Polymer Film Electrodes Research Articles

Voltammetric Identification of Lead(II) and (IV) in Mediaeval Glazes in Abrasion-Modified Carbon Paste and Polymer Film Electrodes. Application to the Study of Alterations in Archaeological Ceramic

Voltammetric Identification of Lead(II) and (IV) in Mediaeval Glazes in Abrasion-Modified Carbon Paste and Polymer Film Electrodes. Application to the Study of Alterations in Archaeological Ceramic

Identification of inorganic pigments from paintings and polychromed sculptures immobilized into polymer film electrodes by stripping differential pulse voltammetry

Inorganic pigments in paintings and polychromed sculptures are studied by cyclic voltammetry and differential pulse stripping voltammetry using micro-sample coatings in Paraloid B72-film modified electrodes. Characteristic cathodic and anodic differential pulse profiles were obtained in the +0.4 to −1.0 V vs. SCE potential range for different cadmium, copper, lead, mercury and zinc pigments used in traditional colour palettes. Under optimized conditions, excellent reproducibility was obtained. Microsamples extracted from polychromed sculptures, wall paintings, canvas paintings, panel paintings and altarpieces from Spain, Ethiopia and Italy from the 12th to the 20th centuries have been analyzed and cadmium, copper, lead, mercury and zinc pigments such as cadmium red, cadmium yellow, azurite, copper resinate, malachite, verdigris, lead–tin yellow, lead white, minium, Naples yellow, vermilion, chrome orange, chrome yellow and white zinc have been identified by this technique in agreement with PLM, SEM/EDX, XRD and FT-IR analysis.

Deposition of Uranium Ions with Modified Pyrrole Polymer Film Electrode

Anodically Polymerized conducting Polypyrrole film electrode was employed to Pick up uranyl ion with the type of Gr/ppy, xylenol orange modified electrode. To have Porous and oriented ppy film, NBR was applied as precoating agent. The rate constant of polymerization was which was 1.6 times smaller value than bare graphite surface. The deposited amount of uranyl iou on of ppy was . The matrix effect in artificial seawater was . The polymer film electrode has a diffusion controlled process in conduction, but the modified Gr/ppy, type was influenced on the ion doping and electronic conduction of film itself owing to increasing of impedance. The capacitance of electrical double layer was respectively enhanced to 56 and 130 times in Gr/ppy, and Gr/ppy, than Grippy type electrode.

Preparation, optimization, and voltammetric characteristics of poly(o-phenylenediamine) film as a dopamine-selective polymeric membrane

Poly(o-phenylenediamine) films were electrochemically prepared on gold electrodes from the corresponding monomer in an aqueous solution at a constant potential. The polymeric films prepared in this one-step procedure were found to be thin and insoluble in the aqueous solution. Cyclic and differential pulse voltammetric techniques were used to examine the permeation properties of ascorbic acid and dopamine at the resultant polymeric film electrode. Then, the effects of the chemical and electrochemical variables (e.g., film thickness, polymerization potential, concentrations of monomer and electrolyte) on the permselectivity characteristics of the polymeric film were systematically investigated and the optimal values for each parameter were determined. Furthermore, it was found that the optimized polymer electrode was found to be stable for the successive runs. As a result, it is claimed that poly(o-phenylenediamine) film can be used as a dopamine-selective polymeric membrane. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 327–332, 2001

Platinum–palladium loaded polypyrrole film electrodes for the electrooxidation of d-glucose in neutral media

Abstract Modified polymer films with metal particles incorporated into the films by electrodeposition are known as possible electrocatalysts for various electrode reactions such as fuel cell applications. This work presents some results concerning the electrooxidation of d -glucose at modified polymer film electrodes prepared on a platinum substrate. This reaction has a great deal of interest in view of its applications to detection systems (glucose sensor), fuel cells (pacemakers) and electroorganic systhesis. The modified polymer film electrodes contain platinum and/or palladium particles dispersed in the polypyrrole film by electrodeposition in neutral media. Addition of palladium to platinum modifies the electrocatalytic behaviour of the electrode drastically. The modification is thought to involve minimisation of the poisoning of the catalyst, hence increasing its electrode activity.

