Nitrobenzene Interface Research Articles

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

A coupled electron-ion transfer reaction at thin organic-film-modified electrodes (TFE) is studied in the presence of glucose oxidase (GOx) under voltammetric conditions. TFE consists of a graphite electrode modified with a nitrobenzene solution of decamethylferrocene (DMFC) as a redox mediator and tetrabuthylammonium perchlorate as an organic-supporting electrolyte, in contact with aqueous buffer solutions containing percholarte ions and GOx. The redox turnover of DMFC coupled with perchlorate transfer across water|nitrobenzene interface composes the coupled electron-ion transfer reaction. Glucose oxidase strongly adsorbs at the liquid|liquid interface affecting the coupled electron-ion transfer reaction by reducing the surface area of the liquid interface, prompting coadsorption of the transferring ion and lowering down slightly the rate of the ion transfer reaction. Although the enzyme exists as a polyvalent anion over the pH interval from 5.6 to 7, it does not participate directly in the ionic current across the liquid interface and percholrate remains the main transferring ion. Raman spectroscopic data, together with the voltammetric data collected by three-phase droplet electrodes, indicate that the adsorption of the enzyme does not depend either on the redox mediator (DMFC) or the organic-supporting electrolyte, while being driven by intrinsic interactions of the enzyme with the organic solvent. The overall electrochemical mechanism is mathematically modeled by considering linear adsorption isotherm of the transferring ion, semi-infinite mass transfer regime, and phenomenological second-order kinetic model.

Assisted Ion Transfer at Organic Film-Modified Electrodes

An 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.

Cyclic Voltammetry of Ion Transfer for Phenylpropanolamine Hydrochloride at Water|Nitrobenzene Interface

AbstractThe transfer on phenylpropanolamine ion, PPAH+, has been studied at the Interface between Two Immiscible Solutions (ITIES). The polarizable potential range was determined by cyclic voltammetry at the interface between an aqueous solution of lithium chloride (LiCl) and a nitrobenzene (NB) solution of electrolyte tetrabutylammonium tetraphenylborate (TBATPB). The half‐wave potential of ion transfer for phenylpropanolamine accross the water|NB interface was found 465.3 mV. The peak separation, the diffusion coefficient, and the standard ion transfer potential of PPAH+ were observed to be 59.1 mV, 1.7 × 10−6 cm2/s, and 104.6 mV, respectively. The temperature of experiment was kept constantly at 25 ± 1 °C using water flow thermostate.

Electrochemistry of saccharinate anion at liquid interfaces

Electrochemistry of saccharinate anion (sacc −) is studied at the liquid water|nitrobenzene (w|nb) interface by means of three-phase electrodes. Saccharinate anion can be effectively transferred across w|nb interface driven by the redox transformation of the lutetium bis(tetra-tert-butylphthalocyaninato), with a standard Gibbs energy of transfer from water to nitrobenzene of 20.17 kJ mol −1. The kinetics of transfer is estimated applying the quasireversible maximum. In addition, the influence of sacc − on the thermodynamics and kinetics of the alkali metal cations transfer is discussed.

Electron transfer between a lutetium bisphthalocyanine and FeIII/II across liquid|liquid interfaces between water and dichlorohexane or nitrobenzene; influence of coupling with ion transfer

The electron transfer across the liquid|liquid interface between aqueous solutions (W) of FeIII/II compounds (hexacyanoferrates, chlorides) and a (t-butyl) substituted LuIIIbisphthalocyanine in dichlorohexane (DCH) or nitrobenzene (NB), has been studied by voltammetry at a microinterface and by spectrophotometry. The electron transfer wave has been observed only at the W|DCH. Coupling with an ion transfer facilitates this electron transfer: the LuIIIbisphthalocyanine has been oxidized or reduced across the W|NB interface, depending on the ion establishing the interfacial potential.

