According to a previous study, the charge required to reduce a monolayer of gold oxides on a polycrystalline gold surface in acidic medium is 489 C cm−2[44].
Based on the integration of the cathodic peak at 0.70 V, a charge (Q) of 27.2 C, which corresponds to an electroactive area of 0.056 cm2, was determined for GC/AuNPs/E. For GC/AuNPs/C, a charge of 27.8 C with an electroac-tive area of approximately 0.057 cm2 was determined. Therefore,no differences between the electroactive areas under our experimental conditions were observed.