonaga Luttinger (TLL). De plus, les calculs numériques ont confirmé que, du fait de l’anisotropie de type Ising dans ce système, la majorité du poids spectral du spectre en énergie est porté par les fluctuations de spins de type longitudinales. Ce résultat est la signature d'un comportement quantique sans analogue classique avec des fluctuations de basses énergies essentiellement longitudinales pilotant la physique du système. Enfin, c’est la première fois que la dynamique de spin dans des chaînes de type Ising a pu être sondée dans cette phase TLL.Les deux dernières études sont préliminaires. Le diagramme de phase de BaCo2V2O8 a été sondé par des mesures calorimétriques sous l’application d’une pression hydrostatique et d’un champ magnétique longitudinal. Afin d’obtenir des pressions allant jusqu’à 10 GPa, nous avons utilisé une cellule à enclumes de diamant. Nous avons effectué des mesures de chaleur spécifique qui nous ont permis de sonder l'effet de la pression sur le Hamiltonien de BaCo2V2O8 au travers de son diagramme de phase $(H, P, T)$. Enfin, nous avons étudié l’effet de la substitution des ions magnétiques Co2+ par des impuretés non-magnétiques Mg2+. Les expériences de diffraction neutronique sous champ longitudinal ont montré que la température et le champ critiques diminuent proportionnellement à la concentration en impuretés. La dynamique de spins à champ magnétique nul a aussi été sondée et révèle l’apparition de modes non-dispersifs, provenant possiblement de l’effet de segmentation des chaînes par les impuretés.En conclusion, nos études expérimentales couplées à des calculs numériques nous ont permis de dévoiler une physique extrêmement riche dans ce composé modèle pour l'étude du magnétisme quantique et des transitions de phase quantiques. / This manuscript is devoted to the study of quantum phase transitions in the BaCo2V2O8 oxide, a quasi-one dimensional antiferromagnet consisting of spin chains of cobalt magnetic ions carrying an effective spin S = 1/2 showing a strong Ising-like anisotropy. To achieve this, we have studied BaCo2V2O8 under the effect of different physical parameters.Our first study concerned the effect of a transverse magnetic field, i.e. applied perpendicularly to the Ising axis. It has been shown that when BaCo2V2O8 is subjected to such a field, an effective staggered magnetic field is induced perpendicularly to both the Ising-axis and the uniform applied field. Using neutron scattering experiments (both elastic and inelastic) compared to numerical calculations, we have proved that this staggered field competes with the Ising-like anisotropy. This leads to a very original quantum phase transition. Our system can actually be mapped onto a quantum field theory called “double sine-Gordon model”, describing the competition between two dual topological excitations. We have thus shown that BaCo2V2O8 under a transverse magnetic field is the first experimental realization of such a theory.The second study was devoted to the effect of a longitudinal magnetic field, i.e. a field applied parallel to the Ising-axis. The spin-dynamics have been investigated by means of inelastic neutron scattering experiments and it has been shown that above a critical field of 4 T, it corresponds to the one expected for a Tomonaga Luttinger liquid phase (TLL). Moreover, numerical calculations have shown that, because of the Ising-like anisotropy in this system, the majority of the spectral weight in the energy spectrum is carried by longitudinal spin fluctuations. This result is the signature of a quantum behavior without classical analogous with low energy longitudinal fluctuations driving the physics of the system. Finally, this is the first time that the dispersion spectrum for an Ising-like spin 1/2 chain could be probed in this TLL phase.The last two studies are preliminary work. The phase diagram of BaCo2V2O8 has been probed by calorimetric measurements under pressure and under a longitudinal magnetic field. Pressures up to 10 GPa have been obtained using a diamond anvil cell. We have then performed specific heat measurements allowing us to investigate the effect of pressure on the Hamiltonian of BaCo2V2O8 through its (H, P, T) phase diagram. Finally, we have also started to study the effect of the substitution of magnetic ions Co2+ by non-magnetic impurities Mg2+. The neutron diffraction experiments under a longitudinal magnetic field have shown that the critical temperature and critical field decrease proportionally to the concentration of impurities. The spin-dynamics at zero-field has also been investigated and reveals the appearance of non-dispersive magnetic modes, which possibly comes from the finite size effect of the spin chains segmented by the non-magnetic impurities.In conclusion, our experimental studies associated to numerical calculations allowed us to unveil a very rich physics in this model compound for the study of quantum magnetism and quantum phase transitions.

