Novel fluorescent polymeric nanoparticles for highly selective recognition of copper ion and sulfide anion in water

In the present study, a fluorescence resonance energy transfer (FRET)-mediated multifunctional sensor based on fluorescent polymeric nanoparticles was synthesized via a combination of a facile one-pot miniemulsion polymerization and subsequently by surface modification technology. Firstly, fluorescent polymeric nanoparticles were obtained by copolymerization of styrene, vinylbenzylchloride and the fluorescent vinylic crosslinking monomer (fluorescein-O,O-bis-propene: FBP) in oil-in-water miniemulsion stabilized with a cationic surfactant (dodecyltrimethyl ammonium bromide: DTAB). Then, 1,4,7,10-tetraazacyclododecane (Cyclen) was selected as ligand to graft onto the surface of nanoparticles. Due to the specific FRET effect between FBP and the Cu2+-Cyclen complex, the as-prepared nanoparticles display highly sensitive (detection limit: 340 nM) on-off-type fluorescence change with high selectivity toward Cu2+ among 11 metal ions (such as K+, Na+, Co2+, Ca2+, Fe2+ and Pb2+) in 100% aqueous solution. Moreover, it is worth to note that the in situ generated nanoparticle-Cu2+ ensemble could recover the quenched fluorescence upon addition of sulfide anion resulting in an off-on-type sensing with a detection limit of 2.1 mu M in the same medium. No obvious interference was observed from other familiar anions such as Cl-, NO3-, SO42-, HCO3-, CO32-, Br-, F-, S2O32-, C1O(4)(-) and HPO42-. Furthermore, the nanoparticle-based dual-ion sensor can be reversibly switched for multi-times by alternative addition of adequate Cu2+ or S2-, was also applicable in a relatively wide pH range (pH 4-10), and exhibited excellent long-term photostability for Cu2+ detection (>= 40 days) in aqueous media. Thus, this approach may reveal a new pathway for selective detection of multiplex analyst in environmental and biological applications. (C) 2014 Elsevier B.V. All rights reserved.