APPLICATION OF DIFFUSING-WAVE SPECTROSCOPY TO PARTICLE SIZING IN CONCENTRATED DISPERSIONS

Diffusing-wave spectroscopy extends the application of dynamic light scattering to concentrated colloidal suspensions. This approach circumvents the problem of multiple scattering by treating the transport of light as a diffusion process. An apparatus exploiting this theory is described and compared to other systems developed for similar studies. The application of all such techniques to measuring particle size without dilution is complicated by the effects of particle interaction. In fluid suspensions up to volume fractions of approximately 0.2, it is demonstrated that a first-order correction for these effects can be made by replacing the solvent viscosity by the suspension viscosity in the Stokes-Einstein expression which defines the diffusional mobility of the particles at infinite dilution.