Dimerization of ion radicals in ionic liquids. An example of favourable "Coulombic" solvation.

International audienceThe irreversible dimerization of the acetophenone radical anion, chosen as an example of a carbon-carbon coupling reaction between two charged species, was investigated in a series of 1,3-dialkylimidazolium and 1,2,3-trialkylimidazolium ionic liquids. Indeed, such ion dimerizations which display slow kinetics despite small activation energies, are controlled by a subtle competition between bond formation, Coulombic repulsion and solvation. The effects of viscosity, "polarity" and ionic solvation on the reactivity of the radical anions were examined. The dimerization rate constants were demonstrated to be only weakly affected by the high viscosity of the medium or its apparent polarity. When the acetophenone radical anion is "solvated" in imidazolium-based ionic liquids, a strong interaction between the negatively-charged intermediates and the imidazolium cation occurs. The ensuing charge stabilization allows a fast dimerization step in all the ionic liquids used. The kinetic effect is even enhanced in the 1,3-dialkylimidazolium salts as compared to the 1,2,3-trialkylimidazolium ones because the interaction between the radical anions and the 1,3-dialkylimidazolium cations are stronger, probably due to the formation of H-bond. The reactivity of the ion radical is demonstrated not only to be mainly dominated by electrostatic interactions, but also that the nature of the ionic liquid cations with respect to that of the ion radical is a major factor that affects the reaction kinetics

Regular poly(para-phenylene) films bound to gold surfaces through the electrochemical reduction of diazonium salts followed by electropolymerization in an ionic liquid

International audienceBy combining the electroreduction of diazonium salts and the electropolymerization of conducting polymers in an ionic liquid, the electrografting of a regular poly(para-phenylene) film on a gold substrate is achieved, leading to the strong and robust anchoring of the PPP polymers on the substrate (Au-PPP hybrid). A thin layer covalently bound to the substrate is first prepared by the reduction of benzenediazonium salt (BD), then, on top of this layer, a thicker layer of poly(para-phenylene) (PPP) is easily grown by the electrochemical oxidation of biphenyl in the [BMIm][PF6] ionic liquid. The resulting material is thoroughly characterized by IR, ToF-SIMS and fluorescence spectroscopies. The analyses show the formation of well regular PPP layers that are wired to the substrate. The key role of the [BMIm][PF6] ionic liquid in the structuration of the polymer is emphasized

Dextrin and conducting polymer containing biocomposites: properties and behavior as cellular matrix

Both α-cyclodextrin and linear dextrin are used to prepare biocomposites with poly(3,4- ethylenedioxythiophene). Materials are prepared electrochemically in aqueous solution. Comparison with the pure polymer indicates that the electroactivity and electrostability decrease with the incorporation of the dextrins while the electrical conductivity is retained. The different properties of the two biocomposites suggest that the linear dextrin is mainly located at the surface, whereas the cyclodextrin is homogeneously distributed in the polymeric matrix. Cell adhesion and proliferation assays indicate that the cellular activity is significantly higher in the dextrin-containing biocomposites.Acknowledgements: Financial support from the MICINN and FEDER (MAT2009-09138) and Generalitat de Catalunya (research group 2009 SGR 925 and XRQTC) is gratefully acknowledged. B.T.-D. acknowledges support from the MICINN through an FPI grant and financial support for his stay at the 3B’s Research Group (Portugal). The support from project PTDC/FIS/115048/2009 (FCTPortugal) is also acknowledged. Authors are indebted to Dr. Elaine Armelin for helpful suggestions and to David Aradilla for assistance in electrical measures and SEM micrographs. Support for the research of C.A. was received through the prize ‘‘ICREA Academia’’ for excellence in research funded by the Generalitat de Catalunya

Up to 425 GHz All Optical Frequency Down‐Conversion Clock Recovery Based on Quantum Dash Fabry‐Perot Mode‐Locked Laser

Postdeadline Session C " OFDM and OTDM "International audienceWe demonstrate that quantum‐dash mode‐locked laser can perform all optical frequency down‐conversion clock recovery up to 425 GHz. We measured 0.3 dB penalty on the optical recovered clock for 170 Gbit/s signal

Insights into water coordination associated with the Cu(II)/Cu(I) electron transfer at a biomimetic Cu centre.

International audienceThe coordination properties of the biomimetic complex [Cu(TMPA)(H2O)](CF3SO3)2 (TMPA = tris(2-pyridylmethyl)amine) have been investigated by electrochemistry combined with UV-Vis and EPR spectroscopy in different non-coordinating media including imidazolium-based room-temperature ionic liquids, for different water contents. The solid-state X-ray diffraction analysis of the complex shows that the cupric centre lies in a N4O coordination environment with a nearly perfect trigonal bipyramidal geometry (TBP), the water ligand being axially coordinated to Cu(II). In solution, the coordination geometry of the complex remains TBP in all media. Neither the triflate ion nor the anions of the ionic liquids were found to coordinate the copper centre. Cyclic voltammetry in all media shows that the decoordination of the water molecule occurs upon monoelectronic reduction of the Cu(II) complex. Back-coordination of the water ligand at the cuprous state can be detected by increasing the water content and/or decreasing the timescale of the experiment. Numerical simulations of the voltammograms allow the determination of kinetics and thermodynamics for the water association-dissociation mechanism. The resulting data suggest that (i) the binding/unbinding of water at the Cu(I) redox state is relatively slow and equilibrated in all media, and (ii) the binding of water at Cu(I) is somewhat faster in the ionic liquids than in the non-coordinating solvents, while the decoordination process is weakly sensitive to the nature of the solvents. These results suggest that ionic liquids favour water exchange without interfering with the coordination sphere of the metal centre. This makes them promising media for studying host-guest reactions with biomimetic complexes

Cytotoxic dendritic cells generated from cancer patients.

