Silica-Encapsulated Core–Satellite Gold Nanoparticle Assemblies as Stable, Sensitive, and Multiplex Surface-Enhanced Raman Scattering Probes

Developing highly sensitive and stable surface-enhanced Raman scattering (SERS) probe systems is an actively pursued goal in sensors and diagnostics. In this study, we present silica-coated core–satellite (CS@SiO2) plasmonic nanoparticle assembly structures that potentially realize this goal. We assemble different-sized gold nanoparticles into core–satellite (CS) configurations using dithiol molecular linkers that also serve as SERS labels. Multiple hot spots in the CS structure and narrow nanogaps in each hot spot produce a significantly enhanced Raman scattering signal with an enhancement factor of ∼8 × 107. Various types of molecules can be inserted into the nanogaps using the mixed self-assembled monolayers with alkanedithiol, enabling multiplex detection. Silica encapsulation of the CS nanoassemblies stabilizes the particles and makes it easy to modify the surface to attach antibodies or DNAs. Many properties of the CS@SiO2, including a wide range of optical resonances, scalability using multiple glass slides, long-term stability in ethanol, and single-particle-level sensitivity, make the material an ideal SERS probe for sensitive and multiplexed detection of diseases and viruses.