Gérard Bidan

Polypyrrole and poly(N-methylpyrrole) films doped with Keggin-type heteropolyanions: preparation and properties

Abstract Solutions of pyrrole in acetonitrile in the presence of Keggin-type heteropolyacids (HPA) such as (SiW12O40)4− and PW12O3−40 yield soluble complexes. Oxidation of the complexes gives polypyrrole films doped by the HPA. The electrochemical behaviour of the HPA immobilized in several film thicknesses is described. It is different for HPA alone in solution because of the lack of conductivity of the polypyrrole and poly(N-methylpyrrole) in the potential range of reduction and in the range of molecular dispersion of HPA in the polymer matrix. The levels of doping of the polymers by HPA are similar to those with classical anions, but here the HPA are retained in the films rather better even upon cycling.

One-step electrochemical immobilization of keggin-type heteropolyanions in poly(3-methylthiophene) film at an alectrode surface: Electrochemical and electrocatalytic properties

Abstract Immobilization of Keggin-type heteropolyanions (HPA), such as PW 12 O 40 −3 , SiW 12 O 40 4− and PMo 12 O 40 3− , in poly(3-methylthiophene is performed by electropolymerization of the thiophene derivative in the presence of the corresponding HPA acid. The polymerization was possible even in the presence of a large amount of water because of the formation of a complex between the HPA and the 3-methylthiophene. The cyclic voltammetry curves in acetonitrile during polymerization are described and also of the polymer films doped with HPA. In the case of the phosphomolybdate anions, we observed in addition to the redox system of the polymer, six monoelectronic transfer from the HPA. These multiple electron transfers can explain the possibilities of such modified electrodes in electrocatalysis. Effectively, we observe an electrocatalytic reduction of oxygen in acetonitrile (0.5 M HClO 4 ) by comparison with an unmodified bare glassy carbon electrode.

3D hierarchical assembly of ultrathin MnO2 nanoflakes on silicon nanowires for high performance micro-supercapacitors in Li- doped ionic liquid

Building of hierarchical core-shell hetero-structures is currently the subject of intensive research in the electrochemical field owing to its potential for making improved electrodes for high-performance micro-supercapacitors. Here we report a novel architecture design of hierarchical MnO2@silicon nanowires (MnO2@SiNWs) hetero-structures directly supported onto silicon wafer coupled with Li-ion doped 1-Methyl-1-propylpyrrolidinium bis(trifluromethylsulfonyl)imide (PMPyrrBTA) ionic liquids as electrolyte for micro-supercapacitors. A unique 3D mesoporous MnO2@SiNWs in Li-ion doped IL electrolyte can be cycled reversibly across a voltage of 2.2 V and exhibits a high areal capacitance of 13 mFcm−2. The high conductivity of the SiNWs arrays combined with the large surface area of ultrathin MnO2 nanoflakes are responsible for the remarkable performance of these MnO2@SiNWs hetero-structures which exhibit high energy density and excellent cycling stability. This combination of hybrid electrode and hybrid electrolyte opens up a novel avenue to design electrode materials for high-performance micro-supercapacitors.

Part I. A comparative electrochemical study of transition metal substituted Dawson type heteropolyanions

Abstract The comparative electrochemical behaviour, in aqueous solutions, of the Dawson lacunary anion [P 2 W 17 O 61 ] 10− and of the Fe III , Cu II , Co II , Ni II , Mn III and Mn II substituted Dawson lacunary heteropolyanions is presented. The literature concerning the latter heteropolyanions has been reviewed and completely new data are presented. The electrochemical behaviour observed for the reduction of the tungsten oxo centres, for all the heteropolyanions investigated, was found to be pH dependent. Electrochemical evidence for the presence of the Fe III , Cu II , Co II and the Mn II and Mn III cations in the ejected tungsten position was obtained with the Ni II cation processing no electroactivity.

Organosilyl/‐germyl Polyoxotungstate Hybrids for Covalent Grafting onto Silicon Surfaces: Towards Molecular Memories

Organosilyl/-germyl polyoxotungstate hybrids [PW(9)O(34)(tBuSiO)(3)Ge(CH(2))(2)CO(2)H](3-) (1a), [PW(9)O(34)(tBuSiO)(3)Ge(CH(2))(2)CONHCH(2)C[triple bond]CH](3-) (2 a), [PW(11)O(39)Ge(CH(2))(2)CO(2)H](4-) (3a), and [PW(11)O(39)Ge(CH(2))(2)CONHCH(2)C[triple bond]CH](4-) (4a) have been prepared as tetrabutylammonium salts and characterized in solution by multinuclear NMR spectroscopy. The crystal structure of (NBu(4))(3)1a.H(2)O has been determined and the electrochemical behavior of 1a and 2a has been investigated by cyclic voltammetry. Covalent grafting of 2a onto an n-type silicon wafer has been achieved and the electrochemical behavior of the grafted clusters has been investigated. This represents the first example of covalent grafting of Keggin-type clusters onto a Si surface and a step towards the realization of POM-based multilevel memory devices.

