A Fe/Zn Dual Single-Atom Nanozyme with High Peroxidase Activities for Detection of Penicillin G

Penicillin G (PG) is a common antibiotic, and its accumulation in the environment can pose a threat to the ecological system and ultimately impact human health. Nanozymes have emerged as highly stable enzyme mimics that can be utilized as sensors to achieve the sensitive detection of specific antibiotics. Herein, we report on a dual single-atom Fe/Zn nanozyme (DSAzyme) synthesized from Fe-imidazole as the guest and zeolite imidazole framework-8 as the host. The DSAzyme exhibits intriguing properties that mimic the activities of two natural enzymes: peroxidase and lactamase. Both activities are utilized for the design of a colorimetric sensor for the specific detection of PG: the peroxidase activity enables color generation from 3,3',5,5'-tetramethylbenzidine and H₂O₂, and the lactamase activity provides the recognition of PG. The nanozyme consists of many Fe-N₄ and Zn-N₄ site and mechanistic characterizations by experimental investigations and theoretical calculations identify Fe-N₄ as the main active center for the peroxidase activity and Zn-N₄ as the main binding site for PG. The sensor can achieve a limit of detection of 47 nM, is able to detect PG from real-life samples, remains fully functional after 8-month storage, and retain high activities after reuse for fives times. Taken together, our study provides a new approach to the detection of antibiotics in environmental samples.