La-doped NiWO4 coupled with reduced graphene oxide for effective electrochemical determination of diphenylamine

Diphenylamine (DPA) is a harmful pesticide widely used to control post-harvest scald of fruits. In this study, rapid and sensitive determination of DPA was realized by the development of an effective electrochemical sensor, which was fabricated by coupling La-doped NiWO4 nanoparticles (La/NiWO4) with reduced graphene oxide (rGO), and the obtained rGO/La/NiWO4 nanocomposite was modified on glassy carbon electrodes (GCEs). The morphologies, structures and compositions were well characterized, and the effects of La doping and the introduction of rGO on the crystal structure and electrochemical performance were discussed. The incorporation of both La and rGO was found to enhance the active surface area and improve conductivity, resulting in the enhanced electrocatalytic performance of rGO/La/NiWO4/GCE, including a wide linear range (0.01-500 μM), a low detection limit (0.0058 μM) and high sensitivity (1.778 μA μM-1 cm-2). The fabricated sensor was further used for DPA detection in fresh apple extract to evaluate its practicality and demonstrated excellent recoveries ranging from 99.52 to 104.70%.