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.
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(2hydroxyphenyl)-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.
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 Vs −1 . However, a loss of conductivity was observed as the number of potential cycles was extended beyond 500.
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.
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