Formation of Stripe Patterns in Charged Colloids during Unidirectional Crystallization in the Presence of Impurity Particles

We examine the spatial distributions of fluorescent-labeled polystyrene (PS) particles added to colloidal silica that resulted after unidirectional crystal growth due to diffusion of pyridine. We find that the PS particles are arranged in a stripe pattern with a submillimeter-sized spacing. The patterning mechanism is attributable to the formation of lamella-shaped crystal grains and exclusion of the PS particles to the crystal grain boundaries.