Sensitive Ratiometric Luminescent FRET Probe for the Detection of Riboflavin

The synthesis of two isomorphic 2D MOFs {[Ln(L)(NO₃)(DMF)₂] DMF} (Ln = Ho and Er, H₂L = 2,5-bis(1,2,4-triazol-1-yl) terephthalic acid) by the solvothermal method enables ratio luminescent sensing of riboflavin (RF), based on the Förster resonance energy transfer (FRET) effect. As sensors for RF, both Ho-MOF and Er-MOF have splendid anti-interference effects, a large Stokes shift with 103 nm, excellent visualization effect, and a low detection limit, as low as 1.72 and 3.90 nM. Ho-MOF, with a better anti-interference capability and a relatively lower detection limit, is selected for further investigations. It possesses the advantages of excellent pH stability in the range of 4-12, rapid response time within 50 s, and even achieving five cycles. Ho-MOF also demonstrates exceptional practical detection potential when tested in real-life environments and samples, with urine and serum exhibiting detection limits of 5.26 and 27.27 nM, respectively, and a recovery range of 96-104% in VB₂ tablets. Mechanism research discovers that FRET serves as the primary sensing mechanism with a calculated Forster distance (R₀) of 3.7 nm, which is consistent with the required distance (1-10 nm). This study successfully achieves rate-luminescent sensing and monitoring of RF in diverse environments.