POLARIZATION OF WATER-MOLECULES AT A CHARGED INTERFACE - 2ND HARMONIC STUDIES OF THE SILICA WATER INTERFACE

Surface second harmonic generation was used to probe the silica/water interface. At pH values where the silica surface is charged, we found that the water molecules near the interface are polarized by the interfacial electric field and are responsible for the observed second harmonic light. Two types of silanol sites having pK(a) values of 4.5 and 8.5 were inferred from the data. A promising result of the studies was the development of a new method for obtaining electric potentials at charged liquid interfaces.