A quantitative ratiometric fluorescent Hddb-based MOF sensor and its on-site detection of the anthrax biomarker 2,6-dipicolinic acid

Abstract

Hydrothermal reactions of 1,3-di(3′,5′-dicarboxylphenyl)benzene (H₄ddb) with Eu³⁺ and Tb³⁺ produced a series of hetero metal–organic frameworks (Tb_xEu_1−x-Hddb). The optimized Tb_0.875Eu_0.125-Hddb showed high stability in organic solvents, HEPES buffer solution, NaOH and HCl solutions with pH = 2–11. Tb_xEu_1−x-Hddb exhibited the combined characteristic transitions of Eu³⁺ (⁵D₀ → ⁷F_J (J = 1–4)) and Tb³⁺ (⁵D₄ → ⁷F_J (J = 6–3)). The sensitivity test of Tb_0.875Eu_0.125-Hddb revealed a linear response of I₅₄₅/I₆₁₃ = 0.0362·C_DPA + 0.3176 with a LOD of 0.8494 μM, and seven interferents did not influence its detection performances. The paper-based MOF sensor Tb_0.875Eu_0.125-Hddb displayed obvious emission color conversions at C_DPA = 60 μM, and a linear equation of G/R = 0.01091·C_DPA + 0.12092 with a LOD of 19.1 μM by recognizing the RGB values of the paper-based MOF, showing a prospect for a rough on-site DPA detection. Tb_0.875Eu_0.125-Hddb and its paper-based sensor are quantitative ratiometric fluorescent sensors for DPA detection with high sensitivity and selectivity, and rapid response and convenience.