Two-dimensional patterns of ultra-fine particles prepared by self-organization

Mesoscopic regular patterns consisting of ultra-fine particles were formed on solid substrate by simply casting of their aqueous colloidal dispersions. Periodic stripes were observed on mica surface parallel to the receding direction of the solution edge. The periodicities were controllable by changing the temperature of the substrate. The thickness of each stripe was equivalent to monolayer of particles. From atomic force microscopy (AFM) and scanning electron microscopy (SEM), it was suggested that the monolayer of ultra-fine particles were hexagonally packed in the stripe patterns. In addition, by increasing the concentration of the aqueous dispersion of ultra-fine particles, some different types of stripe patterns were observed. The patterns were also readily formed by self-organization with low cost and low energy.