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Carboxylic acids are promising candidates for new sustainable strategies in organic synthesis. In this paper, we ascertain the potential of ultrasound for the hydrolysis of nitriles into carboxylic acids through the study of key parameters of the reaction: pH, hydrolysis medium, reaction time and activation technique. The positive influence of ultrasound under basic conditions is due to more than mechanical effects of cavitation. Indeed, the rate of hydrolysis is dramatically increased under sonication in NaOH solutions. A radical mechanism involving the oxide anion radical O(*-) is proposed.

Several earlier studies of the electrochemical oxidation of ferrocene (Fc) in room-temperature ionic liquids revealed an essentially nonlinear dependence of the oxidation current on the Fc concentration in its relatively dilute solutions, with its formally calculated diffusion coefficient strongly increasing with the concentration. Since no plausible mechanism leading to this very unusual finding had been proposed, our study of Fc solutions in 1-butyl-3-methylimidazolium triflimide, [BMIM][NTf(2)], was performed to verify whether the above observation originated from an incorrect determination of the dissolved Fc concentration. Our observations have demonstrated that reliable control of the Fc concentration in solution is complicated by factors such as the low amount of Fc used to prepare small-volume solutions or the great difficulty to dissolve completely a solid powder in a solvent with an extremely high viscosity. An unexpected additional complication is related to a sufficiently high volatility of Fc which manifests itself even at room temperature and especially at elevated temperatures or/and in the course of vacuum treatment of its solutions or its solid powder. Parallel measurements of electrochemical responses and UV-visible spectra for several series of Fc solutions of various concentrations (prepared with the use of different procedures) have shown a perfect parallelism between the peak current and the intensity of the absorption band in the range of 360-550 nm, leading us to the conclusion of a linear relationship between the oxidation current and the molecularly dissolved Fc concentration. The relations of these measured characteristics with the estimated Fc concentration in these solutions have demonstrated a much greater dispersion (attributed to the difficulty of a precise measurement of the latter) but without a significant deviation from the linearity in general. This finding has allowed us to estimate the diffusion coefficient of this species: D = (1.7 +/- 0.2) x 10(-7) cm(2)/s. The extinction coefficients for the maximum of the absorption band (at 440 nm) of Fc have been compared for a series of solvents: [BMIM][NTf(2)], acetonitrile, THF, heptane, CH(2)Cl(2), ethanol, and toluene. A simple method to estimate reliably the concentration of solute Fc in ionic liquids based on spectroscopic measurements has been proposed, owing to the proximity of Fc absorption properties for a great variety of solvents.

International audience; We study the aggregation of charged plate-like colloids, Na-montmorillonite clays, in the presence of ionenes, oppositely charged polymer chains. The choice of the charged polymer allows tuning its linear charge density to match/mismatch the average charge separation on the clay surfaces. We assess the nanoscale structure of the aggregates formed by small-angle X-ray and neutron scattering. The nanoscale features of the formed clay aggregates are dominated by the presence of a stacking peak, giving clear evidence for the formation of clay tactoids, that is, a face-to-face aggregation geometry of the clay platelets. The chain charge density of ionenes influences not only the stacking repeat distance within the clay tactoids but also the extent of stacking and abundance of the tactoids. We may distinguish two regimes as a function of clay and ionene polymer charge densities (ρc and ρp, respectively). The first regime applies to ρp > ρc and ρp ≈ ρc, that is, for highly and “matching” charged chains. Under these conditions, the intercalated chains lie in a flat conformation within the tactoids, irrespective of the ionic strength (within the range studied, i.e., up to 0.05 M NaBr). For weakly charged chains, ρp < ρc, undulation of the ionene chains within the tactoid is seen. The degree of undulation increases with ionic strength due to the decreasing persistence length of the ionene chains. The extent of stacking (5–10 platelets per tactoid) is a general feature of all the systems, and its origin remains unknown. The system corresponding to the closest match in charge separations on the clay surface and on the polymer chain (ρp ≈ ρc) features the highest abundance of tactoids. This coincides with the highest macroscopic density as deduced from simple visual inspection of sediment volumes. This leads to the open question regarding the link between the density at the nanoscale and the macroscopic density and sedimentation behavior of the aggregate.

International audience; S-nitrosothiols (RSNOs) are very important biomolecules that play crucial roles in many physiological and physiopathological processes. They act as NO-donors and are candidates for future medicines. Their identification and quantitation are therefore important for biomedical applications. One, two or more RSNOs can then be combined to design a drug and therefore, the quantification of each is important to establish an acceptable quality control process. Till date, miniaturized devices have been used to detect RSNOs based on their total quantitation without a preceding separation step. This study reports on an original and integrated microdevice allowing for the successive electrokinetic separation of low molecular weight RSNOs, their decomposition under metal catalysis, and their quantitation by amperometric detection of the produced nitrite in the end-channel arrangement, leading to their quantitation in a single run. For this purpose, a commercial SU-8/Pyrex microfluidic system was coupled to a portable and wireless potentiostat. Different operating and running parameters were optimized to achieve the best analytical data, allowing for an LOD equal to 20 μM. The simultaneous separation of S-nitrosoglutathione and S-nitrosocysteine was successfully obtained within 75 s. The proposed methodology using SU-8/Pyrex microfluidic devices opens new possibilities to investigate future drug candidates for NO-donors.

International audience; A new dismountable and reusable microchip for electrophoretic separation coupled to amperometric detection was developed. For this purpose, a new home made three-microbands electrode system was developed and microfabricated based on screen-printing for the inclusion of graphite/polydimethylsiloxane (C-PDMS) composite in microchannels down to 30 μm width. The composition of the composite as well as the fabrication methodology were optimized for an easy handling and an optimized electrochemical behavior. The electrochemical characterization of this composite material was first performed in bulk format (disc-shaped electrode, 6 mm diameter). It was then transposed to the micrometric scale for its integration in an original glass-NOA81®-PDMS microfluidic device allowing for reversible sealing. The microband electrodes were characterized by scanning electron microcopy and cyclic voltammetry, illustrating a good control of the microelectrode width. Then, the analytical performances of the C-PDMS composite microelectrodes were evaluated using Ru(NH3)63+ and FcMeOH as model electroactive molecules. The electrophoretic separation and quantitation of Ru(NH3)63+ were then performed in a background electrolyte made of hydrochloric acid and sodium chloride, leading to a LOD and a LOQ of 3.4 μmol L−1 and 11.3 μmol L−1, respectively. The re-openable NOA-based microdevice permits to regenerate the electrode surface by simply repositioning the microband on a new spot, allowing for robust analysis in a reusable system.

