Tunable synthesis of Prussian Blue in exponentially growing polyelectrolyte multilayer films.

Polyelectrolyte multilayer (PEM) films have become very popular for surface functionalization and the design of functional architectures such as hollow polyelectrolyte capsules. It is known that properties such as permeability to small ionic solutes are strongly dependent on the buildup regime of the PEM films. This permeability can be modified by tuning the ionization degree of the polycations or polyanions, provided the film is made from weak polyelectrolytes. In most previous investigations, this was achieved by playing on the solution pH either during the film buildup or by a postbuildup pH modification. Herein we investigate the functionalization of poly(allylamine hydrochloride)/poly(glutamic acid) (PAH/PGA) multilayers by ferrocyanide and Prussian Blue (PB). We demonstrate that dynamic exchange processes between the film and polyelectrolyte solutions containing one of the component polyelectrolyte allow one to modify its Donnan potential and, as a consequence, the amount of ferrocyanide anions able to be retained in the PAH/PGA film. This ability of the film to be a tunable reservoir of ferrocyanide anions is then used to produce a composite film containing PB particles obtained by a single precipitation reaction with a solution containing Fe(3+) cations in contact with the film. The presence of PB in the PEM films then provides magnetic as well as electrochemical properties to the whole architecture.journal article2009 Dec 15importe

Identifying Individual T Cell Receptors of Optimal Avidity for Tumor Antigens.

Cytotoxic T cells recognize, via their T cell receptors (TCRs), small antigenic peptides presented by the major histocompatibility complex (pMHC) on the surface of professional antigen-presenting cells and infected or malignant cells. The efficiency of T cell triggering critically depends on TCR binding to cognate pMHC, i.e., the TCR-pMHC structural avidity. The binding and kinetic attributes of this interaction are key parameters for protective T cell-mediated immunity, with stronger TCR-pMHC interactions conferring superior T cell activation and responsiveness than weaker ones. However, high-avidity TCRs are not always available, particularly among self/tumor antigen-specific T cells, most of which are eliminated by central and peripheral deletion mechanisms. Consequently, systematic assessment of T cell avidity can greatly help distinguishing protective from non-protective T cells. Here, we review novel strategies to assess TCR-pMHC interaction kinetics, enabling the identification of the functionally most-relevant T cells. We also discuss the significance of these technologies in determining which cells within a naturally occurring polyclonal tumor-specific T cell response would offer the best clinical benefit for use in adoptive therapies, with or without T cell engineering

Catalytic combustion of inflammable gases with metallic oxides,application in the detection of leak in gas turbines

Ces travaux de thèse s'inscrivent dans la recherche de moyens de prévention des risques d'explosion et de pollution liés à l'exploitation d'installations industrielles telles que les turbines à gaz. Ces travaux, en collaboration avec la firme General ElecTo avoid risks of explosion and pollution in industrial combustion installation, such as gas turbines, the detection of residual explosive gases is required. Therefore, in collaboration with General Electric, the work of this thesis was focused on the de

Catalytic combustion of inflammable gases with metallic oxides,application in the detection of leak in gas turbines

