Novel electrochemical sensor based on modified glassy carbon electrode with graphene quantum dots, chitosan and nickel molybdate nanocomposites for diazinon and optimal design by the Taguchi method

[Display omitted] •A new design to chemically modify the electrode has been presented to determine DZ.•A chemometric method was used to optimize several parameters simultaneously.•The electrochemical study of diazinon was investigated using CV and DPV techniques.•This sensor has excellent sensitivity and reproducibility.•This method was used in the real sample in the presence of the matrix effect. In this study, a new sensitive and selective electrochemical sensor was offered based on the modification of activated glassy carbon electrode (GCEox) with graphene quantum dots, chitosan, and nickel molybdate (NiMoO4) nanocomposites for diazinon determination. A simple method of fabricating a sensor was presented based on covalent immobilization of polymer and nanoparticle due to functional groups on the GCEox surface. The surface of the constructed sensor was characterized by field-emission scanning electron microscopy (FE-SEM) and electrochemical impedance spectroscopy (EIS). Optimal factors of experiments have been evaluated and analyzed using Minitab software by the Taguchi method (TM). Under optimized conditions, the constructed sensor illustrated two linear ranges between 0.1 and 330 μM and a limit of detection (LOD) of 30 nM using differential pulse voltammetry methods. Analytical parameters were determined, and the results were compared with similarly reported data. The proposed sensor display reasonable stability, good reproducibility, selectivity to the detection of the diazinon. The effect of interferences was studied on the sensor's function, accompanied by the recovery analysis of diazinon in cucumber and tomato real samples.