Aggregation and surface-enhanced Raman activity study of dye-coated mixed silver-gold colloids

The aggregate morphologies of silver, gold, and mixed silver–gold nanoparticles coated with fuchsine basic were directly investigated by means of transmission electron microscopy. It was found that the aggregation of silver and gold colloids induced by the adsorption of fuchsine basic displayed different aggregate characteristics. The adsorption of fuchsine basic in mixed silver and gold colloidal systems led to altered aggregation and surface‐enhanced Raman scattering (SERS) enhancement behavior. A suitable ratio of mixed silver and gold colloids could form a favorable state of aggregation and significantly increase the SERS activity of mixed colloids compared with single silver and gold colloids. This is the first report of the SERS of fuchsine basic on mixed silver and gold colloids. Copyright © 2004 John Wiley & Sons, Ltd.