Ce and Ni Supported on N-Doped Carbon as a Diatomic Nanozyme and a Colorimetric Sensor for the Detection of Arsenite

In this work, a Ce/Ni metal−organic framework (MOF)-derived carbon-supported Ce-Nx and Ni-Nx dual-site Ce,Ni−N−C SAzyme for cascade catalysis and the H2O2 activation system is successfully constructed for detection of arsenate. Ce,Ni−N−C only displayed peroxidase (POD)-mimicking activity and 1.9- and 1.6-fold enhancement relative to the Ce-NC and Ni-NC SAzymes, respectively. When integrated with uricase (UOx) and Ce,Ni−N−C SAzyme, a cascade enzyme-nanozyme system was developed for selective and sensitive screening of arsenite (As(III)) with detection limits of 0.096 μg/L. The detection mechanism is based on As(III) irreversibly poisoning UOx against hydrolyzing uric acid, and the absorbance of blue oxidized 3,3′,5,5′-tetramethybenzidine at 654 nm is suppressed. Both Ce-Nx and Ni-Nx in Ce,Ni−N−C display a strong binding energy and electron-donating capability to promote H2O2 activation to generate highly hydroxyl radicals. Density functional theory (DFT) calculations reveal that the high POD-like activity of Ce,Ni−N−C is due to the isolated Ce-Nx and Ni-Nx sites and their synergy.