International audience; Oxalate-based aqueous media represent one of the rare options for solubilizing macroscopic amount of niobium (Nb) and tantalum (Ta) without using toxic fluoride-based mixtures. Recent progress in the hydrometallurgy of Nb and Ta also highlighted the potential of oxalate-nitrate media for the separation of Nb and Ta. Nonetheless, the resulting purified aqueous solutions, containing Nb or Ta in HNO3-H2C2O4 mixtures, need to be further processed in order to yield Nb and Ta solid products that can be commercialized. Furthermore, oxalic acid is relatively expensive in the frame of the hydrometallurgy of Nb and its recycling is necessary. In this study, the precipitation of Nb and Ta, as well as their usual minor impurities (Ti and Fe), from oxalic-nitric acid solutions has been investigated for the first time. Neutralization of Nb-HNO3-H2C2O4 mixtures to pH 7-8 by concentrated NaOH or NH4OH was found to be effective at decomposing the oxalate complexes ([NbO(C2O4)3] 3-and [NbO(C2O4)2(H2O)]-) and precipitating Nb in the form of Nb2O5·nH2O while leaving the Page 2/27 oxalate ions in solution. Taking advantage of the solubility difference between nitrate and oxalate salts, the subsequent concentration of the filtrates yields to the recovery of the oxalates as Na2C2O4 or (NH4)2C2O4·H2O and a concentrated solution of sodium or ammonium nitrate. The developed method exhibits high precipitation yields (>99.9%) for Nb and Ta and high recovery yields (>99%) for the nitrates and oxalates. The process was optimized at the laboratory scale (~50 mL) and then validated on industrial Nb and Ta solutions (~225 L) with successful production of purified Nb2O5·nH2O and Ta2O5·nH2O, recovery of the oxalates in the form of Na2C2O4 or (NH4)2C2O4·H2O and a concentration solution of nitrates. Taking together, the proposed precipitation method and the fluoride-free liquid-liquid Nb-Ta separation recently reported pave the way for more suitable hydrometallurgical processes for Nb and Ta.

The production of high purity niobium (Nb) or tantalum (Ta) compounds still relies on processes that require highly acidic conditions and concentrated HF or NH4F solutions. Recent progress in the chemistry of group V elements, along with the evolution of the environmental concerns, call for the development of more sustainable industrial processes for these strategic elements. In sharp contrast with the historical fluoride approach chosen by the Nb and Ta refining industry, there has been a recent surge in the literature concerning the chemistry of these elements in diluted alkaline or oxalate media. We here propose an innovative liquid-liquid extraction process that is amenable to separate Nb and Ta from alkaline feed solutions, can be operated at low acidity and that does not require any fluoride-based chemical. The developed strategy is as follows: first, Nb and Ta are co-extracted from their alkaline solution (pH 12) using a quaternary ammonium salt (Aliquat® 336) dissolved in an organic diluent; then, Nb is selectively back-extracted in a mixture of diluted nitric and oxalic acids; and finally, Ta is stripped in a diluted nitric media. The process also affords purifying Nb from Ti, Fe and Na. Following an optimization at laboratory scale, the full process has been validated during continuous running tests (160 h at 1.4 L h−1) using industrial Nb-Ta caustic solutions coming from the development of the so-called Maboumine process. The developed process works at room temperature, low acidity ([H+] 20 wt% Ta) even when starting from a diluted feed (39 ppm Ta). The proposed strategy paves the way for new Nb and Ta hydrometallurgical processes operating under mild chemical environments and represents a concrete alternative to the current fluoride-intensive industrial methods.

International audience; Introduction : The development and optimization of antibody drug conjugates (ADCs) rely on improving their analytical and bioanalytical characterization, by assessing critical quality attributes (CQAs). Among the CQAs, the glycoprofile, drug load distribution (DLD), the amountof unconjugated antibody (D0), the average drug-to-antibody ratio (DAR), the drug conjugation sites and the residual drug-linker and related product proportions (SMDs) in addition to high and low molecular weight species (H/LMWS) are the most important ones.Areas covered : The analytical and structural toolbox for the characterization of 1st, 2d and 3d generation ADCs was significantly extended in the last 3 years. Here, we reviewed state-ofthe-art techniques, such as liquid chromatography, high resolution native and ion mobility mass spectrometry, multidimensional LC and capillary electrophoresis hyphenated to mass spectrometry, reported mainly since 2016.Expert commentary : These emerging techniques allow a deep insight into important CQAs that are related to ADC Chemistry Manufacturing and Control (CMC) as well as an improved understanding of in vitro and in vivo ADC biotransformations. This knowledge and the development of quantitative bioanalytical assays will continue to contribute to earlydevelopability assessment for the optimization of all the ADC components (i.e., antibody, drug, and linker) and help to bring next-generation candidate ADC into the clinic and hopefully to the marke

The sealing of microfluidic devices remains a complex and time-consuming process requiring specific equipment and protocols: a universal method is thus highly desirable. We propose here the use of a commercially available sealing tape as a robust, versatile, reversible solution, compatible with cell and molecular biology protocols, and requiring only the application of manually achievable pressures. The performance of the seal was tested with regards to the most commonly used chip materials. For most materials, the bonding resisted 5 bars at room temperature and 1 bar at 95 °C. This method should find numerous uses, ranging from fast prototyping in the laboratory to implementation in low technology environments or industrial production.

In quantum dot (QD) solar cells, the ex situ sensitization of wide band gap semiconductors (WBSCs) makes it possible to control the shape and the passivation of the nanosized sensitizer. Hence, ex situ techniques can be used to investigate how the band gap of the sensitizers affects the performance of quantum dot solar cells. The latter can be precisely controlled in 1D confined structures such as quasi-2D nanoplatelets (NPLs), the thickness of which is defined with an atomic precision. In this work, we tested and thoroughly characterized the attachment of 7, 9 and 11 monolayers thick CdSe NPLs (as well as QDs for the sake of comparison) to ZnO and to TiO2 nanorods. A crucial point of the ex situ techniques is the choice of bifunctional ligands that link the nanosized sensitizers to the WBSCs. Besides the well-known mercaptopropionic acid, we also studied two ‘atomic linkers’ (OH− and SH−) to minimize the distance between the sensitizer and the oxide. The as-prepared systems have been analyzed by UV/VIS absorption and Raman spectroscopy. Among them, SH− was found to be the most versatile linker that enabled the efficient attachment of all types of CdSe nanocrystals on ZnO and TiO2 nanorods. Fil: Szemjonov, A.. PSL Research University; Francia. Centre National de la Recherche Scientifique; Francia Fil: Tasso, Mariana Patricia. Laboratoire de Physique Et D'etude Des Materiaux; Francia. Centre National de la Recherche Scientifique; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Ithurria, S.. Laboratoire de Physique Et D'etude Des Materiaux; Francia Fil: Ciofini, I.. PSL Research University; Francia. Centre National de la Recherche Scientifique; Francia Fil: Labat, F.. PSL Research University; Francia. Centre National de la Recherche Scientifique; Francia Fil: Pauporté, T.. PSL Research University; Francia. Centre National de la Recherche Scientifique; Francia

Extraction of tungstate species as highly charged polyoxometalates has been performed with hydrotalcite. An optimum pH around 5 has been determined, correlated with the stability domain of heptatungstate species. Two mechanisms have been shown from in situ infrared spectroscopy and zeta potential measurements: exchange of carbonate ions by heptatungstate species and adsorption as inner-sphere surface complexes. The presence of nitrate, chloride, and sulfate has no effect on the extracted fraction and it was concluded that the extraction is selective toward these anions. The regeneration of the solid was performed with a solution of carbonate sodium at pH 10.

