The main aspects related to the charge transfer reactions occurring at the interface between two immiscible electrolyte solutions (ITIES) are described. The particular topics to be discussed involve simple ion transfer. Focus is given on theoretical approaches, numerical simulations, and experimental methodologies. Concerning the theoretical procedures, different computational simulations related to simple ion transfer are reviewed. The main conclusions drawn from the most accepted models are described and analyzed in regard to their relevance for explaining different aspects of ion transfer. We describe numerical simulations implementing different approaches for solving the differential equations associated with the mass transport and charge transfer. These numerical simulations are correlated with selected experimental results; their usefulness in designing new experiments is summarized. Finally, many practical applications can be envisaged regarding the determination of physicochemical properties, electroanalysis, drug lipophilicity, and phase-transfer catalysis.

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Simple Ion Transfer at Liquid|Liquid Interfaces

Aligned polyaniline (PANI) belts doped with dodecatungstosilic acid (H4SiW12O40, abbreviated as SiW12) are synthesized by interfacial control method without surfactants or templates. The structure and morphology of the PANI are characterized by Fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD) patterns, and scanning electron microscope images (SEM). SiW12, as a doping-acid replacing HCl and offering a strong adhesive action between itself and water molecules, plays an important role in controlling aniline in interface system by the ordering character of water molecule layers along the interface. The alignment of the molecules or particles in the polymer nanostructures has a great influence on its performance. The conductivity of SiW12-doped and HCl-doped PANI prepared under the same conditions is tested. As compared to HCl-doped PANI, SiW12-doped PANI has a superior performance on the conductivity.

Synthesis of Aligned Polyaniline Belts by Interfacial Control Approach

Thermal modulation voltammetry (TMV) with laser heating was successfully performed at an aqueous|nitrobenzene (NB) solution microinterface, by taking advantage of the fact that laser light with a wavelength of 325.0 nm is optically transparent to the aqueous solution but opaque to the NB solution. When the laser beam impinges upon the interface from the aqueous solution side, a temperature is raised around the interface through the thermal diffusion subsequent to the light-to-heat conversion following the optical absorption by the NB solution near the interface. Based on such a principle, we achieved a fluctuating temperature perturbation around the interface for TMV by periodically irradiating the interface with the laser beam. On the other hand, the fluctuating temperature perturbation has influence on currents for transfer of an ion across the interface to produce fluctuating currents synchronized with the perturbation through temperature coefficients of several variables concerning the transfer, such as the standard transfer potential and the diffusion coefficient of the ion. Consequently, TMV has the possibility of providing information about the standard entropy change of transfer corresponding to a temperature coefficient of the standard transfer potential and a temperature coefficient of the diffusion coefficient. In this work, the aqueous|NB solution interface of 30 microm in diameter was irradiated with the laser beam at 10 Hz, and the currents synchronized with the periodical irradiation were recorded as a function of the potential difference across the interface in order to construct a TM voltammogram. TM voltammograms were measured for transfer of tetramethylammonium, tetraethylammonium, tetrapropylammonium, and tetra-n-butylammonium ions from the aqueous solution to the NB solution, and the standard entropy change of transfer was determined for each ion, according to an analytical procedure based on a mathematical expression of the TM voltammogram. Comparison of the values obtained in this work with the literature values has proved that TMV with laser heating is available for the determination of the standard entropy change of transfer for an ion.

Thermal Modulation Voltammetry with Laser Heating at an Aqueous|Nitrobenzene Solution Microinterface: Determination of the Standard Entropy Changes of Transfer for Tetraalkylammonium Ions

The liquid phase deposition (LPD) of metal oxide thin films at the liquid−liquid interface was investigated. Just after the start of the LPD reaction, depositions were observed continually at the liquid−liquid interface. The deposition grew two-dimensionally into a self-standing film with thickness of 1 μm and domain size of up to ca. 1 mm without any solid substrates. The self-standing film was formed with asymmetrical morphology, which consisted of flat surface on the side of the liquid−liquid interface and relatively rough surface on the side of the bulk solution. The structure was characterized by Raman spectroscopy, confirming that metastable ammonium titanium oxide fluoride (NH4TiOF3) was first deposited at the liquid−liquid interface, on which anatase-type titanium oxide (TiO2) was deposited second to forming the asymmetrical bilayer structure. It was suggested that the metal fluoride complex of the precursor was concentrated in the vicinity of the liquid−liquid interface compared with the solid−li...

Deposition of Metal Oxide Films at Liquid-Liquid Interface by the Liquid Phase Deposition Method

Hydrovoltaic cells. Part II: Thermogalvanic cells and numerical simulations of thermal diffusion potentials

A nonisothermal galvanic cell comprising two interfaces between two immiscible electrolyte solutions has been employed to determine the standard entropy ( ) of ion transfer at the nitrobenzene (NB)|water (W) interface. Under the conditions that only one ion (i) can partition between the NB|W interface, the nonisothermal emf has been measured. A nonequilibrium thermodynamic treatment has shown that the peak value (E0) of the nonisothermal emf, being usually observed within 1 min, is related to for ion i. However, E0 has also been shown, both experimentally and theoretically, to be influenced by thermal diffusion potentials arising in the bulk phases. Nevertheless, the contributions from the thermal diffusion potentials can be corrected for if the parameters for the ionic heats of transport are available, or they can be minimized by using adequate supporting electrolytes. Thus, accurate values of have been determined for various cations and anions. The determined values of for relatively hydrophobic cations...

Determination of the Entropy of Ion Transfer between Two Immiscible Liquids Using the Water|Oil|Water Thermocouple

The effect of the temperature on the co-extraction of water molecules with Na+ from water to nitrobenzene (NB) in the presence of dipicrylaminate ion has been studied. The number (n) of water molecules co-extracted with a Na+ ion, as measured by the Karl Fischer method, increased from 3.1 to 5.2 with increasing temperature (6 - 65°C). This observation is in apparent contradiction to the expectation from simple thermodynamics because hydration is generally an entropically unfavorable process. Additional 1H NMR experiments for the selective hydration of Na+ in deuterated NB have confirmed that the association constants of water with Na+ indeed decrease with increasing temperature. On the other hand, however, it has been shown that water solubility into NB substantially increases with temperature. We conclude that the latter effect overwhelms the former unfavorable entropy effect, which results in a net increase of the n-value, as observed.

https://www.jstage.jst.go.jp/article/analsci/19/10/19_10_1375/_pdf

Hajime Ogawa

Papers

Determination of the Entropy of Ion Transfer between Two Immiscible Liquids Using the Water|Oil|Water Thermocouple

Temperature effect on the selective hydration of sodium ion in nitrobenzene