Liquid/Liquid Interfaces, Electrochemistry at

Abstract

This article outlines the electrochemical methodology at the interface between two electrolyte solutions (ITIES). The fundamental concepts of the thermodynamics in biphasic systems are presented in order to show how ions are distributed between the two adjacent phases, and hence how a Galvani potential difference is established at an ITIES. Polarizable and nonpolarizable ITIES are then characterized, and it is further evidenced that the classical electroanalytical methodology at a solid electrode can be directly transposed to the ITIES, thereby allowing reversible charge‐transfer reactions to be easily monitored and interpreted. This theoretical approach is completed by a review of the analytical methods used at ITIES, namely cyclic voltammetry, dropping electrolyte electrodes, optical techniques and microinterfaces (which are the biphasic analogs of microelectrodes). The last part deals with the practical applications that electrochemistry at ITIES has attracted during the last decade in the development of amperometric ion sensors and detectors, in the extraction of metal ions by interfacial formation of a complex and in the assessment of the lipophilicity of ionizable drugs.

Electrodeposition of Prussian Blue/Carbon Nanotube Composites at a Liquid‑Liquid Interface

“…At negative polarization, the transfer takes place with Cl -and BTPPA + from the aqueous and organic phases, respectively. [1][2][3][4][5]50 The presence of the CNTs at the interface increases the current in the voltammetry, as observed in Figure 2. This increase in current could be related to the presence of the Fe species within the CNTs, as no such increase in background current was observed in a previous study with CNTs (single-walled type) adsorbed at the L/L interface.…”

“…1,2 The interface between two immiscible liquids provides a defect-free environment suitable for controlled homogeneous particle deposition. Driven by the decrease in the L/L interfacial free energy, particles dispersed or synthesized in a biphasic system spontaneously migrate to the interface formed by the two liquids.…”

“…11,12 In addition to standard synthetic parameters such as concentration, time or pH, the applied potential and polarization of the interface between the two immiscible electrolyte solutions (ITIES) governs the rate of ion and electron transfer between the phases, allowing significant control over synthetic procedures. 1,2,13,14 By combining these different approaches to utilize the L/L interface, composite structures can be prepared using one material as the support and/or nucleation site for the other. 15,16 Previously, it has been observed that particle or polymer formation was possible, under stirring, on the surface of carbon nanostructures present in a L/L system.…”

Ion transfer of weak acids across liquid|liquid interfaces

“…The transfer of protonated species across liquid|liquid interfaces is reported in several experimental works in the literature [1][2][3][4][5][6][7]. In many of these studies, the transfer of weak acids and bases has been found to depend on the pH of the aqueous phase and on their partition coefficient .…”

“…These ionic partition diagrams were calculated by taking into account the thermodynamic equilibria governing the distribution of the various acidic and basic forms of the molecules involved in the transfer. Therefore, the diagrams define the domains of predominance of each species either in the aqueous or in the organic phase, and they offer a global and direct visualisation of all the transfer mechanisms [1][2][3][4][5]7]. In recent years, a large number of ionisable drugs, such as acids, bases, ampholytes or zwitterionic species, have been characterized using these ionic partition diagrams, showing the usefulness of the methodology [18][19][20]22,26,[46][47][48][49][50][51]56,58,59,[63][64][65][66][67][68][69][70][71][72][73].…”