Bifunctional coatings: coupling an organic adhesion promoter with an anticorrosion inorganic layer

International audienceIn this work, a multifunctional non-toxic chromium free treatment is proposed. Hexavalent chromium, largely used for anticorrosion surface treatments of aluminum alloys in aeronautics, will soon be completely banned due to its high toxicity (European REACH regulation) and new solutions are required. Here, in a first step, a polymeric film was grafted at the aluminum surface by the surface induced reduction of a diazonium salt. In a second step, the grafted surface was submitted to an anodization treatment, forming a thick aluminum oxide layer protecting the underlying metal against corrosion. No change in the organic coating was detected after the second step of the process. This leads to a multilayer coating, which provides competitive results regarding both the adhesion of paint and corrosion protection

Local surface modification via confined electrochemical deposition with FluidFM †

International audienceWe show how the association of AFM with microfluidics, namely FluidFM, is a valuable approach for the versatile electrochemical creation of patterns having diverse shapes and topologies. Localization of the electrochemical reactions was obtained by confining the electroactive species in the microchannel and dispensing them at a precise position through the aperture of FluidFM probes. The force feedback enabled a gentle approach onto the electrode as well as a gentle contact during both the lithography procedure as well as in situ topographical AFM imaging just before or after deposition. As model systems, we demonstrate electroplating of copper and electrografting of organic moieties by reduction of aryldiazonium salts

Electrochemical Nanoprobes for Single-Cell Analysis

The measurement of key molecules in individual cells with minimal disruption to the biological milieu is the next frontier in single-cell analyses. Nanoscale devices are ideal analytical tools because of their small size and their potential for high spatial and temporal resolution recordings. Here, we report the fabrication of disk-shaped carbon nanoelectrodes whose radius can be precisely tuned within the range 5–200 nm. The functionalization of the nanoelectrode with platinum allowed the monitoring of oxygen consumption outside and inside a brain slice. Furthermore, we show that nanoelectrodes of this type can be used to impale individual cells to perform electrochemical measurements within the cell with minimal disruption to cell function. These nanoelectrodes can be fabricated combined with scanning ion conductance microscopy probes, which should allow high resolution electrochemical mapping of species on or in living cells

Localized Reduction of Graphene Oxide by Electrogenerated Naphthalene Radical Anions and Subsequent Diazonium Electrografting

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Localized Functionalization of Graphene Oxide Layers with Scanning Electrochemical Microscopy

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Studying permeable films with scanning electrochemical microscopy (SECM): Quantitative determination of permeability parameter

International audienceA new analysis of scanning electrochemical microscopy (SECM) data is proposed in the case of a substrate covered by a film (porous material or electrolyte film,…) with diffusion-limited reactions. In a lot of experimental situations, the approach curve (measure of the current as function of the tip-substrate distance) is alike the one for a bare substrate with an irreversible kinetics reaction. In all these cases, this work demonstrates a very simple relationship between the apparent irreversible kinetics parameter extracted from the approach curve and film characteristics, giving the ratio between the permeability and the thickness of the film. The validity domain of the new data analysis is carefully determined. It is then applied to experimental data on Nafion films taken from literature

New analytical approximations for negative feedback currents with a microdisk SECM tip

International audienceAnalytical approximations for steady-state negative feedback currents in scanning electrochemical microscopy (SECM) experiments using a microdisk are discussed. Previously published results are precisely discussed and lead to an analytical approximation valid (with an error below ±0.01 on normalized current) for all values of tipsubstrate distances and microdisk with an insulator thickness characterized by Rg values between 57 and 1000. More interesting from an experimental point of view, the use of new mathematical expressions allows the proposition of an analytical expression valid for all values of tipsubstrate distances and microdisk with Rg values between 1.3 and 62

Développement et optimisation de techniques analytiques à l'aide de simulations numériques, pour le microscope électrochimique

Ce travail est une contribution au développement de la microscopie électrochimique (SECM) comme outil d'analyse quantitatif. Il s'appuie sur des simulations numériques par éléments finis, pour différentes situations expérimentales, décrites dans la littérature. L'examen détaillé des résultats numériques obtenus, permettent de proposer à la communauté scientifique des outils quantitatifs d'analyse des données expérimentales qui ne font plus appel à la simulation numérique. Les travaux présentés portent tant sur des situations très classiques comme celles d'un substrat où survient une réaction irréversible d'ordre 1, que sur des activités beaucoup moins courantes comme la transformation localisée de surface. D'autres substrats rencontrés en SECM sont par ailleurs étudiés: caractérisation d'une cinétique enzymatique, de film poreux déposé sur substrat, ou de source réactive sur substrat isolant.In this work, various SECM configurations are studied thanks to finite elements numerical simulations. Rigorous analysis of numerical results, associated with careful attention to SECM community preoccupations lead to simple and reliable method, that can be used without numerical simulations. The research presented here focuses bothon common situations such as first order irreversible kinetics on substrate and on less common ones such as localised surface transformations. Other SECM situations are also studied : enzymatic kinetics, porous film on a surface, surface source spot. A method to assess the geometrical parameters of microdisk tip through approach curves is also suggested.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

A unified new analytical approximation for negative feedback currents with a microdisk SECM tip

International audienceAnalytical approximations for steady-state negative feedback currents in scanning electrochemical microscopy (SECM) experiments using a microdisk are discussed. A precise study of the limit behavior for small tipsubstrate distances and all microdisks leads to an analytical expression without any fit. From this analytical limit a new mathematical function is proposed which is the first expression that accurately fit any negative feedback approach curve with only three adjustable parameters (for a given Rg value, characterizing the insulator thickness of the microdisk electrode, between 1.001 and 1000). Finally a unified new analytical approximation of all negative feedback approach curves with tipsubstrate distances and Rg as variables is demonstrated. Except for very large Rg values (over 200), which is not an experimental interesting configuration, the error is below ±0.01 on normalized current