Tunable local surface plasmon resonance and refractive index sensitivity ability of three-layered dielectric-silver bimetallic nanoshells

Abstract

Optical properties and refractive index sensitivity abilities of three-layered silver/gold-dielectric-silver bimetallic nanoshells are investigated based on quasi-static theory. The results show that absorption spectra of silver/gold-dielectric-silver bimetallic nanoshells can be well tuned by changing the inner core radius, middle dielectric radius and outer shell layer thickness. Local surface plasmon resonance (LSPR) shifts of |ω−−〉 mode show a red-shift with increasing the inner core radius and the thickness of middle dielectric layer, while a blue-shift with increasing the thickness of outer shell. It is interesting to find that the shifts of |ω−+〉 mode are related to the ratio ε2∕ε4, the component of core and nanoshell. In addition, the refractive index sensitivity abilities of three-layered silver/gold-dielectric-silver bimetallic nanoshells are also reported. A higher refractive index sensitivity ability can be obtained by adjusting its geometric size and component. |ω−−〉 mode gets more intensity with increasing the surrounding medium dielectric function, while |ω−+〉 mode fades down. The intensity difference between |ω−−〉 mode and |ω−+〉 mode is mainly effected by the surrounding medium dielectric function, its geometric parameter, middle layer dielectric function, the component of core and nanoshell. Our study provides a way to analyze sensitivity application of nanoshells and broadens the application of nanoshells in sensor ability.