Synthesis And Properties Of Polymer And Small Molecule Based Fluorescence Sensors

Many investigations have been focused on the fluorescence sensor design and its application. The detection guest of fluorescence sensor includes neutral small molecules, chiral molecules, bio-molecules, some important cations and anions. The advantage of this method is its easy-operating, high sensitivity and selectivity. Coumarin, as a natural fluorophore, has been widely used in the design and synthesis of fluorescence sensors, which exhibit high quantum yield, large Stokes'Shift and so on. In addition, fluorescence polymer is designed for metal ions detection, which also serves as an important part for this paper. The advantage of polymer-based fluorescence sensors over small molecules lies in its signal amplification effect due to their rigid configuration and repeating unit in the backbone.Section2:Two coumarin salen-based sensors CS1and CS2can exhibit a pronounced fluorescence enhancement response toward Mg2+as high as36-fold (CS1) and111-fold (CS2) in the presence of Na+as a synergic trigger. More importantly, the fluorescence color of CS1was bright green instead of weak yellow after the addition of Mg2+and Na+together, which can be easily detected by naked eyes. According to the different response behavior to sodium ion, magnesium ion and zinc ion, two logic gates were designed, which stretched the application of this fluorescence system into information technology. Section3:Mg2+can lead to the fluorescence enhancement of a dye molecule as high as47.3-fold while L-proline acts as a promoter in this multicomponent sensory system. And self-recognition for magnesium ion was realized in this multicomponent system. The fluorescence color could be easily detected by the naked eyes under a UV-lamp.Section4:A polymer-based fluorescent sensor was synthesized by polymerization of (S)-6,6'-dibutyl-3,3'-(di-5-salicylde-ethynyl)-2,2'-binaphthol (M-1) with (R,R)-1,2-diaminocyclohexane (M-2) via nucleophilic addition-elimination reaction. The responsive optical properties of the polymer on transition metal ions were investigated by fluorescence and UV-vis spectra. The polymer (1.0×10-5mol/L in THF) could emit fluorescence at550nm and exhibit high selectivity for sensing Zn2+with36.1-fold fluorescence enhancement. Three logic gates were designed according to the different fluorescence responses of this polymer sensor to Zn2+and Cu2+.Section5:The polymer was synthesized by the polymerization of4,4'-((4-iodophenoxy)-methyl)-2,2'-bipyridine (M-1) with4,7-diethynylbenzo[2,1,3]thiadia-zole (M-2) via Pd-catalyzed Sonogashira reaction. The fluorescence responses of the polymer towards various transition metal ions were investigated by fluorescence spectra and UV-Vis spectra. The polymer shows green fluorescence under ultraviolet lamp, which can be quenched by Cu2+completely due to the heavy metal effect. The results suggested that the polymer can be used as a Cu2+-selective sensor via a naked eyes detecting mode.