Avocado oil, coconut oil, walnut oil as true oil phase for ion transfer at nanoscale liquid/liquid interfaces

Abstract

The interface between two immiscible electrolyte solutions (ITIES), typically formed between an organic (oil) phase and an aqueous phase, is essential for chemical sensing and for studying various electron transfer and ion transfer reactions. Solvent, as part of ITIES structure, plays critical roles in electrochemical reactions at ITIES. While different kinds of organic phases, including viscous ionic liquid, have been reported, use of true oils as organic phase has rarely been explored. In this study, we introduce true oils, including avocado oil, coconut oil, and walnut oil as new organic solvents for ITIES. We observed well defined potential windows, and sigmoidal cyclic voltammograms for ion transfer. We further measured the ion transfer rate constants at true oil-water interfaces supported at nanopipette of ∼20–60 nm in radius. Our study offers additional insights on the effect of solvent viscosity on the ion transfer rate at the liquid/liquid interface, with the viscosity of these true oils being ∼ 50–70 times that of 1, 2-dichloroethane. We measured the standard ion transfer rate constants of tetrabutylammonium to be 0.21–0.32 cm / s at these true oil-water interface. This work lays the foundation to expand ITIES platform to explore new reactions, playing critical roles in separation science, chemical sensing, chemical synthesis, catalysis, etc.