Deposition of Au nanoshells on thermally grown patterned Ag nanoparticles from the block copolymer micelle thin films by seeding method

A facile method of fabricating patterned Ag-Au core-shell nanoparticles has been demonstrated using stepwise reduction and seeded deposition from block copolymer (BCP) micelle thin films. Spherical inverse micelles of polystyrene-block-poly(4-vinyl pyridine) (PS-b-P4VP) copolymer in PS-selective toluene produce organic-inorganic complexes by coordinating silver acetate salt (Ag salt) to the hydrophilic P4VP core. Rapid thermal decomposition of Ag salt-loaded BCP micelles at 300 °C for 5 min leads to the formation of stable Ag nanoparticles of 20-25-nm size on a quartz substrate. The variations in annealing temperature, time, and substrate types influence the resulting Ag nanostructures. Transmission electron microscopy investigations reveal that gold (Au) shells of approximately 2.5-nm size on the Ag nanoparticles have been deposited by the seeding method using a selective reducing agent. Ag-Au core-shell nanoparticles can also help to control the hybridized surface plasmon band.