A novel dual-responsive fluorescent probe for moisture detection and hypochlorite sensing

Abstract

In this work, a novel phenothiazine-based organic small molecule fluorescence probe (PEIF) was designed and synthesized through a Knoevenagel condensation reaction for moisture detection and hypochlorite (ClO⁻) sensing. The essential photophysical properties of PEIF were evaluated. Interestingly, the probe emitted intense red fluorescence in 1,4-dioxane compared to that in water. A good linear relationship was achieved between the fluorescent intensity of PEIF at 640 nm and water content (0.0–0.8 vol%) in 1,4-dioxane. The PEIF probe demonstrated outstanding sensitivity towards moisture in 1,4-dioxane with a low detection limit of 0.009% (v/v). Furthermore, the fluorescence detection of ClO⁻ by PEIF featured high sensitivity (LOD = 19.7 nM), good selectivity, a large Stokes shift, and rapid response. The detection mechanism for hypochlorite was proposed and verified by DFT calculations, HRMS, and ¹H NMR methods. To our knowledge, this is the first phenothiazine-based dual-responsive fluorescent probe for the detection of trace water in 1,4-dioxane and ClO⁻. We have proved the potential of the PEIF probe for the effective determination of ClO⁻ in practical water samples. Additionally, this probe was also successfully used for the bioimaging of ClO⁻ in vegetable cells and live zebrafish.