Design and synthesis of fluorescent core-shell nanoparticles with tunable lower critical solution temperature behavior and metal-enhanced fluorescence

In this article, the preparation of fluorescent nanohybrids with core-shell structure and metal-enhanced fluorescence (MEF) effect was presented. The fluorescent core-shell nanohybrids were prepared using silver nanoparticles (AgNPs) as cores and fluorophore tethered thermoresponsive copolymers with tunable lower critical solution temperature (LCST) from 15 to 90 °C as shells. These thermoresponsive copolymers were synthesized by the random copolymerization of oligo(ethylene oxide) acrylate and di(ethylene oxide) ethyl ether acrylate using reversible addition-fragmentation chain transfer polymerization and grafted on to AgNPs surface via Ag-S coordination interaction. By thermal manipulation of polymer spacer between AgNPs and fluorophores, the tunable MEF was achieved. It was also revealed that the fluorescent nanohybrids would exhibit maximal MEF when the polymerization degree was tuned to 350. The manipulation of the solution temperatures below and above LCST resulted in switchable MEF behavior. In addition, the phase transition process of the thermoresponsive copolymer was also studied by MEF effect using this fluorescent core-shell nanohybrid design. © 2013 Wiley Periodicals, Inc.