Ces travaux de thèse s'inscrivent dans la recherche de moyens de prévention des risques d'explosion et de pollution liés à l'exploitation d'installations industrielles telles que les turbines à gaz. Ces travaux, en collaboration avec la firme General Electric, portent ainsi sur l'élaboration et l'étude de systèmes catalytiques pouvant entrer dans la fabrication ultérieure d'un capteur de gaz. Son principe de fonctionnement est basé sur la combustion catalytique du gaz à détecter. Les combustibles ayant fait l'objet d'une étude correspondent à ceux rencontrés dans une installation de turbines à gaz, à savoir le méthane, le n-butane (GPL), l'isooctane (essence), le n-décane (fioul), le monoxyde de carbone, l'éthanol et l'octanoate de méthyle (biodiesel). Dans ce type d'installation, le seuil minimal de détection du capteur est fixé à 5% de la LIE (Limite Inférieure d'Explosivité) du combustible. Il a donc été nécessaire de tester l'activité des catalyseurs en introduisant les combustibles en faible concentration (500 6250 ppm). Notre choix de catalyseur s'est porté sur les oxydes simples et mixtes à base de manganèse, de fer et de cobalt. Les pérovskites non-substituées LaBO3 (B = Mn, Fe, Co) et celles substituées de types La0,8A 0,2BO3 (A = Ba ou Sr et B = Mn ou Co) et LaB0,8B 0,2O3 (B = Mn ou Co et B = Fe ou Cu) ont été préparées par une méthode sol-gel. Les oxydes simples et les pérovskites non-substituées ont été imprégnés sur la silice mésoporeuse SBA-15 et la cérine en suivant la méthode dite des deux-solvants . Une étude approfondie par différentes techniques de caractérisation (DRX, RTP, DTP-O2, spectroscopie Mössbauer, RPE, RMN, XPS, etc.) a permis de mettre en évidence de nombreuses relations entre la structure des catalyseurs et leur activité catalytique.To avoid risks of explosion and pollution in industrial combustion installation, such as gas turbines, the detection of residual explosive gases is required. Therefore, in collaboration with General Electric, the work of this thesis was focused on the development and the study of catalytic systems which can be integrated in a future fabrication of a gas sensor. The principle of these sensors is based on the measurement of the gas concentration as a function of the increase in temperature produced by the heat of combustion reaction on the catalytic surface. The combustion of different hydrocarbons (methane, n-butane, isooctane, n-decane) and oxygenated compounds (carbon monoxide, ethanol, methyl octanoate) that are commonly used in gas turbine units was studied. In this type of installation, recent regulations have implemented a sensor response to detect a concentration as low as 5% of the LEL (Lower Explosive Limit) for the above studied fuels. To fulfill this demanding application constraint, the fuels must be introduced at very low concentration (500 6250 ppm) during the catalytic tests. Simple and mixed metal oxides based on manganese, iron and cobalt were chosen as catalysts. Perovskites LaBO3 (B = Mn, Fe, Co) and substituted perovskites La0,8A 0,2BO3 (A = Ba or Sr and B = Mn or Co) and LaB0,8B 0,2O3 (B = Mn or Co and B = Fe or Cu) were prepared using a sol-gel process. Simple oxides and perovskites LaBO3 were supported on a mesoporous silica SBA-15 and on ceria according to the two-solvents method. A complete set of physico-chemical characterisations of the different catalysts was realized using several techniques (XRD, TPR, TPD-O2, EPR, NMR, XPS spectroscopy, etc.) to correlate the structure of the materials with their catalytic activities

Combustion catalytique de gaz inflammables à l aide d oxydes métalliques (application à la détection de fuites dans des turbines à gaz)

