A luminescent metal-organic framework integrated hydrogel optical fibre as a photoluminescence sensing platform for fluorescence detection

A novel and robust sensing platform based on a metal-organic framework (MOF) integrated hydrogel optical fibre is proposed for fluorescence detection for the first time. The core-clad structure of the hydrogel optical fibre with a step index profile can enable efficient excitation light delivery and luminescence emission collection. Meanwhile, immobilization of the luminescent MOFs in the core of the hydrogel fibre prevents the MOFs from directly contacting the harsh environment, while reserving channels for analyte penetration and interaction with the MOFs. In the representative experiment, water and thermo stable EuNDC (H2NDC = 1,4-naphthalenedicarboxylic acid) is synthesized as a fluorescent material for highly selective detection of explosive picric acid (PA). Fluorescence quenching is visible to the naked eye at a PA concentration of as low as 5.7 ppm. The EuNDC integrated hydrogel optical fibre enables the realization of highly selective detection of explosive picric acid (PA) over other nitroaromatic compounds and metal ions, which demonstrates the potential of the hydrogel fibre as a portable, robust sensing platform for highly selective, on-site and real-time quantitative monitoring.