An electrochemical aptamer sensor based on nano‑silver-decorated covalent organic framework for the detection of malathion in medicinal herbs

Malathion, a broad-spectrum organophosphorus insecticide widely used in pest control for medicinal herbs, poses risks to human health and ecological balance due to its potential residual toxicity. In this study, we report a green method for the synthesis of silver-nanoparticles modified covalent organic frameworks (AgNPs@COFs) based on static in-situ reduction at room temperature. The material was combined with a malathion aptamer to develop a highly sensitive electrochemical aptasensor. The ferrocene-labeled hairpin aptamer was used as a molecular recognition element, and the sensing performance was evaluated using a differential pulse voltammetry (DPV) system. Under optimized conditions, the sensor exhibited a linear detection range of 10–800 ng/L, a low detection limit of 8.2 ng/L (S/N = 3, Δ I  = 0.01255–0.00774 C Mal , R 2  = 0.995), and excellent repeatability ( RSD  < 2.0 %, n  = 3). The proposed platform was successfully applied to quantify malathion in real herbal samples (e.g., panax ginseng , astragalus membranaceus, lycium barbarum , and lonicera japonica ), achieving recoveries of 98.32 %–101.92 % with corresponding RSDs of 1.25 %–3.28 % ( n  = 3). The sensor is expected to be applied to the rapid screening of malathion residues in medicinal herbs.