A surface-graphenized pencil graphite electrode (SGPGE) served as an amperometric sensor for dopamine (DA). It was prepared through a one-step in-situ electrochemical graphene delamination. The graphite particles on the outer surface of the pencil graphite electrode (PGE) were delaminated by controlling the electrochemical delaminating conditions such as the applied anodic voltage and polarization duration, as well as the kind of electrolytes. The best conditions were identified by scanning electron microscopy, Raman spectra, cyclic voltammetry and differential pulse voltammetry (DPV). As a result, the electrode was endowed with an optimum combination of graphene delamination efficiency and electrochemical activity. The electrochemical treatment activates the surface sensing sites and improves the sensing performance. The NaOH-teated anodically graphenized electrode was used to sense dopamine by DPV. The best oxidation voltage of dopamine is at around 0.17 V (vs. SCE). The electrode respondsy to dopamine in the ranges of 0.15 to 45 μM, the detection limit is 8.2 nM (S/N = 3), and the sensitivity is 20.81 μA μM-1 cm-2. In real human urine samples, the sensor exhibited detection recoveries of 97.4-98.8% and low relative standard deviations of 3.49-3.92%. Graphical abstract Schematic presentation of a surface-graphenized pencil graphite electrode (SGPGE) for detecting dopamine. It was prepared by a one-step in situ electrochemical graphene delamination.
Keywords: Ascorbic acid; Differential pulse voltammetry; Electroanalysis; Electrochemical exfoliation; Epinephrine; Graphene; Uric acid; Urine.