Synthesis of Nanosized Gold−Silica Core−Shell Particles

TLDR

Gold colloids were uniformly coated with silica via a silane coupling agent, then transferred to ethanol for Stöber growth, allowing precise control of shell thickness and solvent compatibility to tune the particles’ optical properties. The measured optical spectra of the core–shell particles matched Mie theory predictions.

Abstract

Gold colloids have been homogeneously coated with silica using the silane coupling agent (3-aminopropyl)trimethoxysilane as a primer to render the gold surface vitreophilic. After the formation of a thin silica layer in aqueous solution, the particles can be transferred into ethanol for further growth using the Stöber method. The thickness of the silica layer can be completely controlled, and (after surface modification) the particles can be transferred into practically any solvent. Varying the silica shell thickness and the refractive index of the solvent allows control over the optical properties of the dispersions. The optical spectra of the coated particles are in good agreement with calculations using Mie's theory for core−shell particles.