Cu-N₄ active site sensing platform for point-of-care colorimetric detection of environmental organophosphorus...

Organophosphorus pesticides contamination significantly threatens the ecological environment. Therefore, developing sensitive and efficient point-of-care detection methods is essential.

In this work, Cu-N₄ single-atom nanozymes on nitrogen-doped carbon (Cu SAs/NC) with dual enzyme-mimicking activities (peroxidase-like and oxidase-like) were prepared for point-of-care detection of parathion using acetylcholinesterase inhibition-based colorimetric sensing mechanism. Cu SAs/NC shows high catalytic activity with high turnover number (K_cat) of ∼24.07 min^-1 and K_cat/K_m of ∼1.35 × 10⁵ M^-1 min^-1. Experimental findings in combination with density functional theory simulations demonstrate that Cu centers in Cu SAs/NC play a pivotal role in intermediate binding optimization, which contributes to a decreased reaction energy barrier. Hence, a colorimetric sensing platform based on Cu SAs/NC was constructed for point-of-care detection of parathion, achieving a detection limit of 0.79 ng mL^-1.

This study provides a novel strategy for structuring single-atom nanozymes with enhanced enzyme-mimicking activity, showing great promise for advanced environmental protection.