BROWNIAN-MOTION IN BINARY COLLOIDAL SUSPENSIONS

The statics and dynamics of dilute binary suspensions of charged polystyrene spheres have been investigated by static and dynamic light scattering experiments (SLS and DLS). The samples under study consist of a small amount of large spheres immersed in a system of small spheres. The SLS data of the measured static structure factor are compared with a theoretical approach, the so-called extended resealed mean spherical approximation, for colloidal mixtures. Dynamic light scattering at large wavenumbers was used to measure the self-scattering function which, in general, contains information on the Brownian motion of both species. The experimentally observed self-scattering functions are compared with theoretical calculations based on the single exponential approximation and good agreement has been found within the experimentally accessible time window. It is demonstrated that for appropriately chosen system parameters, the Brownian motion of only the large spheres is observed. © 1992.