Ces travaux de thèse s inscrivent dans la recherche de moyens de prévention des risques d explosion et de pollution liés à l exploitation d installations industrielles telles que les turbines à gaz. Ces travaux, en collaboration avec la firme General Electric, portent ainsi sur l élaboration et l étude de systèmes catalytiques pouvant entrer dans la fabrication ultérieure d un capteur de gaz. Son principe de fonctionnement est basé sur la combustion catalytique du gaz à détecter. Les combustibles ayant fait l objet d une étude correspondent à ceux rencontrés dans une installation de turbines à gaz, à savoir le méthane, le n-butane (GPL), l isooctane (essence), le n-décane (fioul), le monoxyde de carbone, l éthanol et l octanoate de méthyle (biodiesel). Dans ce type d installation, le seuil minimal de détection du capteur est fixé à 5% de la LIE (Limite Inférieure d Explosivité) du combustible. Il a donc été nécessaire de tester l activité des catalyseurs en introduisant les combustibles en faible concentration (500 6250 ppm). Notre choix de catalyseur s est porté sur les oxydes simples et mixtes à base de manganèse, de fer et de cobalt. Les pérovskites non-substituées LaBO3 (B = Mn, Fe, Co) et celles substituées de types La0,8A 0,2BO3 (A = Ba ou Sr et B = Mn ou Co) et LaB0,8B 0,2O3 (B = Mn ou Co et B = Fe ou Cu) ont été préparées par une méthode sol-gel. Les oxydes simples et les pérovskites non-substituées ont été imprégnés sur la silice mésoporeuse SBA-15 et la cérine en suivant la méthode dite des deux-solvants . Une étude approfondie par différentes techniques de caractérisation (DRX, RTP, DTP-O2, spectroscopie Mössbauer, RPE, RMN, XPS, etc.) a permis de mettre en évidence de nombreuses relations entre la structure des catalyseurs et leur activité catalytique.To avoid risks of explosion and pollution in industrial combustion installation, such as gas turbines, the detection of residual explosive gases is required. Therefore, in collaboration with General Electric, the work of this thesis was focused on the development and the study of catalytic systems which can be integrated in a future fabrication of a gas sensor. The principle of these sensors is based on the measurement of the gas concentration as a function of the increase in temperature produced by the heat of combustion reaction on the catalytic surface. The combustion of different hydrocarbons (methane, n-butane, isooctane, n-decane) and oxygenated compounds (carbon monoxide, ethanol, methyl octanoate) that are commonly used in gas turbine units was studied. In this type of installation, recent regulations have implemented a sensor response to detect a concentration as low as 5% of the LEL (Lower Explosive Limit) for the above studied fuels. To fulfill this demanding application constraint, the fuels must be introduced at very low concentration (500 6250 ppm) during the catalytic tests. Simple and mixed metal oxides based on manganese, iron and cobalt were chosen as catalysts. Perovskites LaBO3 (B = Mn, Fe, Co) and substituted perovskites La0,8A 0,2BO3 (A = Ba or Sr and B = Mn or Co) and LaB0,8B 0,2O3 (B = Mn or Co and B = Fe or Cu) were prepared using a sol-gel process. Simple oxides and perovskites LaBO3 were supported on a mesoporous silica SBA-15 and on ceria according to the two-solvents method. A complete set of physico-chemical characterisations of the different catalysts was realized using several techniques (XRD, TPR, TPD-O2, EPR, NMR, XPS spectroscopy, etc.) to correlate the structure of the materials with their catalytic activities.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Acidity versus metal-induced Lewis acidity in zeolites for Friedel–Crafts acylation

International audienceAcid catalysts including Ni, Ag and Fe-loaded zeolites of different structures were prepared either via cationic exchange or impregnation techniques from pristine H-zeolites (BEA, and MFI). Their catalytic activity was evaluated in the liquid-phase Friedel–Crafts acylation of anisole with propanoic acid. It turned out that, whatever the doping procedure was, the zeolite loaded with transition metals led to considerable decrease in propanoic acid conversion, regardless of the nature or the metal content. However, the extent of this detrimental effect followed the order: Ag+ > Ni2+ > Fe3+.Pristine acidic zeolites were not only found to be the most active, but also to be the most selective toward ortho- and para-acylation products. H-ZSM-5 zeolites yielded the highest intrinsic activity, with TOF values of 0.09 h−1. The catalyst activity proved to be essentially attributed to the density and accessibility of Brønsted acid sites, playing a key role in the activation of the reactants. Brønsted sites are proposed to be the most likely catalytic species for performing this Friedel–Crafts acylation.Des cations métalliques (Ni, Ag et Fe) ont été incorporés au sein de zéolithes BEA et ZSM-5 par des techniques d'échange cationique et d'imprégnation afin d'obtenir de nouveaux catalyseurs acides solides. Ces matériaux ont ensuite été testés dans une réaction d'acylation de Friedel–Crafts entre l'anisole et l'acide propanoïque en phase liquide. Il s'est avéré que l'ajout de métaux de transition au sein de la structure zéolithique entraîne une diminution considérable de la conversion, indépendamment de la nature ou de la quantité de métal introduite. Dans des conditions catalytiques similaires, les zéolithes parentes présentent une meilleure activité intrinsèque (TOF), en particulier H-ZSM-5, avec une production plus élevée de produits d'acylation (ortho- et para-), surpassant ainsi les performances catalytiques des zéolithes dopées par des métaux. L'accessibilité et la densité de sites acides de Brønsted se sont avérées déterminantes pour ce type de réaction

