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 H2O2 could cause much more quenching of fluorescent CuNCs/ZIF-8 than that of PEI-CuNCs, which might result from enriching H2O2 by ZIF-8. The CuNCs/ZIF-8 can be designed as a fluorescence probe to selectively and sensitively detect H2O2 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 H2O2 increases by nearly 50-fold, which makes CuNCs/ZIF-8 a desirable probe to detect H2O2 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.