Terpyridine Eu(III) complexes combined with boric acid-functionalized carbon dots for on-site visual ratiometric fluorescence detection of anthrax spore biomarkers.

The development of reliable methodologies for the identification of potential biomarkers holds paramount significance for the early detection of serious diseases and conditions. In this work, we have designed a new terpyridine Eu(III) complexes with boric acid functional carbon dot-based fluorescent probe Eu-Tpy/R-CDs for the ratiometric of detection of dipicolinic acid (DPA). Eu-Tpy/R-CDs nanoprobe were obtained by co-assembly and immobilization of green luminescent Rhodanine B carbon dots to boric acid matrix sites in tripyridine‑europium (III) complexes using the solvent method. The novel nanoprobe Eu-Tpy/R-CDs can be used as a multicolor ratio fluorescence sensing platform for trace DPA in both aqueous media and actual spores. The sensing system exhibited a linear relationship for DPA, with a broad linear range of 6.67-73.33 μM and a limit of detection of 80.34 nM, which is significantly below the infectious dosage of anthrax (∼55 μM). More prominently, combining Eu-Tpy/R-CDs based detection test papers with a smartphone can achieve sensitive, real-time, and visual detection of DPA.