Introduction

Abstract

Colloids comprise a very broad class of materials. Their basic structure consists of a dispersion of one phase into another one, in which the dispersed phase possesses a typical length scale ranging from a fewmolecular sizes up to several microns. Some colloids are thermodynamically stable and generally form spontaneously, whereas others are metastable, requiring energy for preparation and specific properties to persist. Metastable colloids are obtained by two main distinct routes: one is nucleation and growth, including precipitation, and the other is fragmentation. In both cases, as a consequence of the intrinsic off-equilibrium nature of this class of colloids, specific surface properties are required to prevent recombination. Surfaceactive species are generally employed to stabilize freshly formed fragments or growing nuclei, as they are expected to provide sufficient colloidal repulsive forces.