Spectroscopic Tags Using Dye-Embedded Nanoparticles and Surface-Enhanced Raman Scattering

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Abstract
Surface-enhanced Raman scattering is capable of providing rich vibrational information at the level of single molecules and single nanoparticles, but the practical applications of this enormous enhancement effect are still a challenge. Here we report a new class of dye-embedded core−shell nanoparticles that are highly efficient for surface Raman enhancement and could be used as spectroscopic tags for multiplexed detection and spectroscopy. The core−shell particles contain a metallic core for optical enhancement, a reporter molecule for spectroscopic signature, and an encapsulating silica shell for protection and conjugation. A surprising finding is that organic molecules with an isothiocyanate (NCS) group or multiple sulfur atoms are compatible with silica encapsulation. In comparison with fluorescent dyes and quantum dots, enhanced Raman probes contain a built-in mechanism for signal amplification and provide rich spectroscopic information under ambient experimental conditions.