Thermodynamics of Ion Transfer Across the Liquid|Liquid Interface at a Solid Electrode Shielded with a Thin Layer of Organic Solvent

Abstract

Thermodynamics of ion transfer across the liquid|liquid interface at a solid electrode shielded with a thin layer of water-immiscible organic solvent is investigated. The shielded electrode has been made by using a commercial hydrophobic carbon filament material (LSG) as an electrode support and a specially synthesized water-insoluble electroactive polymer (polyphenotiazine, PPTA) as a mediator. Oxidation of PPTA dissolved in the organic layer is accomplished with anion transfer from the aqueous phase to compensate for the positive charge of the mediator. The formal potential of the electrode shielded with PPTA solution in nitrobenzene (NB) is proportional to the Gibbs free energy of anion transfer across the liquid|liquid interface. An enhanced potential window as compared to a “classic” four-electrode setup allowed direct determination of Gibbs free energy for fluoride ion transfer from water to NB. For less polar organic solvents the formal potential of a shielded electrode is mainly determined by the enthalpy of anion transfer across the liquid|liquid interface, whereas the entropy term of Gibbs free energy causes only a minor effect.

Electroactivity of redox-inactive proteins at liquid|liquid interface

“…Shielded electrode requires anion transfer from water to organic phase to compensate a charge of the oxidized mediator in organic solvent. Similar system with redox polymer as a mediator was elaborated for investigation of thermodynamics of ion transfer across liquid|liquid interface [14]. The system allowed operation in non-polar organic solvents [14].…”

Synthesis of new lanthanide naphthalocyanine complexes based on 6,7-bis(phenoxy)-2,3-naphthalodinitrile and their spectral and electrochemical investigation

“…A similar shift of the redox activity potential of a hydrophobic substance to ward the cathodic region was observed earlier for decame thylferrocene, 18-20 metalloporphirines, 21,22 redox active oils, 23-26 and redox active polymers. 27 In conclusion, lutetium naphthalocyanine can be used for the evaluation of hydrophobic properties of anions during their transfer through the interface of two unmixable liquids.…”

Probing the redox activity of T-lymphocytes deposited at electrode surfaces with voltammetric methods

“…Both redox mediators were used as received without further purification. The redox mediator polyphenotiazine (PPTA), a redox polymer, was synthesized as described previously (15). All redox mediators were dissolved in 1,2-dichloroethane (DCE) at a concentration of 10 mM.…”