Electrochemical preparation of poly(o-toluidine) film and its application as a permselective membrane

Poly(o-toluidine) films were electrochemically synthesized on Pt electrodes at a constant potential (0.75 V versus Ag/AgCl) from a deoxygenated aqueous solution of 0.1M toluidine dissolved in 0.1M KCl. To form permselective polymeric film electrodes, poly(o-toluidine) films at different thicknesses were prepared by varying the amount of charge consumed during electrochemical polymerization. Then, experimental parameters (e.g., concentrations of monomer and electrolyte and pH of the phosphate buffer salt solution) affecting the polymeric film thickness were optimized. Permeation of the various electroactive and nonelectroactive species such as ascorbic acid, oxalic acid, hydrogen peroxide, lactose, sucrose, and urea through the optimized poly(o-toluidine)-coated electrodes was investigated using a chronoamperometric technique. From experimental results, it was found that a poly(o-toluidine)-coated electrode permitted the oxidation of hydrogen peroxide and prevented the permeation of the mentioned electroactive and nonelectroactive species. In other words, it was seen that this polymeric electrode responded to only hydrogen peroxide selectively. Thus, it has been claimed that a poly(o-toluidine)-coated Pt electrode can be used as a permselective polymeric membrane to overcome interference problems occurring in the hydrogen peroxide-based biosensor applications. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2141–2146, 1999

An advanced model of the impedance of polymer film electrodes

A new model for the impedance of polymer film electrodes has been developed in that three mobile charge carriers are considered. It has been observed especially in the case of organic conductive polymer that beside the electron diffusion and counterion transport very often hydrogen ions also participate in the charge transport and charge transfer processes in the course of redox transformation of these polymers, i.e. a model describing this case is essential. It has been demonstrated that by the help of reasonable assumptions some of the mathematical problems can be overcome and an analytical solution can be obtained for the complex impedance in the case of low amplitude variation of the electrode polarization. The equations derived for the charge transport and charge transfer impedances are tested by CNLS fitting data obtained for an Au∣poly( o-phenylenediamine) electrode.

Voltammetric determination of trace mercury in concentrated chloride media using polymer-film electrodes modified with polyammonium macrocyclic receptors

Trace amounts of mercury can be determined voltammetrically in aqueous solution on Paraloid B72 film electrodes modified by the macrocyclic polyamine receptors 1,4,7,10,13,16,19,22,25,28-decaazacyclotriacontane and 1,4,7,10,13,16,19,22,25,28,31-undecaazacyclotritriacontane. These receptors are able to form very stable mono-, bi-, and trinuclear complexes with Hg2+ ions in the pH range 3–12, favouring the preconcentration step. Very stable Cl––macrocycle mixed complexes with Hg2+ are also formed, allowing the determination of mercury traces in large concentrated chloride media. Under optimized conditions, this procedure gives good linearity for nanomolar mercury concentrations and a detection limit of 0.2 × 10–10 mol L–1. Results concerning the optimization of the method and lowering of the influence of possible interferents are reported.

Metal ion incorporation in the conducting polymer electrode matrix using an ‘active’ metal substrate

Abstract The incorporation of free transition metal cations (potential redox catalyst centers) into conducting organic films by electrodeposition is relatively rare due to the repulsive nature of the positive cation radicals of the polymer itself during polymerization. This paper shows that such metal cations can be trapped in the polymer matrix as it is being electrodeposited on a metal substrate electrode, which itself simultaneously electro-oxidizes (corrodes). The electropolymerizatiob of 3-methylthiopene on Mo(O), Ni(O) and Fe(O) substrate electrodes (‘active electrodes’) is reported. SEM, EDXRF, and XPS were used to demonstrate the amount of metal cations in and/or on the polymer matrix and to determine the valence states. The rates of diffusion of the incorporated metal ions into an LiClO 4 electrolyte solution were also studied. The presence of trace amounts of all three metal cations were sufficient to destroy the electroactivity of the polymer film electrodes for the oxidation of catechol.

Increased Redox-Reaction Rate of Quinhydrone at N-Substituted Polypyrrole Film Electrodes

Abstract A poly[1-methyl-3-(pyrrol-1-ylmethyl)pyridinium] perchlorate-coated glassy carbon electrode noticeably decreased the charge-transfer resistance (Rt) of quinhydrone relative to a naked glassy carbon electrode. The redox species was not concentrated into a polymer film; this result differs markedly from the very good absorption of anthraquinonesulfonates and indigosulfonates by a polymer film. The dependence of Rt and the interfacial capacitance on the film thickness implies that the charge-transfer process occurs at the film-solution interface, because the polymer film is appreciably electronically conductive at positive potentials. Because of a change in the film conductivities with the potential, the polymer-coated electrode increased the anodic peak current of quinhydrone by three times, but decreased its cathodic peak current by two fifths, relative to that of a naked electrode. Although the decrease in Rt at a polymer-film electrode is somewhat ascribed to an increasing area, which is due to a porous film surface, the electrocatalytic effect of the polymer film can be attributed to an increasing standard rate constant of the charge-transfer process; this increase may be due to the adsorption of quinhydrone on the polymer surface.

