Bare Water-Solvent Interfaces

Liquid-liquid interfaces for ITIES research are limited by the choice of the organic solvent that must, of course, be immiscible with water and able to dissolve electrolytes. As a consequence, electrochemistry at ITIES is often limited to the H2O-NB, H20-1,2-DCE, water-heptanone, and water-2-nitrophenyloctylether (NPOE) systems, the last two having been developed for their low toxicity. 

In the case of the H2O-NB interface, first studied by Michael and Benjamin [13] and recently revisited by Jorge et al. [12], the interface can be viewed as relatively sharp on the molecular scale but with some thermal fluctuations. This recent work suggests the existence of two tightly packed interfacial layers with both molecular planes parallel to the interface and restricted mobility on the normal axis—one water layer on the aqueous side and one nitrobenzene layer on the organic side. 

The H2O-NPOE interface was very recently simulated by Jorge et al. [21] who have shown that the presence of an alkyl chain in NPOE introduces an added degree of hydrophobicity compared to the H2O-NB interface, resulting in an increase of interfacial tension. Also, interfacial NPOE molecules appear less organized than nitrobenzene molecules. 

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The contribution of the metal to the double layer was discussed in Sections 6.6.7 to 6.6.9. However, we have said little about the ions in solution adsorbed on the electrode and how they affect the properties of the double layer. For example, when presenting the Stem model of the double layer (Section 6.6.6), we talked about ions sticking to the electrode. How does an interface look with ions stuck on the metal What is the distance of closest approach Are hydrated ions held on a hydrated electrode i.e., is an electrode covered with a sheet of water molecules Or are ions stripped of their solvent sheaths and in intimate contact with a bare electrode What are the forces that influence the sticking of ions to electrodes ... 

In order to study the formation of interfacial metal phosphate layers, the untreated bare CRS panels were mechanically polished to a mirror finish and used as coating substrates. The ISPC was applied on mirror-finished CRS and cured at 163°C for 15 min. The polymer layer on each panel was removed without damaging the interface by soaking the panel in tetrahydrofuran solvent. The interfacial metal phosphate layer was rinsed with deionized water, dried, and characterized by a Bruker Fourier transform infrared (FTIR) spectrophotometer model Vector 22 equipped with a Spectra Tech FT-80 grazing angle accessory. 

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