Real-space imaging of nucleation and growth in colloidal crystallization

Crystallization of concentrated colloidal suspensions was studied in real s pace with laser scanning confocal microscopy. Direct imaging in three dimen sions allowed identification and observation of both nucleation and growth of crystalline regions, providing an experimental measure of properties of the nucleating crystallites. By following their evolution, we identified cr itical nuclei, determined nucleation rates, and measured the average surfac e tension of the crystal-liquid interface. The structure of the nuclei was the same as the bulk solid phase, random hexagonal close-packed, and their average shape was rather nonspherical, with rough rather than faceted surfa ces.