▎ 摘　　要

In this work an electrochemical label free DNA biosensor (ds-DNA) for the determination of menadione (MD) was developed. The biosensor was constructed using a modified nanocomposite consisting of Fe3O4 nanoparticies decorated reduced graphene oxide (Gr) on a carbon paste electrode (CPE). Scanning electron microscope (SEM), energy dispersive X-ray (EDAX) and Fourier transform infrared (FT-IR) spectroscopy confirmed the structure of the synthesized nanocomposites (electrode composition). The Gr-Fe3O4 nanocomposites formed a sensitive layer with large surface area. Electrochemical studies revealed that modification of the electrode surface with ds-DNA and Gr-Fe3O4 nanocomposite significantly increases the oxidation peak currents and reduces the peak potentials of MD. Under the optimum conditions, calibration curve was linear in the range of 0.3-100.0 nM with a detection limit of 0.13 nM. The relative standard deviation for 50.0 nM was 3.90% (n = 5). The proposed biosensor was successfully applied to the determination of MD. (C) 2018 Elsevier B.V. All rights reserved.