Abstract
Localized surface plasmon (LSP) modes depend strongly on the morphology of nanoparticle and the surrounding dielectric medium. The hollow nanostructure provides a new way to modulate the surface plasmon modes due to the additional cavity surface. In this work, we study systematically the multipolar surface plasmon modes of hollow silver nanoprism (HSN) by simulation of electron energy loss spectroscopy (EELS) spectra based on the boundary element method (BEM). Herein the effects of the cavity size and position are taken into account. The LSP modes of HSNs are compared with those of perfect silver nanoprism (SN). The red-shift behaviors of multipolar modes can be found as increasing the cavity size. Modes A and C have similar red-shift tendency and obey the plasmon ruler equation, which can be explained by dipole-dipole coupling mode. Meanwhile, the degenerate modes will be split by changing the cavity position, and opposite shift tendencies of split degenerate states are observed. These are caused by different coupling nature of degenerate modes. Moreover, high refractive index sensitivity (RIS) can be obtained for HSN by changing the cavity size and position.
Highlights
The optical properties of noble metals at the nanoscale have gained considerable attention during the last decade[1,2,3,4,5,6]
In the frame of scanning transmission electron microscopy combined with electron energy loss spectroscopy (STEM-EELS), the Localized surface plasmon (LSP) modes of nanoparticles are excited by high energy incident electrons and are related to the position of incident electron beam
We focus on the multipolar LSP modes of the hollow silver nanoprism (HSN) by using boundary element method
Summary
The optical properties of noble metals at the nanoscale have gained considerable attention during the last decade[1,2,3,4,5,6] These benefit from the excitations of localized surface plasmon (LSP) modes, which allow the electromagnetic energy to be enhanced around nanoparticle surface as collective oscillations of conduction band electrons at surface. The resonance frequency of LSP mode is highly sensitive to the geometric parameters of nanoparticles (i.e. size and shape) and the surrounding dielectric environment[8]. The effects of the cavity (i.e. size and position) of hollow nanoprism on multipolar LSP modes are less well studied. The effects of both of cavity size and position on RIS are taken into account These results introduce possibilities for applications in sensors and functional plasmonic devices. The dielectric constants of Ag used in our simulations are taken from Johnson and Christy’s data[45]
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