The environmental fate of the tungstate (VI) oxyanion [ e.g. mono tungstate and several polytungstate, generally expressed by W (VI)] is largely controlled by sorption on soil minerals, especially on iron oxide minerals. Molecular scale evaluation of W (VI) retention on iron oxides in the presence of competing oxyanions is scarce in literature. Here we report surface interaction mechanisms of W (VI) on hematite in the presence of phosphate (P) using macroscopic and in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopic experiments. Batch sorption experiments were conducted using 2 g L−1 hematite and 100 μM W (VI) and P, in single ion system and in binary mixtures as a function of pH (4–11). In situ ATR-FTIR spectroscopic evaluation of P and W (VI) sorption on hematite was also carried out. The results from macroscopic experiments indicated that W (VI) sorption on hematite was not affected by P when W (VI) was added first. The influence of P on W (VI) sorption was noticed when W (VI) & P were added simultaneously or P was added first. The in situ ATR-FTIR spectroscopic data corroborated these findings. In addition, the spectroscopic data revealed that in the presence of P, the surface complexation mode of W (VI) differed as noted from either the absence of W O antisymmetric infrared (IR) band or the W O W stretching band. This study provides useful information on molecular level understanding of W (VI) surface complexation on hematite in the presence of competing ions such as P.

AISI 304L is used in Sudoscan(TM) technology (Impeto Medical Inc.) for the early diagnosis of small fiber neuropathy caused by type-2 diabetes or cystic fibrosis. In a recent paper, several substitute electrodes were analyzed, among which the biocompatib

The enzyme glucosamine-6-phosphate synthase (GlmS) is an important point of metabolic control in biosynthesis of amino sugar-containing macromolecules and is therefore a potential target in order to design antibacterial and antifungal drugs. It has two oligomerization states, which are the active dimer and the inactive hexamer. For the first time, the potential of CE to separate and quantify the two forms was studied. After incubating GlmS with the d-glucosamine 6-phosphate (GlcN6P) inhibitor, an electrolyte based on sodium phosphate at pH 7.2 and an ionic strength of 100mM plus GlcN6P (either 2 or 20mM) allowed the hexamer-dimer separation. However, the displacement of the dimer/hexamer equilibrium during the analysis time prevented any improvement of the resolution when varying the effective separation length or the temperature of the analysis. Therefore, the use of a short-end CE method allowed the decrease in the analysis time to about 1min. Some parameters such as the temperature and the time of incubation and the ratio of the inhibitor and enzyme concentrations were studied. Then, it was also possible to test, very rapidly and with a very small amount, some molecules having an inhibition potential for the GlmS enzyme (arabinose-5-phosphate oxime, 2-amino-2-deoxy-d-glucitol 6-phosphate, and glucose-6-phosphate).

International audience; This is an overview of the electrochemical characterization of nickel and stainless steel as electrodes in medical devices for the early diagnosis of small fiber neuropathy that originates from type-2 diabetes or cystic fibrosis. The electrical current responses obtained during the clinical tests are related to the amount of chloride present on the sweat. Stainless steel electrodes are now used to replace nickel because this later not only presents problems with chloride sensitivity but its contact with skin can cause possible allergic reactions for some patients. For the above reasons, several types of stainless steels were studied. It was shown that some of them perform well and have lower costs than Ni electrodes. We discuss the state of the art of the electrochemical studies conducted with nickel and steels under physiological or biomimetic conditions and discuss the advantages of a particular steel over the others depending on the conditions, especially chloride concentration.

International audience

International audience; The influence of hydroxybenzoic acids (HAH$_n$), namely $p$-hydroxybenzoic acid (4 hydroxybenzoic acid, HPhbH) and protocatechuic acid (3,4-dihydroxybenzoic acid, HProtoH2), on the adsorption of europium(III) onto $\alpha$,$\gamma$ Al$_2$O$_3$ particles is studied as a function of acid concentration. After measuring the adsorption edge of the Eu(III)/ $\alpha$,$\gamma$ Al$_2$O$_3$ binary system, and using the previously studied binary component system Eu(III)/HAH$_n$—Moreau et al. (2015) Inorg. Chim. Acta 432, 81—, and HAH$_n$/ $\alpha$,$\gamma$ Al$_2$O$_3$—Moreau et al. (2013) Colloids Surf. A 435, 97—, it is evidenced that HPhbH does not enhance Eu(III) adsorption onto $\alpha$,$\gamma$ Al$_2$O$_3$ in the Eu(III)/HPhbH/ $\alpha$,$\gamma$ Al$_2$O$_3$ ternary system. Conversely, HProtoH$_2$ enhances Eu(III) adsorption onto $\alpha$,$\gamma$ Al$_2$O$_3$ in the Eu(III)/HProtoH$_2$/ $\alpha$,$\gamma$ Al$_2$O$_3$ ternary system. Adsorption of the acids are also found higher in the Eu(III)/acid/ $\alpha$,$\gamma$ Al$_2$O$_3$ ternary systems as compared with the corresponding binary systems assessing synergetic effects. For high HPhbH concentrations a ternary surface species involving $\equiv$AlOH surface sites, Eu(III), and PhbH$^–$ is evidenced by time-resolved luminescence spectroscopy (TRLS). However, in the Eu(III)/HProtoH$_2$/ $\alpha$,$\gamma$ Al$_2$O$_3$ ternary system, chemical environment of Eu(III) is found to be very close to that in the Eu(III)/HProtoH2 binary system. Ternary surface species could not be evidenced in the Eu(III)/HProtoH$_2$/ $\alpha$,$\gamma$ Al$_2$O$_3$ ternary system with TRLS because of the very short decay time of Eu(III) in the presence of protocatechuic acid.

