Universal Scaling of Plasmon Coupling in Metal Nanostructures: Extension From Particle Pairs to Nanoshells

Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA.
Nano Letters (Impact Factor: 13.59). 10/2007; 7(9):2854-8. DOI: 10.1021/nl071496m
Source: PubMed


It has been recently shown that the strength of plasmon coupling between a pair of plasmonic metal nanoparticles falls as a function of the interparticle gap scaled by the particle size with a near-exponential decay trend that is universally independent of nanoparticle size, shape, metal type, or medium dielectric constant. In this letter, we extend this universal scaling behavior to the dielectric core-metal shell nanostructure. By using extended Mie theory simulations of silica core-metal nanoshells, we show that when the shift of the nanoshell plasmon resonance wavelength scaled by the solid nanosphere resonance wavelength is plotted against the shell thickness scaled by the core radius, nanoshells with different dimensions (radii) exhibit the same near-exponential decay. Thus, the nanoshell system becomes physically analogous to the particle-pair system, i.e., the nanoshell plasmon resonance results from the coupling of the inner shell surface (cavity) and the outer shell surface (sphere) plasmons over a separation distance essentially given by the metal shell thickness, which is consistent with the plasmon hybridization model of Prodan, Halas, and Nordlander. By using the universal scaling behavior in the nanoshell system, we propose a simple expression for predicting the dipolar plasmon resonance of a silica-gold nanoshell of given dimensions.

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    • "In the near-field range, plasmonic rulers have been proposed [21] [22] and employed to measure e.g. nuclease activity [23], to follow dimer assembly and DNA hybridization [24]. "
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    ABSTRACT: In this study we lay the groundwork for a graphene-based fundamental ruler at the nanoscale. It relies on the efficient energy-transfer mechanism between single quantum emitters and low-doped graphene monolayers. Our experiments, conducted with dibenzoterrylene (DBT) molecules, allow going beyond ensemble analysis due to the emitter photo-stability and brightness. A quantitative characterization of the fluorescence decay-rate modification is presented and compared to a simple model, showing agreement with the $d^{-4}$ dependence, a genuine manifestation of a dipole interacting with a 2D material. With DBT molecules, we can estimate a potential uncertainty in position measurements as low as 5nm in the range below 30nm.
    New Journal of Physics 07/2014; 16(11). DOI:10.1088/1367-2630/16/11/113007 · 3.56 Impact Factor
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    • "The interaction between these two plasmons leads to hybridization of plasmon resonance into antisymmetric mode and symmetric mode. The strength of plasmon coupling determines the position of the SPR for nanoshells [20] [21]. Hence, the red shift of SPR band observed for synthesized gold nanoshells can be described by hybridization model. "
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    ABSTRACT: In this paper, we report preparation and characterization of monodispersed hollow gold nanoparticles with the average thickness of about 25 nm through the template method. The formation of these hollow nanostructures involves three subsequent steps: preparation and functionalization of silica nanospheres, formation of a thick gold shell around the templates and following selective etching of silica particles by HF solution. In order to obtain monodispersed hollow particles, the optimum amount of trisodium citrate was used as stabilizing agent. The results show that although for both concentrated and diluted HF solution, pure gold nanoparticles were obtained, but the 10 volume percent HF solution destroys the hollow structures and just agglomerated gold particles were generated. Furthermore, by investigation the optical response of the synthesized metallic nanoparticles consisting gold nanoparticles, silica-gold nanoshells and hollow gold nanoparticles, it can be inferred that the hollow structures are capable to absorb wavelengths mainly within near infrared region. Hence, this paper introduces a new strategy to produce the metallic nanostructures with optical response within NIR range which may provide new opportunities for their applications in variety of fields such as photoelectronics, catalysis and cancer therapy.
    Colloids and Surfaces A Physicochemical and Engineering Aspects 09/2013; 436:1069-1075. DOI:10.1016/j.colsurfa.2013.08.028 · 2.75 Impact Factor
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    • "In the case of the core-shell conformation, a dual LSPR peak characteristic of each pure metal can be observed, depending on the thickness of the metallic shell [27]. These LSPR bands are usually weakly dependent on the size of the NPs and the refractive index of the surrounding media, but strongly change with inter-particle distance, for example aggregation of NPs leads to a pronounced color change as a consequence of the plasmon coupling between NPs and a concomitant red-shift of the LSPR absorption band peak [30]. Most of the colorimetric biosensors based on gold and/or silver NPs have been developed considering these changes in color generated by the plasmon coupling between NPs upon aggregation, while other methods have used the LSPR properties of the noble metal NPs just as a colorful reporter (i.e., making use of their superb scattering and/or absorbance properties). "
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    ABSTRACT: In the last decade the use of nanomaterials has been having a great impact in biosensing. In particular, the unique properties of noble metal nanoparticles have allowed for the development of new biosensing platforms with enhanced capabilities in the specific detection of bioanalytes. Noble metal nanoparticles show unique physicochemical properties (such as ease of functionalization via simple chemistry and high surface-to-volume ratios) that allied with their unique spectral and optical properties have prompted the development of a plethora of biosensing platforms. Additionally, they also provide an additional or enhanced layer of application for commonly used techniques, such as fluorescence, infrared and Raman spectroscopy. Herein we review the use of noble metal nanoparticles for biosensing strategies--from synthesis and functionalization to integration in molecular diagnostics platforms, with special focus on those that have made their way into the diagnostics laboratory.
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