A facile fluorescence Eu MOF sensor for ascorbic acid and ascorbate oxidase detection

In this work, a facile fluorescence Eu³⁺-based metal-organic framework (Eu MOF) sensor for ascorbic acid (AA) and ascorbate oxidase (AAO) detection was developed. The fluorescence of the Eu MOF could be effectively quenched by Ce³⁺ but not by Ce⁴⁺ at an appropriate concentration, and thus, when the reductant AA was added into the solution containing Ce⁴⁺, Ce⁴⁺ was chemically reduced to Ce³⁺, which induced the decreased fluorescence signal of the Eu MOF. However, when AAO was introduced, AA was effectively oxidized to dehydroascorbic acid (DHAA) under the catalysis of AAO, and thus, Ce⁴⁺ could not be reduced, resulting in the fluorescence restoration of the Eu MOF. Hence, the concentration of AA and AAO could be determined by the fluorescence decrease and restoration of the Eu MOF. The fluorescent platform showed high sensitivity with a limit of detection of 0.32 μM for AA and 1.18 U L^-1 for AAO, respectively. Moreover, the proposed method was successfully applied for AA and AAO determination in real samples, indicating great potential for biomedical application in complex matrices.