New methods for extracting ultrafast water dynamics at interfaces
Abstract/Contents
- Abstract
- Water dynamics near interfaces and in confined systems, as manifested by vibrational relaxation, orientational relaxation, and spectral diffusion of the water hydroxyl stretch (5% HOD in H2O), are measured via infrared (IR) pump-probe and 2D IR vibrational echo techniques. It is shown that a two component model for population and orientational relaxation accurately describes the dynamics for systems comprised of two types of hydrogen bonding ensembles: waters that are hydrogen bonded to other waters and waters at an interfacial region. Through a combination of spectroscopic and data analysis techniques, the dynamics of these two environments become separable. This two component model is successfully applied to binary mixtures of water and tetraethylene glycol dimethyl ether. The effects of confinement on water dynamics are studied by examining water inside of reverse micelles made with the surfactant Aerosol-OT (AOT), which contains charged head groups. Large reverse micelles (diameter [greater than or equal to] 4.6 nm) can be decomposed into two separate environments: a bulk water core and an interfacial water shell. Each region has distinct dynamics that can be resolved experimentally using the two component model. The core follows bulk water dynamics while interfacial water shows slower dynamics that are independent of size for large reverse micelles. To explore how the chemical composition of the interface influences dynamics, the dynamics of water in AOT reverse micelles are compared to water dynamics in reverse micelles made from the neutral surfactant Igepal CO-520. It is found that the presence of an interface plays the major role in determining interfacial water dynamics and not the chemical composition. A two component model is also developed for spectral diffusion. The two component model for spectral diffusion is an extended version of the center line slope (CLS) analysis procedure, originally developed for single ensemble systems. The modified two component CLS procedure allows the CLS behavior of water at the interface to be back-calculated from known parameters. From the interfacial CLS, the interfacial frequency-frequency correlation function, which describes spectral diffusion, can be determined. It is found that, similar to orientational relaxation behavior in large AOT reverse micelles, the interfacial FFCF does not vary with increasing reverse micelle size.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Copyright date | 2012 |
| Publication date | 2011, c2012; 2011 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Fenn, Emily Elizabeth |
|---|---|
| Associated with | Stanford University, Department of Chemistry |
| Primary advisor | Fayer, Michael D |
| Thesis advisor | Fayer, Michael D |
| Thesis advisor | Dai, Hongjie, 1966- |
| Thesis advisor | Pecora, Robert, 1938- |
| Advisor | Dai, Hongjie, 1966- |
| Advisor | Pecora, Robert, 1938- |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Emily Elizabeth Fenn. |
|---|---|
| Note | Submitted to the Department of Chemistry. |
| Thesis | Ph. D. Stanford University 2012 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2012 by Emily Elizabeth Fenn
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
Also listed in
Loading usage metrics...