An integrated ratiometric fluorescent probe based on the MOF-on-MOF heterostructure for sensitive detection of nerve agent simulant.

As highly toxic organophosphates, nerve agents can lead to the dysfunction of the nervous system, so the detection of nerve agents has become an important topic. Herein, a MOF-on-MOF heterostructure, Eu-BTC@UiO-66-NH₂, was simply prepared via the interfacial growth approach to construct an integrated ratiometric fluorescent probe for the detection of nerve agent simulant diethyl chlorophosphate (DCP) both in the liquid and gas phases. In this detection system, the binding of DCP to the Zr-O clusters in UiO-66-NH₂ blocked a ligand-metal charge transfer (LMCT) process and restored the blue fluorescence of ligand (BDC-NH₂). On the other hand, the affinity of DCP with Eu³⁺ in Eu-BTC hindered a ligand-metal energy transfer (LMET) process, and destroyed the antenna effect, thereby resulting in the weakening of the red fluorescence of Eu³⁺. Using the dual-emission response, this probe enabled ratiometric fluorescence detection of DCP with high accuracy and visualization capability. In addition, the probe was introduced into portable sodium alginate hydrogel to realize direct and sensitive detection of DCP vapor. This work is thus expected to hold great potential for on-site monitoring of nerve agents in a simple yet efficient way.