Synthesis and application of a new chemosensor based on the thiazolylazo-quinazolinone hybrid for detection of F- and S2- in aqueous solutions.

A new chemosensor based on the thiazolylazo-quinazolinone hybrid (TAQH) was designed and synthesized for naked-eye sensitive detection of F- and S2-in aqueous acetonitrile solution. Spectral characterization of TAQH using FT-IR, 1H NMR, and 13C NMR analysis revealed that the probe TAQH was successfully synthesized using a two steps reaction, including the diazotization-coupling and condensation reactions, respectively. The ion sensing ability of TAQH toward a wide range of anions and metal ions was evaluated by naked-eye detection method and UV-Vis absorption spectroscopy. The chemosensor TAQH displayed a fast and clear color change from yellow to red in the presence of F- and S2- ions, enabling easily detect with the naked eye. This clear color change is due to the effective interaction of the basic F- and S2- anions with hydroxyl group of chemosensor as a binding site. The experimental data also revealed that the F- and S2- ions were sensed by the probe TAQH over a wide pH range from 3 to 8. The results also confirmed that the TAQH has a wide linear detection range for F- and S2- ions. From UV-vis titration experiment, the limit of detection (LOD) for F- and S2- ions was found to be 3.1 μM and 5.7 μM, respectively. For quantitative measurements, the paper test strips containing TAQH were successfully fabricated and applied to detect F- and S2- ions in aqueous solutions. Furthermore, Job's plot based on spectroscopic data showed one-to-one stoichiometry for the interaction of anions with probe TAQH. Therefore, the proposed chemosensor with excellent features like the cost-effective, high sensitively and selectively and short response times can be utilized in any physical and biological conditions.