Nature of Cations Critically Affects Water at the Negatively Charged Silica Interface

Ion-specific interfacial potentials at the silica-water interface are compensated by water alignment

We study specific ion effects at the silica water interface using sum-frequency generation spectroscopy. We show that commonly inferred ion-specific interfacial potentials cannot account for the spectroscopic observables. Our results demonstrate that both, the distribution of ions and the orientation of water at the very interface depend on the ion size, yet, their contribution to interfacial electric fields compensate ion-specificities.​