MSE Seminar: Radiation Chemistry, Reactivity and Dynamics in Ionic Liquids
Friday, March 29, 2019
2110 Chem/Nuc Bldg, UMD College Park
Speaker: James F. Wishart, Chemistry Division, Brookhaven National Laboratory
Title: Radiation Chemistry, Reactivity and Dynamics in Ionic Liquids
Being comprised entirely of charged species, ionic liquids (ILs) have dramatically different properties compared to conventional molecular liquids and they provide new and unusual environments to test our understanding of physical chemistry phenomena. We are interested in how IL properties influence physical and dynamical processes that determine the stability and lifetimes of reactive intermediates and thereby affect the courses of reactions and product distributions, for example in the areas of primary and applied radiation chemistry, radical chemistry and charge transfer reactions.
The fundamental radiation chemistry of ILs is our primary focus. They have important potential applications in the recycling of used nuclear fuel to reduce legacy hazards, and as battery electrolytes, lubricants and ion thruster fuel in spacecraft. In both cases, stability towards radiation exposure (radiolysis) is essential. A key issue in IL radiolysis is the competition between the solvation of the initially-formed excess electrons and the scavenging of electrons in different states of solvation. Pre-solvated electron scavenging is especially significant in ILs because their relatively high viscosities make their solvation dynamics 100-1000x slower than in conventional solvents. Pre-solvated electrons are more mobile and show different reactivity patterns than solvated ones. The slower relaxation dynamics of ILs make them excellent media for the general study of fundamental radiolysis processes, in combination with BNL’s Laser-Electron Accelerator Facility (LEAF) for picosecond pulse radiolysis studies. With LEAF we can observe the solvation processes of radiolytically-generated excess electrons and compare and contrast them with the mechanisms of pre-solvated electron scavenging. Recently-developed IR vibrational spectroscopy transient absorption pulse radiolysis capabilities allow us to structurally identify reactive transient species and follow their reactivity.
This work, and use of the BNL Accelerator Center for Energy Research, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences, under contract DE-SC0012704.