Influence of the medium refractive index on the optical properties of single gold triangular prisms on a substrate

Abstract

The surface plasmon resonance of small metal particles is highly sensitive to the refractive index of the surrounding medium. However, for particles dispersed on a glass surface in a polymer matrix, the effective refractive index is ill-defined. The effects of the substrate and solvent refractive indices on the surface plasmon resonance of individual gold nanoparticles (prisms and decahedra) have therefore been investigated by dark field microscopy. It is found that for any given substrate, e.g., glass or quartz, the surface plasmon band red-shifts when the solvent refractive index is increased as expected. However the sensitivity is reduced from that observed in a homogeneous medium, and th..