title: Reversible pH-responsive fluorescence of water-soluble polyfluorenes and their application in metal ion detection.
abstract: A novel water-soluble conjugated polymer poly{(4,4'-azobenzene)-2,7-[9,9-bis(6'-N,N,N,-trimethylammonium)hexyl fluorene]dibromide} (PFAB) has been designed and synthesized via Suzuki cross-coupling the fluorene units and azobenzene units. Through simple photoreduction, the azo group of the nonfluorescent PFAB to hydrazine group using UV light, polyfluorene PFAB-L with turn-on fluorescence in aqueous solution is obtained. The optical measurements illustrate that the generation of the flexible hydrazine group induces face-to-face arrangement of phenyl-fluorene-phenyl moieties. Therefore, the excimer formation of phenyl-fluorene-phenyl moieties was induced in PFAB-L. And the fluorescence of PFAB-L can be controlled through modulating the protonation of the -NH-NH- group in solution with different pH. The pH-responsive property is reversible. Moreover, the Fe(3+) ions can selectively quench the fluorescence of the PFAB-L. This new polymer PFAB-L could be used for selective and sensitive sensing Fe(3+) ions in aqueous solution.
authors.affiliation: School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, PR China.
authors.forename: Lingling
authors.initials: L
authors.lastname: Li
authors.forename: Fang
authors.initials: F
authors.lastname: He
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Wang
authors.forename: Ning
authors.initials: N
authors.lastname: Ma
authors.forename: Lidong
authors.initials: L
authors.lastname: Li
mesh_terms: D001391:Azo Compounds / Q000737:chemistry; D005290:Ferric Compounds / Q000032:analysis; D005449:Fluorenes / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry; D008670:Metals / Q000032:analysis*; D010084:Oxidation-Reduction; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry*
chemical_list: D001391:Azo Compounds; D005290:Ferric Compounds; D005449:Fluorenes; D007477:Ions; D008670:Metals; D011108:Polymers; D014867:Water; C041509:fluorene; C009850:azobenzene