Heterostructure Assembly of Zn-Substituted Fe3O4@NC/CuS@MoS2 for Enhanced Electrochemical Detection of Organophosphorus Pesticide Residues.

A hierarchical Zn-substituted Fe3O4@NC/CuS@MoS2 heterostructure was rationally designed for the electrochemical detection of organophosphorus pesticides such as methamidophos and dichlorvos. Hollow Fe2O3 nanospheres were synthesized hydrothermally, followed by Zn-substitution, polydopamine-derived nitrogen-doped carbon coating, and in situ growth of CuS@MoS2 nanosheets. The Zn-substitution modulates the electronic structure, while the carbon network and the CuS@MoS2 heterojunction synergistically enhance charge transfer kinetics, increase the electroactive surface area, provide abundant sites for acetylcholinesterase immobilization, and ensure favorable biocompatibility. The resulting enhanced interfacial electron transfer reduces the charge transfer resistance to 41.6 Ω. The biosensor exhibits broad linear ranges for methamidophos (7.09 × 10-7 μM to 7.09 × 10-2 μM) and dichlorvos (4.53 × 10-7 μM to 4.53 × 10-2 μM), with detection limits of 8.7 × 10-8 μM and 2.0 × 10-7 μM, respectively. Real-sample analysis in Chinese cabbage and apple yields recoveries of 96.36%-102.40% for methamidophos and 95.92%-101.77% for dichlorvos, confirming its practical viability for trace pesticide monitoring.