Dumbbell-Like Silica Coated Gold Nanorods and Their Plasmonic Properties

Silica coated gold nanorods (GNRs@SiO₂) with dumbbell-like morphology allowing dual functionalization in an individual nanostructure have attracted great attention for applications such as sensing and biological imaging. We report a detailed study on the feasibility of controlling the morphology of silica coating on GNRs. The morphology of the silica shell can be either cylindrical or dumbbell shaped. With constant GNR concentration, the ratio of hexadecyltrimethylammonium bromide (CTAB) and tetraethylorthosilicate (TEOS) concentrations is the key to determine the amount of available TEOS for silica deposition on the GNR since the TEOS will diffuse toward the surface of GNRs. The effect of morphologies on surface-enhanced Raman scattering (SERS) performance was also investigated, and we found that the dumbbell morphology of silica coated gold nanorods has the most significant SERS enhancement. Our study is significant in terms of the capability to control the dumbbell morphology of silica coated gold nanorods, which can eventually broaden the application of these plasmonic nanomaterials.