Eu@metal-organic frameworks encapsulating carbon dots as ratiometric fluorescent probes for rapid recognition of anthrax spore biomarker.

Anthrax spores pose a serious threat to human well-being and life, so it is highly desirable to develop a rapid, sensitive, and selective quantitative assay of calcium pyridine dicarboxylate (CaDPA) as a biomarker of anthrax spores. Herein, carbon dots (CDs) chelated Eu@metal-organic framework (Eu-MOFs) as dual-emissive ratiometric fluorescent (RF) probe was successfully fabricated by a simple one-pot in situ selective self-assembly synthetic strategy. The developed RF probe has an effective self-calibration function, which performs a highly sensitive and selective recognition of CaDPA in water and human serum sample. The blue-emitting CDs was employed as an effective fluorescence reference, while the Eu-MOFs exhibited enhanced red fluorescence signal through the coordination interaction with CaDPA chromophore. The sensing mechanism is attributed to that CaDPA can sensitize Eu intrinsic luminescence due to the energy transfer from CaDPA to Eu. What's more interesting is that with the continuous drop of CaDPA, the emission color of CDs@Eu-MOF changes from blue to red. The results revealed that CDs@Eu-MOFs RF probe can detect CaDPA effectively in the range of 8-170 μg/L with good linear relationship, and exhibited a remarkable selectivity for CaDPA. More interestingly, a paper-based probe has also been devised for on-site detection of CaDPA. In addition, CaDPA is used as input signal to construct an IHIBITION logic gate device which performs the "off-on" mode. The constructed CDs@Eu-MOF probe can achieve exceptionally rapid, highly sensitive and selective detection of CaDPA, which can further expand the application prospects in environmental and biological analysis.