Solubilization-induced surface structural changes of sol particles observed by hyper Rayleigh scattering

Hyper Rayleigh scattering (HRS) and other measurements were carried out to investigate the solubilization of 4-dimethylamino-4′-nitro-azobenzene (DNAB) particles by sodium dodecyl sulfate (SDS) micelles. DNAB is hardly soluble in water and forms micrometer-size particles consisting of H-aggregates. HRS results show that these particles have very small second order optical nonlinearity. For partly solubilized particles, the breaking of H-aggregates on particle surface results in very large HRS intensities. At large SDS concentration, most of the particles are dissolved into monomers that are adsorbed on the outer-layer of the SDS micelles. HRS also reveals that Ostwald ripening process can recover the 'destroyed' particle surface.