Metallodielectric colloidal core-shell particles for photonic applications

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.