Linear or quadratic plasmon peak sensitivities for individual Au/Ag nanosphere sensors

It is crucial to reveal the bulk (i. e. global) and local refractive index (RI) sensitivity for localized surfaceplasmon resonance (LSPR) sensors in order to understand their fundamental optical properties and designminiaturized plasmonic devices. In this paper, we investigate the RI sensitivity responses of individualAg and Au nanosphere (NSP) sensors and disclose that they are featured as quadratic. The underlyingreasons were well elucidated in terms of Rayleigh approximation. In addition, we have developed twodifferent effective medium methods to calculate the LSPR peak wavelengths for individual dielectricshell coated metal NSPs. It turns out that they agree well with the results obtained by finite elementmethod calculations for different core radius NSPs. Their sensitivity and differential sensitivity factorsare discussed as well. (C) 2014 Elsevier B. V. All rights reserved.