Multifunctional Polymer-Nanoparticle Composites for Surface-Enhanced Raman Scattering Applications

To create a multifunctional nanoparticle-based optical sensor, a pH-responsive microgel consisting of 20% polystyrene (PS) and 80% poly(2-vinylpyridine) (P2VP) surface-coated with gold nanoparticle (NP) seeds was synthesized. The pH-responsive microgel serves as a size-tunable scaffold for the assembly of the surface-enhanced Raman scatter active (SERS-active) metal, gold. The random copolymer of PS and P2VP (PS20P2VP80) is sterically stabilized by poly(ethyleneglycol) methyl ether methacrylate (PEGMA) and lightly crosslinked with divinylbenzene (DVB) to allow for reversible pH-swelling over multiple cycles of acid-base titration. The ability to swell and de-swell in response to changes in pH allows for the tuning of gold NP interparticle distance, consequently affecting the SERS activity. The gold NPs adsorbed to the surface of the microgels dramatically enhances the SERS spectroscopy signals depending on their size and spacing. Attempts to encapsulate magnetic NPs were accomplished and would allow for the extraction of microgels from a sample matrix through applying an external magnetic force. These NP-microgel composites are synthesized, characterized, and their SERS-activity is demonstrated