Anisotropic hindered motion close to an interface studied by resonance-enhanced dynamic light scattering

Abstract

The influence of a solid-liquid interface on the diffusion of dispersed spherical particles has been studied using resonance enhanced dynamic light scattering. Particle radii ranging from 11 to 204 nm have been investigated at a fixed penetration depth of the evanescent wave of 200 nm. For particles with radii smaller than 40 nm, the correlation function measured near the interface is similar in shape to the one measured in bulk solution. For particles with radii higher than 40 nm the correlation function loses the distinct single exponential shape. To study particles with radii higher than 40 nm, we had to solve the problem of an unwanted contribution to the correlation function. This problem is generic with dynamic light scattering using single-mode fibre detection and is thus of general interest. This contribution has been identified as stemming from temporal fluctuations in the fibre used. Furthermore, we give an estimation of the effect of rotation on translation for spherical particle mobility near an interface. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.