Influence of shell thickness on the refractive index sensitivity of localized surface plasmon resonance inflection points in silver-coated gold nanorods.

Silver-coated gold nanorods (Ag@AuNRs) have great potential for biological and chemical sensing, because of their sensitive spectral response to the local environment and unique localized surface plasmon resonance (LSPR) properties. Herein, we investigated the sensitivities of single Ag@AuNRs with different shell thickness with respect to variations in the refractive index (RI) of the surrounding environment. Single Ag@AuNRs with thick shell thickness showed higher RI sensitivity than single Ag@AuNRs with thin shell thickness, which demonstrates the improvement of LSPR sensor due to increase in silver layer thickness. Furthermore, we investigated homogeneous LSPR scattering inflection points (IFs) to better understand the RI sensitivity of single Ag@AuNRs with different Ag shell thickness. The LSPR IFs showed higher RI sensitivity when compared with the frequency shifts of counterpart LSPR peaks observed for single Ag@AuNRs. Finally, single Ag@AuNRs with thick Ag shell demonstrated improved RI sensitivity when compared with single AuNRs with thin Ag shell in the homogeneous LSPR IFs.