We developed highly sensitive surface-enhanced Raman scattering (SERS) probes based on SiO2@Au@Ag nanoparticles (NPs) using the Ag growth onto Au NP seeds method.

Ag-coated Au nanoparticle (NP)-embedded silica nanospheres (SiO2@Au@Ag NSs) were prepared using three different Au NPs of 2.5, 7 and 15 nm diameter to investigate their optical properties.

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A hybrid of Ag nanoparticle (NP)-embedded thin silica-coated graphene oxide (GO@SiO2@Ag NPs) was prepared as a surface-enhanced Raman scattering (SERS) substrate. A 6 nm layer of silica was successfully coated on the surface of GO by the physical adsorption of sodium silicate, followed by the hydrolysis of 3-mercaptopropyl trimethoxysilane. Ag NPs were introduced onto the thin silica-coated graphene oxide by the reduction of Ag+ to prepare GO@SiO2@Ag NPs. The GO@SiO2@Ag NPs exhibited a 1.8-fold enhanced Raman signal compared to GO without a silica coating. The GO@SiO2@Ag NPs showed a detection limit of 4-mercaptobenzoic acid (4-MBA) at 0.74 μM.