Enhancing Peroxidase-Like Activity and Photothermal Property of Copper Single-Atom Nanozyme via A Cascade Competition Strategy

Single-atom nanozymes (SANs) are promising enzyme-active catalysts due to their maximum atomic utilization. However, it is still a challenge to precisely regulate the single-atom structure, especially in multimetallic MOFs. Based on the Cu-N4 structure of Zn4Cu1, a cascade competition strategy mediated by a buffer (polydopamine) is proposed for the first time, which induces a one-step nonthermal reaction to precisely remove the inactive Zn site and adjust the Cu coordination environment. Experimental results and theoretical calculations show that the Cu single-atom nanozyme with Cu-N2O2 structure (Cu-N/O) breaks the strong steric restriction, and the exposed Cu active site can better adsorb H2O2, making it have peroxidase-like activity. Compared with traditional bimetallic (Cu4Zn1) and monometallic (Cu-MoF) nanozymes, it has stronger peroxidase-like catalytic activity and photothermal properties, as well as good photocatalytic activity and extremely strong stability. It is successfully applied to Lateral flow immunoassay to achieve three-mode ultrasensitive detection of Escherichia coli O157:H7, and the test strips after detection are subjected to broad-spectrum sterilization treatment.