Graphene oxide was added onto bare surface of GCE by dropping 2.5 lL of a GO-Nafion suspension 0.5 mg mL1 in ethanol containing 0.30% in Nafion. After modification, the electrode was dried
at room temperature. Parameters such as concentration of Nafion
and GO were optimized. Before electrodeposition process, the
GCE was immersed in hydrochloridric acid (37% w/w) for one minute to remove metal impurities from the electrode surface, and
then the electrode was rinsed with ultrapure water. Graphene
oxide suspension (0.50 mg mL1) in Nafion 0.30% were added onto
GCE surface by dripping 2.5 lL of the suspension, according to previous optimization.