Mechanism for hierarchical self-assembly of nanoparticles on scaffolds derived from block copolymers

Lithographically patterned substrates can direct the self-assembly of block copolymer films into aligned structures that, in turn, template the self-organization of colloidal nanoparticles. Deposition on pristine diblock copolymer films does not lead to reproducible selective decoration, but films modified to have nanoscale corrugation act as scaffolds for highly selective nanoparticle adsorption. The mechanism for this selectivity relies on the lateral forces inherent to spin casting to remove all of the nanoparticle suspension not confined within the nanoscopic trenches. This technique does not rely on interactions between the surfactant capping molecules and the polymer and is therefore general to a wide class of nanoparticle materials. Prospects to obtain long-range ordering and associated potential applications are discussed.