Polypyrrole Modified Research Articles

Molecularly Imprinted Polypyrrole Modified Glassy Carbon Electrode: Determination of Polyphenols

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Electrochemical Deoxyribonucleic Acid Damage Treated with Perfluorinated Compounds on Peroxide Polypyrrole Modified Gold Electrode

Abstract The Au/(Peroxide polypyrrole)/DNA electrochemical sensor for organic pollutant perfluorooctanoic acid was prepared. The morphology of the electrode surface was characterized by atomic force microscopy (AFM). Electrochemical response of the sensor to perfluorooctanoic acid was studied by using methylene blue (MB) as the indicator. It was found that the MB peak current decreased with the elongation of damage time and the increase of ionic strength. The results of electrochemical impedance studies showed that DNA damage reduced the electron transfer ability.

Improvement of the Stability of Colloidal Gold Superparticles by Polypyrrole Modification

The colloidal gold superparticle (SP)/polypyrrole (PPy) core/shell composites were successfully prepared by oxidative polymerization of pyrrole monomer on the surface of poly(N-vinylpyrrolidone) (PVP)-grafted colloidal gold SPs. These core/shell composites showed strong catalytic activity and excellent stability. Control experiments indicated that the morphology and the thickness of PPy shell were controllable by adjusting the dosage of pyrrole monomer. Meaningfully, the resulting SP/PPy core/shell composites were quite stable in water, which could be stored for more than half a year without damaging their structures. As an example, we demonstrated the use of these composites as catalyst for the reduction of methylene blue (MB) dye with a reducing agent of sodium borohydride. The composites exhibited highly catalytic activity and long-term stability, implying promising applications of SP/PPy composites in catalysis.

Polypyrrole Modified Copper Electrode for Nitrate and Nitrite Reduction in Neutral Solutions

Conducting polypyrrole (Ppy) film was synthesized electrochemically onto a copper electrode in oxalate, oxalic acid and salicylic acid solutions. The electrochemical oxidation of pyrrole to form polypyrrole film and the electroreduction of nitrate and nitrite ions at synthesized PPy modified copper electrodes (Ppy/Cu) in potassium chloride aqueous solutions were studied by cyclic voltammetry. Polypyrrole film formation and the activity of the modified Ppy/Cu electrode for nitrate and nitrite reduction were found to be dependent on synthesis medium and conditions: pH, content and concentrations of the electrolytes; pyrrole concentration; electrode potential; electrolysis duration. The finishing and storage conditions of the prepared Ppy/Cu modified electrodes, such as drying duration and temperature; soaking duration in water before use, also affect their catalytic activity for nitrate and nitrite reduction. The highest reduction currents of nitrate and nitrite were obtained for the nanoporous structured Ppy film prepared in salicylic acid solution. Nitrate and nitrite reduction occurred at cathodic potentials of ca. -0.70 V and -0.85 V (Ag/AgCl) respectively, and the peak potentials ranged from -1.00 V to -1.15 V (Ag/AgCl). In the potassium chloride aqueous solution the reduction of nitrate and nitrite ions on the Ppy/Cu electrode was found irreversible.

Nanoporous Polypyrrole Modified Copper Electrode for Nitrate and Nitrite Reduction in Neutral Solutions

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Voltammetric Behavior and Determination of Tocopherol in Vegetable Oils at a Polypyrrole Modified Electrode

The voltammetric behavior of α-tocopherol in the presence of vegetable oil is studied at a polypyrrole modified Pt electrode in a 1,2-dichloroethane-ethanol medium with cyclic voltammetry. Cyclic voltammogram of α-tocopherol showed a well-defined oxidation peak; the peak potential shifting toward less positive and a much higher peak current obtained at a polypyrrole modified electrode than that obtained at the unmodified Pt electrode. An electroanalytical method for the determination of α-tocopherol based on its electrochemical oxidation at the polypyrrole modified Pt electrode is developed. Using differential pulse voltammetry, the peak currents were found to increase linearly with the α-tocopherol concentration over the range of 5.0 to 300 μM, with a sensitivity of 5.38×10−2 A L mol−1 and the limit of detection of 1.5 μM (S/N=3), the detection time being about 90 s for each assay. The interference of other synthetic antioxidants such as TBHQ, BHA and BHT to the analysis of α-tocopherol was investigated. The developed method is applied to the quantification of tocopherols in six vegetable oils, showing that the results are in good agreement with those by HPLC method.

