Self-cascade catalytic system constructed using carbon dots and Au nanoparticles co-assembled on MIL-53(Fe)-NH as a three-in-one fluorescent nanozyme for multimodal detection of glucose and maltose in food.

Determination of glucose and maltose is crucial for food production and human health. Herein, a novel Au/CD@MIL-53(Fe)-NH self-cascade nanozyme was constructed via host-guest assembly with "three-in-one" features, including blue fluorescence, HO production as an oxidase mimic, and •OH generation as a peroxidase mimic. Theoretical and experimental results proved that the incorporation of carbon dots renders the composite with high peroxidase-like activity and extremely high affinity for HO (K: 0.011 mM), 336 times higher than that of the natural enzyme. The self-cascade catalytic process could oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue ox-TMB, which further quenched the fluorescence and produced a photothermal effect. Consequently, colorimetric/fluorescence/photothermal-based multimodal detection of glucose and maltose was first achieved, obtaining low detection limits of 12/7.5/1.1 and 18/11.3/1.4 μM, respectively. This study offers a promising strategy for designing efficient nanozyme-based cascade systems that help enhance food quality determination.