Extraction of Cations from an Ionic Liquid Droplet in a Dielectric Liquid under Electric Field

Abstract

Ionic liquids show great promise as excellent solvents or catalysts in energy and biological fields due to their unique chemical and physical properties. In this work, the characteristics of various ionic liquids are investigated with the electrophoresis of a charged droplet (ECD) method. Under normal situation, a charged droplet in a dielectric liquid shows back-and-forth bouncing motion between the positive and negative electrodes continuously. However, for some special ionic liquids, interesting retreating behavior of a charged droplet has been observed. This retreating behavior is due to the loss of positive charges of the droplet, and it suggests that only the positive ions are extracted from the droplet under the applied electric field. Based on this hypothesis of ion extraction, Fourier transform infrared (FTIR) spectroscopy analysis has been performed. The retreating behavior is also discussed from the intermolecular point of view according to the ion species.