On the relationship between the basicity of a surface and its ability to catalyze transesterification in liquid and gas phases: the case of MgO

International audienceGas or liquid phase transesterification reactions are used in the field of biomass valorization to transform some platform molecules into valuable products. Basic heterogeneous catalysts are often claimed for these applications but the role of basicity in the reaction mechanism depending on the operating conditions is still under debate. In order to compare the catalyst properties necessary to perform a transesterification reaction both in liquid and gas phases, ethyl acetate and methanol, which can be easily processed both in these two phases, were chosen as reactants. The catalyst studied is MgO, known for its basic properties and its ability to perform the reaction. By means of appropriate thermal treatments, different kinds of MgO surfaces, with different coverages of natural adsorbates (carbonates and hydroxyls groups), can be prepared and characterized by means of CO2 adsorption followed by IR spectroscopy and hept-1-ene isomerization model reaction. New results on the basicity of the natural MgO surface (covered by carbonate and hydroxyl groups) are first given and discussed. The catalytic behavior in the transesterification reaction is then determined as a function of the adsorbate coverage. It is shown that the transesterification activity in the liquid phase is directly correlated with the kinetic basicity of the surface in agreement with the mechanism already proposed in the literature. On the reverse, no direct correlation with the basicity of the surface was established with the transesterification activity in the gas phase. A very high activity, in the gas phase, was observed and discussed for the natural surface pre-treated at 623 K. Preliminary DFT modeling of ester adsorption and methanol adsorption capacity determination were performed to investigate plausible reaction routes

Nanosized Layered TOT Magnesium-Silicates: Equilibrium Morphologies and Surface Speciation, a Computational and Experimental Study

International audienceThe morphology, surface speciation, NMR, and IR spectroscopic properties of nanosized layered magnesium silicate isostructural to talc at equilibrium in an aqueous environment were computed from first principles. The theoretical predictions were successfully compared with experimental results obtained on a commercial magnesium silicate hydrate, revealing insights relevant for understanding the catalytic and other surface properties of such materials of promising industrial applications

Influence of acid–base properties of Mg-based catalysts on transesterification: role of magnesium silicate hydrate formation

International audienceThe transesterification reaction assisted through heterogeneous basic catalysis was thoroughly studied because of its importance in transforming biomass, as for biodiesel production or lactone opening. As catalysts with the strongest basic properties are not always the most efficient ones, a series of magnesium-based materials, exhibiting a large range of acido–basic properties, was investigated. Moreover, in order to compare gas and liquid phases operating conditions, a model reaction (transesterification of ethyl acetate with methanol) was chosen. It appears that gas phase transesterification (at 393 K) requires strong basic sites, whereas magnesium silicate, exhibiting moderate basicity together with acidic properties, is a very reactive catalyst in the liquid phase (at 333 K) depending on its preparation method. The set of experimental data (XRD, XPS, DRIFTS, MEB, 29Si and 25Mg NMR) demonstrated that a magnesium silicate hydrate structure (MSH) is formed at the surface of the most active silicates. It is thus concluded that different mechanisms operate under gas and liquid conditions, and that among the magnesium silicate materials, the MSH phase exhibits specific acido–basic properties beneficial to this kind of reaction