INTERROGATION OF NANOSCALE SILICON DIOXIDE WATER INTERFACES VIA HYPER-RAYLEIGH SCATTERING

Hyper-Rayleigh scattering (HRS) experiments performed on nanometer-sca le SiO2/water interfaces (aqueous colloidal suspensions) display finit e, measurable signals. HRS is not constrained by the orientational, si ze, and/or charge restrictions inherent to conventional interfacial se cond harmonic generation (SHG) or electric-field-induced SHG measureme nts. Thus, apparently for the first time, the second-order nonlinear o ptical (NLO) response of ultrasmall interfaces has been measured. pH- and electrolyte-dependent experiments show the response to be sensitiv e to changes in chemical composition at the silicon dioxide/solution i nterface. HRS provides detailed information about the surface of these technologically interesting and important particles in their native s olution-phase environment.