A multidimensional luminescent sensor for specific and in situ visual detection of dopamine

Dopamine (DA) is a neurotransmitter with biologically important properties that play an important role in the function of the central nervous and cardiovascular systems. Abnormal DA concentrations in human biological fluids are thought to be associated with many neurological disorders. Luminescence have now become an effective method for the detection of DA. Ratiometric luminescent sensors with self-calibration exhibit higher sensitivity and selectivity than conventional single-emission sensors. In addition, Ln-MOFs sensors constructed based on lanthanide ions doping have the significant advantages of simple synthesis, green, and high stability. In this study, Eu_xTb_yGd_1-x-y-dpdf with tunable emission properties was developed by introducing Eu³⁺ and Tb³⁺ ions, which emit red and green light, as the luminescent centers. Then the framework was doped with inert Gd³⁺ to tune the energy levels. The introduction of Gd³⁺ realizes multiple emission centers from both the visible and UV regions. Ratiometric luminescence detection of DA was achieved by using the ligand-based peak (390 nm) as an internal reference and the emission centers of Tb³⁺ (545 nm) and Eu³⁺ (617 nm) as indicators. The optimized Tb_0.24Eu_0.16Gd_0.6-dpdf showed excellent sensitivity and low detection limit for DA in aqueous solution. In addition, nanofiber films of probes were prepared by electrostatic spinning technique for visual detection of DA, demonstrating the potential for practical applications. This work provides a novel design strategy for ratiometric luminescent probes, which can be doped with inert Ln³⁺ and regulate the ratio between different ions to achieve energy level matching. The ratiometric luminescent sensor constructed based on this method significantly improves the selectivity and sensitivity of DA detection, which provides valuable implications for biomedical and clinical diagnosis.