Novel Fluorescent Probes For Visual Detection Of Ions

Chapter 1:The concept and principles of fluorescent probe design are introduced. And the latest research progress in recent years on the development of fluorescent probes for ion recognitionin is reviewed.Chapter 2:Based on the displacement strategy, a new and simple sulfide-selective chemosignaling system was devised using 1,4-dihydroxyanthraquinone (DHAQ)-Cu2+ ensemble. In aqueous solution containing 10% ethanol (HEPES buffer, pH7.4), DHAQ could give rise to a visible yellow-to-pink color change with the addition of Cu2+. The resulting pink solution changed to yellow upon subsequent addition of sulfide anion. Moreover, DHAQ displays an "ON-OFF-ON" mode fluorescence change with alternately added Cu and S2-. Experimental results show a low interference response toward other common anions. The selective switch-on fluorescence response of the sensing ensemble to S2" makes it suitable for sensing of S22- in aqueous solution. The detection limit is 5.98×10-8M.Chapter 3:A novel color-metric method for the detection of fluoride ions has been developed using indigo and indigo carmine as probes. In DMSO, both probes could give rise to a color change from blue to yellow green with the addition of F". The colorimetric responses of indigo and indigo carmine to F- can be conveniently detected by the naked eye, which provides a facile method for visual detection of F-.The probes exhibit good selectivity and sensitivity toward F-.The detection limit is 0.363μmol/L for Indigo and 0.177μmol/L for indigo carmine. The results of UV-Vis titrations indicate that both probes bind to F- in a 1:2 molar ratio. The association constants are 8.70×105 L·mol-2 and 7.24×107 L·mol-2 for indigo and indigo carmine, respectively. NMR spectroscopy was used to ascertain the sensing machnism. In addition, the Indigo-F-ensemble probes can be used for the detection of trace water in organic solvents.Chapter 4:A novel colorimetric and spectrofluorimetric method for the determination of Hg2+ has been developed using Azomethine-H (A-H). Exhibiting absorption and fluorescence changes in the presence of Hg2+, A-H could be used as a colorimetric and fluorescent chemosensor for the detection of Hg2+ in neutral water. In the presence of Hg2+ions, A-H undergoes fluorescence quenching at 424nm. Moreover, the color of the solution changes from colorless to yellow, which can be recognized by the ’naked eye’. The selective response of A-H to Hg2+makes it suitable for sensing of Hg2+ in pure water. The detection limit is 3.67×10-7 mol/L mol/L. The results indicate that A-H chelates to Hg2+in a 1:1 molar ratio and the association constant is 1.23±105 L·mol-1...