Porous and Electrically Conductive Polypyrrole−Poly(vinyl alcohol) Composite and Its Applications as a Biomaterial

Bulk modification of polypyrrole (PPY) with poly(vinyl alcohol) (PVA) was carried out by the electropolymerization of pyrrole in the presence of PVA in the reaction solution, with tetraethylammonium perchlorate (TEAP) as the electrolyte. The surface morphology of the as-synthesized PPY-TEAP-PVA film was investigated using scanning electron microscopy, and the film was further characterized using X-ray photoelectron spectroscopy, electrical conductivity, the water contact angle, and BET surface area measurements. The PPY-TEAP-PVA composite is electrically conductive, hydrophilic, and microporous with a high surface area. Its potential as a biomaterial was investigated with respect to its blood compatibility and function as a substrate for biosensor fabrication and cell culture. The presence of PVA in the film attenuates blood protein adsorption, and the porous nature of the PPY-TEAP-PVA film results in a 10-fold increase in the amount of glucose oxidase covalently immobilized on the film over that on a nonporous PPY film. PC12 cell attachment and growth on the PPY-TEAP-PVA film was also shown to be enhanced compared with that on tissue culture polystyrene. The attached cells proliferated and formed a monolayer on the film surface after 48 h of seeding.

Characterization and electrocatalytic application of silver modified polypyrrole electrodes

Silvermodified polypyrrole electrodes were prepared with the aim of testing them for the electro oxidation of formaldehyde in alkaline solution. The modification of polypyrrole by immersion in aqueous AgNO3 solution was studied by cyclic voltammeter and vacuum techniques (AES and XPS). The influence of time of immersion and the thickness of the polypyrrole film, prepared by electrochemical polymerization, on the modification of the polymer were examined. The results acquired from both electrochemical and spectroscopic examinations show that immersion of a polypyrrole electrode in a AgNO3 solution results in its modification with silver, which is deposited in the elemental state on the surface. The quantity of silver deposited depends not only on the immersion time but also on the thickness of the polymer film. A modified PPy/Ag electrode exhibits catalytic activity for the electro oxidation of CH2O in NaOH. In spite of the low quantity of silver, the activity of the electrode for this reaction is comparable to that of a polycrystalline silver electrode.

Modified diamond electrodes for electrolysis and electroanalysis applications

The outstanding properties of diamond make it a very attractive material for use in many potential applications. In particular, the superior electrochemical properties of highly boron-doped conductive diamond films, prepared by the chemical vapor deposition (CVD) process, have received attention from electrochemists. This paper reports several diversified applications of boron-doped diamond electrodes; highly sensitive and interference-free microfiber electrodes with over-oxidized polypyrrole modification, integrated electrochemical detector for microchip capillary electrophoresis (CE), and smoothing treatments of micro-polycrystalline surface. Studies have been made of the electrochemical properties of each system and their application in electroanalysis is discussed.

Syntheses, Structures and Redox Properties of New Macrocyclic Triazatriolefinic Pd0 Complexes and Their Polypyrrole Modified Electrodes − Application to Heterogeneous Catalytic Suzuki Cross‐Coupling Reactions

AbstractNew triolefinic macrocyclic ligands of the type (E,E,E)‐1,6,11‐tris(arenesulfonyl)‐1,6,11‐triazacyclopentadeca‐3,8,13‐triene (aryl: a = ferrocenyl, b = 4‐pyrrol‐1‐ylphenyl, c = 4‐methylphenyl) and their Pd0 complexes (1aab, 1abb and 1bcc) have been prepared and characterized. Further structural characterization in the solid state has also been performed by means of X‐ray diffraction analysis for the complex 1bcc. The redox properties of both the ligands and their Pd complexes have been studied using cyclic voltammetric and coulombimetric techniques. In particular, complexes and ligands containing the pyrrole group do polymerize upon exposure to sufficiently positive potentials, on glassy carbon electrodes, generating highly stable modified electrodes. The new modified electrodes are efficient and selective heterogeneous catalysts for Suzuki cross‐couplings, benefiting from simple removal of the catalyst from the reaction vessel. As an example, more than 2·105 metal cycles are achieved at 65 °C in the coupling of phenylboronic acid and cinnamyl bromide. Iodoarenes and phenylboronic acid are also converted into biphenyls with relatively good conversions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Biotinylated Polypyrrole Modified Quartz Crystal Microbalance for the Fast and Reagentless Determination of Avidin Concentration

A quartz crystal microbalance (QCM) bioaffinity sensor for avidin, based on electropolymerized biotinylated polypyrrole film, was developed. The functionalization of one of the Au quartz electrode has been achieved by controlled potential oxidation of a biotinyl pyrrole monomer in CH3CN. The modified quartz resonator was placed in a QCM flow cell. In the presence of avidin solutions, gravimetric measurements indicated the reproducible formation of a compact avidin layer via the specific avidin-polymerized biotin interaction. The polymerized biotin retained identical bioaffinity properties for avidin over a period of one month. The initial slope of the frequency change as a function of time was recorded and related to avidin concentrations. Avidin concentration in the range 1.5×10−9–3.7×10−5 M can be measured by this method.

Surface modification of polypyrrole films via grafting of poly(ethylene glycol) for improved biocompatibility

Modification of polypyrrole (PPY) films in the salt and deprotonated forms was carried out via UV-induced surface graft copolymerization with methoxy-poly(ethylene glycol) monomethacrylate (PEGMA) macromonomer. Contact angle and X-ray photoelectron spectroscopy (XPS) measurements were used to characterize the surface-modified PPY films. The biocompatibility of the PEGMA polymer-modified films was compared to that of the pristine films based on their ability to reduce protein adsorption, platelet adhesion and blood coagulation (antithrombogenicity property). The studies performed showed that the graft-modified films exhibited excellent biocompatibility based on all three criteria.

