Highly Bright SERS Nanotags with Multiplexing Fingerprints for Sensitive Immunoassays

Surface‐enhanced Raman scattering (SERS) nanotags are regarded as good optical probes for bioimaging and detection owing to their distinct advantages over fluorescent dyes. However, the difficulty of making bright and reproducible SERS nanotags has limited their applications. Here, a new strategy is reported to develop ultrabright SERS nanotags via the creation of extreme high‐density of SERS hotspots and maximal loading of Raman reporters. The one‐pot formation and self‐assembly of gold (Au) nanoparticles (NPs) create high‐density of nanogaps for SERS enhancement, and direct addition of Raman reporters during AuNP formation enables maximal loading of the Raman reporters within the nanotags. This strategy can generate bright SERS nanotags carrying up to four Raman reporters. Moreover, the as‐synthesized SERS nanotags show great performance as a label in the immunoassay of staphylococcal enterotoxins B. It is envisioned that the SERS nanotags can find more applications in biological detection and imaging.