Alain Pailleret

Electrochemical recognition of metal cations by poly(crown ether ferrocene) films investigated by cyclic voltammetry and electrochemical impedance spectroscopy

Abstract The electrochemical behavior of the pyrrole-substituted crown ether ferrocene 1 was investigated in detail in 0.1 M TBAP+CH 3 CN by cyclic voltammetry (CV) and chronoamperometry. In the potential range 0–0.7 V, a reversible diffusion-controlled process was observed with a formal potential of 0.53 V corresponding to the ferrocene/ferricinium redox couple. Electro-oxidative polymerization of 1 was accomplished either by repeated CV scans, or by controlled potential electrolysis. The resulting polymer films were tested in acetonitrile electrolyte for the amperometric recognition of alkali and alkaline earth metal cations. Their remarkable recognition properties towards Ca 2+ and Ba 2+ cations have been confirmed by electrochemical impedance spectroscopy (EIS). EIS allowed construction of a calibration curve based on the variation of the low frequency capacity of the film as a function of the guest cation concentration, reflecting the variation of the formal potential between the free and the complexed immobilized redox couple. Capacity measurements using EIS appear to be an attractive method for cation sensing with films based on molecular redox receptors.

Nickel tetrasulfonated phthalocyanine based platinum microelectrode array for nitric oxide oxidation

We report in this paper on the electrochemical formation of nickel tetrasulfonated phthalocyanine (NiTSPc) based films on bulk Pt disk microelectrodes (diameter d = 50 μm) and thin-film Pt microdisk (diameter d = 10 μm) arrays for the realisation of Pt based nitric oxide sensors. Our results show that, despite the simultaneous formation of platinum oxides, NiTSPc deposited film offers an interesting alternative to elaborate new electrode configuration.

Electrochemical oxidation of a hexasulfonated calix[6]arene

The water-soluble calixarene p-hexasulfonato-calix[6]arene 1 was subjected to voltammetric studies of its oxidation. At glassy carbon or platinum electrodes in aqueous electrolyte solutions, oxidation was observed at E>0.7 V versus SCE in pH 2 solution. On glassy carbon, a stable derivatisation of the electrode surface was inferred from the perturbation in the electrochemistry of the anionic probe species Fe(CN)63−/4− while the electrochemistry of the cationic probe Ru(NH3)63+/2+ was unchanged. Investigation of the electrochemistry of 1 as a function of pH (2<pH<10) showed the expected dependence on the acid–base chemistry of 1 for the derivatisation of the electrode surface. On platinum electrodes, the electrochemical derivatisation was less stable and less obvious than on carbon, indicating a weakly adsorbed modifying layer.

Electrochemical activity of phenolic calixarenes

Abstract A preliminary evaluation of the electrochemical behaviour of phenolic calix[ n ]arenes ( n =4,6) possessing either H- or tert-butyl functionality at the para -phenol position has been undertaken by cyclic voltammetry. Electrochemical activity of these calixarenes is an inherent property, due to oxidation of the phenolic moiety in both types of calixarene. Oxidation of the p -H-substituted calixarenes leads to an electrode passivation process whereas oxidation of the p -t-butyl-substituted calixarenes does not. The former is attributed to electropolymerisation via intermolecular reaction of calixarene phenoxy radical species at the para -position to produce a non-conducting deposit on the electrode surface. This process is not possible with the p -t-butyl-substituted calixarenes.

