The charge transport process at poly(orthoaminophenol) film electrodes

Poly(o-aminophenol) (POAP) films were deactivated and then reactivated, and dependences of the different charge-transport and charge-transfer parameters on the degree of deactivation (θc ) were obtained by employing Electrochemical Impedance Spectroscopy. While some parameters, such as interfacial metal-film and film-solution resistances the high-frequency capacitance and the redox capacitance exhibit a continuous variation without hysteresis between deactivation and reactivation processes within the whole θc range, others, such as electron and ion diffusion coefficients show not only marked changes of slope from given θc values but also hysteresis between consecutive deactivation and reactivation processes.Fil: Tucceri, Ismael Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentin

Nickel hydroxide films in contact with an electroactive solution. A study employing electrochemical impedance measurements

The deactivation of nickel hydroxide films after prolonged storage times without use was studied. This study was carried out in the context of the Rotating Disc Electrode Voltammetry (RDEV) andElectrochemical Impedance Spectroscopy (EIS) when the nickel hydroxide film contacts an electroactive solution and a redox reaction occurs at the Au-Ni(OH)2|electrolyte interface. Deferasirox (4-(3,5-bis(2-hydroxyphenyl)-1,2,4-triazol-1-yl) benzoic acid) was employed as redox species in solution. Limiting currents vs. electrode rotation rate dependences allowed one to obtain variation of the charge transport rate on the storage time. EIS was employed to obtain a more complete series of charge-transport parameters, that is, electron and ion diffusion coefficients and different interfacial resistances related to the gold/nickel hydroxide and nickel hydroxide/solution interfaces.Fil: Tucceri, Ismael Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentin

Poly(o-aminophenol) as material of biosensors

Some interesting practical uses of nonconducting poly(o-aminophenol) (POAP) films in the fields of bioelectrochemistry and electrocatalysis are discussed in this paper. Particular emphasis is given to the effects of applied potential, solution pH and interferents on the response current of biosensors based on POAP. Also, the behavior of POAP to improve the electroactivity of some electrocatalysts and its own electrocatalytic activity in coenzyme detection are describedInstituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Nonconductiong poly(o-aminophenol) films in the field of the bioelectrochemistry

The practical use of non-conducting poly(o-aminophenol) (POAP) films in the field of the bioelectrochemistry is discussed in this paper. Particular emphasis is given to the effects of applied potential, solution pH and interferents on the response current of biosensors based on POAP.Facultad de Ciencias ExactasInstituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

A Study of the Charge Transport Process at Nickel Hydroxide-Gold Modified Electrodes employing Rotating Disc Electrode Voltammetry and Ac Impedance Measurements

The aim of the present work was study how the charge-transport process of a nickel hydroxide film electrochemically synthesized on a gold substrate is modified when the electrode is stored without use for long time. It was found that nickel hydroxide films deactivate under storage, that is, films become less conductive than immediately prepared ones (nondeactivated). This study was carried out in the context of the Rotating Disc Electrode Voltammetry (RDEV) and Electrochemical Impedance Spectroscopy (EIS) when the modified electrode contacts an electroactive solution and a redox reaction occurs at the Au−Ni(OH)2|ectrolyte interface. Variations of anodic limiting currents with the electrode rotation rate, for both nondeactivated and deactivated films in the presence of the electroactive solute deferasirox (4-(3,5-bis(2-hydroxyphenyl)-1,2,4-triazol-1-yl) benzoic acid) allowed one obtaining a charge transport rate across a nickel hydroxide film, which decreases with the increase of the storage time. Interpretation of impedance spectra obtained at potential values corresponding to the anodic limiting currents on the basis of an impedance model that considers an uniform and nonporous nickel hydroxide film deposited in a conductive substrate and no penetration of redox species (deferasirox) from the solution, allowed one obtaining different interfacial resistances and electron and ion diffusion coefficients for the Au−Ni(OH)2|ectrolyte system.Fil: Tucceri, Ismael Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de la Plata; Argentin

