Kechadi M.,French National Center for Scientific Research |
Kechadi M.,University Pierre and Marie Curie |
Kechadi M.,Laboratoire dElectrochimie |
Gamby J.,French National Center for Scientific Research |
And 6 more authors.
Electrochimica Acta | Year: 2013
The present work describes a new methodology for contact free impedance of a solution in a polymer microchip taking into account the role played by the surrounding polymer on the impedance accuracy. Measurements were carried out using a photoablated polyethylene terephthalate (PET) microchannel above two embedded microband electrodes. The impedance diagrams exhibit a loop from high frequencies to medium frequencies (1 MHz-100 Hz) and a capacitive behavior at low frequencies (100-1 Hz). The impedance diagrams were corrected by eliminating from the global microchip response the contribution of the impedance of the PET layer between the two microband electrodes. This operation enables a clear observation of the impedance in the microchannel solution, including the bulk solution contribution and the interfacial capacitance related to the surface roughness of the photoablated microchannel. Models for the impedance of solutions of varying conductivity showed that the capacitance of the polymer-solution interface can be modeled by a constant phase element (CPE) with an exponent of 0.5. The loop diameter was found to be proportional to the microchannel resistivity, allowing a cell constant around 4.93 × 10 5m-1 in contactless microelectrodes configuration. © 2013 Elsevier Ltd. All rights reserved.
Zidane Y.,National Graduate School of Chemistry, Rennes |
Zidane Y.,European University of Brittany |
Zidane Y.,Laboratoire dElectrochimie |
Ourari A.,Laboratoire dElectrochimie |
And 6 more authors.
Journal of Electroanalytical Chemistry | Year: 2010
MnIIICl-salen complex of tetradentate Schiff base ligand was incorporated into layers of clay montmorillonite by using an in situ flexible ligand method. The obtained modified clay was examined by X-ray diffraction, FT-IR and by using a cavity microelectrode (CME) to perform the electrochemical studies of the catalyst in the supported solid phase. Experiments show a well-defined and chemically reversible redox system of the manganese complex incorporated into the clay, similar to that observed in solution but with apparent diffusion coefficient around 2.3 × 10-9 cm-2 s-1. Dioxygen activation in catalytic conditions that was found to be efficient in the modified material is studied with the CME. It demonstrates the absence of formation of μ-oxo dimers and peroxo-bridged compounds and a good penetration of the different reactants into the clay. Moreover, this analysis illustrates the interest of CME as a powerful tool for the study of similar supported catalyst implying the biomimetic activation of molecular oxygen. © 2010 Elsevier B.V. All rights reserved.