title: Systematic study of antibonding modes in gold nanorod dimers and trimers.
abstract: Using on-wire lithography to synthesize well-defined nanorod dimers and trimers, we report a systematic study of the plasmon coupling properties of such materials. By comparing the dimer/trimer structures to discrete nanorods of the same overall length, we demonstrate many similarities between antibonding coupled modes in the dimers/trimers and higher-order resonances in the discrete nanorods. These conclusions are validated with a combination of discrete dipole approximation and finite-difference time-domain calculations and lead to the observation of antibonding modes in symmetric structures by measuring their solution-dispersed extinction spectra. Finally, we probe the effects of asymmetry and gap size on the occurrence of these modes and demonstrate that the delocalized nature of the antibonding modes lead to longer-range coupling compared to the stronger bonding modes.
authors.affiliation: Department of Materials Science and Engineering, ‡Department of Chemistry, and International Institute for Nanotechnology, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Kyle D
authors.initials: KD
authors.lastname: Osberg
authors.forename: Nadine
authors.initials: N
authors.lastname: Harris
authors.forename: Tuncay
authors.initials: T
authors.lastname: Ozel
authors.forename: Jessie C
authors.initials: JC
authors.lastname: Ku
authors.forename: George C
authors.initials: GC
authors.lastname: Schatz
authors.forename: Chad A
authors.initials: CA
authors.lastname: Mirkin
mesh_terms: D000268:Adhesiveness; D003198:Computer Simulation; D019281:Dimerization; D006046:Gold / Q000737:chemistry*; D008027:Light; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D008956:Models, Chemical; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D012542:Scattering, Radiation; D020349:Surface Plasmon Resonance / Q000379:methods*
chemical_list: D006046:Gold
keywords: On-wire lithography; nanoparticle arrays; nanorods; plasmon coupling; plasmonics