Phenanthrene-imidazole-based fluorescent sensor for selective detection of Ag+ and F− ions: real sample application and live cell imaging

Abstract

4-Methyl-2,6-bis(1H-phenanthro[9,10-d]imidazol-2-yl)phenol (probe-MPIP) conjugate has been designed as a selective fluorescent probe for silver (Ag+) ions. The probe-MPIP exhibits selectivity towards Ag+ in DMSO-H2O (1:9 v/v) in 50 mM HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) at pH 7.4. Moreover, the detection of probe-MPIP towards Ag+ ions could be realized with a “naked eye” with a color conversion from greenish yellow to orange. The linear relationship between fluorescence intensity and Ag+ ion concentration indicates that probe-MPIP can be used for quantification of Ag+ ions. The probe-MPIP can be used in a broad range of pH from 3 to 11. The limit of detection (LOD) and association constant (Ka) of MPIP-Ag+ complex have been determined and found to be 1.8 nM and 8.24 × 105 M−1, respectively, according to fluorescence titrations. Moreover, the binding ratio of probe-MPIP and Ag+ was found to be 1:1 by Job’s method. Furthermore, MPIP-Ag+ complex subsequently acted as a secondary fluorescent turn-on probe for fluoride (F−) ion recognition among the other anions. To assess the real-world efficacy of probe-MPIP and MPIP-Ag+ complex, a real water sample of silver and fluoride ions (Ag+ and F−) was evaluated. Furthermore, probe-MPIP and MPIP-Ag+ complex have been successfully applied to cell imaging studies.