A ratiometric lanthanide-free fluorescent probe based on two-dimensional metal-organic frameworks and carbon dots for the determination of anthrax biomarker

A lanthanide-free fluorescent probe has been constructed for the first time based on two-dimensional metal-organic frameworks (2D MOFs) and carbon dots (CDs) for ratiometric determination of dipicolinic acid (DPA), the biomarker of Bacillus anthracis. The fluorescence intensity at 659 nm increased due to the release of organic ligands TCPP resulting from the selective interaction between DPA and Zn2+ of 2D MOFs. CDs provided a reference signal at 445 nm which was almost unaffected, realizing self-calibration DPA sensing. F659/F445 versus the concentration of DPA shows good linear relationships in the range 0.01–0.2 μM and 0.2–10 μM under 390-nm excitation, with a detection limit of 7 nM. The ratiometric probe was prepared from 2D lanthanide-free MOFs so that the drawbacks of lanthanide-based probes were overcome. The proposed sensing system was successfully applied to the determination of DPA in spiked biological samples. These results suggest that a novel, simple, and selective strategy of determining DPA with 2D lanthanide-free MOFs is implemented.