The electrostatic environment of aqueous systems is an essential ingredient for the physicochemcal properties of the system. To understand the electrostatic properties and its molecular foundation in three dimensional nano to micron sized systems, we use angle resolved non-resonant second harmonic (SH) scattering to determine the surface potential of silica particles in solution, without making assumptions on the structure of the interfacial region. The scattered SH light, emitted from the particle interface and the diffuse double layer appears in two independent scattering patterns that have different polarization states. The angular shape and intensity are determined by the surface potential and the second-order surface susceptibility. Calibrating the response with the SH intensity of bulk water, a single, unique surface potential value can be extracted. Performing measurments on silica particles with different sizes and under varying conditions of salt and pH we find dramatic changes in surface potential and orientational ordering of water consisitent with either a a single diffuse double layer or with charge condensation/Stern layer formation.

Optical label- and model-free probing of the surface potential of nanoscale silica particles in aqueous solution

256th National Meeting (2018)

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