Coumarin-based colorimetric fluorescent chemical sensors for highly selectively and accurately detect Cu2+ ions in water and living cells

Coumarin-structured ( E )-7-(diethylamino)-3-(1-(2-(4-methylbenzo[ d ]thiazol-2- yl)hydrazono)ethyl)-2 H -chromen-2-one (HTM) was synthesized in two steps using N , N -diethylsalicylaldehyde, ethyl acetoacetate and 4-methyl-2-hydrazine-benzothiazole as raw materials. The HTM was characterized by FT-IR, 1 H NMR, 13 C NMR and HR-MS. It was found that the probe HTM has rapid and highly selective recognition ability for Cu 2+ in EtOH/H 2 O (1:1, v /v). The spectral characteristics of the probe HTM were investigated using fluorescence spectroscopy and ultraviolet-visible spectroscopy. The results showed that the binding of probe HTM to Cu 2+ produced a significant fluorescence quenching effect, and the influence of other metal ions was negligible. In visible light, when HTM interacts with Cu 2+ , the solution changes from yellow to orange as observed by the naked eye. Subsequently, the binding mechanism of the probe HTM to Cu 2+ was explored by Job's plot, 1 H NMR titration and DFT calculations, and it was found that they cooperated in a 1:1 manner. Linear equations for ultraviolet-visible and fluorescence intensities at different Cu concentrations were fitted, and the detection limits (LOD) were calculated to be 5.22 nM and 3.70 nM, respectively. Experimental studies on the recovery rates of standard additions indicated that the probe HTM could be used for the quantitative detection of Cu 2+ in actual water samples. The potential application of this probe in fingerprint detection was also investigated. In addition, the probe has been successfully applied to Cu 2+ monitoring in living cells.