A turn-off Eu-MOF@Fe2+ sensor for the selective and sensitive fluorescence detection of bromate in wheat flour.

A new europium metal-organic framework (Eu-MOF) was prepared by simple hydrothermal method. The product exhibited intense red fluorescence, long fluorescence lifetime (0.454 ms) and excellent fluorescence stability. The fluorescence titration result showed that Fe3+ could completely quench the fluorescence of Eu-MOF, while the fluorescence quenching effect of Fe2+ or bromate was negligible. Considering the strong oxidizing property of bromate, a "turn off" Eu-MOF@Fe2+ sensor toward bromate was designed by generating Fe3+ due to the redox reaction. The results showed that the sensor displayed a wide linear range (0-0.2 mM), high sensitivity (LOD = 3.7 × 10-6 mol/L), good selectivity and resistant to possible interferences in real four sample. Furthermore, the detection mechanism was investigated by PXRD, XPS and UV-Vis methods. More importantly, the Eu-MOF@Fe2+ sensor was further applied to detect bromate in wheat flour with satisfactory recovery (95.30%-104.38%) and accuracy (RSD < 2.85%). These results suggest that Eu-MOF@Fe2+ can be used as a potential sensor to detect bromate in food industry.