Spectroscopy, Imaging, and Modeling of Individual Gold Decahedra

Gold nanodecahedra (pentagonal bipyramids) exhibit striking optical properties spanning the visible and near-IR spectral regions, which together with a high electric-field enhancement at their tips, makes them very promising materials for sensing-related applications. The effective design of biosensors based on these nanocrystals requires a detailed investigation and understanding of their surface plasmon resonances. For that purpose, we have used correlated electron microscopy imaging and optical dark-field spectroscopy on individual decahedra to investigate their size and orientation-dependent optical properties at the single particle level. We have also investigated the effects of tip truncation and local refractive index changes on single particle plasmon resonances. The experimental results are supported by theoretical modeling based on a fully 3D, boundary element method (BEM-3D).