Fluorescence Recognition of Carbon Disulfide Biomarker 2- Thiazolidinethione-4-Carboxylic Acid in Simulated Urine by Terbium(Ⅲ) Metal-Organic Framework Material

Using 3-(3',5'-dicarboxypheny) phthalic acid (H₄L) as ligand, a terbium(Ⅲ) metal-organic framework material (Tb-MOF) was synthesized by hydrothermal method. The structure and properties of the material were characterized by Fourier infrared spectroscopy, thermogravimetric analysis and X-ray powder diffraction. The fluorescence property of Tb-MOF was analyzed by fluorescence spectrophotometry at the excitation wavelength of 335 nm and the emission wavelength of 546 nm, and used to identify 2-thiazolidinethione-4-carboxylic acid (TTCA) in simulated urine. It was shown that the Tb-MOF with good thermal stability at 400 ℃ and water stability in 12 h was successfully synthesized, which yield was 37%. TTCA could effectively quench the green fluorescence of Tb-MOF, and the relative fluorescence intensity (relative to Tb-MOF) was about 20%. It was speculated that the fluorescence quenching mechanism was that the competitive absorption of ligand H₄L and TTCA led to the reduction of energy transferred from ligand to terbium(Ⅲ), thus reducing the fluorescence intensity of Tb-MOF. The relative fluorescence intensity of 2 mL of 1 g·L^-1 Tb-MOF disperse suspension was more than 88% after adding 0.01 mol·L^-1 simulated urine components including ammonium chloride, potassium chloride, creatine, creatinine, sodium chloride, sodium sulfate, glucose and urea, which had little interference with TTCA detection. The relative fluorescence intensity of 2 mL of 1 g·L^-1 Tb-MOF disperse suspension was about 60% after 0.01 mol·L^-1 uric acid was added, which interfered with TTCA detection to some extent. When the concentration of TTCA ranged from 25 μmol·L^-1 to 196 μmol·L^-1, the quenching process of TTCA on Tb-MOF was consistent with the Stern-Volmer equation, with detection limit of 3.84×10^-2μmol·L^-1.