Aging of the Nonlinear Optical Susceptibility of colloidal solutions

TL;DR

This study investigates how the nonlinear optical response of Rhodamine B in a water-clay solution changes with aging, revealing gelation involves network structuring rather than aggregation.

Contribution

It provides new insights into the aging process of colloidal solutions by linking nonlinear optical measurements with gelation mechanisms.

Findings

Nonlinear optical susceptibility decreases with age.

Gelation occurs via network structuring, not aggregation.

Diffusion and relaxation times are correlated.

Abstract

Using Z-scan and dynamic light scattering measurements we investigate the nonlinear optics response of a colloidal solution undergoing dynamics slowing down with age. We study the high optical nonlinearity of an organic dye (Rhodamine B) dispersed in a water-clay (Laponite) solution, at different clay concentrations (2.0 wt% - 2.6 wt%), experiencing the gelation process. We determine the clay platelets self diffusion coefficient and, by its comparison with the structural relaxation time, we conclude that the gelation process proceeds through the structuring of interconnecting clay platelets network rather than through clusters growth and aggregation.