International audience; Complexation of Eu(III) by two hydroxybenzoic acids, namely p-hydroxybenzoic acid (4 dihydroxybenzoic, HPhbH), and protocatechuic acid (3,4-dihydroxybenzoic, HProtoH2), is studied by time-resolved luminescence spectroscopy (TRLS) in mildly acidic solution. Comparable formation constants are determined at 0.1 mol/L NaCl for EuPhbH[2+] – log10β°(EuPhbH[2+]) = 2.18 ± 0.09 (1sigma) – and 0.01 mol/L NaCl for EuProtoH2[2+] – log10β°(EuProtoH2[2+]) = 2.72 ± 0.07 (1sigma). The stoichiometry and carboxylate complexation of the EuProtoH2[2+] complex is ascertained by varying both pH and ligand concentration. The luminescence decay time of EuPhbH[2+] (τ = 107 ± 5 µs) is comparable with that of Eu(H2O)n[3+] (τ = 110 ± 3 µs), suggesting that luminescence quenching processes compensate the expected increase in decay time due to the dehydration associated with complexation. For EuProtoH2[2+], the luminescence decay time is even shorter (τ = 20 ± 5 µs), evidencing intricate quenching processes.

International audience; One of the present challenges for the commercialisation of planar solid oxide fuel cell is the reduction of its operating temperature, which requires the optimisation of the electrolyte nature and ionic conductivity. Thin layer technology seems suitable to decrease the electrolyte resistance at lower operating temperatures. Bilayered electrolytes are proposed and studied in terms of electrical performance. They are constituted of a gadolinia-doped ceria (GDC) layer (the most suitable candidates for IT solid oxide fuel cells (SOFC) in terms of ionic conductivity) protected by an ultra-thin YSZ layer (as electronic barrier). This work analyses the feasibility of bilayered GDC/YSZ electrolyte elaborated by DC magnetron spectroscopy. The bilayer was deposited on the state-of-the-art SOFC porous cathode, strontium-doped lanthanum manganite (LSM). The analysis of the electrical properties of such layers was performed by impedance spectroscopy. Experimental difficulties in order to obtain reliable results and interpretations are discussed.

Cloud-point extraction (CPE) was used with lipophilic chelating agent to extract uranium(VI) from aqueous solutions. The methodology used is based on the formation of metal complexes soluble in a micellar phase of a non-ionic surfactant, Triton X-114. The metal ions complexes are then extracted into the surfactant-rich phase at a temperature above the cloud-point temperature. The influence of surfactant concentration on extraction efficiency was studied and the advantage of adding 8-hydroxyquinoline (8HQ) as lipophilic chelating agent was evidenced. High extraction efficiency was observed, indicating the feasibility of extracting U(VI) using CPE. This study describes a four-step process—(1) extraction, (2) thermo-induced phase splitting, (3) back-extraction and (4) second phase splitting—for the recovery of uranium from water. In our conditions, the extraction yield is quantitative and the concentration factor obtained is superior to 100. After stripping with a diluted nitric acid solution (pH < 1), the system can be recycled through a new four-step cycle. Copyright © 2006 Society of Chemical Industry

In order to adapt the anodisation technique to SOFC application, zirconium and zirconium–niobium alloys were tested in various electrolytic media and applied potentials (up to 420 V). The elaborated ZrO 2 insulating layers were characterised in situ by electrochemical impedance spectroscopy and their thicknesses were determined as ranging up to 1 μm. The effect of thermal annealing treatment of layers prepared in various experimental conditions was investigated by X-ray diffraction (XRD) and solid-state electrochemical impedance spectroscopy in a planar configuration. The effect of the growing conditions on significant parameters such as zirconia crystallite size, zirconia conductivity and activation energy were deduced up to 800 °C. The possibility of using the anodisation process for fuel cell devices is discussed. This study demonstrates that it surely requires the use of more efficient dopants, such as yttria.

International audience; In the present paper, we validate and assess a correlation functional based on the so-called meta generalized gradient approximation, whose form and parameters are entirely derived only from first-principles criteria. In particular, we have carried out a detailed comparison with the most common, parametrized correlation functionals. Next, we propose a new model in which the correlation functional proposed by Kriger, Chen, Iafrate, and Savin is integrated in a hybrid Hartree-Fock/density functional theory scheme. In such approach only one, or two in the G2-optimized version, parameters are adjusted on experimental data, all the others being derived from purely theoretical considerations. The results obtained for a set of molecular properties, including H-bonded complexes, proton transfer model, SN2 reaction and magnetic properties, are satisfactory and comparable, if not better, with those delivered by the most common functionals including heavy parametrization. The way in which the whole functional is derived and the few empirical parameters used make the new exchange-correlation functional widely applicable.

Effects of the averaging over disorder realizations (samples) on the phase behavior are analyzed in terms of the mean field approximation for the random field Ising model with infinite range interactions. It is found that the averaging is equivalent to a drastic modification in the statistics of the quenched variables. In its turn, this lowers the critical temperature of a second-order phase transition or, depending on the sampling, even suppresses the ordered phase. Possible first order transitions are shown to be softened by the sample averaging. Common issues and differences in the interpretation of these effects in the context of the simulation and experimental studies are discussed.

International audience; Adsorption of three phenolic acids, namely parahydroxybenzoic acid (4-hydroxybenzoic acid, H$_2$Phb), protocatechuic acid (3,4-dihydroxybenzoic acid, H$_2$Proto) and gallic acid (3,4,5-trihydroxybenzoic acid, H$_2$Gal) onto $\alpha$,$\gamma$-Al$_2$O$_3$ particles was studied vs. ligand concentration at pH 5.0, and vs. pH. The oxide surface was characterized with both potentiometric titrations and electrophoretic measurements; a difference in the point of zero salt effect (PZSE) and the isoelectric point (IEP) was evidenced, which could be attributed to the presence of impurities or to the heterogeneity of the oxide. The potentiometric titration experiments lead to the determination of a PZSE of 8.5. Moreover, the particular shape of the curves were fitted in the framework of the constant capacitance model (CCM), using FITEQL 4.0 software, to determine the oxide parameters (protolytic properties and site density). The electrophoretic measurements were fitted in the framework of the double diffuse layer model (DLM) and an IEP of 9.5 was determined. The constant-pH isotherms of the acids were fitted using the CCM. Constant-pH isotherms of H$_2$Gal and H$_2$Proto onto the Al$_2$O$_3$ surface sites at pH 5 were similar. Two adsorption sites of different affinities were clearly evidenced for H$_2$Gal and can also be proposed for H$_2$Proto. H$_2$Phb showed a lower affinity for the surface than the two other acids, as the logK$_{sorb}$ for H$_2$Phb is one and a half time lower than the one for H$_2$Proto when adsorption is described with one adsorption site. As expected for a carboxylic acid, adsorption of H$_2$Phb decreased with pH and experimental data were well fitted using three adsorbed species $\equiv$MOH$_2$H$_2$Phb$^+$, $\equiv$MHPhb$^−$, and $\equiv$MPhb$^−$). Adsorption of H$_2$Proto and H$_2$Gal did not change significantly upon increasing pH, meaning that the different functional groups on the aromatic ring (carboxylate and phenolate) were involved in adsorption as pH increases. Dissolution of the oxide was also estimated by measuring the amount of soluble aluminum at pH 5. Increasing acid concentration promoted dissolution, especially for the low concentration range ([acid] < 3 mmol L$^{−1}$), but higher acid concentration lowers the increase of the solubility increase, likely due to adsorption on surface of an aluminum-organic complex.