Proton transfer across liquid∣liquid interfaces facilitated by the disproportionation reaction of a lutetium bisphthalocyanine: A voltammetric study at the microinterfaces between water and nitrobenzene or 1,6-dichlorohexane

Proton transfer across the water∣solvent (nitrobenzene, 1,6-dichlorohexane) interface is facilitated by the presence in the organic phase of a lutetium bisphthalocyanine. The driving force of the facilitated transfer of H + is the redox disproportionation reaction of this compound (M 0) occurring at the liquid∣liquid interface in the presence of proton: 2 M S 0 + H W + ⇄ HM S + M S + a reaction induced by the very high affinity of M −, the reduced bisphthalocyanine, for H + ( K A = 10 −13.5 mol −1 l). The lutetium bisphthalocyanine, which exits as the molecular form M 0 over ∼0.4 V ( K d = 10 −6.4) in the neutral solvent, disproportionates completely in acidic solutions (e.g., in nitrobenzene: K dH = 10 7.1 mol −1 l). At the water∣nitrobenzene interface, this disproportionation reaction facilitates the proton transfer by almost 0.30 V. Voltammetry at a rotating disk electrode in nitrobenzene confirms the redox disproportionation reaction and the basicity of the reduced lutetium bisphthalocyanine.

Electrochemical study of hydrophilic ion transfers across cholesterol modified water–nitrobenzene interface by means of thin film electrodes

Electrochemically driven ion transfer reactions of ClO 4 - , NO 3 - , SCN −, and K + across a cholesterol modified water–nitrobenzene (W–NB) interface have been studied by means of square-wave and cyclic voltammetry at thin organic film modified electrodes. It has been found that cholesterol exhibits a profound accelerating effect toward the kinetics of ClO 4 - , NO 3 - , SCN − transfers, whereas a retarding kinetic effect was observed for K +. Besides, the cholesterol layer alters significantly the mechanism of ion transfer, prompting adsorption of all studied ions as a consequence of specific interactions between cholesterol molecules and the transferring ion.

Simple Electrochemical Method for Deposition and Voltammetric Inspection of Silver Particles at the Liquid−Liquid Interface of a Thin-Film Electrode

A novel experimental methodology for depositing and voltammetric study of Ag nanoparticles at the water-nitrobenzene (W-NB) interface is proposed by means of thin-film electrodes. The electrode assembly consists of a graphite electrode modified with a thin NB film containing decamethylferrocene (DMFC) as a redox probe. In contact with an aqueous electrolyte containing Ag(+) ions, a heterogeneous electron-transfer reaction between DMFC((NB)) and Ag(+)((W)) takes place to form DMFC(+)((NB)) and Ag deposit at the W-NB interface. Based on this interfacial reaction, two different deposition strategies have been applied. In the uncontrolled potential deposition protocol, the electrode is immersed into an AgNO(3) aqueous solution for a certain period under open circuit conditions. Following the deposition step, the Ag-modified thin-film electrode is transferred into an aqueous electrolyte free of Ag(+) ions and voltammetrically inspected. In the second protocol the deposition was carried out under controlled potential conditions, i.e., in an aqueous electrolyte solution containing Ag(+) ions by permanent cycling of the electrode potential. In this procedure, DMFC((NB)) is electrochemically regenerated at the electrode surface, hence enabling continuation and voltammetric control of the Ag deposition. Hence, the overall electrochemical process can be regarded as an electrochemical reduction of Ag(+)((W)) at the W-NB interface, where the redox couple DMFC(+)/DMFC acts as a mediator for shuttling electrons from the electrode to the W-NB interface. Ag-particles deposited at the W-NB interface affect the ion transfer across the interface, which provides the basis for voltammetric inspection of the metal deposit at the liquid-liquid interface with thin-film electrodes. Voltammetric properties of thin-film electrodes are particularly sensitive to the deposition procedure, reflecting differences in the properties of the Ag deposit. Moreover, this methodology is particularly suited to inspect catalytic activities of metal particles deposited at the liquid-liquid interface toward heterogeneous electron-transfer reactions occurring at the at the liquid-liquid interface.

