Novel benzothiazole-based fluorescent probe for efficient detection of Cu²⁺/S^2- and Zn²⁺ and its applicability in...

In recent years, environmental pollution has been increasing due to the excessive emission of toxic ions, which has caused serious harm to human health and ecological environment. There are various methods for detecting Cu²⁺, S^2- and Zn²⁺, but the traditional ion detection methods have obvious disadvantages, such as poor selectivity and long detection time. Therefore, it is still crucial to develop simple, efficient and rapid detection methods.

A fluorescent probe based on benzothiazole, (E)-N'-(3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methylbenzylidene)-3,4,5-tris(benzyloxy)benzohydrazide (BT), was designed and synthesized. It was characterized using ESI-MS, ¹H NMR, and ¹³C NMR. BT can be used as a chemosensor to detect Cu²⁺, S^2- and Zn²⁺ in CH₃CN/H₂O (7:3, v/v, pH = 7.4, HEPES buffer: 0.1 M), with detection limits of 0.301 μM, 0.017 μM, and 0.535 μM, respectively. At an excitation wavelength of 320 nm, BT exhibits an "on-off-on" response to Cu²⁺/S^2- and enhanced fluorescence response to Zn²⁺, with a change in fluorescence color from orange to green. The coordination ratio of ions to the probe was determined to be 1:1 through Job's plot and hydrogen spectral titration. The recognition mechanism was discussed in conjunction with theoretical calculations. Furthermore, the probe has been successfully used in test strips and medical swabs colorimetry, as well as live cell imaging.

The probe BT lays the foundation for the design and synthesis of multifunctional fluorescent probes. As a portable detection method, probe BT was used to detect Cu²⁺, S^2- and Zn²⁺ on strips. Furthermore, the probe was applied to biological cells to detect target ions with low cytotoxicity and excellent cell permeability. This indicating that it can be used as a potential candidate for tracking Cu²⁺ and S^2- in clinical diagnostics and biological systems.