Graphene-like carbon nitride nanosheet as a novel sensing platform for electrochemical determination of tryptophan

In this paper, a new and facile strategy has been demonstrated for the electrochemical determination of tryptophan (Trp), based on graphite-like carbon nitride (g-C₃N₄) nanosheets modified glassy carbon (CNNS/GC) electrode. The g-C₃N₄ nanosheets were obtained via exfoliating bulk graphitic carbon nitride (bg-C₃N₄), which was synthesized using a thermal poly-condensation process. The obtained g-C₃N₄ nanosheets were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). The results confirmed graphite-like structure with thickness of about 6-8nm. The as-synthesized g-C₃N₄ nanosheets were closely attached to the surface of GC electrode to construct electrochemical sensor without needing any film-forming agents. The CNNS/GC electrode exhibited good electrocatalytic activity towards Trp, and hereby some parameters, including scan rate and pH effect on Trp determination were investigated. Under the optimum experimental conditions, the oxidation peak currents had good linear relationship with Trp concentrations in the range of 0.1-110μM and a detection limit of 0.024μM (S/N=3) was achieved. In addition, the obtained sensor showed good sensitivity, favorable repeatability, and long-term stability. Finally, the proposed electrochemical sensor has been successfully applied for the determination of Trp concentration in real samples with satisfactory results.