Effect of silver particles deposited at the water∣nitrobenzene interface on the voltammetric response of thin-film electrodes

A novel experimental methodology for studying silver particles deposited at the water∣nitrobenzene (W∣NB) interface is proposed by means of thin-film electrodes. The electrode assembly consists of a graphite electrode (GE) covered with a thin NB film containing decamethylferrocene (DMFC) as a redox probe. The W∣NB interface was modified with silver particles in an AgNO 3 aqueous solution, where a heterogeneous electron transfer reaction between DMFC (NB) and Ag ( W ) + takes place to form a Ag-deposit at the W∣NB interface, and DMFC + and NO 3 - in the organic phase. The Ag-modified thin-film electrode was inspected by voltammetry in a contact with an aqueous electrolyte free of Ag ( W ) + . The overall reaction at the thin-film electrode proceeds as a coupled electron–ion transfer reaction. Ag-particles deposited at the W∣NB interface affect significantly the ionic transfer, which provides the basis for a voltammetric inspection of the metal deposition at the W∣NB interface. When the concentration AgNO 3(W) is close to the concentration of DMFC (NB), a dense Ag-film is formed that prevents completely the ionic transport, hence resulting in a complete vanishing of the voltammetric response. In a presence of [ Fe ( CN ) 6 ] ( W ) 3 - , the response of the electrode is restored, having properties of a reductive catalytic electrode mechanism. The overall mechanism couples two simultaneous electron transfer reactions undergoing at separate interfaces, i.e. the reduction of DMFC ( NB ) + to DMFC (NB) at the GE∣NB interface and the heterogeneous redox reaction between DMFC (NB) and [ Fe ( CN ) 6 ] ( W ) 3 - to form DMFC ( NB ) + and [ Fe ( CN ) 6 ] ( W ) 4 - at the Ag-modified W∣NB interface. Under these conditions the Ag-film acts as an effective conductive medium for fast electron exchange between DMFC (NB) and [ Fe ( CN ) 6 ] ( W ) 3 - . The methodology proposed is particularly suited to inspect catalytic activities of metal particles deposited at the liquid∣liquid interface towards heterogeneous electron transfer reactions between reactants embedded in immiscible liquids.

Studying the coupled electron–ion transfer reaction at a thin film-modified electrode by means of square-wave voltammetry

The coupled electron–ion transfer reaction at a thin film-modified electrode is studied under conditions of square-wave voltammetry (SWV). It is assumed that the electrode is covered with a thin film of an electrochemically inactive organic solvent, immiscible with water, containing a neutral redox probe and an electrolyte. The electrode is immersed in the aqueous electrolyte. The oxidation or reduction of the redox probe at the solid electrode|organic solution interface is accompanied by a simultaneous ion transfer across the liquid|liquid (L|L) interface. The overall reaction is modeled considering the diffusion of the redox probe and of the transferring ion within the limited boundaries of the thin film, and the diffusion of the transferring ion in the aqueous phase under semi-infinite conditions. Both reversible and quasireversible cases are considered. Under conditions of SWV, the quasireversible reaction exhibits unique properties, providing an insight into the kinetics of the overall process, which could be controlled either by the electron transfer or the ion transfer across the L|L interface. The theoretical predictions are confirmed by experiments with decamethylferrocene and a series of lutetium phthalocyanine complexes dissolved in nitrobenzene and deposited as a micro-film on the surface of a pyrolytic graphite electrode. The coupled electron–ion transfer reactions of these compounds are quasireversible and controlled by the kinetics of ion transfer ( ClO 4 - , NO 3 - , Cl −) across the water|nitrobenzene interface. It is demonstrated that SWV in combination with the thin film-modified electrode is a new and promising tool for measuring the kinetics of ion transfer across the L|L interface.

Studying the kinetics of the ion transfer across the liquid|liquid interface by means of thin film-modified electrodes

The kinetics of the ion transfer across the liquid|liquid interface is studied by means of a thin film-modified electrode in combination with square-wave voltammetry. The thin film-modified electrode consists of an edge plane pyrolytic graphite electrode covered with a thin film of a water immiscible electroinactive organic solvent containing a neutral redox probe and a suitable electrolyte. The overall electrochemical process, proceeding as a coupled electron–ion transfer reaction, is controlled either by the electron transfer across the graphite electrode|organic solvent or by the ion transfer across the organic solvent|aqueous electrolyte interface. The theoretical model enabling to distinguish the rate limiting step is developed. The theory is used to measure the kinetics of ClO 4 - , NO 3 - , Cl −, SCN −, Na +, K +, (CH 3) 4N +, and (C 4H 9) 4N + across the water|nitrobenzene interface utilizing lutetium bis(tetra- tert-butylphthalocyaninato) as a redox probe.

