1,3,4-Thiadiazole and quinolinone based multifunctional probes for fluorescence turn-on and colorimetric monitoring of Al3+ and Fe3+ in food and aqueous environment applications

To achieve the development of fluorescence turn-on probe and dual detection of Al 3+ and Fe 3+ , three organic molecules (named KN , KP and KS ) were synthesized based on quinolinone, Schiff base, 1,3,4-thiadiazole or benzothiazole units. Their fluorescence characteristics and response mechanism were investigated thoroughly. The recognition process created obvious color change under sunlight and nearly 30 to 66 folds fluorescence enhancement under ultraviolet light. The formation of stable complexes leads to inhibition of intramolecular charge transfer, restriction of imine isomerization and consequent optical behaviors. For KN , Al 3+ and Fe 3+ could be distinguished via different UV–vis response or by using masking agent with detection limits of 0.18 μM and 0.20 μM, respectively. Another satisfactory result for distinguishing two ions was achieved with KS under pH = 2 or 10 condition. More importantly, KN and KS were successfully used to detect Al 3+ or Fe 3+ in foods, water samples and pharmaceutical products.