Nikolay A. Mirin

Plexcitonic Nanoparticles: Plasmon-Exciton Coupling in Nanoshell-J-Aggregate Complexes

Stable Au nanoshell-J-aggregate complexes are formed that exhibit coherent coupling between the localized plasmons of a nanoshell and the excitons of molecular J-aggregates adsorbed on its surface. By tuning the nanoshell plasmon energies across the exciton line of the J-aggregate, plasmon-exciton coupling energies for these complexes are obtained. The strength of this interaction is dependent on the specific plasmon mode of the nanoparticle coupled to the J-aggregate exciton. From a model based on Gans theory, we obtain an expression for the plasmon-exciton hybridized states of the complex.

Fano Resonances in Plasmonic Nanoparticle Aggregates

We investigate the plasmonic properties of a symmetric silver sphere septamer and show that the extinction spectrum exhibits a narrow Fano resonance. Using the plasmon hybridization approach and group theory we show that this Fano resonance is caused by the interference of two bonding dipolar subradiant and superradiant plasmon modes of E(1u) symmetry. We investigate the effect of structural symmetry breaking and show that the energy and shape of the Fano resonance can be tuned over a broad wavelength range. We show that the wavelength of the Fano resonance depends very sensitively on the dielectric permittivity of the surrounding media with one of the highest LSPR sensitivities reported for a finite nanostructure.

Nanoshells Made Easy: Improving Au Layer Growth on Nanoparticle Surfaces

The growth of a continuous, uniform Au layer on a dielectric nanoparticle is the critical step in the synthesis of nanoparticles such as nanoshells or nanorice, giving rise to their unique geometry-dependent plasmon resonant properties. Here, we report a novel, streamlined method for Au layer metallization on prepared nanoparticle surfaces using carbon monoxide as the reducing agent. This approach consistently yields plasmonic nanoparticles with highly regular shell layers and is immune to variations in precursor or reagent preparation. Single particle spectroscopy combined with scanning electron microscopy reveal that thinner, more uniform shell layers with correspondingly red-shifted optical resonances are achievable with this approach.

Optical properties of a nanosized hole in a thin metallic film.

Subwavelength holes are one of the most important structures in nanophotonics, providing a useful geometry for nanosensing and giving rise to extraordinary transmission when patterned in arrays. Here we theoretically and experimentally examine the optical properties of an individual nanohole in a thin metallic film. In contrast to localized plasmonic nanostructures with their own characteristic resonances, nanoholes provide a site for excitation of the underlying thin film surface plasmons. We show that both hole diameter and film thickness determine the energy of the optical resonance. A theoretical dispersion curve was obtained and verified using spectral measurements of individual nanoholes.

Reshaping the plasmonic properties of an individual nanoparticle.

When symmetry is broken in plasmonic nanostructures, new optical properties emerge. Here we controllably reshape an individual Au nanoshell into a reduced-symmetry nanoegg, then a semishell or nanocup by a novel electron-beam-induced ablation method, transforming its plasmonic properties. We follow the changes in the plasmonic response at the single nanostructure level throughout this reshaping process, observing the splitting of plasmon modes and the onset of electroinductive plasmons upon controlled, incremental opening of the outer metallic layer of the nanoparticle.

Au Nanorice Assemble Electrolytically into Mesostars

Star-shaped mesotructures are formed when an aqueous suspension of Au nanorice particles, which consist of prolate hematite cores and a thin Au shell, is subjected to an electric current. The nanorice particles assemble to form hyperbranched micrometer-scale mesostars. To our knowledge, this is the first reported observation of nanoparticle assembly into larger ordered structures under the influence of an electrochemical process (H(2)O electrolysis). The assembly is accompanied by significant modifications in the morphology, dimensions, chemical composition, crystallographic structure, and optical properties of the constituent nanoparticles.

Effect of detachments in asymmetric simple exclusion processes

Asymmetric simple exclusion processes are important for understanding low-dimensional multi-particle dynamic phenomena. The effect of irreversible detachments of particles on dynamics of asymmetric simple exclusion processes is studied using analytical and computer simulation techniques. In the simplest model, where particles can only detach from a single site in the bulk of the system, a theory is presented and used to calculate explicitly phase diagrams and particle density profiles. The complexity of the phase behavior is discussed in terms of a recent domain-wall theory for driven lattice systems. The theoretical results qualitatively and quantitatively agree with computer Monte Carlo simulations.