A Combined EQCM and Probe Beam Deflection Study of Salicylate Ion Transfer at a Polypyrrole Modified Electrode

A Combined EQCM and Probe Beam Deflection Study of Salicylate Ion Transfer at a Polypyrrole Modified Electrode

Surface Modification of Electroactive Polymer Films by Ozone Treatment

Surface modification of polypyrrole (PPY), polyaniline (PAN) and poly(3-alkylthiophene) films by ozone was studied by angle-resolved x-ray photoelectron spectroscopy (XPS). In the case of the N-containing polymers, oxidation occurs readily and mainly at the carbon atoms, resulting in the formation of C-O, C=O, COOH and even O-COOH (especially for PAN) species. The carbon atoms of doped PPY and PAN films are significantly more resistant to ozone oxidation, but the samples suffer some loss of the dopant in the surface region. Ozone treatment does not involve the direct oxidation of the nitrogen heteroatoms to form the - NO x species, even at high extent of carbon oxidation. In addition, a substantial decrease in the intrinsic oxidation state ([=N-]/[-NH-] ratio) was observed in the 25% deprotonated PPY (DP-PPY) base, the 50% intrinsically oxidized emeraldine (EM) base and the 75% intrinsically oxidized nigraniline (NA) base after ozone treatment and subsequent atmospheric exposure. In the case of the S-containing polymers, ozone treatment results predominantly in the oxidation of sulphur heteroatoms to give rise to the sulphone and peroxide species. The oxidized sulphur species, however, are readily reduced or consumed in a photochemical reaction.

Surface Modification of Electroactive Polymer Films by Ozone Treatment

Surface modification of polypyrrole (PPY), polyaniline (PAN) and poly(3-alkylthiophene) films by ozone was studied by angle-resolved x-ray photoelectron spectroscopy (XPS). In the case of the N-containing polymers, oxidation occurs readily and mainly at the carbon atoms, resulting in the formation of CνO, CξO, COOH and even OνCOOH (especially for PAN) species. The carbon atoms of doped PPY and PAN films are significantly more resistant to ozone oxidation, but the samples suffer some loss of the dopant in the surface region. Ozone treatment does not involve the direct oxidation of the nitrogen heteroatoms to form theνNOx species, even at high extent of carbon oxidation. In addition, a substantial decrease in the intrinsic oxidation state ([ξNν]/[νNHν] ratio) was observed in the 25% deprotonated PPY (DP-PPY) base, the 50% intrinsically oxidized emeraldine (EM) base and the 75% intrinsically oxidized nigraniline (NA) base after ozone treatment and subsequent atmospheric exposure. In the case of the S-containing polymers, ozone treatment results predominantly in the oxidation of sulphur heteroatoms to give rise to the sulphone and peroxide species. The oxidized sulphur species, however, are readily reduced or consumed in a photochemical reaction.

Chemical modification of polypyrrole. II. Thermal stability, dielectric, and conductivity characteristics of polypyrrole substituted with phthalic and pyromellitic dianhydride

AbstractPolypyrrole (PPY) was electrophilically polycondensed with phthalic anhydride (PA) and pyromellitic dianhydride (PMDA). PPY–PA and PPY–PMDA polycondensates were evaluated in regard to their thermal stability and dielectric and conductivity behavior. The overall thermal stability is in the order PPY < PPY–PA < PPY–PMDA, which may be rationalized in terms of intra‐ and intermolecularly cross‐linked structures of the polycondensates. IR spectral analyses of PPY–PA and PPY–PMDA subjected to heating at 300, 400, 500, and 550°C, respectively, were conducted to understand some of the structural changes in the polymer matrices. Both PPY–PA and PPY–PMDA exhibit high dielectric constants (200 and 125) at low frequency (103 Hz), which fall monotonically with increasing frequency, suggesting the possibility of interfacial polarization. The conductivity values of PPY–PA and PPY–PMDA are in the range 10−3–10−4 ohm−1 cm−1, which are conspicuously lower than that for unmodified PPY (2.5). This is due to the adverse effect of incresing temperature on the PPY chain stability, whereby structural conjugation and eventually conductivity will be affected. © 1994 John Wiley & Sons, Inc.

Control of the interface properties of conducting polypyrrole

Chemical modification of polypyrrole by 3-substitution of the monomer results in different kinds of new interface properties for the corresponding material. Alkylation allows a marked increase in the hydrophobicity and its regulation by the substituent length. Polyether chains increase the reversibility of the polymer redox system in organic electrolyte, and thus the power capability and the long-term stability of polypyrrole as an electrode material for batteries. Substituted carboxylic groups give rise to a linear pH-dependence of the formal redox potential of polypyrrole in acidic media.