Formation and size tuning of colloidal microcapsules via host-guest molecular recognition at the liquid-liquid interface.

Stimuli-responsive colloidal microcapsules have been fabricated at the oil-water interface using molecular recognition between functionalized gold nanoparticles. Water-soluble beta-cyclodextrin-capped gold nanoparticles and organo-soluble adamantyl-functionalized gold nanoparticles are self-assembled at the water-toluene interface via specific host-guest molecular interactions to provide robust microcapsules. Multivalent interactions of complementary ligands on the nanoparticle surface provide stability to these capsules. Unlike covalently cross-linked microcapsules, the reversible nature of these bridging interactions can be used to manipulate the size of these capsules via introduction of competing adamantane containing amphiphilic guest molecules. Partial disruption of interfacial cross-linking allows microcapsules to coalesce with each other to form larger capsules.