Short-time self-diffusion of weakly charged silica spheres at aqueous interfaces

Department of Physics, Hong Kong University of Science and Technology - Clear Water Bay, Kowloon, Hong Kong

Corresponding author: penger@ust.hk

Received: 7 April 2008
Accepted: 9 September 2008

Abstract

Optical microscopy and multi-particle tracking are used to study the short-time self-diffusion of weakly charged silica spheres at a water-air interface. The measured short-time self-diffusion coefficient D^S_S has the form, D^S_S/D₀=α (1-β n), where n is the area fraction occupied by the particles and D₀ is the Stokes-Einstein diffusion coefficient of individual particles in the bulk fluid. The obtained values of α and differ from those obtained for bulk suspensions, indicating that hydrodynamic interactions between the interfacial particles have interesting new features when compared with their three-dimensional counterpart.