▎ 摘　　要

Modification of glassy carbon electrode (GCE) using cysteine immobilized Fe3O4@Au core-shell nanoparticles (Fe3O4@Au@Cys) and reduced graphene oxide (rGO) nanocomposite has been offered to fabricate a nitritesensitive electrochemical sensor. The offered sensor (Fe3O4@Au@Cys/rGO/GCE) depicted the catalytic effect toward nitrite (NO2) monitoring using voltammetric methods. The techniques of field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and electrochemical impedance spectroscopy (EIS) were applied to recognize the morphology and structure of the prepared nanocomposite. This sensor depicted an excellent electrocatalytic response for NO2 detection under optimized conditions. Two linear segments in the calibration plot have been obtained in the range of 0.03-344 and 344-2215 mu M with the limit of detection (LOD) 8 nM. The prepared sensor results for the quantitative measurement of NO2 in human serum, urine, and water were admissible. The fabricated sensor in all evaluations illustrated high stability and reproducible demeanor. The analytical results were determined and compared with the reported results of a similar method in the literature.