Ratiometric fluorescence detection of an anthrax biomarker by modulating energy transfer in hetero Eu/Tb-MOFs

As one of the most important biomarkers of anthrax, accurate and sensitive detection of 2,6-dipicolinic acid (DPA) is essential to protect against anthrax disease or biological terrorist attack. This work presented seven MOFs of two different structures based on the same ligand H3BTB: five single Ln-MOFs [Ln(BTB)(DMF)] (Ln = Y3+ (1), Eu3+ (2) and Tb3+ (3)) and [Ln(BTB)(H2O)] (Ln = Eu3+ (5), Tb3+ (6)), and two optimized hetero Eu/Tb-MOFs [Tb0.9Eu0.1(BTB)(DMF)] (4) and [Tb0.9Eu0.1(BTB)(H2O)] (7). This work aimed at the crystal structures and energy transfer processes regulation of the fluorescence properties and detecting DPA. These two hetero Eu/Tb-MOFs 4 and 7 exhibit different energy transfer efficiency from Tb3+ to Eu3+ (4: 15.23%; 7: 96.86%), and the above energy transfer process could be influenced by DPA. Radiometric fluorescence detection of DPA was first studied in contrast by modulating the structure and energy transfer process in hetero Eu/Tb-MOFs. The detection limits of 4 and 7 for DPA were 0.078 μM (4) and 0.24 μM (7). In addition, 13 interferents did not affect the DPA detection. The high selectivity and good reproducibility of sensing DPA make hetero Eu/Tb-MOFs promising materials for applications in convenient bacillus anthracis detection.