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.
The resonance light scattering and scattering quantum yield (SQY) of Ag-Si-Ag multi-nanoshells (ASAMN) have been investigated in dipole approximation. The results show that the SQY at resonance wavelength of ASAMN can be enhanced to obtain an intense light scattering with high efficiency meanwhile, when the volume ratio fraction of silver to the multi-shells increases with the radius of inner silver sphere increasing or the inner radius of outer silver shell decreasing. By modulating the geometrical structure of the ASAMN, the frequency bands of the maximum SQY can be tuned in the visible and near-infrared regions. The physical mechanism has been illustrated by using the effective medium theory. It has been found that the effective dielectric constant plays an important role to affect the SQY in metal-dielectric core-shell nanostructures.
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