A novel ratiometric fluorescent sensing strategy of arginine based on lanthanide-based metal-organic framework

Arginine (Arg) has been recognized as a crucial biomarker for cystinuria, with its concentration levels markedly influencing human health. In this study, Eu-TATB were synthesized via a solvothermal method using 4,4',4″-s-triazine-2,4,6-triyl-tribenzoic acid (H₃TATB) as the organic ligand and Eu ions. Eu-TATB, benefiting from its intrinsic photosensitive characteristics and the characteristic Eu³⁺ emission at 618 nm, was utilized to construct a novel ratiometric fluorescent sensor. By harnessing the photosensitization of Eu-TATB under ultraviolet light irradiation, significant oxidation of arginine was catalyzed, leading to the emergence of a new blue fluorescence peak at 430 nm. The intensity of this blue fluorescence increased proportionally with the arginine concentration, while the red emission at 618 nm gradually decreased. Utilizing the cross response of this dual-emission intensity, Eu-TATB exhibits ratiometric fluorescence sensing property for arginine, with a broad linear range of 0.1-2 mM and a low limit of detection (LOD) of 3.22 μM, and validated the practicality of the proposed sensor through the quantitative detection of arginine in human serum. Notably, the variable luminescence colors that are visible to naked eye endow the feasibility of Eu-TATB for in situ visualization analysis of arginine.