A dual-responsive phenothiazine-based fluorescent probe for differential visual imaging of HClO and N2H4 in food, plant, soil, and biological samples.

Hypochlorous acid (HClO) and hydrazine (N2H4) are both toxic to the soil and water environments. Developing a probe that can accurately and sensitively detect HClO and N2H4 in biological and environmental systems is of great significance for revealing detection methods of various pollutants and their related physiological and pathological functions. In this study, a long-wavelength fluorescence probe (PT-A) for visual colorimetric detection of HClO and N2H4 was successfully developed and designed, which was composed of a phenothiazine-coupled coumarin moiety and an enol-β-diketone part. Probe PT-A could simultaneously detect of HClO and N2H4 through distinct fluorescence channels (cyan and red) without signal crosstalk. Furthermore, probe PT-A had the advantages of good selectivity, low detection limits (16.3 nM for HClO; 0.152 μM for N2H4), large stokes shift, and turn-on with blue-shift response for the colorimetric detection of HClO and N2H4. It was particularly worth noting that the detection mechanism of N2H4 involved the classic Knorr pyrazole cyclization reaction, which ultimately formed a pyrazole ring. The PT-A had strong applicability in actual samples and could quantitatively detect HClO and N2H4 in water and food juices with recoveries of 95.14% to 104.67%. More importantly, the functionalized test strips and soil samples could be easily prepared using the PT-A, enabling portable detection and quantitative monitoring of HClO and N2H4 with the help of a smartphone. Imaging of plants, living cells, and zebrafish further supported its suitability for in situ and colorimetric detection in complex systems. Collectively, these results introduce a versatile and potent tool for environmental and biological sensing of HClO and N2H4.