LaFeO₃/g-C₃N₄ heterostructure nanozyme with enhanced peroxidase-like activity for colorimetric detection of...

Tetracycline (TC) residues in food and the environment pose serious health risks, highlighting the need for efficient detection methods. Herein, a series of LaFeO₃/g-C₃N₄ (LFCN) heterostructure nanozymes with varying LaFeO₃-to-urea ratios were synthesized via an in-situ growth method. Structural characterizations confirmed the successful formation of the heterostructure, with LaFeO₃ nanoparticles uniformly dispersed on g-C₃N₄ nanosheets. Among the composites, LFCN-20 (LaFeO₃-to-urea = 1:20) exhibited the highest peroxidase-like activity and a lower Michaelis-Menten constant than that of natural horseradish peroxidase. It effectively catalyzed the H₂O₂-mediated oxidation of 3,3',5,5'-tetramethylbenzidine (TMB), generating a blue product with an absorption peak at 652 nm. Notably, the absorbance signal was significantly enhanced in the presence of TC. Based on this effect, a colorimetric sensor was constructed, exhibiting a linear response to TC from 0.25 to 2.50 μg/mL, with a low detection limit of 0.076 μg/mL, and achieving recoveries of 93.9%-108.2% in spiked egg samples. These findings highlight the potential of LaFeO₃/g-C₃N₄ nanozymes for the sensitive and selective detection of tetracycline, offering a practical approach for ensuring food safety.