The Effect of Local Electric Field in the Middle Dielectric Wall on the Infrared Plasmonic Shift of the Concentric Gold Double Nanotubes

The effect of inserted gold nanotube on the localized surface plasmon resonance (LSPR) shifting and local electric field enhancement of concentric gold double nanotubes has been studied by using the quasi-static electricity. Because of the combined effect from inter-surface and inter-tube plasmon coupling, the LSPR in gold double nanotubes could be easily tuned into the infrared wavelength region. The calculation results indicate the plasmon peak shifting is quite sensitive to the thickness of the inner gold tube and the gap between the inner and outer gold tubes. The physical mechanism has been attributed to the local field effect of the separate dielectric layer. Because of the additional attraction from the inner gold tube to the free electrons at outer gold tube, the decreasing electric field in the middle dielectric spacer layer reduces the restoring force and lead to intense red shift of LSPR.