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

Interfacial molecular dynamics are key to understanding many phenomena in technology and life sciences. We demonstrate a first step toward accessing vibrational dynamics at liquid-liquid and nanoscopic (bio)-interfaces using time-resolved sum-frequency scattering to probe the interfaces of a nanodroplet platform. The free induction decay of the vibrational modes of dodecylsulfate amphiphiles from the interface of dispersed nanoscopic oil droplets was measured. We probed the vibrational response of both the functional headgroup and the alkyl tail of the amphiphiles. In the molecular fingerprint region, a beating of vibrational modes was observed. Simultaneous modeling of the time- and frequency-resolved response revealed modes at ∼995 and ∼1065 cm(-1) that can be assigned to C-O-S and SO3 stretch vibrations.