Ultrafast 2D-IR spectroscopy of chemical and conformational dynamics in ionic solutions
Abstract/Contents
- Abstract
- The solute-solvent interactions dictate many physical and chemical properties of ionic solutions, as well as the equilibrium structure of ionic assemblies in solution, ranging from free ions, ion pairs, ion-pair dimers, ion-pair tetramers to nanoparticles and ionic crystals. These interactions include hydrogen bonding, charge-charge, charge-dipole, dipole-dipole interactions, etc. Because of the very fast timescales involved, we need novel time-resolved spectroscopic techniques to investigate the microscopic dynamics in the solution. Ultrafast two-dimensional infrared (2DIR) spectroscopy is a unique tool to study equilibrium chemical dynamics on the picosecond timescale. In this thesis, I present my graduate studies of chemical and conformational dynamic in ionic solutions using 2DIR, focusing on two main systems: aqueous ionic solutions and organic ionic solutions. In aqueous solutions, we have applied polarization-selective 2DIR to investigate the H-bond exchange mechanism in aqueous NaClO4 solution, using hydroxyl stretches of water as vibrational markers. The results show that a water molecule shifts its H-bond partners between water and perchlorate by means of large, prompt angular rotation. Using a jump-exchange kinetic model, we extract an H-bond exchange dynamics of ~6 ps and an average jump angle of 50 degree, in agreement with the jump angle observed in molecular dynamics simulations. We also investigate ligand exchange dynamics between different anions in the first solvation shell of magnesium cation in aqueous solution at an exchange time of 50 ps, with CN stretch of thiocyanate as a marker. In nonaqueous ionic solutions, we study the dynamics of ionic assemblies, including the ion pairing and dimerization processes in different organic solvents. The dimerization of LiNCS ion-pair to form (LiNCS)2 dimer is measured to happen on 20-50 ps, while ion pairing dynamics is as slow as hundreds of picoseconds. The ion pairing study complicates from multiple exchange process involved, such as self-ligand exchange which is also investigated by concentration dependent measurements.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Copyright date | 2011 |
| Publication date | 2010, c2011; 2010 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Ji, Minbiao |
|---|---|
| Associated with | Stanford University, Department of Physics |
| Primary advisor | Gaffney, Kelly |
| Thesis advisor | Gaffney, Kelly |
| Thesis advisor | Bucksbaum, Philip H |
| Thesis advisor | Fayer, Michael D |
| Advisor | Bucksbaum, Philip H |
| Advisor | Fayer, Michael D |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Minbiao Ji. |
|---|---|
| Note | Submitted to the Department of Physics. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2011. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2011 by Minbiao Ji
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