Mini-Review on Water–Oil Emulsions through Vibrational Sum Frequency Generation

Abstract

Interfacial interactions between water and oil phases are present in various fields in which additives, such as surfactants, are utilized to minimize the surface stress between these phases to form an emulsion. However, the consequence of adding additives is not always easy to understand or to control due to the plethora of parameters that control the production of an emulsion phase. There are several macroscopic techniques to study the properties of emulsions. Nevertheless, these techniques cannot describe the mechanistic steps at the molecular level for interfaces with nanometer thicknesses. Among surface-sensitive techniques, vibrational sum frequency generation (VSFG) has been effectively utilized to study various parameters that control the formation of surfactant monolayers at water−oil interfaces. In this mini-review, a summary of molecular outputs by utilization of VSFG for studying the water−oil interfaces will be presented.

Tools to Investigate Structure at Hydrocarbon–Air Interfaces: Field-Induced Droplet Ionization Mass Spectrometry and Sum-Frequency Generation with Pulsed Lasers

“…FIDI can be very nicely supplemented by another surface-sensitive measuring technique that relies on the interaction of laser light at interfaces. It is referred to as vibrational sum frequency generation (VSFG) or sum frequency generation (SFG) and it has proven to provide exceptional information about molecules at surfaces and interfaces. , SFG is a spectroscopic surface-sensitive method that can monitor the dynamics of molecules at interfaces. − Moreover, SFG can provide detailed information about the symmetry of adsorbed species by changing the polarization of the interacting laser beams. Thus, the orientation of the molecules residing at interfaces can be obtained from SFG.…”