A dual-channel 'turn-on' fluorescent chemosensor for high selectivity and sensitivity detection of CN¯ based on a coumarin-Schiff base derivative in an aqueous system

Novel strategies still need to be proposed that can be used to identify and detect toxic environmental pollutants. In this paper, two channels of colorimetry and fluorescence 'turn-on' fluorescent probe 1 (7-hydroxy-8-[(2-hydroxy-phenylimino)- methyl]-4-methylbenzopyran-2-one) for the simple yet highly selective detection of CN¯ have been successfully designed and synthesized. Crystal features of probe 1 were defined using X-ray single crystal diffractometry. Probe 1 showed a strongly colorimetric and fluorescence response to CN¯ that induced obvious naked-eye colour changes in aqueous solution (DMSO/H₂ O, 3:1 v:v). In addition, probe 1 for CN¯ detection displayed low detection limits of 3.91 × 10^-8  M, which were significantly lower than the 1.9 × 10^-6  M maximum level specified by the World Health Organization (WHO) for potable water. The sensing mechanism for probe 1 was attributed to the deprotonation process as shown by ¹ H NMR titration. Moreover, based on the visible colorimetry and fluorescence change for probe 1 to CN¯, measurement was performed for simulated water samples containing CN¯. This study provides a broad prospect for solving other pollution problems and promoting the design of new fluorescent materials.