Kinetics of Anion Transfer across the Liquid | Liquid Interface of a Thin Organic Film Modified Electrode, Studied by Means of Square-Wave Voltammetry

The electrochemical oxidation of lutetium bis(tetra-tert-butylphthalocyaninato) (LBPC) and decamethylferrocene (DMFC), as well as the reduction of LBPC, lutetium bis(phthalocyaninato) (LPC), and lutetium (tetra-tert-butylphthalocyaninato hexadecachlorphthalocyaninato) (LBPCl), has been studied in a thin nitrobenzene (NB) film deposited on the surface of a graphite electrode (GE) by means of square-wave voltammetry (SWV). The organic film-modified electrode was immersed in an aqueous (W) electrolyte solution and used in a conventional three-electrode configuration. When the aqueous phase contains ClO4-, NO3-, or Cl- (ClO4-, or NO3- only, in the case of DMFC), both LBPC and DMFC are oxidized to stable monovalent cations in the organic phase. The electron transfer at the GE | NB interface is accompanied by a simultaneous anion transfer across the W | NB interface to preserve the electroneutrality of the organic phase. LBPC, LPC, and LBPCl are reduced to stable monovalent anions accompanied by expulsion of the anion of the electrolyte from the organic into the aqueous phase. In all cases, the overall electrochemical process comprises simultaneous electron and ion transfer across two separate interfaces. Under conditions of SWV, the overall electrochemical process is quasireversible, exhibiting a well-formed "quasireversible maximum" that is an intrinsic property of electrode reactions occurring in a limiting diffusion space. For all the redox compounds that have been studied, the kinetics of the overall electrochemical process is controlled by the rate of the ion transfer across the liquid | liquid interface. Based on the quasireversible maximum, a novel and simple methodology for measuring the rate of ion transfer across the liquid | liquid interface is proposed. A theoretical background explaining the role of the ion-transfer kinetics on the overall electrochemical process at the thin organic film modified electrode under conditions of SWV is presented. Comparing the positions of the theoretical and experimental quasireversible maximums, the kinetics of ClO4-, NO3-, and Cl- across the W | NB interface was estimated. The kinetics of the overall process at the thin organic film modified electrode, represented by the second-order standard rate constant, is 91 +/- 8, 90 +/- 4, and 133 +/- 10 cm(4) s(-1) mol(-1), for the transfer of ClO4-, NO3-, and Cl- respectively.

Lutetium Bis(tetra-tert-butylphthalocyaninato): A Superior Redox Probe To Study the Transfer of Anions and Cations Across the Water|Nitrobenzene Interface by Means of Square-Wave Voltammetry at the Three-Phase Electrode

The redox properties of lutetium bis(tetra-tert-butylphthalocyaninato) (LBPC) have been studied in nitrobenzene that is deposited as a microfilm on the surface of highly oriented pyrolytic graphite electrodes. The behavior of the modified electrode, which is immersed in an aqueous electrolyte solution, is typical for the three-phase electrode (Scholz, F.; Komorsky-Lovrić, S.; Lovrić, M. Electrochem. Comm. 2000, 2, 112-118). LBPC can be both oxidized and reduced in one electron reversible processes. The oxidation and the reduction of LBPC at the graphite/nitrobenzene interface is accompanied by the transfer of anion or cation, respectively, from the aqueous phase into the organic layer. Thus, using LBPC as a redox probe for the three-phase electrode, the transfer of both anions and cations across the water/nitrobenzene interface can be studied in a single experiment. The hydrophobicity of LBPC is so high that it enables inspection of cations and anions with Delta (nb)(w) (G)(theta)(Cat+) < or = 43 kJ/mol and Delta (nb)(w) (G)(theta)(X-) < or = 50 kJ/mol, respectively. The direct transfer of Na(+) and Li(+) from water to nitrobenzene, mutually saturated, is achieved for the first time at a macroscopic water/nitrobenzene interface.

