Cu2+-functionalized Zr-MOF triggers O-phenylendiamine oxidation for ultrasensitive ratiometric fluorescence detection of nerve agent simulant

Developing a fluorescence sensor capable of precisely identifying highly toxic nerve agents has become a focus of research, given that they are easily available and can be used by terrorists to threaten the security of the world. In this work, we designed a ratiometric fluorescence sensing platform with Cu2+-modified UiO-66-NH2 (Cu2+@UiO-66-NH2) and o-phenenediamine (OPD) as signal indicators and successfully used for the liquid and gas detection of the nerve agent simulant diethyl chlorophosphate (DCP). UiO-66-NH2 obtained oxidase activity by simple Cu2+ modification, which catalyzed the oxidation of OPD to give a yellow fluorescent product 2, 3-diaminophenazine (DAP). In this detection system, the fluorescence of UiO-66-NH2 was greatly enhanced by blocking the ligand metal charge transfer (LMCT) process inside the framework by DCP. At the same time, the amino group of DAP was phosphorylated by DCP, and the attenuation of DAP fluorescence was observed by the static quenching effect. In addition, the Cu2+@UiO-66-NH2/OPD loaded agarose hydrogel device can be used to detect DCP vapor with naked eyes and showed satisfactory detection result (LOD: 6.65 ppb).