Assisted Ion Transfer at Organic Film-Modified Electrodes

Abstract

International audienceAn experimental and theoretical study of a complex electrochemical mechanism at three-phase and thin organic film-modified electrodes, where the coupled electron–ion transfer reaction is complicated by complexation reaction of the transferring ion, is reported. The transfer of monovalent and divalent cations across water|nitrobenzene interface, coupled with the complexation reactions with the ionophore valinomycin, is studied. Both types of electrodes are assembled of an edge plane pyrolytic graphite electrode modified with a nitrobenzene solution of lutetium bis(tetra-tert-butylphthalocyaninato) as a redox mediator and valinomycin as an ionophore. The reversible redox transformations of the redox mediator to either a monovalent hydrophobic anion or cation serve to drive the ion transfer across the liquid|liquid interface. In contact of the modified electrode with an aqueous electrolyte containing alkali or earth alkaline metal cations, significant partition of the aqueous electrolyte is taking place, due to the interfacial complexation of the cation with valinomycin. Thus, the thermodynamics and kinetics of the interfacial complexation–partition reaction at the liquid|liquid interface affect markedly the overall electron–ion transfer reaction at the modified electrodes under voltammetric conditions. Experiments are qualitatively compared with theoretical data collected by simulation of two different electrochemical mechanisms coupled with chemical reactions under conditions of square-wave voltammetry. It has been concluded that the overall electrochemical mechanism at three-phase electrodes can be described as a specific CrE reaction scheme, where Cr represents the reversible interfacial complexation–partition reaction of the transferring ion with valinomycin at the liquid|liquid interface

Square‐Wave Voltammetry: A Review on the Recent Progress

“…The last decade has been also marked by important contributions of SWV in studying the charge transfer processes across liquid/liquid interfaces (L/L) [35,48,55,[68][69][70][71][72][73][74][75][76][77][78][79][80]. Most of these studies are related with thin-organic film [70, 73-76, 78, 79] and three-phase electrodes [71,72,77].…”

Studying the ion transfer across liquid interface of thin organic-film-modified electrodes in the presence of glucose oxidase

“…Over the last two decades, thin organic-film-modified electrodes [1][2][3][4][5][6][7][8] (TFEs) and three-phase electrodes [9,10] (TPEs) emerged as a simple but powerful experimental tool for studying complex coupled electron-ion transfer reactions. Their application spans over analysis of ion [11][12][13][14] or electron-transfer [15,16] reactions across liquid|liquid (L|L) interface, study of the mechanism of redox transformation in the organic film [17][18][19], nanoparticle preparation [20], electrocatalysis [21], and bioelectrochemical studies of redox-inactive proteins [22,23].…”

Theory of Kinetically Controlled Electrode Reaction Coupled to Ion Transfer across the Liquid/Liquid Interface

“…[1][2][3][4][5] This parameter can be measured using a conventional three-electrode configuration if either a thin film [6][7][8] or three-phase [9][10][11][12] working electrodes are used. [13,14] The first type of modified electrode consists of a graphite rod covered by a thin film of a water-immiscible organic solvent in which a lipophilic redox probe is dissolved. [15,16] In the three-phase version, the organic solution of the probe is attached to the surface of a graphite electrode in the form of a single droplet.…”