Co–Ni Codoped ZIF-8 Anchored on Halloysite Nanotubes for Detection of Thiram in Foods

Zeolitic imidazolate framework-8 (ZIF-8), a porous metal–organic framework, was codoped with cobalt and nickel ions to form a bimetallic structure (CNZ-8) and then anchored onto halloysite nanotubes (HNTs) to fabricate a hierarchical CNZ-8/HNT nanocomposite. The resulting hybrid material was employed as a modified electrode, forming an efficient CNZ-8/HNT sensor for the voltammetric detection of thiram (THM), which is a widely used dithiocarbamate fungicide. The CNZ-8/HNT-modified electrode exhibited remarkable electrocatalytic activity, attributed to the synergistic effect of dual-metal active sites and the tubular HNT structure, which facilitated rapid electron transfer and enhanced surface accessibility. Under optimized conditions, the sensor demonstrated a wide linear response range from 0.199 to 1181.1 μM and a low detection limit (LOD) of 2.9 nM. The proposed sensor showed excellent selectivity and stability and was successfully applied for the quantification of THM residues in various real food matrices including tomato, cabbage, green bell pepper, pumpkin seeds, millet, dried green peas, almonds, and apple peels. The recoveries ranged from 92.9% to 100.5%, confirming the reliability of the developed method for practical food safety monitoring.