Voltammetric detection of NO in the rat brain with an electronic conducting polymer and Nafion® bilayer-coated carbon fibre electrode

An NO sensor based on a carbon fibre microelectrode modified by a poly(N-methylpyrrole) incorporating [(H2O)FeIIIPW11O39]4− sublayer and coated by a Nafion® external layer is described. It is based on the NO oxidation,current measured by differential normal pulse voltammetry. In solution, a linear response is obtained between this oxidation current and the NO concentration in the range 10−7 to 10−3 M with a sensitivity of 2.65 ± 0.15 nA μM−1. A comparative study has been carried out with poly(N-methylpyrrole) doped with ClO4−, polypyrrole doped with sulfonated nickel porphyrin, polypyrrole and poly(N-methylpyrrole) doped with Nafion®. This sensor implanted in the rat brain is efficient to detect in real time the NO released. The validation of in vivo measurements is made by injecting the rat with an NO-synthese inhibitor.

Behaviour of some poly(pyrrole-anthraquinone) films in DMSO electrolytes

Abstract Several films of poly(pyrrole-anthraquinone) have been prepared by the electropolymerization in organic media of anthraquinones adequately substituted by some N-alkylpyrroles. These films have been studied mainly by electrochemical methods in DMSO with either TEAFB or LiClO4 as the supporting salt. Bonded anthraquinones can be reversibly reduced to their radical anions or dianions with a fair yield, except on slow or prolonged cycling where the protonation effect modifies this behaviour. Spectroelectrochemical studies confirm these facts and additionally allow the probable complex formations in fully reduced films to be detected.

Conducting polymers as a link between biomolecules and microelectronics

Abstract Biosensors based on electronic conducting polymers (ECPs) appear particularly well suited to the requirements of modern biological analysis: multiparametric assays, high information density and miniaturization. We describe a new methodology for the preparation of addressed DNA matrices. The process includes an electrochemically directed copolymerization of pyrrole and oligonucleotides bearing on their 5′ end a pyrrole moiety. The resulting polymer film deposited on the addressed electrode consists of pyrrole chains bearing covalently linked oligonucleotides. An oligonucleotide array was constructed on a silicon device bearing a matrix of 48 addressable 50 μm x 50 μm gold microelectrodes. This technology was successfully applied to the genotyping of Hepatitis C Virus in blood samples. Fluorescence detection results show good sensivity and a high degree of dimensional resolution. The need for versatile processes for the immobilization of biological species on surface led us to extend our methodology. A biotinylated surface was obtained by co-electropolymerization of pyrrole and biotin-pyrrole monomers. The efficiency for recognition (and consequently immobilization) of R-phycoerythrin-avidin was demonstrated by fluorescence detection. Copolymerization of decreasing ratios of pyrrole-biotin over pyrrole allowed us to obtain a decreasing scale of fluorescence.

Synthesis of high quality reduced graphene oxide nanosheets free of paramagnetic metallic impurities

A facile and cost-effective method to prepare paramagnetic-metal free graphene nanosheets based on stannous chloride reduction of graphene oxide (GO) in a strongly acidic medium is reported. Simultaneous exfoliation and reduction is achieved in this room temperature process. Compared to the chemical reduction of GO using hydrazine or iron, the present method showed that Sn–rGO is several orders of magnitude less magnetic and hence does not contain any paramagnetic metallic impurities. With high reduction degree, this simple method shows promising application in energy and magnetic related studies.

Part II. Role of pH and the transition metal for the electrocatalytic reduction of nitrite with transition metal substituted Dawson type heteropolyanions

Abstract The parent Dawson and lacunary anion were both seen previously to have a catalytic effect (redox mediation) upon the reduction of nitrite at a pH equal to 2.00. However, at a pH value of 4.50 no electrocatalytic effect was observed for low concentrations of nitrite. It was shown that at the latter pH value the presence of certain transition metals substituted into the lacunary anion is necessary to observe the electrocatalytic reduction (chemical catalysis) of low concentrations of nitrite. It was found that the Fe III and Cu II substituted Dawson heteropolyanions Fe III HPA and Cu II HPA respectively were the most efficient at pH 4.50 for the electroreduction of nitrite. In addition, despite the lack of direct electroactivity of the Ni II site in Ni II HPA, the Ni II site is demonstrated by the observation of a catalytic effect for nitrite reduction at pH 4.50.