Multifunctional Au@Ag@SiO2 Core–Shell–Shell Nanoparticles for Metal-Enhanced Fluorescence, Surface-Enhanced Raman Scattering, and Photocatalysis Applications

Au@Ag@SiO2 core-shell-shell nanoparticles (NPs) were prepared by a facile one-pot synthetic technique. The Au@Ag core size and SiO2 shell thicknesses are readily controlled by adjusting the precursor concentration. The multilayered NPs with dielectric SiO2 outer shells and bimetallic Au@Ag cores exhibited both the chemical stability of Au with the high scattering efficiency of Ag. Furthermore, the SiO2 shell is beneficial to the metal-enhanced fluorescence for biomedical applications. Metal-enhanced fluorescence, surface-enhanced Raman scattering, and photocatalytic activities of silica-coated Au@Ag, Ag, Au, and Au/Ag core-shell NPs were compared and discussed. The size and structure of Au@Ag@SiO2 core-shell-shell NPs were optimized to maximize their optical and catalytic activities.