The performances of Proton Exchange Membrane Fuel Cells (PEMFCs) are strongly influenced by the proton conductivity of the solid electrolyte. The azole-based polymers are among the most promising materials to improve the effectiveness of these systems. A theoretical study of proton transfer (PT) reaction in protonated imidazole, 1,2,3-triazole, and tetrazole dimers has been performed. The developed DFT protocol has been applied on more complex systems. The results obtained from the investigation performed on Poly(4-vinyl-imidazole) (P4VI) suggest that the commonly accepted (Grotthuss) conduction mechanism, based on a sequential proton transfer between imidazole moieties, could be impeded in this system because of the backbone constraint. Such a study, performed through a combined Density Functional Theory (DFT) / Molecular Dynamics simulations (MD) approach, allowed to hypothesize an alternative mechanism of conduction. A further study performed on phosphoric-acid (H3PO4) included models has revealed as low concentrations of H3PO4 could allow for the Grotthuss mechanism despite the polymeric constraint. The underpinning role played by the backbone topology on the conductivity has been then confirmed by the investigation carried out on a second polymer: the wire tethering position can strongly affect the mechanism of conduction. In short, the obtained simulations show how the polymeric matrix play a crucial role in the conductivity mechanism. The present research represents a first effort for a more systematic study of the relationship between backbone connectivity and efficiency of the charge transport, Les performances des piles à combustible à échange de protons (PEMFC) sont fortement influencées par la conductivité protonique de l'électrolyte solide. Les polymères à base d'azole sont parmi les matériaux les plus prometteurs pour améliorer l'efficacité de ces systèmes. Une étude théorique de réaction du transfert de protons (PT) en dimères protonée du imidazole, 1,2,3-triazole et tétrazole a été effectuée. Le protocole DFT mis au point a été appliqué sur des systèmes plus complexes. Les résultats obtenus à partir de l'étude réalisée sur le poly(4-vinyl-imidazole) (P4VI) suggèrent que le mécanisme de conduction communément admis (Grotthuss) pourrait être entravé dans ce système en raison de l'effet de la matrice polymérique. Cette étude, réalisée par le biais d'une approche combinée théorie du fonctionnelle de la densité (DFT) / simulations de Dynamique Moléculaire (MD), a permis de proposer un mécanisme alternatif de conduction. Une étude supplémentaire réalisée sur des modèles avec du acide phosphorique (H3PO4) a révélé que faibles concentrations de H3PO4 pourrait permettre le mécanisme de Grotthuss malgré la matrice polymérique. Le rôle crucial joué par la matrice polymérique sur la conductivité a été ensuite confirmée par l'étude menée sur un second polymère : la position d'attache du imidazole peut fortement affecter le mécanisme de conduction. En bref, les simulations obtenus montrent comment la matrice polymérique jouent un rôle crucial dans le mécanisme de la conductivité. La présente recherche représente une première tentative pour une étude plus systématique de la relation entre la connectivité de la matrice polymère et l'efficacité du transport de charge

International audience; The bicarbonate-activated peroxide (BAP) system has been shown to constitute an excellent and versatile combination for the epoxidation of olefins. Herein, we demonstrate that the benign H2O2/NaHCO3 oxidative combination can be used for the enantioselective epoxidation of olefins using a chiral manganese porphyrin as a catalyst. This unprecedented result was made possible by the use of an ionic liquid with ultrasound, which leads to the activation of Mn-porphyrin catalysis.

International audience; In this proof of concept study, the advantageous properties of both H(2)O(2)/NaHCO(3)/imidazole/Mn(TPP)OAc oxidation system and MOPyrroNTf(2) ionic liquid have been combined under ultrasonic irradiation to give an exceptionally favorable environment for Mn(TPP)OAc catalyzed olefin oxidations. The results reveal the crucial role played by the ultrasonic irradiations that influence drastically the oxidation process. In MOPyrroNTf(2) and under ultrasonic irradiation, the mechanism probably involves an oxo-manganyl intermediate at the expense of the classical bicarbonate-activated peroxide route.

International audience; We present an experimental study of disordered packings of deformable spheres. Fluorescent hydrogel spheres immersed in water together with a tomography technique enabled the imaging of the three-dimensional arrangement. The mechanical behavior of single spheres subjected to compression is first examined. Then the properties of packings of a randomized collection of deformable spheres in a box with a moving lid are tested. The transition to a state where the packing withstands finite stresses before yielding is observed. Starting from random packed states, the power law dependence of the normal force versus packing fraction or strain at different velocities is quantified. Furthermore, a compression-decompression sequence at low velocities resulted in rearrangements of the spheres. At larger packing fractions, a saturation of the mean coordination number took place, indicating the deformation and faceting of the spheres.

International audience; Photovoltaic energy: bolts and perspective This paper aims to present and compare the technologies used and envisaged to be used in the future for photovoltaic conversion. In addition to devices based on silicon (be they monocrystalline, polycrystalline, thin layer and so on), which have at least reached a certain industrial maturity, other emerging routes based on inorganic thin layer devices (such as CdTe and CIS types) and semi-conducting polymers are discussed. All these technologies are considered to be complementary and will be necessary to effectively confront the energy needs of the 21(st) century.

