NH2-MIL-53(Fe)-based fluorescent sensor for detection of tetracycline in food matrices

Metal–organic frameworks (MOFs) have emerged as advanced crystalline materials with a periodic network structure made up of metal ions and organic ligands. The tailorable structure, pore size, surface area, and fluorescence of MOFs have led to their applications in diverse fields such as catalysis, sensing, gas storage, and photovoltaic. In the present study, a water-stable and dispersible iron-based MOF, i.e., NH₂-MIL-53(Fe), was hydrothermally synthesized, and demonstrated for the fluorescent detection of tetracycline (TC) antibiotic. The fluorescence of as-prepared NH₂-MIL-53(Fe) was quenched in the presence of TC due to the bonding between OH (of TC) and –NH₂ (of NH₂-MIL-53(Fe). This effective fluorescence quenching of NH₂-MIL-53(Fe) in the presence of TC can be attributed to a combination of the inner filter effect (IFE) and photo-induced electron transfer (PET) process from the ligand of NH₂-MIL-53(Fe) to TC, as described by theoretical and experimental studies. Under the optimum conditions, the ratio of fluorescence intensity and TC concentration showed a good linear range (0.05–1 µM) with a detection limit of 53 nM. Furthermore, the sensing probe was also used to detect TC in the spiked milk and juice samples with good recoveries, i.e., 91.3–98.5% and 95.7–104%, respectively. These results demonstrated the potential of NH₂-MIL-53(Fe) nanosensor to detect TC in real food samples.

Graphical abstract