Directing the formation of nanostructured rings via local oxidation.

We provide compelling evidence that ring formation in solutions of thiol-passivated Au nanoparticles is driven by breath figure dynamics. A method for the controlled placement of rings of nanoparticles on a solid substrate, which exploits variations in substrate wettability to fix the positions of the submicrometer water droplets formed in the breath figure process, has been developed. This is achieved by heterogeneously patterning hydrogen-terminated silicon substrates with oxide regions that act as adsorption sites for the droplets. The droplets in turn template the formation of thiol-passivated Au nanoparticle rings during spin-casting from volatile solvents.