Polarised liquid/liquid micro-interfaces move during charge transfer

The externally polarised micro-interface between two immiscible electrolyte solutions (ITIES) has been visualised during ion transfer using confocal laser scanning microscopy (CLSM). A water|1,2-dichloroethane (DCE) micro-interface was formed at the tip of a glass micropipette. The DCE phase contained Nile Red, a fluorophore, which was used to visualise movements in the interface with CLSM. During voltammetric transfer of tetraethylammonium cation from the aqueous phase to DCE (in the micropipette), the interface - with and without adsorbed lipid - was found to undergo significant expansion. The movement of the interface was found to be completely reversible and rapid, as evident from potential step measurements. The studies reported herein have implications for studies of charge transfer at micro-ITIES which generally assume a static interface.