One-pot synthesis of the CuNCs/ZIF-8 nanocomposites for sensitively detecting H2O2 and screening of oxidase activity

The fluorescent CuNCs/ZIF-8 nanocomposites were facilely prepared by mixing the PEI protected CuNCs with the precursors of ZIF-8, and characterized by UV–vis absorption, fluorescence, FT-IR, TEM , XRD and XPS . The quantum yield of the CuNCs/ZIF-8 is 15 times that of the PEI-CuNCs. Furthermore, the CuNCs/ZIF-8 possesses better stability and higher fluorescence response due to protective and confinement effects of MOFs . It was found that H 2 O 2 could cause much more quenching of fluorescent CuNCs/ZIF-8 than that of PEI-CuNCs, which might result from enriching H 2 O 2 by ZIF-8. The CuNCs/ZIF-8 can be designed as a fluorescence probe to selectively and sensitively detect H 2 O 2 with a linear range from 0.01 to 1.5   µM and a LOD of 0.01   µM, while those with PEI-CuNCs are 0.5–30   µM and 0.50   µM, respectively. Through formation of CuNCs/ZIF-8 hybrid, the sensitivity for the detection of H 2 O 2 increases by nearly 50-fold, which makes CuNCs/ZIF-8 a desirable probe to detect H 2 O 2 content in human serum samples. Also, we successfully demonstrated the potential application of the CuNCs/ZIF-8 for screening and evaluating activities of oxidase using glucose oxidase as a model. The glucose oxidase activity can be detected in a range of 0.1–10   mU/L with a LOD of 0.1   mU/L.