Electrochemical biomimetic sensor based on oxime group-functionalized gold nanoparticles and nitrogen-doped graphene composites for highly selective and sensitive dimethoate determination

A novel, sensitive, and selective electrochemical sensor based on oxime-functionalized gold nanoparticles (AuNPs) and nitrogen-doped graphene (NG) composites (NG/AuNPs) was developed for the direct electrochemical detection of dimethoate, a non-electroactive organophosphorus pesticide (OP). 2-(4-Mercaptobutoxy)-1-naphthaldehyde oxime (MNO), a new organic molecule containing –SH and oxime synthesized by our group, was decorated onto electrodes through the S–Au bond between –SH of MNO and AuNPs. NG/AuNPs were modified on the electrode to provide acting sites for MNO and to amplify current response. The results indicated that the reduction current of MNO was increased, and the selectivity, sensitivity, and stability of the sensor were improved. Dimethoate was detected by using MNO as an electroactive probe through the nucleophilic substitution between oxime and dimethoate. Under optimal conditions, the sensor displayed a linear range from 1 × 10−12 to 4 × 10−8 M with a low detection limit of 8.7 × 10−13 M (S/N = 3). Results indicated that the sensor was successfully applied to detect dimethoate in water, tomato, and orange samples. Interference study analyses were investigated using the prepared electrode, which exhibited an acceptable result.