Smartphone-integrated ratiometric fluorescent probe based on G-CDs@Eu-MOFs for on-site detection of phosphate ions

Excessive levels of phosphate ions (PO 4 3- ) pose serious risks to human health and environmental ecosystems. In this work, a ratiometric fluorescent probe, G-CDs@Eu-MOFs composite, was designed and synthesized via a post-synthetic modification strategy. The composite was employed for selective detection of phosphate ions. The resulting probe displays two well-resolved fluorescence emission peaks at 419 nm and 616 nm, which exhibits distinct responses to phosphate ions, thereby providing an intrinsic self-calibration capability. Upon interaction with PO 4 3- , the probe demonstrates a strong linear response (I 419 /I 616 ) over the concentration range of 10 −4 M to 4.5 × 10 −3 M, with a high correlation coefficient (R 2 = 0.9986). The detection limit (LOD) is determined to be 0.927 μM. A clear fluorescence color shift from blue-red to blue allows for rapid visual identification of phosphate. Furthermore, by integrating the probe with a smartphone-based platform, a user-friendly, accurate, and portable approach is established for on-site and real-time monitoring of phosphate. This strategy shows considerable promise for environmental and biomedical applications.