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Abstract: The oxidation of dimethylamine borane (DMAB) on polycrystalline gold electrodes has been investigated using a number of electrochemical techniques. The oxidation of borohydride has been studied to provide a comparison: for DMAB we observe two, sequential oxidation processes on gold. At low potentials, three electrons are extracted from the molecule, implying that hydrogen is not oxidised, whereas at high potential a six electron oxidation occurs. The dimethylamine fragment is also oxidised on gold, albeit at higher potentials, in contrast to assumptions made in previous literature. DMAB oxidation is also studied on platinum and glassy carbon: the data suggests that only part of the amine–borane dissociates in alkaline solution, in particular cleavage of the B−N bond requires prolonged exposure to metallic surfaces. [Copyright &y& Elsevier]

Alumina membranes, with mean pore diameters of 100 nm, have been used as templates to control the electrodeposition of palladium. Deposition occurs at the polarised water–organic interface, leading to the formation of nanoparticles. The particles are formed at the mouth of the alumina pores, the locus of their formation being dictated by the position of the organic–water interface. It is shown that the relative position of the liquid phases with respect to the alumina is controlled by the surface wetting properties of the liquids, rather than gravity. This in turn controls the interfacial position and hence the size of the particles deposited. The presence of the alumina membrane prevents agglomeration. Electrochemical and electron microscopy data are presented in support of this proposed deposition mechanism. [Copyright &y& Elsevier]

Recent progress in the field of liquid–liquid electrochemistry is reviewed, with a particular focus on two notable trends that have come to the fore over the last decade, the electrochemical properties of particle-modified interfaces and the related topic of electrocatalysis at the liquid–liquid interface. [ABSTRACT FROM AUTHOR]

Abstract: Liquid/liquid electrochemistry has been used to study the transfer of weakly ionised species across the interface between water and 1,2-dichloroethane. It is shown that while transfer of a fully ionised species can be readily used for determination of its diffusion coefficient, transfer of a partially ionised species, such as many common pharmaceutical agents, involves complex ionisation/distribution behaviour, which invalidates the conventional analysis. As a result, the aqueous diffusion coefficient of the transferred species is underestimated by at least one order of magnitude. An alternative method to study the transfer of partially ionised drug molecules employing a rotating liquid/liquid interface is proposed and reported. The alternative approach, which is based on a previously reported rotating diffusion cell approach, employs a lipophilic membrane that stabilises the liquid/liquid interface and allows stirring. This hydrodynamically controlled configuration was successfully applied to transfer of partially ionised drug species, and expected values of the aqueous diffusion coefficient were obtained. [Copyright &y& Elsevier]

Abstract: We present two novel UV–vis absorption spectroelectrochemical cells for the study of electrochemical processes at polarized liquid|liquid interfaces based on the parallel incidence of the light beam with respect to the interface. The first one is a crude design (Cell 1) based on an existing cylindrical cell for liquid|liquid electrochemistry. The second design (Cell 2) is superior and based on the assembly of the four-electrode set-up inside a rectangular quartz spectrophotometric cuvette. In both cases it is demonstrated that absorption spectroelectrochemistry in parallel beam configuration can be a sensitive probe of processes such as ion transfer at the polarized liquid|liquid interface, if the contribution from the bulk of the sampled phase is removed. In particular, the electrochemical and spectroscopic performance of both cell designs was evaluated using the well-known transfer of Ru(bpy)3 2+ across the water|1,2-DCE interface as a model reaction. [Copyright &y& Elsevier]

Graphene oxide (GO) and reduced graphene oxide (rGO) membranes have attracted significant attention as a potential technology for energy storage, gas separation, and water purification applications. However, these membranes have a significant drawback as they became swollen, hence unstable, after exposure to aqueous solutions. Here, we describe membranes produced from graphene prepared by liquid phase exfoliation, possessing a low oxygen content, unlike the GO/rGO systems typically used, and demonstrate their applicability for ion sieving in aqueous solutions. These low oxygen content graphene membranes formed from flakes of varying size were used to determine the effect of flake morphology on ion transport. Interestingly decreasing flake length and thickness leads to an increase in the number and tortuosity of nanochannels between the layers, resulting in a significant reduction of ion transport. The smaller flakes show an increased surface charge, due to the level of defects, which impedes chloride mobility allowing for both physical sieving and charge repulsion. Moreover, the graphene membranes reported here exhibit excellent Na+ rejection properties (∼97%) with water permeance ∼ 10 times higher than those reported for GO membranes, while demonstrating high stability in aqueous solutions with no observed swelling. These materials are therefore extremely promising for future applications in water purification. Image 1 [ABSTRACT FROM AUTHOR]

The interfacial adsorption of single-walled carbon nanotubes and few-layer graphene flakes, prepared by solution phase exfoliation, is compared. Strong adsorption of carbon nanotubes was observed at the water/1,2-dichloroethane interface, while a weaker adsorption of the graphene dispersion was seen. Addition of electrolyte to the organic phase was found to have a strong effect on the adsorption of graphene. A simple surface energy model does not fully explain these observations, rather residual charges and their distribution appears to be the key factor behind this difference in adsorptive behaviour. Carbon nanomaterials adsorbed at the liquid-liquid interface can function as bipolar electrodes: a preliminary investigation of the oxidation of the 1,2-dichlorobenzene by metal-modified graphene particles is performed. [ABSTRACT FROM AUTHOR]

The properties of lipid monolayers at the interface between two immiscible electrolyte solutions (ITIES) have attracted much attention over the last 30 years. This is mainly because of the biological relevance of lipids and the possibility of controlling ion and electron transfer across one leaflet of a cellular membrane. In the last decade, the electrochemical characterization of phosphatidylcholine (PC) adsorbed monolayers at ITIES suggested that the transfer of aqueous cations across the interface is facilitated by the complexation of aqueous cations with the PC zwitterionic head groups, followed by the depletion of lipids from the interface. In this work, we present a study on the effects of applied electric fields and electrolyte concentration on the interfacial structure of the ITIES by combining neutron reflectometry (NR) and electrochemical characterization techniques including the effects of an adsorbed lipid layer. Our results confirm that lipid depletion occurs as cations are transferred. However, we found that the presence of lipids favors the intermixing of the two-liquid phases on a length scale of a few tens of nanometers. To our knowledge, this has been the first NR-electrochemistry study of the ITIES. We believe that our findings could open new possibilities for coupling bioelectrochemical characterization and scattering based techniques at the liquid-liquid interface. [ABSTRACT FROM AUTHOR]