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Ultrafast structure and dynamics of ionic liquids revealed by two-dimensional infrared spectroscopy

Ren, Zhe (2018) Ultrafast structure and dynamics of ionic liquids revealed by two-dimensional infrared spectroscopy. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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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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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Ren, ZheZHR3@pitt.eduZHR30000-0001-7793-1581
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairGarrett-Roe, Ssgr@pitt.eduSGR
Committee MemberWaldeck, DHdave@pitt.eduDAVE
Committee MemberCoalson, Rcoalson@pitt.eduCOALSON
Committee MemberKim,
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


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