Improve the refractive index sensitivity of gold nanotube by reducing the restoring force of localized surface plasmon resonance

The core refractive index sensitivity of a gold nanotube was investigated by calculating the shift of local surface plasmon resonance (LSPR). It was found that the core refractive index sensitivity can be improved by reducing the wall thickness or the surrounding refractive index. The sensitivity increases exponentially with decreasing wall thickness, but increases linearly with decreasing surrounding refractive index. This multi-factor controlled sensitivity of gold nanotube enlarges the ability of optimizing the refractive index sensors. The physical origin of this tunable refractive index sensitivity of gold nanotube was also investigated based on the plasmon hybridization and repulsive effects on the restoring force of plasmon oscillation. This physical mechanism can be used for designing core-shell metallic nanostructures for effective LSPR chemical and biological sensing.