Surface Plasmon Resonance from Bimetallic Interface in Au-Ag Core-Shell Structure Nanowires

Abstract

Transverse surface plasmon resonances (SPR) in Au-Ag and Ag-Au core-shell structure nanowires have been investigated by means of quasi-static theory. There are two kinds of SPR bands resulting from the outer surface of wall metal and the interface between core and wall metals, respectively. The SPR corresponding to the interface, which is similar to that of alloy particle, decreases and shifts obviously with increasing the wall thickness. However, the SPR corresponding to the outer surface, which is similar to that of pure metal particle, increases and shifts slightly with increasing the wall thickness. A mechanism based on oscillatory surface electrons under coulombic attraction is developed to illuminate the shift fashion of SPR from bimetallic core-shell interface. The net charges and extra coulombic force in metallic wall affect the SPR energy and the shift fashion.

Figure 1

Core–shell structure bimetallic nanowire geometry. ε₁, ε₂, ε₃are the dielectric functions for the metallic core, metallic wall and embedding regions, respectively;r₁denotes the core radius andr₂denotes the wall radius

Figure 2

Calculated light absorption spectra of Ag–Au core–shell structure nanowires with varying wall thickness, the core radiusr₁ = 10 nm

Figure 3

aAbsorption cross section versus wavelength in Ag–Au core–shell structure nanowires with different gold wall thickness;babsorption cross section versus wavelength in Au–Ag core–shell structure nanowires with different silver wall thickness. The core radius is 10 nm

Figure 4

Schematic illustration of SPR from interface of Ag–Au core–shell structure nanowire