Tom Welton

Abstract:

Ionic liquids are liquids composed entirely of ions. These ions are in constant motion. Ionic liquids have found use in a wide range of electrochemical applications, such as batteries, fuel cells and solar cells. In these applications ionic liquids are exposed to electric fields. It is, therefore, surprising that the dynamics of ions in ionic liquids has been hardly studied. This paper reports our results on the diffusion of solutes in ionic liquids using Fluorescence Correlation Spectroscopy. We show that the diffusion of these ions slow on the application of an electric field. Further to this, we show that the relaxation of this motion after discharge of the cell is remarkably slow on the timescale of tens of minutes. We also report a study of the rotation of molecular rotors by Fluorescence Lifetime Spectroscopy, which can be correlated with the viscosity of the solvent in the cybotactic region of the probe rotor. These results show that the slower motion of ions is associated with an increase in this viscosity. We have also been studying these systems with molecular dynamics simulations. These are giving an insight into how the ionic liquid ions behave in electric fields.