Ratiometric fluorescence detection of sulfide ions based on lanthanide coordination polymer using guanosine diphosphate as ligand.

The efficiency of energy transfer from guanine nucleotide to terbium ion (Tb) is affected by the phosphate group significantly. Compared with the biomolecules 5'-GMP (guanosine monophosphate), guanosine diphosphate (GDP) exhibits better sensitize ability to Tb ions luminescence. Assisted with the carboxycoumarin ligand, we synthesized a more stable optical Coumarin@GDP-Tb polymer with the characteristic emission peaks located on 440 nm and 545 nm in this work. The Coumarin@GDP-Tb polymer is not only rich in metal binding sites, but also maintains a moderate ionic binding force, which helps metal ions to bind or leave it easily. Experiment result shows that Coumarin@GDP-Tb polymer has the appropriate binding force for Fe ions, which can be destroyed by sulfur ions (S) as the formation of FeS precipitation. Based on this, Coumarin@GDP-Tb was designed as the ratio fluorescence probe for sulfur ions detection, where the fluorescence at 545 nm can be selectively quenched by Fe ions, while that at 440 nm was unaffected, in the presence of S ions, the quenched fluorescence can be recovered remarkably. With the increasing S ions from 0.1-45 μM, the ratio of fluorescence intensity at 545 nm to 440 nm (F/F) is linear to S concentration, and the detection limit of S was calculated to be 0.073 μM. Contrast to those fluorescence probes with single wavelength emission, Coumarin@GDP-Tb displays a comparable sensitivity, the introduced self-adjust wavelength improved the detection accuracy efficiently. The above 98.1 % recovery rates of S ions in the actual water sample demonstrated the practicability of Coumarin@GDP-Tb fluorescence probe.