Nanosphere-in-a-Nanoshell: A Simple Nanomatryushka

Spherically concentric nanoparticles, composed of a silica-coated gold nanosphere surrounded by a gold shell layer, possess highly geometrically tunable optical resonances in a compact, sub-100 nm size range. The plasmon modes of this nanostructure, a rudimentary "nanomatryushka", arise from the hybridization of nanosphere plasmons with the bonding and antibonding modes of the surrounding Au shell. Here, Au/SiO2/nanoshells are fabricated in sub-100 nm and sub-150 nm size ranges. Changing the internal geometry of the nanoparticle not only shifts its resonance frequencies, but can also strongly modify the relative magnitudes of the absorption and scattering cross sections, independent of nanoparticle size.