Synthesis of Bimetallic Colloids with Tailored Intermetallic Separation

The synthesis of bimetallic colloid concentric spheres is described through an example involving Au and Ag spaced by amorphous SiO2. The procedure involves a careful combination of existing methods for synthesis of Au nanoparticles, silica coating, and deposition of silver on silica. The choice of materials is motivated by their strong plasmon absorption bands, which allow us to follow the synthetic steps spectrophotometrically. TEM images demonstrate the concentric geometry of the particles prepared.