Single-atom Cu nanozyme anchored on carbon nitride with enhanced peroxidase-like activity for colorimetric detection...

Nanozyme-based colorimetric biosensors for foodborne pathogens are promising, but their sensitivity is often limited by the insufficient catalytic performance of nanozyme probes. Herein, a copper single-atom nanozyme anchored on carbon nitride (Cu-SA-CN), with a Cu loading of 24.1 wt%, was fabricated via a novel supramolecular self-assembly and pyrolysis strategy. The material features atomically dispersed Cu-N₃ sites and exhibits superior peroxidase-like activity (V_max = 51.4 ×10^-8 M s^-1) by efficiently catalyzing H₂O₂ to generate reactive oxygen species (ROS). Leveraging the abundant surface amino groups of Cu-SA-CN for antibody conjugation and its high activity for signal amplification, a sensitive immunomagnetic colorimetric biosensor was constructed for Salmonella typhimurium (S. typhimurium) detection, where magnetic beads enable target enrichment and Cu-SA-CN serves as a robust signal amplifier. This biosensor achieved a low detection limit of 12.7 CFU mL^-1 with a linear range from 3.8 × 10¹ - 3.8 × 10⁶ CFU mL^-1. Importantly, the sensor exhibited excellent long-term stability. Successful application in spiked chicken samples highlighted its practicality. This work not only provides an effective strategy for creating high-performance single-atom nanozymes but also offers a new approach for the sensitive and specific detection of pathogenic bacteria in complex food matrices.