title: DNA-assembled nanoparticle rings exhibit electric and magnetic resonances at visible frequencies.
abstract: Metallic nanostructures can be used to manipulate light on the subwavelength scale to create tailored optical material properties. Next to electric responses, artificial optical magnetism is of particular interest but difficult to achieve at visible wavelengths. DNA-self-assembly has proved to serve as a viable method to template plasmonic materials with nanometer precision and to produce large quantities of metallic objects with high yields. We present here the fabrication of self-assembled ring-shaped plasmonic metamolecules that are composed of four to eight single metal nanoparticles with full stoichiometric and geometric control. Scattering spectra of single rings as well as absorption spectra of solutions containing the metamolecules are used to examine the unique plasmonic features, which are compared to computational simulations. We demonstrate that the electric and magnetic plasmon resonance modes strongly correlate with the exact shape of the structures. In particular, our computations reveal the magnetic plasmons only for particle rings of broken symmetries, which is consistent with our experimental data. We stress the feasibility of DNA self-assembly as a method to create bulk plasmonic materials and metamolecules that may be applied as building blocks in plasmonic devices.
authors.affiliation: Fakultät für Physik and Center for Nanoscience, Ludwig-Maximilians-Universität München , Geschwister-Scholl-Platz 1, 80539 Munich, Germany.
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Roller
authors.forename: Larousse Khosravi
authors.initials: LK
authors.lastname: Khorashad
authors.forename: Michael
authors.initials: M
authors.lastname: Fedoruk
authors.forename: Robert
authors.initials: R
authors.lastname: Schreiber
authors.forename: Alexander O
authors.initials: AO
authors.lastname: Govorov
authors.forename: Tim
authors.initials: T
authors.lastname: Liedl
mesh_terms: D004247:DNA / Q000737:chemistry*; D004560:Electricity; D008280:Magnetics; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry*; D013057:Spectrum Analysis
chemical_list: D004247:DNA
keywords: DNA origami; nanoparticles; plasmonic metamaterials; self-assembly