Surface-Enhanced Raman Scattering in Tunable Bimetallic Core-Shell

In this paper, optical properties of multilayer spherical core-shell nanoparticles based on quasi-static approach and plasmon hybridization theory are investigated. Calculations show that light absorption spectrum of bimetallic multilayer core-shell has three intense plasmon resonance peaks, which are more suitable for multiplex biosensing based on surface-enhanced Raman scattering (SERS) and localized surface plasmon resonance (LSPR). The plasmon resonance peaks in bimetal nanshells are optimized by tuning the geometrical parameters. In addition, the optimal geometry is discussed to obtain the Raman enhancement factor in bimetallic multilayer nanoshell. SERS enhancement factor is calculated with consideration of dampings due to both the electron scattering and the radiation at the boundary and modified Drude model in dielectric function of bimetallic nanoshell. It is shown that bimetallic nanoshell with the small size exhibits strong SERS enhancement factor (similar to 6.63 x 10(5)) with additional collision dampings and similar to 2.9 x 10(9) with modified Drude model which are suitable for biosensing applications. In addition, any variation in blood concentration and oxygen level can be detected by this bimetallic core-shell nanoparticle with sensitivity of Delta lambda/Delta n = 264.91 nm/RIU.