The metal/electroactive polymer interface studied by surface resistance

The experimental arrangement in this investigation was one in which a poly(o-aminophenol) (POAP) film was sup- ported on a thin gold film electrode whose thickness is of the order of the mean free path of conduction electrons of gold. This arrangement allows one to apply the surface resistance technique to study the electrochemical processes oc- curring at the metal film surface coated with the polymer film. The dependence of the resistance change of the thin gold film electrode on the external electrolyte composition for polymer thickness lower than 0.25 mC·cm–2, was attributed to a competition, at the gold film surface, between the redox process of the polymer and adsorption of different ion species contained in the electrolyte. This competition reflects a discontinuous character of polymer thickness lower than 0.25 mC·cm–2 at the metal polymer interface. The resistance response of the metal film becomes independent of both the external electrolyte composition and polymer thickness for polymer thickness higher than 0.8 mC·cm–2. Then, POAP thicknesses higher than 0.8 mC·cm–2 seem to be compact enough at the metal polymer interface to prevent the interac- tion of the species contained in the supporting electrolyte with the gold film surface. The increase of the gold film re- sistance in going from the reduced to the oxidized state for POAP thicknesses higher than 0.8 mC·cm–2 was attributed to the redox conversion of poly(o-aminophenol) from amine to imine groups. This resistance increase was explained as a transition from specular to diffuse scattering of conduction electrons of gold at the gold poly(o-aminophenol) interface due to a less compact distribution of oxidised sites of POAP as compared with that of the reduced ones. An attenuation of the resistance response of the gold film was observed when the POAP films were deactivated either by contact with a ferric cation solution or prolonged potential cycling. The deactivation of the polymer film was attributed to the creation of inactive gaps within the redox sites configuration of POAP. The surface resistance technique allows one to detect different redox sites configurations of POAP on the gold film, according to the method used to deactivate the polymer films. In this work, it is demonstrated that the surface resistance technique can be employed to study not only the ability of a POAP film to inhibit the interaction of different species in solution with a metal surface but also the deactivation of the polymer film.Fil: Tucceri, Ismael Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; Argentin

Nickel hydroxide films in contact with an electroactive solution : A study employing electrochemical impedance measurements

The deactivation of nickel hydroxide films after prolonged storage times without use was studied. This study was carried out in the context of the Rotating Disc Electrode Voltammetry (RDEV) and Electrochemical Impedance Spectroscopy (EIS) when the nickel hydroxide film contacts an electroactive solution and a redox reaction occurs at the Au-Ni(OH)2|electrolyte interface. Deferasirox (4-(3,5-bis(2-hydroxyphenyl)-1,2,4-triazol-1-yl) benzoic acid) was employed as redox species in solution. Limiting currents vs. electrode rotation rate dependences allowed one to obtain variation of the charge transport rate on the storage time. EIS was employed to obtain a more complete series of charge-transport parameters, that is, electron and ion diffusion coefficients and different interfacial resistances related to the gold/nickel hydroxide and nickel hydroxide/solution interfaces.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Poly(o-aminophenol) as material of biosensors

Some interesting practical uses of nonconducting poly(o-aminophenol) (POAP) films in the fields of bioelectrochemistry and electrocatalysis are discussed in this paper. Particular emphasis is given to the effects of applied potential, solution pH and interferents on the response current of biosensors based on POAP. Also, the behavior of POAP to improve the electroactivity of some electrocatalysts and its own electrocatalytic activity in coenzyme detection are describedFil: Tucceri, Ismael Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de la Plata; Argentin

Nonconductiong poly(o-aminophenol) films in the field of the bioelectrochemistry

The practical use of non-conducting poly(o-aminophenol) (POAP) films in the field of the bioelectrochemistry is discussed in this paper. Particular emphasis is given to the effects of applied potential, solution pH and interferents on the response current of biosensors based on POAP.Fil: Tucceri, Ismael Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; Argentin

Effect of prolonged electrode potential cycling on the conduction properties of poly(o-aminophenol) film electrodes

The aim of this work was to study the effect of prolonged potentiodynamic cycling (PPC) on the conducting properties of poly(oaminophenol (POAP) film electrodes. PPC reduces strongly the electron transport rate at POAP films. This effect is called herein deactivation. Cyclic Voltammetry (CV), Rotating Disc Electrode Voltammetry (RDEV) and Electrochemical Impedance Spectroscopy (EIS) were employed in this study. The attenuation of the voltammetric response of the polymer with the increase in the number of oxidation-reduction cycles allowed one to define a degree of deactivation. RDEV and EIS were employed to obtain the dependence of some charge-transport parameters on the degree of deactivation of the polymer. RDEV data were interpreted in terms of the electron hopping model. Impedance spectra were analysed on the basis of a model which considers a protonation reaction coupled with a self-exchange process between oxidized and reduced sites. POAP films maintain their conducting properties almost unaltered for about 500 potential cycles at a scan rate of 0.010 Vs1. However, a loss of conductivity was observed as the number of potential cycles was extended beyond 500.Fil: Tucceri, Ismael Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de la Plata; Argentin