Abstract
The strong light scattering from SPR has received an extraordinary attention due to the useful applications in photodetectors and cell and biomedical imaging. However, the applications using light scattering require a high scattering cross-section along with low absorption losses near the resonance wavelength. In this paper, effective plasmonic scattering of three-layered Au–Ag bimetallic nanoshells with a dielectric separate layer has been studied using the quasi-static approximation of classical electrodynamics. Because of the surface plasmon resonance (SPR)-induced intense light absorption, the effective scattering intensity is much weaker than that of scattering cross-section. However, the effective scattering intensity could be improved by tuning the geometric dimension and local dielectric environment of the nanostructure. It has been found that the greatest effective scattering takes place when the outer Ag nanoshell has a thick thickness or the dielectric separate layer has a small dielectric constant. The effective scattering also depends on the inner Au sphere radius and outer surrounding dielectric constant. Because of the mode transformation of the SPR, the effective scattering could also be greatly improved when the inner Au sphere has a very small or large size. However, the effective scattering intensity changes non-monotonously as the surrounding dielectric constant increases. The greatest effective scattering could be obtained when the surrounding dielectric constant has an intermediate value. This tunable effective plasmonic scattering of Au@Ag three-layered nanoshells presents a potential for design and fabrication of plasmonic optical nanodevice based on resonance light scattering.
Highlights
The plasmonic optical properties of gold and silver nanoparticles with core-shell structure have been studied extensively in literature
When the surface plasmon resonance (SPR) has been excited, the collective motion of the surface free electrons oscillates like a simple dipole and results in strong light absorption and scattering, the sum of the absorption and scattering is defined as extinction
Bansal et al reported the scattering and absorption efficiencies of semiconductor-coated gold nanoshell using the extended Mie theory [15]. They found that both the scattering and absorption efficiencies blue shift with an increase of gold shell layer thickness and the increase of surrounding dielectric constant, whereas the corresponding SPR peaks shift towards longer wavelength
Summary
The plasmonic optical properties of gold and silver nanoparticles with core-shell structure have been studied extensively in literature. Bansal et al reported the scattering and absorption efficiencies of semiconductor-coated gold nanoshell using the extended Mie theory [15] They found that both the scattering and absorption efficiencies blue shift with an increase of gold shell layer thickness and the increase of surrounding dielectric constant, whereas the corresponding SPR peaks shift towards longer wavelength. Whereas for bonding plasmon mode, the dielectric coating thickness-dependent monotonic intensity decrease of the local field peak only takes place when the Au-Ag nanoshell has a very small or a very large gold core. Effective plasmonic scattering of Au-Ag bimetallic three-layered nanoshells has been studied theoretically It has been found the effective scattering greatly depends on the geometric dimension and local dielectric environment of the nanostructure. The effective scattering could be greatly improved when the inner Au sphere has a very small or large radius
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