Le fil conducteur des recherches que j'ai effectuées depuis 1995 est la compréhension de la réactivité de surface des oxy-hydroxydes métalliques et de son implication dans les processus de sorption et d'adhésion. J'ai débuté ces recherches par une thèse sur l'étude des interactions des ions iodure avec plusieurs composés du cuivre (oxydes, carbonates et sulfures) par des méthodes spectroscopiques (XPS, Raman) et électrochimiques pour caractériser les composés formés. L'application de ces recherches au stockage souterrain des déchets radioactifs (l'iode étant un vecteur potentiel de contamination) a justifié leur financement par l'ANDRA. Ces premiers travaux m'ont dévoilé l'étendue des études nécessaires à l'avancée des connaissances dans le domaine des interfaces oxydes/solution. Mon embauche au CNRS m'a permis de mettre en œuvre un programme de recherche basé sur une approche multiéchelle (des colloïdes aux substrats massifs) et multitechnique (caractérisation en masse et en surface). Dans une première étape, j'ai utilisé des solides de référence pour améliorer les méthodes de caractérisation acido-basiques et les modèles de complexation de surface. La plate-forme expérimentale du CECM, laboratoire spécialisé dans les matériaux, a permis de réaliser une caractérisation approfondie des solides, au-delà des analyses réalisées habituellement par des chercheurs n'ayant pas un accès direct à ces moyens analytiques (MET, XRD, ATG, XPS,...). J'ai ainsi mis en évidence l'instabilité de la surface de l'alumine gamma en solution, alors que ce composé était utilisé depuis plusieurs dizaines d'années comme un solide de référence. Aidé d'un stagiaire, j'ai synthétisé un hydroxyde d'aluminium (bayerite) avec différentes morphologies pour prendre en compte la cristallographie sur la réactivité de surface, en accord avec les modèles les plus récents. La sorption des anions reste une problématique importante pour le stockage souterrain des déchets radioactifs puisqu'ils seraient les principaux vecteurs de contamination dans la géosphère. Avec une doctorante, nous avons travaillé sur le système sélénite/hématite pour aboutir à la publication de la première étude approfondie sur la sorption de cette espèce anionique du sélénium sur ce minéral. A cette occasion, la nécessité de disposer d'informations spectroscopiques en présence de solution m'a conduit à développer un système permettant de réaliser des spectres infrarouges en mode ATR (réflexion totale atténuée). J'ai ainsi analysé plusieurs systèmes (sulfate, carbonate, uranyle/hématite, uranyle/rutile,...) pour lesquels j'ai obtenu la spéciation des espèces sorbées, notamment en distinguant les complexes de sphère interne et externe. Ces expériences m'ont permis de publier la première étude française avec ce moyen d'investigation de la sorption. Ces études ont été suivies par un séjour de près d'un an à EDF R&D, résultat de la volonté de cette entreprise de développer ses activités de recherche sur la réactivité des produits de corrosion colloïdaux dans les circuits de refroidissement des réacteurs à eau pressurisée (REP), et de mon souhait de renforcer ma connaissance du milieu industriel et de la recherche finalisée. De retour dans un laboratoire CNRS, j'ai appliqué mes compétences sur la sorption aux phénomènes d'adhésion, de la mise en place d'essais en laboratoire jusqu'à l'analyse des retours d'expérience des centrales nucléaires. De manière étonnante, les interactions entre particules colloïdales et matériaux de structure ont fait l'objet de peu d'études, à l'inverse des systèmes modèles (latex/verre, mica,...) dont les conditions expérimentales sont très éloignées des applications. En parallèle à mes activités dédiées à la sorption, j'ai alors porté mes efforts sur cette thématique. Un premier volet a été consacré à la caractérisation acido-basique des matériaux, colloïdaux ou massifs, avec acquisition d'instruments commerciaux ou développement de méthodes originales de mesure de l'adhésion. Cette approche a permis de dégager les processus majeurs à la base de la déposition des particules (interactions électrostatiques et hydrodynamique). La caractérisation de la réactivité des produits de corrosion colloïdaux envers les ion dissous (sulfate, nickel,...) ainsi que la détermination du point de charge nulle ont été réalisées en conditions simplifiés (température ambiante) jusqu'aux conditions industrielles (320°C, présence d'hydrogène).

L'association entre un métal de transition et des cyclodextrines est d'un grand intérêt pour développer de nouveaux catalyseurs, mimes enzymatiques, capteurs ou fils moléculaires. L'interaction entre un complexe métallique et une cyclodextrine ouvre de nouvelles opportunités dans la chimie de coordination où de nouvelles réactivités et sélectivités sont attendues. Dans ce contexte, plusieurs composés totalement originaux de type cobalt(II)-cyclodextrines et cuivre(II)-cyclodextrines ont été synthétisés et caractérisés par voie électrochimique. La réactivité des espèces bas-valentes électrogénérées a été également étudiée vis-à-vis de dérivés halogénés alkyles et aromatiques. Il a été démontré que la dualité stabilité / réactivité des espèces transitoires pouvait être modulée en fonction de la nature du ligand greffé sur la cyclodextrine. Des études spectrophotométriques UV-Visible et spectroscopiques on été associées à ce travail, afin d'étudier la structure en solution d'un de ces complexe métallo-cyclodextrines. Ce travail original ouvre de nouvelles opportunités dans l'utilisation d'effets supramoléculaires biomimétiques dans les processus catalytiques afin de les rendre plus efficaces et sélectifs aussi bien en solvants organiques qu'en milieu aqueux (chimie verte)., No data

International audience; A detailed analysis concerning the effect of the exchange-correlation functional on a prototypical agostic niobium complex has been carried out, with particular attention to a fundamental property of the functional, namely, the recovering of the uniform electron gas limit. The obtained results allow for revisiting the role of this limit for a proper description of the beta-H agostic interaction. Starting from these results, a new criterion for the bond analysis based on the electron density behavior is proposed. Indeed, the density homogeneity between the metal and the involved hydrogen has been evaluated at the bond critical point, as defined in the framework of Bader's atoms in molecules theory, by calculating the average variation rates of the (reduced) density gradients. Such descriptors not only provide useful insights on the nature of such an interaction but also could be used as a starting point for a deep (and new) analysis of the chemical bond

This paper is the first part of a global study on the oxidation process of a Fe–9Cr–1Mo martensitic steel (T91) in static liquid Pb–Bi. It focuses on the oxygen transport mode across the oxide scale. The oxide layer has a duplex structure composed of an internal Fe–Cr spinel layer and an external magnetite layer. Oxygen 18 tracer experiments are performed: they show that the magnetite layer grows at the Pb–Bi/ oxide interface whereas the Fe–Cr spinel layer grows at the metal/oxide interface. Oxygen seems to diffuse across the oxide scale dissolved inside nanometric lead penetrations called nano-channels. Specific experiments are performed to characterize the nano-channels.

The key step in the mechanism of the Palladium-catalyzed homocoupling of arylboronic acids ArB(OH)(2)(Ar = 4-Z-C(6)H(4) with Z = MeO, H, CN) in the presence of dioxygen, leading to symmetrical biaryls, has been elucidated by using density functional theory. In particular, by starting from the peroxo complex O(2)PdL(2)(L = PPh(3)), generated in the reaction of dioxygen with the Pd(0) catalyst, the fundamental role played by an intermediate formed by coordination of one oxygen atom of the peroxo complex to the oxophilic boron atom of the arylboronic acid has been pointed out. This adduct reacts with a second molecule of arylboronic acid to generate a cis-Ar-Pd(OOB(OH)(2))L(2) complex that can form the stable intermediate trans-Ar-Pd(OH)L(2) (experimentally characterized) through a sequence of hydrolysis and isomerization reactions. All theoretical insights are in agreement and do substantiate the experimentally postulated mechanism. Furthermore, direct comparison of experimental and computed spectroscopic parameters (here, (31)P chemical shifts) allows us to confirm the formation of the intermediate.

This work falls within the context of the general pattern of individual monitoring of workers exposed to a risk of internal contamination with actinides. The aim is to propose a new procedure for analyzing Pu traces from urine media and in the presence of uranium. The extractant molecule used is a calix[6]arene bearing hydroxamic acid functions. The affinity of this molecule towards Pu(IV) and U(VI) has been studied and the possibility to separate both elements has been shown. © 2006 Elsevier B.V. All rights reserved.

