Push-pull electronic effects on benzothiazole derived probes for the detection of Zn2+: Exploring the sensing strategies and its applications

Abstract

The diverse polarity of electron-donating 4-(diethylamino)salicylaldehyde (S-D), and electron-withdrawing 4-nitrosalicylaldehyde (S–W) were conjugated with benzothiazole (BT) to develop BTS-D and BTS-W probes, respectively. The probes exhibited the excited-state intramolecular proton transfer and intramolecular charge transfer sensing mechanisms in detecting Zn2+. BTS-D and BTS-W achieved a quantitative detection of Zn2+ followed by a strong cyan to green in the emission spectra, and from colorless to yellow in the UV–Vis spectra, respectively. The sensing pathways and coordination affinities between the probes and Zn2+ were explored using a series of spectroscopic evaluations, 1H NMR, 1H–1H COSY (2D NMR), HR–MS, XPS and DFT calculations. The probes demonstrated excellent selectivity, good water solubility, and high sensitivity, securing low LOD values: 0.15 μM for BTS-W in colorimetric analysis and 14 nM for BTS-D in fluorimetric analysis in aqueous media. The advantages of the probes assessed for the detection of Zn2+ in various water samples, Whatman paper-based sensor strips, and PC3 live cells. The findings revealed the encouraging on-site visualization in wastewater systems and bio-contents.