Dual-pathway synergistic catalytic mechanism based on FeN₃P-CoN₃P active sites: A three-channel colorimetric sensing...

Herein, we pioneered a P-doped heteronuclear Fe-Co dual-atom nanozyme (FeCoP-NC), in which 0.1 % P-doping substantially increased oxidase-like (OXD) activity by 48.3 % compared to FeCo-NC. The enhanced OXD activity resulted from a synergistic dual-pathway mechanism involving direct two-electron transfer and ·O₂^- mediation at FeN₃P-CoN₃P active sites. By utilizing FeCoP-NC's high OXD activity and differential coloring of two chromogenic agents (TMB and DPD), a three-channel colorimetric sensing array was constructed, achieving high-selectivity discrimination of five organophosphorus pesticides (OPs) in environmental/food samples, with a detection limit of 3.3 nM. Owing to the independence of the colorimetric reactions of TMB and DPD, a "blue TMB gel-pink DPD solution" integrated kit was developed, exhibiting distinctly spatial separation of two-phase chromogenic signals. This smartphone-based device enabled rapid malathion detection with a detection limit of 0.17 μM. Utilizing zebrafish (Danio rerio) as model invertebrates, the biocompatibility of FeCoP-NC-based colorimetric system was confirmed through embryonic-larval morphological observations, swim behavior, and light/dark stimulation responses. BAGI analysis further demonstrated its greenness with a score of 80, providing novel insights into the design of green nanozymes and on-site detection of OPs residues in environmental and food media.