International audience; Affinity CE (ACE) method was developed to characterize the complex formation between seven alkyl(methyl)methylimidazolium-based ionic liq. (IL) cations and eight neutral cyclodextrins (CD). The effective mobility data of the IL cations were processed according to classical nonlinear and linear treatments to obtain the complex stoichiometry and formation const. K. The majority of systems followed a 1:1 complexation stoichiometry model but in four cases a 1:2 stoichiometry was better satisfied. The K values obtained for each IL were compared to elucidate the main influences of IL and CD nature. The availability of these data should lend support to various application areas, including the screening and tailoring of new interactions in the soln. for CE.

A thin silicate film containing imidazolium cationic groups surface was obtained by sol–gel processing of ionic liquid – 1-methyl-3-(3-trimethoxysilylpropyl)imidazolium bis(trifluoromethyl-sulfonyl)imide together with tetramethyl orthosilicate on the indium tin oxide electrode. The formation of silicate film was confirmed by FTIR spectroscopy. This electrode when immersed into aqueous solution act as a sponge for Fe(CN)63− dissolved in aqueous solution. The corresponding voltammetric peak current is by almost two orders of magnitude larger than for electrode covered by ionic liquid precursor only. The repelling of Ru(NH3)63+ cations by this electrode is also demonstrated. Keywords: Ionic liquid, Voltammetry, Supported ionic liquid, Fe(CN)63−, Sol–gel

Ferric product powders were synthesised. The purity of each compound was controlled by FTIR and XRD analysis; the BET surface area and electrical conductivity were also reported. The galvanostatic electrochemical reduction of graphite/ferric product composite electrodes was investigated at 25 °C in mildly alkaline pH-buffered solutions containing chloride, sulphate or bicarbonate anions. The efficiency of the reduction process (Fe III -to-Fe II reaction) was quantified by reporting the potential value obtained at half the transition time, E τ /2 , on the E – t transient, as a function of Q τ , the coulombic charge obtained at the end of the reduction. The possibilities for a galvanic coupling to occur have been discussed based on the reduction efficiency plots and corrosion potential values of iron in the various media.

Besides the numerous applications of magnetic particles in the fields of medicine, diagnostics, molecular biology and bioinorganic chemistry, a high potential exists for these particles in environmental sciences. Several methods have been proposed these last years for the separation of metals from wastewater using either micro- or nano-magnetic particles. We describe here the synthesis of such particles, compare their magnetic properties, and discuss the possibility of selectivity for metals ions, namely radionuclides. To cite this article: A.-F. Ngomsik et al., C.R. Chimie 8 (2005).

A coupling of structural and thermodynamic fluctuations in the course of various-type insertion processes is investigated within a combination of Gibbsian statistics and the information theory approach. It is shown that the coupling makes it possible to restore (at least partially) the information, inaccessible from experimental tests. This enables one to make physically reasonable predictions under limited information on the system.

In this paper we show that the existence of a primarily discrete space-time may be a fruitful assumption from which we may develop a new approach of statistical thermodynamics in pre-relativistic conditions. The discreetness of space-time structure is determined by a condition that mimics the Heisenberg uncertainty relations and the motion in this space-time model is chosen as simple as possible. From these two assumptions we define a path-entropy that measures the number of closed paths associated with a given energy of the system preparation. This entropy has a dynamical character and depends on the time interval on which we count the paths. We show that it exists an like-equilibrium condition for which the path-entropy corresponds exactly to the usual thermodynamic entropy and, more generally, the usual statistical thermodynamics is reobtained. This result derived without using the Gibbs ensemble method shows that the standard thermodynamics is consistent with a motion that is time-irreversible at a microscopic level. From this change of paradigm it becomes easy to derive a $H-theorem$. A comparison with the traditional Boltzmann approach is presented. We also show how our approach can be implemented in order to describe reversible processes. By considering a process defined simultaneously by initial and final conditions a well defined stochastic process is introduced and we are able to derive a Schroedinger equation, an example of time reversible equation., Comment: latex version

The electrode based on silicate carbon composite material was modified with redox probe (t-butylferrocene) solution in ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate or 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide). After immersion into an aqueous solution it was studied by cyclic voltammetry. It exhibits electrochemical signal connected with electrode reaction of the redox probe dissolved in ionic liquid. The heterogeneous structure of electrode material enhances substantially efficiency of the electrode process in comparison to the drop deposited on flat electrode surface. The midpeak potential depends on the hydrophobicity of the anion present in the aqueous solution indicating significant contribution of anion injection into the ionic liquid following the electron transfer. The efficiency of the electrode process is much larger than that of similar electrode modified with the redox probe solution in less viscous organic polar solvent. Keywords: Carbon ceramic electrode, Ionic liquid, Redox reaction, Sol–gel, Cyclic voltammetry

The phase transition of a fluid adsorbed in a heterogeneous system is studied with two simple lattice gas models within the framework of a mean-field theory. Despite the different origin of the heterogeneity (spatial variation of binding energy or fluid coordination numbers), the fluid can undergo two phase transitions if the hosting system is sufficiently heterogeneous. It is clearly shown that such a polymorphism in the confined fluid results from the successive condensations in distinct spatial regions of the host. We have found the precise conditions at which one two phase transitions occur. The insight gained from the present study allows one to understand better some recent puzzling simulation results., 9 pages, 4 figures

Employing the lattice gas model, combined with the linear elasticity theory, a correlation between the equilibrium and transport properties of intercalated species is investigated. It is shown that the major features of the intercalation isotherms and the concentration dependence of the chemical diffusion coefficient can be well understood in terms of the change of the host volume in the course of intercalation. Theoretical predictions are compared to the experimental observations on PdH_x, Li_xWO_3 and Li-graphite systems., Comment: 7 pages, 5 figures

It is shown that there is a mapping of the replica approach to disordered systems with finite replica index $n$ on the Tsallis non-extensive statistics, if the average thermodynamic entropy differs from the information entropy for the probability distribution. In the case of incomplete information the entropic index $q=1-n$ is shown to be related to the degree of lost information., Comment: 5 pages