International audienceKnown for years as professional APCs, dendritic cells (DCs) are also endowed with tumoricidal activity. This dual role of DC as killers and messengers may have important implications for tumor immunotherapy. However, the tumoricidal activity of DCs has mainly been investigated in animal models. Cancer cells inhibit antitumor immune responses using numerous mechanisms, including the induction of immunosuppressive/ tolerogenic DCs that have lost their ability to present Ags in an immunogenic manner. In this study, we evaluated the possibility of generating tumor killer DCs from patients with advanced-stage cancers. We demonstrate that human monocyte-derived DCs are endowed with significant cytotoxic activity against tumor cells following activation with LPS. The mechanism of DC-mediated tumor cell killing primarily involves peroxynitrites. This observed cytotoxic activity is restricted to immature DCs. Additionally, after killing, these cytotoxic DCs are able to activate tumor Ag-specific T cells. These observations may open important new perspectives for the use of autologous cytotoxic DCs in cancer immunotherapy strategies

Thermal, dielectric, and electrochemical study of decanoic acid–tetrabutylammonium chloride deep eutectic solvent

A mixture based on decanoic acid (DA) and tetrabutylammonium chloride (TBACl) is a simple and prototypical deep eutectic solvent (DES) useful for extracting compounds that are poorly soluble in water or in electrochemical applications. The most widely studied composition is DA–TBACl with a molar ratio equal to 2:1. The composition of DESs has a strong impact on their physicochemical properties. Herein, a comparative study of thermal, dielectric, and ionic conductivities and electrochemical properties of DA–TBACl is carried out with varying molar compositions 2:1, 1:1, and 1:2. All the molar compositions lead to a stable fluid whose properties depend on the composition, providing better understanding and further insights into the chemical interactions that prevail in those materials

Ionic liquids at electrified interfaces

Until recently, “room-temperature” (<100–150 °C) liquid-state electrochemistry was mostly electrochemistry of diluted electrolytes(1)–(4) where dissolved salt ions were surrounded by a considerable amount of solvent molecules. Highly concentrated liquid electrolytes were mostly considered in the narrow (albeit important) niche of high-temperature electrochemistry of molten inorganic salts(5-9) and in the even narrower niche of “first-generation” room temperature ionic liquids, RTILs (such as chloro-aluminates and alkylammonium nitrates).(10-14) The situation has changed dramatically in the 2000s after the discovery of new moisture- and temperature-stable RTILs.(15, 16) These days, the “later generation” RTILs attracted wide attention within the electrochemical community.(17-31) Indeed, RTILs, as a class of compounds, possess a unique combination of properties (high charge density, electrochemical stability, low/negligible volatility, tunable polarity, etc.) that make them very attractive substances from fundamental and application points of view.(32-38) Most importantly, they can mix with each other in “cocktails” of one’s choice to acquire the desired properties (e.g., wider temperature range of the liquid phase(39, 40)) and can serve as almost “universal” solvents.(37, 41, 42) It is worth noting here one of the advantages of RTILs as compared to their high-temperature molten salt (HTMS)(43) “sister-systems”.(44) In RTILs the dissolved molecules are not imbedded in a harsh high temperature environment which could be destructive for many classes of fragile (organic) molecules

Brain Vitamin E Deficiency During Development Is Associated With Increased Glutamate Levels and Anxiety in Adult Mice

Vitamin E, the most important lipophilic radical scavenging antioxidant in vivo, has a pivotal role in brain. In an earlier study, we observed that adult mice with a defect in the gene encoding plasma phospholipid transfer protein (PLTP) display a moderate reduction in cerebral vitamin E levels, and exacerbated anxiety despite normal locomotion and memory functions. Here we sought to determine whether dietary vitamin E supplementation can modulate neurotransmitter levels and alleviate the increased anxiety phenotype of PLTP-deficient (PLTP−/−) mice. To address this question, a vitamin E-enriched diet was used, and two complementary approches were implemented: (i) “early supplementation”: neurotransmitter levels and anxiety were assessed in 6 months old PLTP−/− mice born from vitamin E-supplemented parents; and (ii) “late supplementation”: neurotransmitter levels and anxiety were assessed in 6 months old PLTP−/− mice fed a vitamin E-enriched diet from weaning. Our results show for the first time that an inadequate supply of vitamin E during development, due to moderate maternal vitamin E deficiency, is associated with reduced brain vitamin E levels at birth and irreversible alterations in brain glutamate levels. They also suggest this deficiency is associated with increased anxiety at adulthood. Thus, the present study leads to conclude on the importance of the micronutrient vitamin E during pregnancy