Plasmonic Nanocrevice-Gap Nanosnowman Particles Enabling Colocalization of Raman Reporters with Super-Localized Electric Fields for Highly Sensitive, Specific, and Quantitative Surface-Enhanced Raman Scattering Biosensing

Surface-enhanced Raman scattering (SERS) is based on a highly localized electric field (E-field), i.e., hotspot, on plasmonic nanostructures and enables a wide variety of ultrasensitive molecular-fingerprint sensing applications. However, reliably forming and controlling hotspots, and positioning molecules within them to reproducibly obtain maximal and quantitative Raman signals, remains challenging. Here, we designed and synthesized gold nanocrevice-gap nanosnowman particles (AuNCNSs) that feature a superlocalized E-field inside the nanocrevice gap via surface-modified DNA-directed nanostructure growth chemistry. AuNCNSs facilitate a capacitive plasmon mode with an intense, broadly distributed near-field enhancement, yielding a 157-fold amplification (analytical SERS enhancement factor = ∼3.1 × 1010). Remarkably, ∼10% of Raman dyes confined within the nanocrevice gap contribute to ∼90% …