Electron transfer at conducting polymer film electrodes: mechanism and kinetics of ferrocene oxidation at poly(3-octylthiophene)

Abstract Oxidation of ferrocene at a poly(3-octylthiophene) (POT) film electrode has been investigated by using cyclic voltammetry, rotating disc electrode voltammetry and electrochemical impedance spectroscopy. The POT film electrode was prepared by galvanostatic electropolymerization of 3-octylthiophene on a rotating Pt disc electrode. In the medium used, i.e. 0.1 M LiBF 4 + propylene carbonate, the formal redox potentials of ferrocene and POT are 0.4 and 1.1 V vs. Ag|AgCl respectively. This makes it possible to study the oxidation of ferrocene at both undoped (semiconducting) POT and at doped (electronically conducting) POT. The voltammetric data show that the oxidation of ferrocene is kinetically controlled at undoped or lightly doped POT while ferrocene is oxidized at a diffusion limited rate at highly doped POT. Impedance data on the POT film electrode in solutions containing different concentrations of supporting electrolyte and ferrocene indicate that the ferrocene oxidation occurs in parallel with the doping process, resulting in a competition between ferrocene and doping ions for the available ‘sites’ at the polymer|solution interface. The kinetics of electron transfer at the polymer|solutio interface are discussed based on the Butler-Volmer formulation of electrode kinetics.

Electrocatalytic Hydrogenation of Organic Compounds on a Poly[N-(5-hydroxypentyl)pyrrole] Film-Coated Electrode Incorporating Palladium Microparticles

A poly[N-(5-hydroxypentyl)pyrrole] film-coated carbon-fiber electrode incorporating palladium metal microparticles was prepared and the catalytic ability in the electrochemical hydrogenation of organic compounds was investigated. This electrode exhibited a high catalytic ability and a strong physical stability with respect to hydrogen evolution. By using this electrode, the electrocatalytic hydrogenation for organic compounds in an organic solvent–buffer solution led to an efficient formation of hydrogenated products, such as saturated compounds, amino compounds, and hydroxy compounds, in high yields and current efficiencies. Furthermore, a catalytic polymer film electrode was successfully applied to the hydrogenative deprotection of a benzyl group and the dehalogenation of bromobenzene in electroreduction media.

In situ ATR-FTIR- and Raman-investigations on the polymerization of 2,2′-thienylpyrrole and the redox behaviour of thin film poly(thienylpyrrole) electrodes in aqueous electrolytes

The polymerization of 2,2′-thienylpyrrole and the redox behaviour of the resulting polymer film electrodes were studied in order to improve the stability and the response time of miniaturized thin film pH-sensors based on this polymer. The polymerization process was studied in aqueous solutions of different pH containing NaClO 4, LiClO 4 and NaBF 4. In electrolytes containing perchlorate ions dense and homogeneous poly(thienylpyrrole) films were produced, exhibiting a conductivity ranging between 0.1 and O.3S.cm −1. During in situ FTIR-ATR experiments, the detection of oligomeric structures was not possible. The polymerization of the monomer starts in a very narrow potential range quite rapidly and by in situ Raman spectroscopy an intermediate state was detectable during potentiostatic polymerization. The poly(thienylpyrrole) films exhibit in perchlorate containing electrolytes in the pH range 1 to 8 a relatively reversible and similar redox behaviour. In contrast to poly(thienylpyrrole) films produced in non-aqueous electrolytes, the films polymerized in aqueous media show at higher redox cycles (> 1000) a reduced stability connected with a reduced degree of reversibility.

Electrocatalytic Hydrogenation of Acetylenes on Palladium Incorporating Poly [N-(5-Hydroxypentyl) Pyrrole] Film-Coated Electrode

Abstract The catalytic polymer film electrode which was coated with poly[N-(5-hydroxypentyl) pyrrole] film on carbon materials and incorporated palladium metal microparticles in film was prepared. By use of the electrode the electrocatalytic hydrogenation of acetylenes in organic solvent-HCl buffer solution led to the efficient formation of ethanes in high current efficiencies.

