A Eu 3+ /Tb 3+ -functionalized MOF ratiometric fluorescence sensor for ciprofloxacin detection and its agarose hydrogel for anticounterfeiting application

Abstract

Luminescent metal-organic frameworks (MOFs) have a prospect in visualization detection for antibiotics. This work presented a europium/terbium functionalized MOF of Eu0.125Tb0.875-DDB (H4DDB = 1,3-di(3',5'-dicarboxylphenyl)benzene) and an agarose hydrogel of Eu0.125Tb0.875-DDB@agarose. Eu0.125Tb0.875-DDB acted as a ratiometric fluorescence sensor for ciprofloxacin (CPFX) detection, showing the linear relationships: I488/I612 = 0.00479CCPFX + 0.06906 (I488/I612 = the ratio of emission intensities at 488 and 612 nm) within CPFX concentration (CCPFX) = 3-20 μM; I488/I612 = 0.00178CCPFX + 0.129 within CCPFX = 20-45 μM. The limits of detection (LODs) for these two CCPFX ranges were 0.315 and 0.848 μmol·L–1 (μM) respectively. Eu0.125Tb0.875-DDB sensing CPFX was not interfered by the common cations/anions, amino acids, and antibiotics. The accuracy of the fluorescence assay using Eu0.125Tb0.875-DDB was demonstrated in lake water and milk with the measured CCPFX close to the spiked CCPFX. A smart-phone assisted method was used to recognize the blue values (B) of the images of Eu0.125Tb0.875-DDB@agarose sheets, thus establishing a quantitative model of B = 0.98857CCPFX + 110.8381 with LOD = 0.9189 μM. The allochroic rose mold of Eu0.125Tb0.875-DDB@agarose exhibited an anti-counterfeiting through a series of color changes under a certain UV light irradiation time. This work provides not only a fluorescence assay for CPFX visualization detection by a heterometallic MOF but also an agarose hydrogel for anti-counterfeiting.