Beneficial impact of oxygen on the electrochemical performance of dopamine sensors based on N-doped reduced graphene oxides

Abstract Graphene-based electrochemical sensors are promising devices for direct and easy dopamine determination. In this work, N-doped reduced graphene oxides (N-rGOs) were prepared via hydrothermal treatment of graphene oxide (GO) and amitrole (3-amino-1,2,4-triazole) under different experimental conditions (varying reaction temperature and time), which resulted in each material having different oxygen content. Furthermore, the dopant nitrogen content was comparable in the three N-rGOs and it was primarily pyridinic in nature. The three synthesized N-rGOs were characterized by X-ray photoelectron spectroscopy, Fourier transformed infrared spectroscopy, scanning electron microscopy, and nitrogen sorption at 77 K. Glassy carbon electrodes modified with N-rGOs were prepared and used as active electrode materials in electrochemical sensors of dopamine (DA). The optimal operational pH was determined to be 7.4, which is also the physiological value. During the electrochemical detection of DA, it was found that there is a direct relationship between the oxygen content in N-rGO and electrochemical performance of these sensors. Thus, the detection of DA in the presence of ascorbic and uric acids was more sensitive and selective when the least reduced N-rGO sample was used. The attraction between the electronegative oxygen in the graphene structure and cationic DA facilitates the adsorption process which could explain these results. However, the limit of detection (LOD) was also higher in this case due to decreased conductivity.