Paper PL+BI-TuM10
Controlled Plasmonic Coupling in Reconfigurable Nanoparticle Assemblies

Tuesday, October 16, 2007, 11:00 am, Room 619

Metal nanoparticles (MNPs) support localized surface plasmon resonances that are sensitive to particle shape, size, composition, and the presence of other polarizable particles and materials. Advances in MNP synthesis and surface chemistry have yielded biomolecule nanoparticle conjugates that interact specifically with oligonucleotides, peptides, and proteins. The specific recognition properties of these components have been exploited in responsive plasmonic systems with formats that range from amorphous solution phase particle networks to immobilized colloidal monolayers and individually responsive particles. For molecular detection applications, various formats have various advantages, with single particle sensors generally offering ease of control and multi-particle systems offering strong plasmon modulation. Here, we report plasmon modulation in pre-formed, few particle assemblies linked by reconfigurable DNA nanostructures. The investigation is motivated by the potential of reconfigurable few particle assemblies to provide control of plasmon coupling in a format that displays high responsiveness per molecule. In the coupled system upon which we report, DNA nanostructures tether satellite MNPs to a core MNP. The DNA nanostructures use duplex DNA to control interparticle separation and are responsive to target strands that modulate interparticle helix length. The reconfigurable assemblies are characterized in two states, using dynamic light scattering and transmission electron microscopy to monitor structure and scattering spectroscopy to monitor plasmonic properties. A two state structural model is tested by comparison of spectroscopic data with spectra calculated for structures defined by core/satellite stoichiometry from TEM and interparticle separations from measurements in DNA-linked networks. Thermodynamic properties derived from melting transition data collected from the reconfigurable DNA linker ex-situ are reported and reviewed as a source of insight into DNA nanostructure control of system stability.