Electrostatic interactions play a large role at the silica/aqueous interface, and these interactions are dictated by the protonation state of surface silanols. Using the nonlinear optical methods second harmonic generation (SHG) and vibrational sum frequency generation (SFG), we aim to identify how the composition of the aqueous phase impacts silanol acidity. Utilizing non-resonant SHG, changes in the interfacial potential are explored in the presence of different alkali and alkaline earth chlorides as a function of pH. The complementary technique vibrational SFG is employed to monitor the hydrogen bonded structure of water for the same aqueous systems. By comparing the results from non-resonant SHG and resonant SFG, we gain insight into the different populations of ordered water present at the interface. The results from this comparison and the molecular picture of the electric double layer that emerges will be discussed.

Combining nonlinear optical methods to understand the interplay of water structure and surface potential at the silica/aqueous ion interface

251st National Meeting (2016)

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