In this report, microgel particles, comprised of 2-vinyl pyridine (P2VP) and styrene, are explored as pH-responsive scaffolds to assemble metallic nanoparticles (NPs) for surface-enhanced Raman scattering (SERS) based detection strategies.  SERS is a highly sensitive spectroscopic technique for analyzing simple molecular mixtures to complex collections of molecules or biological structures.  The high sensitivity of SERS arises from the enormous enhancement (&gt;10<sup>6</sup>) of the Raman scattering cross sections of molecules that are adsorbed to roughened metal surfaces, such as metallic NP).  Anchoring SERS-active NPs to polymer substrates has been explored as a method for improving the reproducibility of the SERS enhancement phenomenon.  Microgels of P2VP are promising candidates for such a role owing to the multifunctionality of the pyridine residues located throughout the macromolecular network.  We will present a study of the synthesis of a sterically-stabilized latex consisting of a random copolymer of polystyrene (PS) and P2VP.  The dimensions of the latex, and its transition to a microgel are studied by acid-base titration and monitored by dynamic light scattering.  Loading the copolymer microgels with gold NPs through surface chemical reduction is also described. The gold NP-loaded microgels exhibit strong SERS-activity that can be used as to sense the local chemical environment by changes in the SERS spectra of adsorbed reporter molecules.   These microgel-NP composites are characterized, and their pH-responsive behavior is demonstrated to be reversible at the single-particle level.

Multi-functional polymer-nanoparticle composites for surface-enhanced Raman scattering sensing applications

ACS Spring 2022

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