Zirconium-based metal–organic framework loaded agarose hydrogels for fluorescence turn-on detection of nerve agent simulant vapor

Developing reliable sensors that accurately detect deadly chemical gases is critical to global security. Nerve agents are one of the most dangerous chemicals in the world and are often found in gaseous forms in the environment, which remain a challenge to detect because of their low levels. In this paper, a fluorescent probe based on a Zr-based metal–organic framework UiO-66–NH2 was proposed. The specific binding between the Zr–O site of UiO-66–NH2 and diethyl chlorophosphate (DCP) blocked the ligand-to-metal charge transfer (LMCT) process in UiO-66–NH2, thereby enabling the fluorescence turn-on detection of DCP. More importantly, a simple and portable hydrogel soft-solid platform (UiO-66–NH2@Aga) was constructed by incorporating UiO-66–NH2 into the formation process of agarose (Aga) hydrogel for fast and sensitive detection of gaseous DCP. When the hydrogel was exposed to a low concentration of DCP vapor, its fluorescence changed from colorless to bright blue, allowing visualization of the DCP gas for analysis. The UiO-66–NH2@Aga integrated solid-state platform showed an excellent response to DCP vapor in the detection range of 1.98 to 9.90 ppm and with a detection limit of 1.16 ppm. This work opened up a unique way to design a convenient, low cost and practical gas physical examination platform.