Electrochemical recognition of metal cations by redox-active receptors in homogeneous solution and in polymer films: some relevant examples

Abstract Examples of several molecular redox-active receptors containing a ferrocene redox centre and crown ether or bipyridyl moieties as binding site are presented. Their electrochemical recognition properties towards groups I and II (crown ether-based receptors) and Cu + (2,2′-bipyridine-based receptors) metal cations have been investigated by cyclic voltammetry in homogeneous solution. Among the four ferrocene-crown ether studied, Fcc 3 allowed the effective amperometric recognition of Ba 2+ and Ca 2+ cations owing to the growth of a new redox peak system at the expense of the original Fc/Fc + wave (two-wave behavior). In addition, comparison of the electrochemical features in the presence of Cu + cations of ferrocene monosubstituted (Fcb 1 ) and disubstituted (Fcb 2 ) by bipyridyl groups emphasized the beneficial “sandwich” effect on the recognition behavior of ferrocene-based receptors. Polymer films coated onto electrodes surfaces by electropolymerization of pyrrole-substituted Fcc 3 and Fcb 2 retained the complexation and the amperometric properties, studied by cyclic voltammetry, of the molecular receptors. Furthermore, capacity measurements using electrochemical impedance spectroscopy (EIS) appeared as a good method for detection and titration of metal cations with these polymer-modified electrodes.

Electrochemical sensing of nitric oxide for biological systems: methodological approach and new insights in examining interfering compounds.

We report here on the appropriate analysis of some examples of interfering compounds that should be done to assess the specificity of the electrochemical sensing of nitric oxide in solution. To do so, we describe the design of a nickel porphyrin and Nafion(R)-coated carbon microfibre and discuss the methodological approach in examining interfering compounds.

Electrosynthesis and coordination chemistry of poly(ferrocenebipyridyl) films

Abstract The pyrrole-containing 1,1′-bis(bipyridyl)-substituted derivative of ferrocene L exhibits electrochemical recognition properties towards CuI and NiII in homogeneous solution. PolyL films synthesised by its oxidative electropolymerisation are able to coordinate CuI ions, whereas they do not display coordinating ability for NiII. In contrast, electropolymerisation of L in the presence of CuI or NiII ions readily obtain pre-structured metallated films. These films can be demetallated electrochemically, and then partially remetallated.

Atomic Force Microscopy Study of the Adsorption of Surfactant Corrosion Inhibitor Films

The properties of an adsorbed corrosion inhibitor—tall oil fatty acid (TOFA) imidazolium chloride—on mica, gold, and X65 steel were studied using in situ atomic force microscopy (AFM). Topography i...

Electrochemical oxidation of a tetraester calix[4]arene

Abstract The electrochemical oxidation of tetraethyl ester p -tert-butyl calix[4]arene 1 was observed in acetonitrile solution at a platinum electrode, using either cyclic or square wave voltammetry. The oxidation occurred in a number of processes, with the lowest, process I at a peak potential of 1.10 V vs. Ferrocene, being the best defined response. This was attributed to the one-electron oxidation of the aryl ether functionality present in the calixarene and so should provide a route to the electrochemical detection of calixarenes in non-aqueous mixtures. The oxidation behaviour was dependent on the presence of alkali metal cations in solution. Shifts in the oxidation potentials observed were in good agreement with the order of selectivity for the alkali metal cations.

Electropolymerized Metalloporphyrin Metallophthalocyanine and Metal Schiff Base Complex Films: Applications to Biomimetic Electrocatalysis and Bioelectroanalysis

Molecular engineering and design of new controlled spatial assemblies and architectures is a field undergoing wide growth1. A large variety of disciplines, especially bioinorganic chemistry, are now making profit from the design of molecular systems. Indeed, bioinorganic structural motifs can potentially model metalloenzyme structures and functions. The aim of such modelling is to mimic natural properties in order to elucidate fundamental aspects of reactivity and mechanism. The desire to mimic enzymatic systems has led to an active area of research involving synthetic porphyrin models of enzyme active sites, especially for monooxygenase enzymes of the cytochrome P-4502–4. An analysis of comparative studies dealing with the selectivity, efficiency and stability for both synthetic porphyrin models and natural systems has shown that efficiency arises from the control of the environment of the enzyme active site4–7. Thus, in a first approach, the design of synthetic supramolecular architecture for porphyrin models