Multipole plasmon resonance in gold nanobipyramid: Effects of tip shape and size

Abstract Gold nanobipyramids (Au NBPs) are thought to have the same localized surface plasmon resonance (LSPR) peaks as gold nanorods but with narrow bandwidths in experimental spectra. However, the actual LSPR of Au NBPs is still confused because of an extra peak always appearing in simulated spectra without definite attribution. In this study, the plasmonic properties of Au NBPs were investigated based on the discrete dipole approximation (DDA). The simulated electric field enhancement confirmed that the extra LSPR peak came from the multipole plasmon resonance of Au NBPs. According to the polarized charges distribution, we defined the multipole plasmon resonance order of the extra LSPR peak as l = 5. Then, the effects of tip shape and size on the multipole plasmon resonance (l = 5) were investigated. The above results will help to understand multipole plasmon resonance in Au NBPs and design the nanobipyramids with fascinating properties.