Synthesis and application of azo-based fluorescent probe for sequential recognition of Al3+and F-
2-(2-Hydroxy-4-methylbenzene-azo)-l-naphthol,fluorescent probe(NA-M),was synthesized from 6-amino-m-cresol and 1-naphthol,and characterized by 1HNMR,13CNMR,FTIR,HRMS.The selective recognition of Al3+by the probe NA-M and of F-by the complex formed with Al3+(NA-M+A13+)were analyzed,with the interaction mechanism between the probe NA-M and Al3+and F-speculated.The application of probe NA-M in practical samples was further evaluated.The results showed that in V(methanol)∶V(N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid)=9∶1 solvent with pH=7.4,the fluorescence of the probe NA-M and Al3+was significantly enhanced at 590 nm.The probe exhibited Al3+detection limit of 8.4× 10-7 mol/L with high selectivity,resistance to metal ion interference and good sensitivity.Furthermore,Al3+and probe NA-M formed NA-M+Al3+with a coordination ratio of 1∶2,which displayed a significant fluorescence quenching phenomenon after addition of F-,which was attributed to the capture of Al3+in NA-M+A13+by F-resulting in fluorescence changes.NA-M+A13+demonstrated outstanding selectivity and anti-interference capability towards F-by quenching the fluorescence,with a detection limit for F-of 9.5× 10-7 mol/L.When the pH of the system was 5～10,the probe NA-M exhibited a good effect in recognizing Al3+and F-.The addition of Al3+and F-alternately could cause a reversible change in the fluorescence intensity.The probe NA-M could be used for sequential recognition of Al3+and F-through the"off-on-off'transformation of the fluorescent signal.In actual samples,the recoveries of Al3+ranged from 98.8％to 107.0％with relative standard deviations(RSD)of 2.6％～4.3％,while those of F-ranged from 97.8％to 101.4％with RSD of 1.4％～2.3％.
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