We present a new set-up that allows for simultaneous measurements of zeta-potential and second harmonic generation on one sample. As the Wesolowski consortium has shown with the impressive and comprehensive work, the combination of methods on ONE system yields the valuable insight into the complex  mineral water interface that is required to advance. The use of experimental set-ups that permit the study of a given sample with different methods avoids sample handling and improves transferability of results. Our set-up currently allows the study of flat surfaces. The samples encompass single crystal surfaces of defined cut, prisms, half-spheres and half-cylinders, ideally exposing a defined cut of the material. We have carried out experiments on some selected systems to verify both the second harmonic generation measurements under flow and the zeta-potential results with the combined set-up. Second harmonic generation measurements on fluorite show similar as reported in the literature that with increasing applied pressure the non-linear optical response to fresh solution increases. In a NaF solution the response is constant again confirming literature results. Similar measurements with a hydrophobic surface do not show any changes of the non-linear optical response with fresh solutions of constant pH, while a change in pH does. For the hydrophobic surface the measured zeta-potentials show that the isoelectric point is at pH 4, which is typical for hydrophobic surfaces. As indicated, the current set-up is applicable to any flat surface that can be inserted in the cell and that can be studied by non-linear optics. We plan to do temperature dependent measurements with this set-up on mineral water interfaces in the future.<br/>

A setup for combined zeta-potential and second harmonic generation measurements

255th National Meeting (2018)

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