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Synthesis of Ionic Liquid Based Electrolytes, Assembly of Li-ion Batteries, and Measurements of Performance at High Temperature
Published on: December 20, 2016
Heterogeneous solute dynamics in room temperature ionic liquids.
Hui Jin1, Xiang Li, Mark Maroncelli
1Department of Chemistry, The Pennsylvania State University, 104 Chemistry Building, University Park Pennsylvania 16802, USA.
The Journal of Physical Chemistry. B
|November 10, 2007
Summary
Ionic liquids exhibit dynamic heterogeneity, meaning different molecular groups move at varying speeds. This study reveals that solute dynamics, like rotation and isomerization, depend on excitation wavelength, especially at longer wavelengths.
Area of Science:
- Physical Chemistry
- Materials Science
- Chemical Physics
Background:
- Room temperature ionic liquids (RTILs) are gaining attention as designer solvents.
- Understanding their dynamic properties is crucial for their application.
- Dynamic heterogeneity, where molecular motions occur at different rates, is a key characteristic of complex fluids.
Purpose of the Study:
- To investigate the presence and extent of dynamic heterogeneity in two common RTILs.
- To explore how solute dynamics (rotation, solvation, isomerization, charge transfer) are affected by excitation wavelength.
- To establish a general understanding of subnanosecond dynamics in RTILs.
Main Methods:
- Utilized time-resolved emission spectroscopy.
- Studied the kinetics of various solutes: coumarin 153, malononitriles, and crystal violet lactone.
- Analyzed the dependence of solute relaxation rates on excitation wavelength, particularly on the red edge of absorption bands.
Main Results:
- Demonstrated significant excitation wavelength dependence of emission kinetics for all studied solutes.
- Observed that relaxation rates vary distinctly for energetically selected solute subpopulations.
- Confirmed dynamic heterogeneity in dimethyl-isopropyl-propyl-ammonium bis(trifluoromethylsulfonyl)imide and N-propyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide.
Conclusions:
- Subnanosecond dynamical processes in typical ionic liquids at room temperature are characterized by dynamic heterogeneity.
- Excitation wavelength selection provides a sensitive probe for revealing these heterogeneous dynamics.
- The findings highlight the complex nature of molecular motion within ionic liquids.
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