Toward vibrational dynamics at liquid-liquid and nano-interfaces: time-resolved sum-frequency scattering

Area of Science:

• Physical Chemistry
• Surface Science
• Spectroscopy

Background:

• Interfacial molecular dynamics are crucial for understanding diverse phenomena in technology and life sciences.
• Probing molecular behavior at interfaces, especially liquid-liquid and nanoscopic scales, remains challenging.

Purpose of the Study:

• To develop and demonstrate a method for accessing vibrational dynamics at liquid-liquid and nanoscopic interfaces.
• To investigate the interfacial molecular dynamics of amphiphiles using a nanodroplet platform.

Main Methods:

• Utilized time-resolved sum-frequency scattering (TR-SFS) to probe interfaces.
• Employed a nanodroplet platform for studying liquid-liquid and nanoscopic interfaces.
• Measured the free induction decay of vibrational modes of dodecylsulfate amphiphiles.

Main Results:

• Successfully probed vibrational responses of both the headgroup and alkyl tail of amphiphiles at the interface.
• Observed a distinct beating of vibrational modes in the molecular fingerprint region.
• Identified specific vibrational modes at ~995 cm⁻¹ (C-O-S stretch) and ~1065 cm⁻¹ (SO3 stretch) through simultaneous time- and frequency-resolved modeling.

Conclusions:

• Time-resolved sum-frequency scattering on a nanodroplet platform is a viable approach for studying interfacial molecular dynamics.
• The study provides insights into the vibrational behavior of amphiphiles at nanoscopic liquid-liquid interfaces.
• The identified vibrational modes offer a molecular-level understanding of interfacial structures and dynamics.