Crystallization of dyes by directed aggregation of colloidal intermediates: a model case.

The crystallization of two oil-soluble dyes, oil red and oil blue, from the 125-nm-sized nanodroplets of miniemulsions, results in larger well-crystallized species of high quality, which must have been grown by aggregation of colloidal intermediates. This model case not only allows the existence of this nonclassical crystallization process to be proven but also gives evidence for the presence of "super-van der Waals" forces operating between the single nanocrystalline moieties.