Probing interactions within complex colloidal systems using PGSE-NMR

Pulsed‐gradient spin‐echo NMR (PGSE‐NMR) has evolved into a powerful technique for probing colloidal structure, particularly that of complex mixtures. Indeed, with the exception perhaps of neutron scattering, no single technique has such universal applicability. The parameter of interest, the (self‐) diffusion coefficient, is of fundamental importance as it is determined by both the chemistry of the system—the size and shape of the individual molecular species—and its physical environment/state—dissolved, dispersed, aggregated, constrained within boundaries, etc. Understanding such behaviour is of central importance in the biological and colloidal fields. The basis of using diffusion as a probe of such systems relies on the fact that each species in a mixture can be separated by differences in their diffusion coefficient and/or by the chemical specificity of NMR. Binding, aggregation and structure elucidation studies have undergone a renaissance in the last decade owing to the increased commercial availability of hardware and improved data processing. This paper highlights just a few of the many and diverse applications to which PGSE‐NMR can be put. Copyright © 2002 John Wiley & Sons, Ltd.