Radial growth of plasmon coupled gold nanowires on colloidal templates.

The library of plasmonic nanosystems keeps expanding with novel structures with the potential to provide new solutions to old problems in science and technology. We report the synthesis of a novel plasmonic system based on the growth of gold nanowires radially branching from the surface of silica particles. The nanowires length could be controlled by tuning the molar ratio between metal salt and surface-grafted seeds. Electron microscopy characterization revealed that the obtained one-dimensional nanoparticles are polycrystalline but uniformly distributed on the spherical template. The length of the nanowires in turn determines the optical response of the metallodielectric particles, so that longer wires display red-shifted longitudinal plasmon bands. Accurate theoretical modeling of these complex objects revealed that the densely organized nanowires display intrinsically coupled plasmon modes that can be selectively decoupled upon detachment of the nanowires from the surface of the colloidal silica template.