The importance of pyrochemistry is being increasingly acknowledged and becomes unavoidable in the nuclear field. Molten salts may be used for fuel processing and spent fuel recycling, for heat transfer, as a homogeneous fuel and as a breeder material in fusion systems. Fluorides that are stable at high temperature and under high neutron flux are especially promising. Analysis of several field cases reveals that corrosion in molten fluorides is essentially due to the oxidation of metals by uranium fluoride and/or oxidizing impurities. The thermodynamics of this process are discussed with an emphasis on understanding the mass transfer in the systems, selecting appropriate metallic materials and designing effective purification methods. High temperature molten salts based on chloride or fluoride compounds have several applications in the nuclear field. In the front-end nuclear fuel cycle, molten salts are used for the purification and production of zirconium alloy, which is used as fuel cladding. Then, a pyrochemical treatment in NaCl-AlCl3 molten salt at 350 °C enables the separation of zirconium and hafnium, which is a neutronic poison1. In the nuclear fuel fabrication process, conversion of uranium oxide ore requires large quantities of fluorine that is obtained by the electrolysis of 2HF-KF molten salt at 95 °C2. Several pyrochemical processes based on chloride or fluoride molten salts have also been conceived in the back-end nuclear fuel cycle, to separate actinides from lanthanides during nuclear waste recycling3, 4, 5, 6, 7, 8 and 9. Because fluoride mixtures are thermodynamically stable at high temperature, with very high boiling points, these liquids have been considered as heat transfer or cooling fluids, as coolants for thermal energy10 and 11and in nuclear fission and fusion systems. Several criteria have to be considered when choosing a structural material: mechanical strength at high temperature, irradiation resistance (in the case of materials under neutron flux) and chemical corrosion resistance (which depends on the material composition and microstructure, and on the physical chemistry of the molten salt). As it will be shown, in order to avoid corrosion the liquid fluoride salt coolant must be thermodynamically stable relative to the chosen materials. If molten salts are already industrially used in the front-end nuclear fuel cycle or considered for alternative nuclear spent fuel recycling in the back-end fuel cycle, then the material development and the corrosion studies are essentially performed within the frame of the development of future nuclear reactors: Molten Salt Reactors (MSR), Advanced High Temperature Reactors (AHTR) and Tokamak fusion power plants. For all these cases, the selected molten salt is a fluoride salt mixture. Indeed, the material resistance is a key issue in all applications, but especially so in the case of reactor core use; not only because of the irradiation damage, but also because the operating temperature is determined by the fission reaction and cannot be decreased e...

A series of [Re(N^N)(CO)(X)] (N^N = diimine and X = halide) complexes based on 4-(2-pyridyl)-1,2,3-triazole (pyta) and 1-(2-pyridyl)-1,2,3-triazole (tapy) diimine ligands have been prepared and electrochemically characterized. The first ligand-based reduction process is shown to be highly sensitive to the nature of the isomer as well as to the substituents on the pyridyl ring, with the peak potential changing by up to 700 mV. The abilities of this class of complexes to catalyze the electroreduction and photoreduction of CO were assessed for the first time. It is found that only Re pyta complexes that have a first reduction wave with a peak potential at ca. -1.7 V vs SCE are active, producing CO as the major product, together with small amounts of H and formic acid. The catalytic wave that is observed in the CVs is enhanced by the addition of water or trifluoroethanol as a proton source. Long-term controlled potential electrolysis experiments gave total Faradaic yield close to 100%. In particular, functionalization of the triazolyl ring with a 2,4,6-tri-tert-butylphenyl group provided the catalyst with a remarkable stability.

Electrogeneration of reducers at a microelectrode allows us to locally debrominate a surface bound polymerization initiator. Once submitted to atom transfer radical polymerization, patterns of nanometer polymer structures are formed on the surfaces. The surface reduction rate, controlled by the microelectrode scan rate and the reducer strength, affects the dimensions of the patterns. The reducer strength allows to tune the surface density of the initiator layer and then the elongation of the polymer brushes grown in the locally etched regions.

The potential of a series of newly synthesized poly(N,N-dimethylacrylamide) (PDMA) grafted polyacrylamide (PAM) copolymers (P(AM-PDMA)) as a replaceable separation medium for protein analysis was studied. A comparative study with and without copolymers was performed; the separation efficiency, analysis reproducibility and protein recovery proved that the P(AM-PDMA) copolymers were efficient in suppressing the adsorption of basic proteins onto the silica capillary wall. Furthermore, the size-dependent retardation of native proteins in a representative P(AM-PDMA) copolymer was demonstrated by Ferguson analysis. The results showed that the P(AM-PDMA) copolymers combine the good coating property of PDMA and the sieving property of PAM and could be applied as a sieving matrix for the analysis of native proteins.

Scanning electrochemical microscopy (SECM) is employed to characterize the transport of redox-active probe ions through quenched polyelectrolyte brushes. The counterion exchange through polyelectrolyte brushes is also investigated by infrared spectroscopy in attenuated total reflection (FTIR-ATR), X-ray photolectron spectroscopy (XPS), and cyclic voltammetry (CV). The synthesis of poly(methacryloyloxy)ethyl trimethylammonium chloride (PMETAC) brushes is performed using surface-initiated atom transfer radical polymerization followed by in situ quaternization reaction. The chloride (Cl(-)) counterions of the positively charged polymer brush are exchanged by ferrocyanide (Fe(CN)(6)(4-)) and ferricyanide (Fe(CN)(6)(3-)) ions that are both detectable by spectroscopy and electrochemically active. A good agreement is found when comparing the results obtained by spectroscopic (FTIR-ATR and XPS) and electrochemical (SECM and CV) methods. The counterions exchange is completely reversible and reproducible. We show that (Fe(CN)(6)(4-)) and (Fe(CN)(6)(3-)) species form stable ion pairs with the quaternary ammonium groups of the polymer brush. The transport of iodide (I(-)) redox-active ions is also investigated. In all cases (ferrocyanide, ferricyanide, or iodide), we find that chloride counterions are partially replaced by electroactive ions. This partial exchange may be attributed to an osmotic effect, since the external salt concentration for the exchange is much lower than the counterion concentration inside the brush.

The change in charge-transfer resistance (Rct) was found to be linear with DCL concentration in the 30 pM-1 µM range. The detection limit was calculated to be 0.02 nM. The improvement of the limit of detection can be mainly attributed to the threedimensional environment of the hydrogel matrix which improves the grafting density of aptamer and the affinity of the aptamer to DCL.

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The detection of reactive oxygen and nitrogen species is of utmost importance in several pathological situations. Indeed, these reactive species are biomarkers of oxidative stress and their real-time monitoring is crucial to adapt medical treatments. We report here on the electrochemical detection of nitric oxide (NO •) in the presence of hydrogen peroxide (H 2 O 2). The detection was performed by using different sensing microdevices involving either static solutions in wells or flowing solutions in microfluidic channels. Furthermore, an original strategy was proposed to further enhance the selectivity of NO • detection at Pt/poly(eugenol) modified platinum electrodes by designing a dual-electrode microfluidic device based on a pre-electrolysis of interfering species including H 2 O 2 at an upstream electrode prior to NO • detection.