Tunable dual-emission Eu-MOF-based portable smartphone platform for visual detection of anthrax biomarker via analyte further “ignited” antenna effect

Abstract

Developing affordable and portable detection strategies for 2,6-pyridine dicarboxylic acid (DPA), a biomarker of anthrax, is crucial in food safety and anthrax infection prevention. Herein, this study synthesized a dual-ligand europium metal–organic framework (Eu-MOF) for ratiometric fluorescence and smartphone–assisted visual detection of DPA. The Eu-MOF, denoted as Eu-H₄betc/BDC-NH₂, was prepared using 1,2,4,5-benzene tetracarboxylic acid (H₄betc) and 2-amino terephthalic acid (BDC-NH₂) as dual-ligands and Eu³⁺ as metal node via a mild solvothermal method. It exhibited dual-emission from BDC-NH₂ and Eu³⁺ at 450 nm and 621 nm, respectively, upon excitation at 255 nm, with the emission ratio adjustable by varying the H₄betc/BDC-NH₂ ratio. The addition of DPA enhanced the fluorescence at 621 nm due to its further “ignited” antenna effect on Eu³⁺ based on H₄betc as “fuse”, while the fluorescence at 450 nm remained almost stable. A visible fluorescence color change from blue-purple to purple-red was observed with increasing DPA concentration. By combining a smartphone’s portability with a color recognition app, a sensitive and intelligent detection platform for DPA was successfully developed. Real-sample feasibility was validated through recovery experiments. This work not only advances the design of MOFs with tunable dual-emission but also offers a promising approach for rapid, on-site DPA detection.