Depletion-induced crystallization in colloidal rod-sphere mixtures

We report the observation of depletion-induced phase separation in a mixture of colloidal silica spheres and colloidal silica rods with light microscopy and confocal scanning laser microscopy. We show that very low rod concentrations are sufficient to induce sphere crystallization. This qualitatively agrees with theoretical predictions and demonstrates that rodlike colloidal particles are highly efficient depletion agents.