Dual-ligand two-dimensional Europium-organic gels nanosheets for ratiometric fluorescence detecting anthrax spore biomarker

A series of novel dual-ligand two-dimensional Europium-organic gels (2D Eu-MOGs) nanosheets, namely, 2D EuPB MOG 1, 2D Eu-PB MOG 2 and 2D Eu-PB MOG 3 nanosheets, were constructed via simply blending the reaction mixture of Eu salts, 1,10-phenanthroline-2, 9-dicarboxylic acid (Phen), and 2-aminoterephthalic acid (BDC-NH2) at room temperature. 2D Eu-PB MOGs nanosheets had excellent dipicolinic acid (DPA) sensing properties exhibiting dual emission originated from BDC-NH2 and Eu3+ at 417 and 610 nm. An energy transfer between Eu3+ nodes and DPA in 2D Eu-PB MOGs nanosheets enhanced the red fluorescence at 610 nm while the blue fluorescence from BDC-NH2 kept stable, resulting in ratiometric fluorescence response to DPA. Besides, the introduction of DPA could replace coordinated H2O in 2D Eu-PB MOGs nanosheets minimizing the nonradiative quenching of Eu3+, which greatly improved the sensitivity. As a novel ratiometric fluorescence probe, 2D Eu-PB MOGs nanosheets exhibited a good linear response toward anthrax spores from 2.1 x 10(4) CFU & BULL;mL(-1) to 1.26 x 10(5) CFU & BULL;mL(-1). The present study not only proposed an efficient method for the construction of 2D MOGs but also made a new way for the design of fluorescence probe with remarkable sensing property.