Tunable Fano Resonances in Three-Layered Bimetallic Au and Ag Nanoshell

Abstract

The plasmon coupling in a three-layered Au/SiO2/Ag nanoshell has been investigated by means of Mie scattering theory. The dipole–dipole and dipole–quadrupole Fano resonances have been observed in the extinction spectra of Au/SiO2/Ag nanoshells. With increase of the thickness of the middle layer, the dipole–dipole Fano resonance shows a blue shift and the magnitude of this Fano profile enhances while the dipole–quadrupole Fano resonance shows a red shift and reduces. With increase of the thickness of the outer shell, the dipole–dipole Fano minimum shows a blue shift and its magnitude decreases while both the energy and magnitude of dipole–quadrupole Fano resonance increase. All of the behaviors have been discussed with the plasmon hybridization model. In addition, the Au/SiO2/Ag nanoshell is found to show strong near-field enhancements in several regions, especially in the infrared region, which may provide effective applications in surface enhanced spectroscopy.

Multiple Fano resonances in bimetallic layered nanostructures

“…This type of nanostructure starts to become the focus of strong attention in chemical and bimolecular sensing, lasing and SERS [4,38]. The MNS nanostructure has also the ability to generate higher-order tunable Fano resonances, which could find applications in plasmon line shaping and multi-wavelength SERS [4,5].…”

Boosting Fano resonances in single layered concentric core–shell particles

“…An alternative widely studied structure for generation of plasmonic FR are core-shell single particles, that have isotropic optical response and can be synthesized by large-throughput and cost-efficient chemical methods. The electromagnetic response of core-shell particles has been largely investigated since this system enables achieving total scattering cancellation and hence represents a canonical example of cloacking device 23 .. Multi-layered coreshell particles can give place to FR arising from the interaction between hybridized modes that result from the coupling of plasmons excited at different metal-dielectric interfaces [24][25][26] . Additional FR can be also observed in non-concentric core-shell particles 24,[27][28][29] , since symmetry breaking induces electromagnetic coupling between otherwise non-interacting orthogonal modes 30 .…”

Modulation of anisotropic middle layer on the plasmon couplings in sandwiched gold nanoshells

“…A special interesting structure is metal-dielectric-metal three-layered nanoparticle, whose optical properties highly depend on the couplings between the plasmons of inner core and outer shell [6][7][8]. Changing the internal geometry of this nanoparticle not only shifts its resonance frequencies, but also strongly modifies the relative magnitudes of the absorption and scattering cross sections [5].…”

“…The dielectric functions of inner metal core ɛ 1 and outer metal shell ɛ 3 have real and imaginary frequency-dependent components, which are affected by the scattering of the conduction electrons in the particle surfaces. Thus, ɛ 1 and ɛ 3 are usually accounted by replacing the ideal Drude part in the dielectric function with a sizedependent one [8]. Light scattering by a spherical particle can be expressed through Debye potentials [16].…”

“…The embedding medium is assumed to .7689). The plasmon resonances in the Au/ SA/Au nanoshell can be considered as an interaction between the plasmons of a gold nanosphere and a gold nanoshell [5,8,18]. As shown in Fig.…”