An in situ microscopic spectroelectrochemical study of a three-phase electrode where an ion transfer at the water|nitrobenzene interface is coupled to an electron transfer at the interface ITO|nitrobenzene

Coupled electron and ion transfer was studied at a three-phase arrangement where decamethylferrocene was dissolved in a droplet of nitrobenzene that was sandwiched between an optically transparent ITO electrode and a glass plate. The sandwiched droplet was surrounded by an aqueous electrolyte solution in which the auxiliary and the reference electrodes were positioned. The oxidation of decamethylferrocene was followed by in situ spectroscopy with the help of a spectrometer interfaced to an optical microscope. The fast progression of the reaction starting at the three-phase junction and advancing towards the middle of the droplet is explained on the basis of a simplified model that assumes a progressive activation of the working electrode|nitrobenzene interface due to the ingress of transferred anions and decrease of ohmic resistance inside the nitrobenzene phase.

The Role of Coexisting Ions in a Chemical Oscillation Induced by Ionic Surfactant Molecules at a Water/Nitrobenzene Interface

Chemical oscillation induced by ionic surfactant molecules at a water (W)/nitrobenzene (NB) interface is investigated by simultaneous monitoring of electrochemical potential and interfacial tension. The presence of hydrophilic ions in the organic (NB) phase is found to drastically accelerate the relaxation process of electrical potential, indicating that ion exchange critically affects the desorption of ionic surfactant molecules from the interface and the deformation of an electrical double layer at the interface. In addition, two-step relaxation of the electrical potential is found, that provides information on the origin of the electrical potential generated in chemical oscillations. The mechanism for the nonlinear oscillatory behavior of the ionic surfactant molecules at the W/NB interface is considered in terms of the remarkable difference in diffusion speed in the aqueous bulk phase and across the W/NB interface due to the contribution of the water molecules that hydrate the surfactant molecules.

Determination of the standard Gibbs energies of transfer of cations and anions of amino acids and small peptides across the water nitrobenzene interface.

The standard Gibbs energies of transfer of anions and cations of amino acids and small peptides across the water nitrobenzene interface were determined with the help of a novel electrochemical technique using three-phase electrodes. This is the first time that reliable data are reported for the anions of amino acids. The main result is that the standard Gibbs energies of transfer of the anion and cation of an amino acid are almost the same.

Standard Gibbs energies of transfer of halogenate and pseudohalogenate ions, halogen substituted acetates, and cycloalkyl carboxylate anions at the water|nitrobenzene interface

Download options Please wait... Article information DOI https://doi.org/10.1039/B210356G Article type Paper Submitted 24 Oct 2002 Accepted 27 Jan 2003 First published 07 Feb 2003 Download Citation Phys. Chem. Chem. Phys., 2003,5, 1284-1289 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Standard Gibbs energies of transfer of halogenate and pseudohalogenate ions, halogen substituted acetates, and cycloalkyl carboxylate anions at the water|nitrobenzene interface R. Gulaboski, K. Riedl and F. Scholz, Phys. Chem. Chem. Phys., 2003, 5, 1284 DOI: 10.1039/B210356G To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Rubin Gulaboski Kai Riedl Fritz Scholz

Determination of the standard Gibbs energies of transfer of cations across the nitrobenzene|water interface utilizing the reduction of iodine in an immobilized nitrobenzene droplet

When a nitrobenzene (NB) droplet containing iodine is attached to a graphite electrode and immersed into a chloride containing aqueous (AQ) solution, the electrochemical reduction of iodine is accompanied by a transfer of chloride ions from NB to water. These chloride ions enter the NB phase in a preceding partition between the AQ and the NB phases, supported by formation of I 2Cl − ions in NB and accompanied by the transfer of stoichiometric amounts of cations. The overall electrode reaction is of CE rev type, where C refers to the preceding chemical step forming I 2Cl −, and E rev refers to the reversible reduction of iodine at the graphite|NB interface and the simultaneous transfer of chloride from NB to water. If the chloride concentration in NB is insufficient to compensate by leaving the NB the amount of electrochemically produced iodide, a second voltammetric signal occurs at more negative potentials due to the transfer of iodide from NB to water. The kinetics and thermodynamics of the preceding chemical step C, determine the voltammetric behaviour of the system in such way that the ratio of peak currents of the first and second signals depends linearly on the Gibbs energy of transfer of the co-partitioned cations. The method was validated for cations of known Gibbs energies of transfer, and it was applied to cations of amino acids.

