Brownian dynamics close to a wall, measured by quasi-elastic light scattering from an evanescent wave

International audienceThe Brownian dynamics of a colloidal suspension is measured in the immediate vicinity of a rigid surface by the evanescent quasi-elastic light-scattering technique. A net decrease of the measured diffusion coefficient is observed, due to the hydrodynamic slowing down of the particles very close to the wall. This effect is all the more important when the particles are allowed to get close to the wall, i.e., when the range of the static wall/particle repulsive interaction decreases. It thus provides a mean for testing the particle/wall static interactions via a dynamic light-scattering measurement. The data are analyzed by Brownian dynamic simulations which are proven to be quite valuable to interpret light-scattering data from “hindered” scatterers, such as particles confined in the neighborhood of a wall, or trapped in a porous media or a gel