Selective transfer of Ag+ at the water|1,2-dichloroethane interface facilitated by complex formation with a calixarene derivative

The facilitated transfer of silver, Ag⁺, has been studied at the Interface between Two Immiscible Electrolyte Solutions (ITIES). The transfer was achieved with the assistance of a calixarene-based silver ionophore. An investigation of the mechanistic details of the transfer was conducted using cyclic voltammetry at both micro and macro liquid|liquid interfaces. The mechanism was found to follow a Transfer by Interfacial Complexation (TIC)/Transfer by Organic phase Complexation (TOC) mechanism. The complex stoichiometry was found to shift from 1:1 to 1:2, metal:ligand, with increasing ionophore concentration. The logarithms of the complex association constants, $\log {\beta }_1^{\mathrm{o}}\mathrm{and}\log {\beta }_2^{\mathrm{o}}$, were estimated at 12.4 and 14.5, respectively. The charge transfer current was also found to be limited by diffusion of the transferring species and was unchanged by the presence of a range of interferents. The system thus shows promise for selective analytical applications.     

Dynamics of lipid adsorption at the electrified water∣1,2-dichloroethane interface

A recently introduced setup to measure the dynamic interfacial tension of expanding drops was used to compare the adsorption behaviour of a series of lipids at the electrified water∣dichloroethane interface. Phospholipids with saturated carbon chains of different length (DMPC, DPPC, DSPC, DAPC, DBPC), an unsaturated phospholipid (DOPC) and an ethanolamine (DSPE) were compared. It was found that the adsorption decreases with increasing chain length. Also, the increase of the flow rate reduces the degree of adsorption effectively. On the timescale of the experiments, the DSPE, DAPC and DBPC adsorption showed no potential dependence, whereas the adsorption of DOPC was stronger than that of the saturated lipids. Adsorption was modelled using the Langmuir adsorption isotherm; the potential dependence of adsorption is discussed.     

Charge transfer at an electrified liquid|liquid interface immobilised in fibre

Charge transfer across the liquid|liquid interface was studied in the system where the organic phase was impregnated in fibre. Both electron and ion transfer reactions were carried out by controlling the Galvani potential difference across the phase boundary with the aid of a common, potential determining ion present in the aqueous and organic phases. The purpose of this work was to study the possibility of expanding the use of liquid|liquid interfaces in the direction of a continuous redox reactor. The experiments showed that this kind of system can, indeed, be created, provided that the volume and stability of the organic phase is sufficiently large.     

Electroactivity of redox-inactive proteins at liquid|liquid interface

We report on an observation of electroactivity of redox-inactive proteins at liquid|liquid interface. Since except for small polypeptide protamine, using ‘classic’ four-electrode setup it is impossible to facilitate a transfer of proteins across liquid|liquid interface, to observe protein electroactivity a carbon electrode shielded with thin layer of organic solvent was taken. Voltammograms of such shielded electrodes are sensitive to thermodynamics of anion re-solvation. To decrease Gibbs free energy of protein transfer from water to organic phase, and, thus, to record protein electroactivity at liquid|liquid interface, the reversed micelles of surfactants able to solubilise proteins in organic solvent were formed. Varying proteins and surfactants, as well as polarity of organic solvent, we proved that the observed raise in current of shielded electrodes, which in certain cases exceeds background by the two orders of magnitude, is indeed provided by the presence of proteins. Analytical parameters of shielded electrode are dependent on protein molecular weight and its interfacial properties. Electroactivity of redox-inactive proteins registered at liquid|liquid interface gives promise for wide application of electroanalytical chemistry in proteomics.     

Platinum–polyaniline nanofilms synthesized at a liquid|liquid interface with enhanced conductivity

In this work, a novel route for fabrication of platinum–polyaniline nanofilms at a liquid|liquid interface is proposed. This method synthesizes Pt nanoparticles incorporated in conductive PANI by reduction of H₂PtCl₆ to Pt nanoparticles and chemical oxidation polymerization of aniline simultaneously. The liquid|liquid interface offers a unique microenvironment for confining the 2D growth of PANI to form Pt–PANI nanofilms. The Pt–PANI nanofilms are characterized by field emission scanning electron microscopy, UV–Vis absorption spectroscopy, FTIR spectroscopy, X-ray photoelectron spectroscopy, ¹H NMR spectroscopy and electrochemical impedance spectra. The Pt–PANI nanofilms show enhanced electrical conductivity compared to the chemically polymerized PANI. The conductivity of Pt–PANI nanofilms is potential-dependent, which makes them promising reversibly potential-switchable materials.