Ordering of Interfacial Water Molecules at the Charged Air/Water Interface Observed by Vibrational Sum Frequency Generation.
Abstract
The molecular structure and orientation of interfacial water molecules at the air/water interface in the presence of soluble cationic and anionic surfactants has been characterized. We have employed vibrational sum frequency generation (VSFG) to probe the orientation of interfacial water molecules as a function of both bulk surfactant concentration and solution ion strength. The observed ordering of interfacial water molecules is manifested by an enhancement of the OH stretching modes in the VSFG spectra. We attribute the observed enhancement to an ordering of the interfacial water molecules induced by the large electrostatic field present at these charged interfaces. From the VSFG measurements we find that both the interfacial surfactant and water molecules attain their highest degree of order at sub-monolayer concentrations. The nature of this enhancement is further explored by studying mixed (cationic and anionic) surfactant systems as well as surfactant systems at different ionic strengths.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1997
- Accession Number
- ADA326863
Entities
People
- B. M. Mccarty
- D. E. Gragson
- Geraldine L. Richmond
Organizations
- University of Oregon