STRUCTURE OF CONCENTRATED SOLUTIONS OF LITHIUM SALTS IN AMMONIA. AN EXPERIMENTAL APPROACH OF THESE SYSTEMS

The electrical conductivities, viscosities and NH3 vapor pressure data for lithium salts ammoniates are reported. These measurements allow the apprehension of the nature of the solvation shell of ions by ammonia and the quantification of the NH3- Salt bonding energy which are essential for application of ammoniates as non aqueous electrolytes in lithium batteries

Electrochemical polymerization of 1,2-ethanedithiol as a new way to synthesize polyethylenedisulfide

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Study of structural and electronic properties of polyethylenimine hemihydrate

International audienceFrom all of the known polyethyleneimine crystalline forms, we focused our study on the hydrate one that can have 0.5 water molecule per ethyleneimine monomeric unit. The hydration of the anhydrous polyethyleneimine made of double - stranded helix yields planar zigzag polymer chains. From the partial hemihydrate crystal lattice, we propose a resolved and optimized complete structure by means of ab initio density functional theory calculations. Water molecules take place in the center of a tetrahedron quasi square planar structure made of four nitrogen atoms. Contrary to the small gap semiconducting anhydrous polyethyleneimine, the hemihydrate polyethyleneimine has an insulating character

Electrocatalyzed synthesis of polypeptides on platinum surface in concentrated glycine electrolytes and ab initio calculations coupled to spectroscopic analysis

International audienceThe anodic oxidation of glycine in aqueous electrolyte on smooth platinum electrode was carried out by electrochemical quartz crystal microbalance coupled to cyclic voltammetry technique. Here, we performed electrochemical experiments in concentrated glycine-based electrolyte. Contrary to studies made in diluted medium, the reaction we describe leads to a strongly grafted polymer on the surface at pH values superior to 6, and up to 13, in an irreversible way. The electrodeposited mass is even very significant at pH 13. Several methods such as AFM topography and spectroscopic techniques were performed to characterize the resulting coating. The polymer growth in alkaline conditions during the anodic oxidation of glycine in water probably involves an electrocatalytic step. We showed the presence of amide bonds and then polypeptide formation on the smooth platinum surface. Periodic ab initio calculations on polyglycine II were performed and compared to XPS and vibrational spectr

Fabrication of a miniaturized cell using microsystem technologies for electrochemical applications

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Synthesis of polymer materials for use as cell culture substrates

Up to today, several techniques have been used to maintain cells in culture for studying many aspects of cell biology and physiology. More often, cell culture is dependent on proper anchorage of cells to the growth surface. Thus, poly-l-lysine, fibronectin or laminin are the most commonly used substrates. In this study, electrosynthesized biocompatible polymer films are proposed as an alternative to these standard substrates. The electrosynthesized polymers tested were polyethylenimine, polypropylenimine and polypyrrole. Then, the adhesion, proliferation and morphology of rat neuronal cell lines were investigated on these polymer substrates in an attempt to develop new and efficient polymer materials for cell culture. During their growth on the polymers, the evolution of the cell morphology was monitored using both confocal microscopy and immunohistochemistry, leading to the conclusion of a normal development. An estimation of the adhesion and proliferation rates of rat neuronal cell cultures indicated that polyethylenimine and polypropylenimine were the best substrates for culturing olfactory neuronal cells. A method to favour the differentiation of the neuronal cells was also developed since the final aim of this work is to develop a biosensor for odour detection using differentiated neuronal cells as transducers. Consequently, a biosensor was microfabricated using silicon technology. This microsystem allowed us to culture the cells on a silicon wafer and to position the cells on certain parts of the silicon wafer

Behaviour of a fluorine-doped tin oxide electrode: a study by quartz crystal microbalance in propylene carbonate

International audienceFluorine-doped tin oxide (FTO) was deposited onto a gold electrode evaporated onto a quartz crystal. The FTO material was cycled in propylene carbonate in the presence of 1 M LiClO4. Voltammetric and gravimetric responses of the FTO electrode were recorded between +2.75 and +0.75 V vs. Li|Li+ for 180 cycles. During the first few cycles, reduction of trace water was predominant so that the growth of a film of lithium hydroxide was instantaneous. This layer was porous so that ions entering and leaving this layer could explain the presence of the typical doping-dedoping electrochemical curves