An ultrasensitive ″OFF–ON″ fluorogenic sensor based on thiazole derivative for Zn2+: Food supplement, water and bio–imaging applications

Abstract

In the present study, the design of a novel turn–on fluorescent probe ((E)–5–methoxy–4–((thiazol–2–ylimino)methyl)benzene–1,3–diol) (TBD) was reported. TBD showed an excellent fluorogenic response (λex = 420 nm, λem = 530 nm) to sense Zn2+ in HEPES buffer/MeCN (5/95, v/v; pH = 7.4) media. The quantum (Φ) yield of the probe TBD increased importantly with Zn2+ and was calculated for TBD (Φ = 0.073) and TBD–Zn2+ complex (Φ = 0.78). The LOD and binding constant (Ka) of TBD were 1.29 nM and 1.102 × 106 M−1, respectively. The sensing process of TBD toward Zn2+ (1:1) was verified by the Job's plot, MALDI–TOF–MS, and 1H NMR titration studies. The ''off–on'' fluorogenic response of TBD was qualified to the photo–induced electron transfer (PET) process. The experimental outcomes were also verified by theoretical DFT studies. Furthermore, TBD had been successfully utilized to detect Zn2+ in food supplement products, drinkable water samples and living–cells for on–site analysis.