A ratiometric fluorescent paper–based sensor based on Fe/Eu-MOF for visual and sensitive detection of diethylstilbestrol

Diethylstilbestrol (DES), a synthetic estrogen, is associated with severe endocrine disruption and carcinogenic risks, posing persistent biological and environmental hazards. Herein, a bimetallic Fe/Eu–based metal–organic framework (Fe/Eu–MOF) with distinct multi–emission properties was developed as a ratiometric fluorescent sensor for sensitive and intelligent visual detection of DES. The Fe/Eu–MOF exhibited stable red emission at 615 nm and DES–responsive blue emission at 410 nm, enabling self–referenced quantification. The sensor showed two linear ranges (0.005–2 and 2–30 μg/mL), a low detection limit (1.78 ng/mL), and excellent selectivity against potential interferents. Its practicality was validated in milk and shrimp, demonstrating excellent recovery and reproducibility. Additionally, a paper–based sensor integrated with smartphone RGB analysis enabled rapid, on–site, and instrument–free detection. Mechanism studies revealed that DES coordination with Fe centers suppressed non–radiative decay and enhanced fluorescence. This work provides a robust and intelligent platform for portable monitoring of DES residues, offering significant potential for real–time biohazard surveillance and visual diagnostics in resource–limited settings.