Hexagonal spiral growth in the absence of a substrate.

Experiments on the formation of spiraling hexagons (350-1000 nm in width) from a solution of nanoparticles are presented. Transmission electron microscopy images of the reaction products of chemically synthesized cadmium nanocrystals indicate that the birth of the hexagons proceeds without assistance from static screw or edge dislocations, that is, they spiral without constraints provided by an underlying substrate. Instead, the growth mechanism relies on a dynamical dislocation identified as a dense aggregate of small nanocrystals that intersects the spiraling hexagon at the crystal surface. This nanocrystal bundle, which we term the "feeder," also appears to release nanocrystals into the spiral during the growth process.