Plasmon coupling in binary metal core-satellite assemblies

Controlled plasmon coupling is observed in nanoparticle assemblies composed of 20 nm silver 'satellite' nanoparticles tethered by reconfigurable duplex DNA linkers to a 50 nm gold 'core' particle. The assemblies incorporate silver nanoparticle-oligonucleotide conjugates prepared using a new conjugation method in which the recognition strand is anchored by a 10 base pair, double strand spacer that presents adjacent 3'- and 5'-thiols to the silver surface. Reconfiguration of the DNA linkers from a compact to an extended state results in decreased core-satellite coupling and a blue-shift in the gold core plasmon resonance. The structural basis for the observed resonance modulation is investigated through simulation of the scattering spectra of binary assemblies with various core-satellite separations. Additional simulations of core-satellite assemblies composed of gold satellite particles bound to silver cores and of assemblies composed entirely of silver particles are used to clarify the dependence of the coupling response on the composition of the components and their distribution within the assembly.