No description available.

PEG-lipid stabilized bilayer disks have been found in lipid mixtures containing polyethylene glycol (PEG)-lipids where the combination of a high bending rigidity and low PEG-lipid/lipid miscibility favours disk formation. The disks are planar and circular in shape and their long-term stability is excellent. Theoretical calculations and experimental observations suggest that the micelle forming PEG-lipid are situated at the rim of the aggregate, protecting the hydrophobic lipid chains in the bulk of the aggregate from contact with water. This thesis deals with fundamental aspects concerning the lipid distribution in the disks, as well as with development, optimization, and initial evaluation of the disks as model membranes in partition and interaction studies. Small angle neutron scattering was used to study the partial segregation of components within the bilayer disk. The experiments verified that the PEG-lipids segregate and accumulate at the bilayer disk rim. The proof of component segregation is important from a fundamental point of view and useful, as exemplified in the below-mentioned study of melittin-lipid interaction, when interpreting partition or binding data obtained from studies based on bilayer disks. Today liposomes are often used as model membranes in partition and interaction studies. Using liposomes to predict, e.g., drug partitioning can however have certain drawbacks. In this thesis the disks were proven to be attractive alternatives to liposomes as model membranes in partition studies. The formation of bilayer disks by a technique based on detergent depletion enabled incorporation of a transmembrane protein in the bilayer disks and opened up for the use of disks as model membranes in membrane protein studies. Further, bilayer disks were used in a comparative study focused on the effect of aggregate curvature on the binding of the peptide melittin. Various techniques were used to perform initial evaluations of the bilayer disks as model membranes. Of these, capillary electrophoresis and biosensor-based technology had not been used before in combination with bilayer disks.

This thesis focuses on the study of the interactions between polyelectrolytes and surfactants in aqueous solutions and at interfaces, as well as on the structural changes these molecules undergo due to that interaction. Small–angle neutron scattering, dynamic, and static light scattering were the main techniques used to investigate the interactions in bulk. The first type of polymer studied was a negatively charge glycoprotein (mucin); its interactions with ionic sodium alkyl sulfate surfactants and nonionic surfactants were determined. This system is of great relevance for several applications such as oral care and pharmaceutical products, since mucin is the main component of the mucus layer that protects the epithelial surfaces (e.g. oral tissues). Sodium dodecyl sulfate (SDS) on the other hand, has been used as foaming agent in tooth pastes for a very long time. In this work it is seen how SDS is very effective in dissolving the large aggregates mucin forms in solution, as well as in removing preadsorbed mucin layers from different surfaces. On the other hand, the nonionic surfactant n-dodecyl β-D-maltopyranoside (C12-mal), does not affect significantly the mucin aggregates in solution, neither does it remove mucin effectively from a negatively charge hydrophilic surface (silica). It can be suggested that nonionic surfactants (like the sugar–based C12-mal) could be used to obtain milder oral care products. The second type of systems consisted of positively charged polyelectrolytes and a negatively charged surfactant (SDS). These systems are relevant to a wide variety of applications ranging from mining and cleaning to gene delivery therapy. It was found that the interactions of these polyelectrolytes with SDS depend strongly on the polyelectrolyte structure, charge density and the solvent composition (pH, ionic strength, and so on). Large solvent isotopic effects were found in the interaction of polyethylene imine (PEI) and SDS, as well as on the interactions of this anionic surfactant and the sugar–based n-decyl β-D-glucopyranoside (C10G1). These surfactants mixtures formed similar structures in solutions to the ones formed by some of the polyelectrolytes studied, i.e. ellipsoidal micelles at low electrolyte concentration and stiff rods, at high electrolyte and SDS concentrations. / QC 20100901