(619a) pH-Responsive Polymer-Nanoparticle Hybrids for Enhanced SERS Detection

We report a pH-sensitive polymer coating on plasmonic nanoparticles that provides a rapid and reversible means to modulate interparticle distances, thereby regulating Surface-Enhanced Raman Scattering (SERS) intensity in solution. Serving as a multidentate ligand that envelops each nanoparticle rather than forming brush-like structures, the polymer facilitates reversible clustering while maintaining excellent colloidal stability. Upon altering the pH, nanoparticles transition from a dispersed “OFF” state to tightly packed aggregates, creating intense electromagnetic hotspots that significantly increase Raman signals. By incorporating a functional motif with high binding affinity for the target molecule into the polymer, this switchable behavior extends the detectable concentration range of the target molecules without requiring extensive sample preparation. Additionally, it enables multiple acid-base cycles for reusable sensing applications. Furthermore, the polymer’s conformational response precisely tunes the interparticle gap—key to achieving strong plasmon coupling—while negating the need for intricate solid substrates. The outcome is a robust, solution-based platform well-suited for portable or point-of-care diagnostics across various applications.