Noble metal nanoparticle arrays: control of size, shape and placement via chemical self-assembly

Selective patterning of chemical functional groups on polymer surfaces is utilized for controlled placement of monodisperse noble metal nanoparticles. Self-assembled diblock copolymer films deposited on hydrophobic silicon substrates are used as a template for metal nanoparticle organization. By varying the processing conditions of polymer templates, micelle and cylindrical polystyrene-b-poly(methyl methacrylate) diblock copolymer templates were fabricated. Functional groups on the surface of poly(methyl methacrylate) domains in the diblock copolymer films were chemically modified from an ester group to a carboxylate using a base catalyzed hydrolysis step. Gold and silver nanoparticles were fabricated in solution in order to achieve size and shape control. After gold nanoparticle synthesis, a ligand exchange reaction was performed to produce nanoparticles with amine functional groups for chemical attachment on chemically modified poly(methyl methacrylate) surfaces. Atomic force microscopy and scanning electron microscopy images demonstrate that this fabrication route results in preferential attachment of metal nanoparticles on poly(methyl methacrylate) thin films and on poly(methyl methacrylate) domains in polystyrene-b-poly(methyl methacrylate) diblock copolymer thin films.