Interface-Enhanced Raman Scattering Sensor Enabled by Hairy-Particle-Analyte Noncovalent Coupling

Raman enhancement in practical sensing is dominated by surface-enhanced Raman scattering (SERS), where signal amplification relies on localized plasmonic hotspots but is often limited by inefficient analyte access. Conventional SERS platforms further require multistep assembly on rigid substrates, exhibit ligand-limited stability associated with thiol-metal coordination, and rely on time-consuming off-site detection (>12 h), limiting reproducibility and practical deployment. Here, we develop an interface-engineered SERS strategy, referred to as interface-enhanced Raman scattering (IERS), in which a polymer-grafted plasmonic interface regulates analyte enrichment and access to electromagnetic hotspots. Diblock copolymer-grafted gold nanoparticles form "hairy" particles, in which an N-heterocyclic carbene-functionalized block drives spontaneous interparticle hotspot formation, while a poly(acrylic acid) block promotes noncovalent analyte enrichment and nanoconfinement. This interfacial nanoconfinement suppresses fluorescence and is consistent with an additional charge-transfer contribution. As a result, IERS enables rapid fabrication via simple mixing of "hairy" particles in soft hydrogels, robust stability through multidentate NHC coordination, and fast on-site detection (<15 min). The sensor achieves broadband trace detection, strong tolerance to fluorescent interference, and excellent batch-to-batch reproducibility. The conformal sensing capability was further demonstrated by proof-of-concept detection of prothioconazole on a pesticide-spiked curved apple surface.