Hierarchical MOF-derived NiCoS/rGO composite for high-performance electrochemical detection of methyl parathion in fruits and vegetables.

The rapid and reliable detection of organophosphorus pesticide residues in food is essential for ensuring food safety and public health. In this study, a hierarchical metal-organic framework-derived nickel‑cobalt sulfide/reduced graphene oxide composite was fabricated as a high-performance electrochemical sensing platform for methyl parathion (MPN). Bimetallic nickel cobalt framework precursors with tunable metal ratios were synthesized by a solvothermal method and subsequently converted into nickel cobalt sulfide (NiCoS) nanoparticles uniformly anchored on reduced graphene oxide (rGO) sheets through thioacetamide-assisted hydrothermal sulfurization and calcination. The resulting particle on sheet architecture provided abundant accessible active sites and accelerated interfacial electron transfer. Owing to the synergistic redox activity of mixed valence nickel cobalt centers and the reduced graphene oxide network, the NiCoS/rGO-2/GCE sensor achieved sensitive MPN detection with a low detection limit of 2.1 nM. The sensor showed excellent repeatability, reproducibility, and anti-interference performance, and was applied to fruit and vegetable samples with satisfactory recoveries.