The dynamics and structure at interfaces often differ significantly from their bulk counterparts, necessitating the development of interface-specific techniques. Despite much research, experimentally accessing interfaces buried between two condensed phases remains difficult. Second harmonic generation (SHG) and sum frequency generation are used extensively to study buried interfaces. However, it has long been known that, in the presence of surface charge, signal is generated not only near the dividing plane of the interface, but throughout the electrical double layer (EDL) as well. We report the development of a method, based on recent advances in the understanding of the nonlinear optical signal generation process at charged interfaces, that isolates the Stern layer from the diffuse layer response of the EDL through detection of both the phase and amplitude of the SHG signal with heterodyne-detected (HD-) SHG. We discuss how this method can be used to directly probe structure and dynamics near the dividing plane of the interface, as well as quantify, all-optically, the important macroscopic parameter of the interfacial potential.

Direct access to Stern and diffuse layer dynamics over charged interfaces with HD-SHG

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.