Dual-emission FS@Eu-TDA for fluorescence detection of PO4^3- in tap water and serum

A novel dual-emission metal-organic framework composite, FS@Eu-TDA, was fabricated for the ratiometric fluorescence detection of phosphate (PO₄^3-). This composite was prepared via an in-situ encapsulation strategy, in which fluorescein sodium molecules were incorporated as guest chromophores into Eu-MOF. The FS@Eu-TDA composite achieves a low limit of detection of 0.12 μM for PO₄^3-. Benefiting from its dual-emission response, the composite enables visual PO₄^3- detection. Specifically, its fluorescence color distinctly changes from red to green under UV light as the PO₄^3- concentration increases. The practical applicability of FS@Eu-TDA was successfully validated in real samples, including tap water and fetal bovine serum. To address the limitations of powder suspension systems and achieve convenient detection, a flexible FS@Eu-TDA@PVP/PES composite hydrogel film was further fabricated, which exhibits a visual detection limit of 0.21 μM for PO₄^3-. This work demonstrates that FS@Eu-TDA serves as a highly sensitive, accurate, and practical sensing platform for PO₄^3- detection in environmental and biological samples.