Selective controlling transverse plasmon spectrum of pentagonal gold nanotube: from visible to near-infrared region.

In this paper, the optical properties and local electric field distribution of transverse plasmon mode of a single pentagonal gold nanotube are studied for the first time by the discrete dipole approximation (DDA). The theoretical simulation results of pentagonal gold nanotube are closer to the actual experiment compared with circular section. We find that the transverse plasmon peaks can be exponentially red shift from visible to infrared region via controlling the inner diameter. In addition, the transverse plasmon peak firstly blue shifts and then red shifts in the visible region with the increase of outer diameter. Further analysis shows that the spectra red shift with the increase of outer diameters when scattering is dominant. Local electric field analysis reveals that thin tube wall is easier to excite higher-order plasmons modes. Localized surface plasmon resonance (LSPR) peaks of gold nanotube mainly come from dipole resonance and quadrupole resonance. The surface charges of inner and outer tube walls are changed by tuning the inner diameter and outer diameter parameters of pentagonal gold nanotube. The selective controlling transverse plasmon spectra of gold nanotube are realized, which is of great significance to the study of optical properties of gold nanotube and the application of molecular detection and biological imaging.