Plasmonic Nanostructures: Artificial Molecules

Department of Chemistry, Rice University, Houston, Texas 77005, USA.
Accounts of Chemical Research (Impact Factor: 22.32). 02/2007; 40(1):53-62. DOI: 10.1021/ar0401045
Source: PubMed


This Account describes a new paradigm for the relationship between the geometry of metallic nanostructures and their optical properties. While the interaction of light with metallic nanoparticles is determined by their collective electronic or plasmon response, a compelling analogy exists between plasmon resonances of metallic nanoparticles and wave functions of simple atoms and molecules. Based on this insight, an entire family of plasmonic nanostructures, artificial molecules, has been developed whose optical properties can be understood within this picture: nanoparticles (nanoshells, nanoeggs, nanomatryushkas, nanorice), multi-nanoparticle assemblies (dimers, trimers, quadrumers), and a nanoparticle-over-metallic film, an electromagnetic analog of the spinless Anderson model.

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    • "Like the Mie formulation, this method is particularly well suited to study the modal response of localized plasmons. There are different approaches in the literature concerning study of SPPs modal characteristics, based on the Mie theory for spheres [13] [14] and on the surface integral eigenvalue technique [15] or the plasmon hybridization theory [16] for more complex structures , but none of them using the NFM. This paper is mainly concerned with the description of single particle plasmon modes based on the NFM calculation and using an analytical representation of the resonant part of optical response in form of singular functions. "
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    ABSTRACT: An analytical representation of plasmon resonance modes of a metal particle is developed in the basis of the null-field method and its modal expansion of the particle optical response. This representation allows for the characterization of plasmon modes properties, as their spectral position, bandwidth, amplitude and local field enhancement. Moreover, the derivation of a phenomenological equation governing such resonances relates them to open resonator behavior. The resonance bandwidth corresponds to the plasmon life-time, whereas its amplitude is related to the coupling coefficient with the incident excitation. An efficient algorithm is used to compute and characterize the resonance parameters of silver spheroids as function of the particle geometry. The normal modes present on spheres are split into different azimuthal resonant modes in the case of spheroids, with amplitude depending on the incident polarization and position dependent on the particle aspect ratio.
    Journal of Quantitative Spectroscopy and Radiative Transfer 10/2014; 146. DOI:10.1016/j.jqsrt.2014.01.014 · 2.65 Impact Factor
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    • "Photoacoustic methods are increasingly taking advantage of 10 plasmonic systems, such as gold and silver nanoparticles of various 11 size and shape [1] [2]. One of the reasons for this growing interest is 12 the flexibility with which plasmon resonances can be optimized to 13 tune and enhance the optical response [3] [4] [5] [6] [7] [8]. This, in turn, can give 14 rise to heat conversion – and to the subsequent pressure wave 15 generating the photoacoustic signal – with an especially high 16 efficiency, due to the large absorption cross section of metal 17 nanoparticles and to their negligible radiative relaxation. "
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    ABSTRACT: The wavelength dependence of the laser-induced photoacoustic signal amplitude has been measured for water dispersions of 10, 61, and 93 nm diameter gold nanospheres. The whole region of the localized surface plasmon resonance has been covered. This “photoacoustic excitation profile” can be overlayed with the extinction spectrum between 450 nm and 600 nm in the case of the smallest nanoparticles. At variance, the larger-sized nanoparticles display a progressive deviation from the extinction spectrum at longer wavelength, where the photoacoustic signal becomes relatively smaller. Considering that photoacoustics is intrinsically insensitive to light scattering, at least for optically thin samples, the results are in agreement with previous theoretical work predicting i) an increasing contribution of scattering to extinction when the nanoparticle size increases, and ii) a larger scattering component at longer wavelengths. Therefore, the method has a general validity and can be applied to selectively determine light absorption by plasmonic systems.
    Photoacoustics 03/2014; 2(1). DOI:10.1016/j.pacs.2013.12.001 · 4.60 Impact Factor
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    • "Therefore, field coupling inside a helix is pronounced, similar to coupling between electric dipoles as described in metallic nanoparticles [18] or coupling between magnetic dipoles as discussed in chiral metallic nanostructures [19]. It has been shown that the coupled plasmon modes of metallic Vol. 5, No. 2, April 2013 2700510 IEEE Photonics Journal Resonances of Helix Metamaterials nanostructures exhibit the same manner as overlapped atomic orbitals in molecules presented by hybridization in molecular orbital theory [20]. By applying a plasmon hybridization model, electric plasmon responses have been studied in several configurations, such as in nanoshells [21], nanoparticle assemblies [22], [23], and nanorods [24]. "
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    ABSTRACT: Metallic helix metamaterial has been demonstrated to show strong circular dichroism and is promising for photonic applications such as broadband circular polarizers. In this paper, we present the analysis on the resonances of gold helix metamaterials by dipolar interactions and hybridization and discuss the origin of the broadband feature. Coupling effects among induced dipoles in the helices are examined by the current and field distributions of a single-helix metamaterial. Such analysis is also applied to explain the geometry-dependent resonance of a double-helix metamaterial, and optical properties are discussed. Our analysis provides a physical understanding of the resonant behaviors that can guide the design of metallic helix metamaterials and manipulate their resonant properties.
    IEEE Photonics Journal 04/2013; 5(2):2700510-2700510. DOI:10.1109/JPHOT.2013.2259583 · 2.21 Impact Factor
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