Surface-Imprinted Core−Shell Nanoparticles for Sorbent Assays

In this paper, we present a general protocol for the making of surface-imprinted core−shell nanoparticles via surface reversible addition−fragmentation chain-transfer (RAFT) polymerization using RAFT agent functionalized model silica nanoparticles as the chain-transfer agent. In this protocol, trichloro(4-chloromethylphenyl)silane was immobilized on the surface of SiO2 nanoparticles, forming chloromethylphenyl functionalized silica (silica-Cl). RAFT agent functionalized silica was subsequently produced by substitute reaction of silica-Cl with PhC(S)SMgBr. The grafting copolymerization of 4-vinylpyridine and ethylene glycol dimethacrylate using surface RAFT polymerization and in the presence of 2,4-dichlorophenoxyacetic acid as the template led to the formation of surface-imprinted core−shell nanoparticles. The resulting surface-imprinted core−shell nanoparticles bind the original template 2,4-D with an appreciable selectivity over structurally related compounds. The potential use of the surface-imprinted core−shell nanoparticles as the recognition element in the competitive fluorescent binding assay for 2,4-D was also demonstrated.