A dual responsive molecular probe for the efficient and selective detection of nerve agent mimics and copper (II) ions with controllable detection time

Abstract

The bifunctional azoaniline-based colorimetric and fluorometric molecular probe [(E)-4-((2,4-diaminophenyl)diazenyl)phenol] (Azo) was synthesized in this study for the sensing of diethylchlorophosphate (DCP), a nerve agent mimic, whereby a tunable detection time was concurrently obtained. Azo exhibited an excellent sensitivity and selectivity toward DCP through a formation of the electron-deficient NH-PO(OEt)2 group in acetonitrile (Azo-N). The probe showed a 63nm red shift in its absorption maximum upon the addition of DCP that was accompanied by a change in the color of the solution from pale yellow to dark red. In addition to the detection of DCP, Azo also showed colorimetric and turn-on fluorometric responses, also with a high selectivity and sensitivity, toward Cu2+ ions via a Cu2+-ion-catalyzed cyclization reaction that forms a benzotriazole ring (Azo-Cu); moreover, the consecutive sensing was achieved through a sequential process, whereby the addition of the Cu2+ ions was followed by the addition of DCP (Azo-Cu-N). Interestingly, the detection time of the Azo-Cu toward DCP after the sensing of the Cu2+ ions is much slower than that of Azo, indicating that the detection time toward DCP could be controlled by the cyclization extent through a changing of the amount of Cu2+ ions that is added.