H 2O 2 from an oxidase enzyme can be detected cathodically using metal microparticles dispersed in a polymeric film electrode

H 2O 2 from an oxidase enzyme can be detected cathodically using metal microparticles dispersed in a polymeric film electrode

Electrochemical Study on the Growth of Multilayer Film Electrodes of the Conducting Polymers PPP, Pot and of the Copolymer of PPP and Pot

ABSTRACTMultilayer polymer film electrodes were prepared from the electrochemically synthesized conducting polymers poly(paraphenylene), PPP, poly(3-octylthiophene), POT and from the electrochemically synthesized copolymer of PPP and PO.T. The electrochemical behavior of the multilayer film electrodes made from PPP and POT is compared with the response of a copolymer layer. The structure of the copolymer film could be changed by varying the polymerization potential and the concentration as well as the ratio of the concentration of the two starting materials. Due to the slightly lower (0.15 V) oxidation potential of the POT monomer in comparison to the oxidation potential of biphenyl, POT is usually present to a higher extent than PPP in the electrochemically produced copolymer. The copolymer electrodes, the single polymer film layers and the multilayer polymer film electrodes showed different electrochemical response of the charging-discharging cycle.

Charge Transport at Polypyrrole Film Electrodes: Effect of the Electrolyte Concentration

Abstract From measurements of the a.c. response of polypyrrole film electrodes in KNO3 solution, we found that solvent swelling of the polymer greatly influences the kinetic behaviors of the polymer film electrodes. Electric migration in bulk film was due to background electrolyte ions which permeated through the film. Inside the film in contact with a supporting electrolyte solution, the mobility of the electrons may be much smaller than that of ions. The charge-transfer resistance of a partially oxidized film decreases along with increasing concentration of the electrolyte solution, because of a resultant increase in the activity of polarons. Such an increased activity of polarons also brings about a smaller Warburg coefficient, and thus a smaller limiting diffusion resistance (RL). The pseudocapacitance appearing at low frequencies increases along with an increase in the concentration of the electrolyte solution, which is opposed to the change in RL. These results corroborate that variations in the charge-transport parameters with the electrolyte concentration can be ascribed to an increase in the polaron activity with increasing ion concentration inside the polymer film.

A potentiometric iodide (and other) ion sensor based on a conducting polymer film electrode: Part II. effect of electrode conditioning and regeneration techniques

A novel potentiometric halide sensor electrode for iodide, based on the entrapment of iodide/iodine/triiodide into a poly(3-methylthiophene) conducting polymer, had previously been developed using a potentiostatic technique for film formation. The effect of film thickness (with the film thickness controlled by the amount of charge passing in the electrolytic cell during the polymerization) has been studied. Also, the effects of various pre- and postconditioning parameters on the electrode performance and life time were examined and compared. The life time of the electrode was extended up to one year by storing its sensing tip in a newly designed cap. The cap consisted of two chambers linked with a special orifice; the first contained iodine adsorbed on silica or alumina and the second housed the electrode tip. The linear dynamic range of the new sensor electrode was 1 × 10 −7-5 × 10 −1 M iodide and the detection limit was 1 × 10 −8 M iodide. The working temperature range, response time and working pH range of the electrode are 0–50°C, 1722̄0 s and 2–11, respectively. The potential for bromide, chloride, and sulfite selective electrodes based on these conducting polymer films are also presented and compared to those obtained for iodide. Moreover, the effect of changing the type of conducting polymer using poly (3-methylthiophene), poly ( N-methylpyrrole) or poly (aniline) are given and compared.

Application of the Kramers-Kronig transformation for the data validation of impedance spectra of electroactive polymer films on electrodes

A procedure concerning the application of Kramers-Kronig transformation for the validation of the impedance data in the case of thin electroactive films on electrodes is described. The treatment is based on a hypothetical shunting of the network corresponding to the polymer film electrode and the computer simulation of the altered impedance spectra.

Impedance analysis of polymer film electrodes

A new model is elaborated which can explain some anomalies of the impedance spectra of polymer films on electrodes. The model assumes two capacitances associated with the double layers at the substrate/film and at the film/solution interfaces, respectively. The latter capacitance is considered as a constant phase element due to the inhomogeneity of the polymer network and to energetically non-equivalent bonding sites for counterions. The effect of a low dc current, ie a slow reaction of the redox sites in the film with solution species, is also investigated. The electrochemical impedances characteristic of the model have been derived. The simulated impedance spectra were compared with those obtained experimentally.