Cetyltrimethylammonium bromide assisted preparation of Au@SiO2 particles

Abstract

Coating silica on Au particles has been known to be effective to improve their stability and performance. In this work, we demonstrated a cetyltrimethylammonium bromide (CTAB) assisted approach for preparation of Au@SiO2 particles in ethanol/water mixtures. At ethanol content of 0.25, Au particles were well dispersed, while at ethanol content of 0.50, the aggregated Au particles were gradually dispersed with increasing CTAB concentration, attributed to the gradual formation of CTAB bilayer on the particle surface. When tetraethyl orthosilicate and ammonia were added directly to the Au particle dispersions, the Au@SiO2 particles formed at the low ethanol content (0.25) were red in color and spherical in shape with a core composed of single Au particles, and these formed at the medium ethanol content (0.50) were purple in color and fractal-like in shape with a core composed of multiple Au particles.