Analyte‐Targeted Plasmonic Hotspots on Superlattice Mirror Enable Ultra‐Broad‐Range SERS Sensing of Acetylcholinesterase

Surface-enhanced Raman spectroscopy (SERS) enables molecular fingerprinting, but its widespread application is limited by poor detection sensitivity and signal reproducibility due to inefficient analyte retention in hotspots, less than 1 in 100, 000 molecules. To address this, we present a dynamic sensing strategy that actively couples in-situ analyte recognition with the real-time formation of plasmonic hotspots. The system integrates a resonant plasmonic nanoparticle superlattice monolayer as a 2D optical cavity and gap-enhanced Au-Ag superparticles functionalized with cyclodextrin molecular spacers. Enzymatic recognition of acetylcholinesterase (AChE), a pivotal neurofunctional enzyme, induces the self-assembly of high-density nanoparticle-on-"superlattice mirror" (NPoSM) nanocavities through competitive host-guest displacement during acetylthiocholine hydrolysis. This active guidance ensures spatiotemporal synchronization between nanocavity formation, hotspot activation, and target binding. The system achieves high specificity with background-free, ultrasensitive AChE detection over a 9-order dynamic range (10^-8 to 10 U/L), offering a restricted detection platform for SERS sensing in molecular diagnostics, neurotoxicity assessment, and environmental monitoring.