Conventional optical microscopy of colloidal suspensions

Optical microscopy can resolve detail at the larger end of the colloidal le ngth scale, and to image suspensions at an individual particle level of res olution would allow the investigation of local behaviour in a way denied to the established scattering techniques. However, to achieve high-contrast s ingle-particle resolution in dense suspensions that are thick enough to sho w behaviour the same as would be expected in the bulk is not a trivial exer cise. We build on established advanced techniques of the conventional (i.e. non-confocal) light microscopy of phase objects to develop a suitable expe rimental protocol. Furthermore, we demonstrate the effectiveness of this pr otocol by means of an 'atlas' of the hard-sphere crystalline solid (where r andom stacking results in many complex facets), which should serve as a com pendium for future study. (C) 2001 Elsevier Science B.V. All rights reserve d.