Manipulated localized surface plasmon resonances in silver nanoshells coated with a spherical anisotropic layer

The influences of the anisotropy of the outer spherically anisotropic （SA） layer on the far-field spectra and near- field enhancements of the silver nanoshells are investigated by using a modified Mie scattering theory. It is found that with the increase of the anisotropic value of the SA layer, the dipole resonance wavelength of the silver nanoshell first increases and then decreases, while the local field factor （LFF） reduces. With the decrease of SA layer thickness, the dipole wavelength of the silver nanoshell shows a distinct blue-shift. When the SA layer becomes very thin, the modulations of the anisotropy of the SA layer on the plasmon resonance energy and the near-field enhancement are weakened. We further find that the smaller anisotropic value of the SA layer is helpful for obtaining the larger near-field enhancement in the Ag nanoshell. The geometric average of the dielectric components of the SA layer has a stronger effect on the plasmon resonance energy of the silver nanoshell than on the near-field enhancement.