A portable fluorescence sensing platform integrating smartphone and high quantum yield Eu-MOF probe for the detection of CrO and Hg in aqueous solutions.

The efficient detection of highly toxic CrO and Hg is of significant importance. Herein, a novel Eu-MOF with high quantum yield was synthesized via a one-step hydrothermal method. Through the strategic design and combination of ligands [2,2'-biquinoline]-4,4'-dicarboxylic acid (HL) and 1,10-phenanthroline (Phen), the Eu-MOF exhibits excellent thermal stability, water stability, pH stability, photostability, and reproducibility. It also demonstrates outstanding sensing performance and anti-interference capability toward CrO and Hg. It has a Ksv of  M and a LOD of 3.78 nM for CrO detection, and a Ksv of M and a LOD of 1.39 nM for Hg detection, which may be attributed to its high quantum yield. The sensing mechanism for CrO involves fluorescence quenching due to competitive absorption of excitation energy between the Eu-MOF and CrO. In contrast, Hg detection occurs via coordination of free nitrogen atoms sites in the Eu-MOF with Hg, forming a complex that quenches fluorescence. Test paper uniformly coated with the Eu-MOF was further developed. Finally, a portable fluorescence sensing platform integrating a smartphone and the Eu-MOF test paper was constructed, enabling convenient, rapid, and low-cost detection of CrO and Hg. This study provides a reference for preparing high quantum yield Eu-MOF and advancing portable sensing platforms.