Ren, Zhe
(2018)
Ultrafast structure and dynamics of ionic liquids revealed by two-dimensional infrared spectroscopy.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Two-dimensional infrared spectroscopy (2D-IR) is a non-linear spectroscopy that is capable of resolving molecular dynamics with picosecond time resolution and molecular-level spatial resolution. 2D-IR has been successfully implemented in a myriad of solution systems to study the local solute and solvent dynamics. Ionic liquids are a unique type of liquid with each formula unit a pair of cation and anion. The structure grants it unique properties that are suitable for many potential applications, and the chemical structure can be modified to be “task-specific”.
In this thesis, I describe our implementation of 2D-IR to understand different aspects of the solvation dynamics of ionic liquids, including solvent dynamics, ultrafast structures and dynamics of small solutes, and the dynamics of ionic liquids under confinement. A direct correlation between the microscopic solvent dynamics and the macroscopic viscosity has been observed, indicating the molecular origin of viscosity in ionic liquids is possibly the ion-cage lifetime. Some small inorganic salts form ion-pairs in the ionic liquids, and have a Gibbs free energy of ~8 kJ/mol. Some uncharged small molecules can cluster in ionic liquids, like water clusters with thiocyanate anion. The detailed structural and reorientation dynamics of ionic liquid-surfactant complexes imply a random cluster picture, rather than previously-believed reverse micelle picture; the shape of the dynamic correlation function also indicates a non-isotropic local orientation distribution that could originate from the ion-exchange between anionic surfactants and ionic liquids.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
|
| Date: |
28 June 2018 |
| Date Type: |
Publication |
| Defense Date: |
21 December 2017 |
| Approval Date: |
28 June 2018 |
| Submission Date: |
10 January 2018 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
177 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Chemistry |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
ionic liquids, thiocyanate, 2D-IR, solvation dynamics. |
| Date Deposited: |
28 Jun 2018 19:28 |
| Last Modified: |
28 Jun 2018 19:28 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/33693 |
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