Energy transfer-based ratiometric fluorescence sensing anthrax biomarkers in bimetallic lanthanide metal-organic frameworks

A series of bimetallic lanthanide metal-organic frameworks (Ln-MOFs), namely Tbx/Eu1−x-BTC, were prepared by wet grinding with a green and facile process. The as-prepared Tbx/Eu1−x-BTC showed an adjustable dual emission performance for dipicolinic acid (DPA, Bacillus anthracis biomarker) ratiometric sensing. The highly efficient energy transfer from Tb3+ to Eu3+ endowed the strong red emission at 616 nm, even in Tbx/Eu1−x-BTC with high proportion of Tb3+. Meanwhile, the energy transfer between Tb3+ and Eu3+ nodes could be blocked by the introduced DPA, showing a strong green emission at 544 nm, and thus resulting in a ratiometric fluorescence response. As a novel ratiometric fluorescence probe, the Tb0.4/Eu0.6-BTC exhibited an excellent linearity with DPA concentrations from 50 nM to 3 μM with high selectivity and low detection limit of 4.9 nM. The present work not only provided a green efficient method for the construction of bimetallic MOFs, but also proposed a new insight for designing fluorescence sensor with remarkable sensing performance.