Ruthenium is one of the fission products in the reprocessing of irradiated fuels that requires a specific processing management. Its elimination, upstream by the PUREX process, has been considered. A process, called electro-volatilization, which take advantage of the RuO4 volatility, has been optimised in the present study. It consists in a continuous electrolysis of ruthenium solutions in order to generate RuO4 species that is volatilized and easily trapped. This process goes to satisfying ruthenium elimination yields with RuNO(NO3)3(H2O)2 synthetic solutions but not with fuel dissolution solutions. Consequently, this work consisted in the speciation studies of dissolved ruthenium species were carried out by simulating fuel solutions produced by hot acid attack of several ruthenium compounds (Ru(0), RuO2,xH2O, polymetallic alloy). In parallel with dissolution kinetic studies, the determination of dissolved species was performed using voltammetry, spectrometry and spectro-electrochemistry. The results showed the co-existence of Ru(IV) and RuNO(NO2)2(H2O)3. Although these species are different from synthetic RuNO(NO3)3(H2O)2, their electro-oxidation behaviour are similar. The electro-volatilisation tests of these dissolution solutions yielded to comparable results as the synthetic RuNO(NO3)3(H2O)2 solutions. Then, complexity increase of models solutions was performed by in-situ generation of nitrous acid during ruthenium dissolution. Nitrous acid showed a catalytic effect on ruthenium dissolution. Its presence goes to quasi exclusively RuNO(NO2)2(H2O)3 species. It is also responsible of the strong p-bond formation between Ru2+ and NO+. In addition, it has been shown that its reducing action on RuO4 hinders the electro-volatilization process. Mn2+ and Ce3+ cations also reveal, but to a lesser extent, an electro-eater behaviour as well as Pu4+ and Cr3+ according to the thermodynamics data. These results allow one to purpose a dissolution mechanism of RuO2,xH2O species in nitric acid as well as quantify, thanks to the determination of oxidation and volatilization apparent constants, the baneful effect of nitrous acid on the electro-volatilization process. An explanation of the low yield of ruthenium electro-volatilization from irradiated fuel solutions has been proposed., Le ruthénium est l'un des produits de fission les plus pénalisants pour le procédé de retraitement du combustible irradié. Son élimination en amont du procédé PUREX est envisagée. Un procédé, appelé électro-volatilisation, tirant profit de la volatilité de RuO4, a été optimisé pour cette étude. Il consiste à électrolyser en continu les solutions de ruthénium afin de générer RuO4 qui est ensuite volatilisé puis aisément piégé. Ce procédé conduit à des rendements d'élimination du ruthénium satisfaisants, sur des solutions synthétiques de RuNO(NO3)3(H2O)2 mais pas sur les solutions de dissolution de combustible. Ce travail a donc consisté à étudier la spéciation des espèces dissoutes du ruthénium en simulant la dissolution du combustible par attaque dans l'acide nitrique à chaud de diverses espèces du ruthénium (Ru(0), RuO2,xH2O, alliage polymétallique). Parallèlement à une étude cinétique de dissolution, a été menée l'étude de spéciation des espèces dissoutes grâce à la voltammétrie, la spectrométrie et la spectro-électrochimie. Cette étude a révélée la co-existence des espèces Ru(IV) et RuNO(NO2)2(H2O)3. Bien que différentes de l'espèce synthétique RuNO(NO3)3(H2O)2, leurs comportements en électro-oxydation sont analogues. Les essais d'électro-volatilisation de ces solutions de dissolution ont conduit à des résultats comparables à ceux obtenus sur les solutions synthétiques. Une complexification des solutions modèles a alors été réalisée par génération d'acide nitreux in-situ au cours de la dissolution. L'acide nitreux a montré un effet catalytique sur la dissolution du ruthénium. Sa présence conduit presque exclusivement à l'espèce RuNO(NO2)2(H2O)3. Il est donc responsable de la formation de la forte liaison  entre Ru2+ et NO+. De plus, son action très réductrice sur RuO4 s'est révélée être pénalisante lors des essais d'électro-volatilisation. Dans une moindre mesure, les cations Mn2+ et Ce3+ se sont également montrés électrophages et les données thermodynamiques laissent penser que Pu4+ et Cr3+ le sont également. L'ensemble des résultats permet d'une part de proposer un mécanisme de dissolution de l'espèce RuO2,xH2O dans l'acide nitrique et d'autre part de quantifier, grâce aux calculs des constantes apparentes d'oxydation de volatilisation, les effets néfastes de l'acide nitreux sur le procédé d'électro-volatilisation. Une explication probable quant aux faibles rendements d'électro-volatilisation du ruthénium des solutions de dissolution de combustible irradié est alors proposée.

International audience

On the basis of the information theory approach we propose a novel statistical scheme for analyzing the evolution of coupled adsorbate-substrate systems, in which the substrate undergoes the adsorbate-induced transformations. A relation between the substrate morphology and the adsorbate thermodynamic state is established. This allows one to estimate the surface structure in terms of incomplete experimental information and the one concerning the adsorbate thermodynamic response to the structural modifications., 5 pages, 3 figures

International audience; Electrodeposition is a low cost method for WO3 thin film preparation. The starting dissolved tungsten precursor is a peroxo-compound which can be prepared by an equimolar mixing of sodium tungstate and hydrogen peroxide. The precursor preparation as well as the electrodeposition and precursor solution aging processes have been studied by X-ray absorption spectroscopy (XAS) at the W L3 edge. By extended X-ray absorption fine structure (EXAFS) analysis, the local structure of the first oxygen octahedral shell around the W absorber has been characterized both in the colloidal oxide formed after deposition solution aging and in electrodeposited films. The colloidal compound could be fitted with the same procedure as that successfully used with a monoclinic WO3 reference and involving two different W−O interatomic distances. The aging product is identified as amorphous WO3. If the spectra of as-electrodeposited films could not be fitted by the same procedure, the structural parameters of those cycled electrochemically in a lithium ion containing organic medium have been determined. If compared to crystallized WO3, the mean W−O distances in amorphous WO3 (films and colloids) are found significantly shorter, whereas the Debye−Waller factors are much larger. The condensation process has been investigated by analyzing the variation of the X-ray absorption near edge structure (XANES) spectra. We show that the white line height of the W L3 edge is a good indicator of the condensation state of the matter during the deposition. According to this parameter, the electrodeposited WO3 films would undergo a dramatic reorganization process during the first potential cyclings in the lithium ion containing organic medium. The same behavior is observed with electrochromic films deposited by sputtering, a more classical method.

The interaction of proteins with polysaccharides represents a major and challenging topic in glycobiology, since such complexes mediate fundamental biological mechanisms. An affinity capillary electrophoresis method has been developed to evidence the complex formation and to determine the binding properties between an anticoagulant polysaccharide of marine origin, fucoidan, and a potential target protein, antithrombin. This method is a variant of zonal electrophoresis in the mobility shift format. A fixed amount of protein was injected into a capillary filled with a background electrolyte containing the polysaccharide in varying concentrations. The effective mobility data of the protein were processed according to classical linearization treatments to obtain the binding constant for the polysaccharide/antithrombin complex. The results indicate that fucoidan binds to antithrombin in a 1:1 stoichiometry and with an affinity depending on the molecular weight of the polysaccharide. For heparin, the binding constant obtained similarly is in accordance with the literature. This is the first report showing the implementation of a capillary electrophoresis method contributing to the mechanistic understanding of the biological activities of fucoidan and providing evidence for the complex formation between fucoidan and the protein inhibitor of the coagulation antithrombin. (C) 2003 Elsevier Science (USA). All rights reserved.