Probing Thermodynamic Aspects of Electrochemically Driven Ion-Transfer Processes Across Liquid|Liquid Interfaces: Pure versus Diluted Redox Liquids

The voltammetry of the water-insoluble redox liquids para-N,N,N‘,N‘-tetraalkylphenylenediamines (TAPDs; A = butyl, hexyl, heptyl, octyl, and nonyl) at the TAPD|electrode|electrolyte interface is studied. The ion-transfer processes between the aqueous and the organic phaseconsequent of the necessity to maintain charge neutrality during electrochemical oxidation and reduction reactions in the organic phaseare elucidated as a function of the Gibbs free energy of transfer of the electrolyte anions, of the concentration of TAPD in the organic phase, and of the length of the alkyl chain of the phenylenediamines. Two conditions are considered: the voltammetry of microdroplets of the pure redox liquids and the voltammetry of the TAPDs dissolved in nitrobenzene, either deposited as microdroplets at an electrode surface. The oxidation of the neutral redox liquids, accompanied by the uptake of anions from the adjacent aqueous solution leads to the formation of ionic liquid phases, TAPD+X- and TAPD2+X-2 (X- = monovalent electrolyte anions). Despite the high concentration of redox centers in the microdroplets, the redox potentials of the TAPDs are exclusively determined by the Gibbs free energy of the electrochemically driven transfer of anions between the aqueous and the redox liquid phase. There is no evidence for ion pair formation of the TAPD+ and TAPD2+ with the transferred anions X- either in the pure redox liquid phase or in the nitrobenzene matrix. Depending on the Gibbs energy of transfer of the electrolyte anions two different reaction mechanisms are observed: At low ΔG values, a reversible transfer of electrolyte anions across the liquid/liquid interface as a consequence of the redox process takes place. However, anions with high transfer energies do not enter the organic phase. Instead, upon oxidation TAPD mono- and dications are transferred from the organic into the aqueous phase, which leads to the diminution of the voltammetric signals due to the loss of material from the droplets. From the voltammetric data, the Gibbs energy of transfer of the different TAPD cations and of the hexafluoroarsenate anion were derived for the water|nitrobenzene interface. Whereas the oxidation of the TAPD in the nitrobenzene droplets due to its low concentration does not measurably affect the properties of the nitrobenzene|water interface of the droplet, the oxidation of the pure redox liquids leads to a considerable change of the liquid|liquid interface upon ionic liquid formation. This change depends on the nature of the inserted anion: the more hydrophilic the inserted anion is, the less hydrophobic the ionic liquid becomes.

Cyclic voltammetry of decamethylferrocene at the organic liquid ∣ aqueous solution ∣ graphite three-phase junction

Drops of nitrobenzene and 1,2-dichloroethane containing only 0.1 mol l −1 decamethylferrocene (dmfc) are attached to the surface of a paraffin-impregnated graphite electrode (PIGE) and immersed into various aqueous electrolytes. The oxidation of dmfc and the reduction of the cation dmfc + are enabled by the simultaneous transfers of anions between the aqueous electrolyte and the organic solvents. The reaction starts at the three-phase junction. A linear relationship is observed between the mid-peak potentials of cyclic voltammograms of dmfc and the standard Galvani potential differences of the anions, and the influence of the anion concentration on the intercepts of these straight lines is explained. The standard Gibbs energies of transfer of acetate anions and dmfc + cations on the water ∣ nitrobenzene interface are estimated as: ΔG tr,Ac − 0,nb→ w =−33.4 kJ mol −1 and ΔG tr,dmfc + 0,nb→ w =35±2 kJ mol −1, respectively.