Achieving the rapid and cyclic detection of nerve agent mimic with a reversible colorimetric and ratiometric fluorescent probe

The rational development of a versatile tool capable of rapid and cyclic detection of nerve agents is of great significance due to their extreme toxicity. Herein, we report a reversible colorimetric and ratiometric fluorescent probe ( DMC-Py ) for rapid and cyclic detection of nerve agent mimic (diethyl chlorophosphate, DCP) base on intramolecular charge transfer (ICT) mechanism. When exposed to DCP, the pyridine unit of DMC-Py is quickly converted to pyridinium salt (<7 s); meanwhile, the toxic DCP is simultaneously transformed into non-toxic neutral phosphate ester, accompanying by a rapid color change from light green to dark yellow, and fluorescence change from cyan to orange red because of the enhancement of the ICT effect. The probe exhibits high sensitivity and specificity in solution. For DCP vapour detection, the filter paper shows a distinct color transition, precisely quantifiable via a smartphone application. A linear correlation between the R/G ratio and 0 – 10.24 ppm DCP has been established, vividly illustrating its potential for field applications. The addition of triethylamine to the corresponding DMC-PyH product can regenerate the original DMC-Py . Alternate exposure of DMC-Py to DCP and triethylamine can induce the color and dual-emission changes in both solution phase and filter paper, thereby achieving the reversibility of the probe. This strategy provides a critical framework for rationally designing reversible ratiometric fluorescent probes for cyclic detection of nerve agents.