Metallodielectric Colloidal Core−Shell Particles for Photonic Applications

TLDR

The study presents a new synthesis route for colloidal gold shell particles with dielectric cores, enabling hollow shells and additional outer silica coatings. Gold nanoclusters are attached to functionalized silica, then reductively grown and coalesced into a tunable gold shell; the core can be dissolved to yield hollow shells, and an extra silica layer can be added. The particles exhibit optical behavior matching theory, low polydispersity leads to large submicron crystals, and the reduced van der Waals forces aid functionalization for photonic use.

Abstract

A new approach for the synthesis of colloidal gold shell particles with a dielectric core is described. Small gold nanoclusters were attached to the functionalized surface of colloidal silica particles. Reductive growth and coalescence of these clusters lead to the formation of a closed gold layer. By variation of the thickness of this gold layer and the radius of the shell it is possible to adjust the plasmon resonance of the gold shell particles over the whole visible and infrared region of the spectrum. The optical properties of the particles made are in good agreement with theoretical calculations for core−shell particles. Because of their low polydispersity, these gold shell particles form large crystals with submicron lattice constants. It is also possible to produce hollow gold shells by dissolution of the silica core. Further, a new method to coat the silica core gold shell particles with an additional outer silica shell is presented. This allows for a reduction in the van der Waals forces and facilitates functionalization of the particles for use in various photonic applications.