<br/>The physicochemcal properties of silica and other materials are greatly influenced by the electrostatic environment of the silica surface in contact with the aqueous solution. To understand the electrostatic properties and its molecular foundation in three dimensional nano to micron sized systems, we developed angle resolved non-resonant second harmonic (SH) scattering. This method allows 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 together with a surface second-order susceptibility value can be measured. Performing measurments on silica particles with different sizes and under varying conditions of salt and pH we find regions were the surface potential starts to deviate from the electrostatic potential. In these regions the interfacial water orientation flips, both signs of the formation of a condensed charge or Stern layer. All measurments combined the electrostatic field within the Stern layer can be determined. <br/>

Surface chemistry of silica particles in aqueous solution

2019 Fall National Meeting

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