Simulation of triple-bands LSPR based on exposed-core MOF with multilayered nanoshell: application in multiplex RI sensing

A localized surface plasmon resonance (LSPR) refractive index (RI) sensor based on exposed-core micro-structured optical fiber (EC-MOF) with a multilayered nanoshell (MNS) is designed. The triple-bands LSPR provided by the MNS, which consists of a gold core and a silver shell that separated by a dielectric layer, can realize the detection of three different targets simultaneously for the first time to our best knowledge. The novel characteristics of intense and distinct resonance peak at shorter wavelength is different from the higher order SPR modes, and the physical mechanism of MNS is illustrated by plasmon hybridization theory. The RI sensing ability is investigated at 1.33–1.42 in both wavelength and amplitude interrogations with sensitivities of 2082 nm/RIU and 202 RIU −1 . Peak 1 exhibits ultrasharp LSPR with full width half maximum (FWHM) only 6 nm, leading to figure of merit (FOM) of 347 RIU −1 , about 6–356 times higher than other similar works. The influences of MNS structure, number, position and length in EC-MOF are all analyzed in detail. Results indicate that the sensing characteristics can be optimized by adjusting the geometrical dimensions of MNS and the sensor exhibits relative strong tolerance, which show great potential for multiplex biosensing used in harsh environment.