Enhancement of localized surface plasmon resonance by inter-band transitions in an Au based nanoshell structure

We present a theoretical study on plasmonic properties of an Au based nanoshell structure in which the localized surface plasmon resonances (LSPRs) and the inter-band electronic transitions (IBTs) are presented. The optical properties of Au nanoshell are depicted by a corrected dielectric function of Drude-Lorentz mode, and Mie theory is applied to calculate the absorption efficiencies. It shows that there are two localized surface plasmon absorption peaks, which are induced from the outside LSPRs and the inside LSPRs, respectively. The positions of these two peaks can shift by changing core radius and shell thickness. By varying the core radius and thickness of the shells, the LSPRs are modulated with the IBTs, leading to the strong interactions between the LSPRs and the IBTs. It is found that the LSPRs and IBTs can couple with each other and the new resonance absorption peaks can be observed. Our results show that the LSPRs are enhanced by the IBTs. This enhancement can be applied to improve biosensor signals and advanced plasmonic applications.