Bimetallic CuFe@TMDP Nanozyme with Controllable Laccase/Peroxidase-like Activities for Colorimetric Detection of o-Chlorophenol and Tetracycline

Inspired by the active sites of natural enzymes and bimetallic synergistic effect, a bimetallic CuFe@TMDP nanozyme with laccase-like and peroxidase-like activities was successfully constructed using a Schiff base as a ligand. The precise doping of Cu/Fe was confirmed by EDS, PXRD, XPS, and FT-IR, and the unique structure of the Schiff base coordination polymer gave the nanozyme excellent stability, salt resistance, organic solvent tolerance, and recyclability under extreme conditions. Steady-state kinetic analysis showed that both laccase-like and peroxidase-like activities showed high substrate affinity and catalytic efficiency, and the activity could be regulated by the metal ratio. Based on the synergistic effect of bimetallics, two possible catalytic mechanisms for enzyme activity were proposed. Benefiting from its excellent laccase-like activity, this nanozyme can achieve highly sensitive detection of o-Chlorophenol (linear range of 0.01-1.2 mM, detection limit of 7 μM). In addition, this method shows good recovery results for spiked samples. The inhibitory effect of tetracycline on peroxidase-like activity was explained by density functional theory (DFT), and a colorimetric detection method for tetracycline was constructed (linear range of 0.01-0.1 mM, detection limit of 5 μM). Compared with other antibiotics, amino acids, and ions, they exhibited good selectivity and anti-interference ability. A smartphone-based colorimetric sensing platform with standard colorimetric cards was further developed to realize the rapid visual detection of the two pollutants. This study provides new ideas for the design of Schiff base bimetallic nanozymes and promotes their practical application in the field of environmental monitoring.