Bismarck brown-assisted hydrothermal synthesis of nitrogen-modified reduced graphene oxide for selective electrochemical detection of dopamine

Abstract

Metal-free nitrogen-modified reduced graphene oxide (N-rGO) samples were prepared by convenient and cost-effective hydrothermal treatment of graphene oxide using two different concentrations of Bismarck Brown, namely 20 wt.% (rGO_BB20) and 50 wt.% (rGO_BB50). The synthesized N-rGO samples served as an electroactive platform for the highly selective electrochemical detection of dopamine (DA). Structural characterization using XPS demonstrated that Bismarck Brown-assisted hydrothermal treatment of GO leads to incorporation of nitrogen functional groups into the structure of graphene-based material, as evidenced by an increase in the nitrogen content in rGO_BB20 (3.8 at.%) and rGO_BB50 (10.6 at.%). Raman spectroscopy revealed increased FWHM(G) values for both samples, indicating interrupted carbon lattices and higher defective degrees due to nitrogen incorporation. Notably, rGO_BB20 exhibited a higher concentration of quaternary nitrogen species (6.1%), a larger specific surface area (52 m2 g−1), and higher electrical conductivity compared to rGO_BB50. This led to superior electrochemical performance, with rGO_BB20 demonstrating a lower detection limit (45 nM), higher sensitivity (0.61 μA μM−1 cm−2) in a 0–15 μM linear range, and 0.39 μA μM−1 cm−2 sensitivity in a wider 15–476 μM linear detection range compared to rGO_BB50. The proposed sensor displayed exceptional selectivity, reproducibility, repeatability, and stability.