Electrochemical quantification of the electro-active surface area of Au nanoparticles supported onto an ITO electrode by means of Cu upd

•Au nanoparticles, AuNPs, were chemically synthesized and supported onto ITO.•Cu upd was carried out on the AuNPs-modified ITO electrode from H2SO4.•Cu upd electric charge, q, was evaluated from cycle voltammetry and chronoamperometry.•AuNPs’s electroactive surface area was evaluated from the recorded q values.•AuNPs-ITO electrode remains unaltered after this surface quantification process.

The active surface area, Asa, of gold nanoparticles, AuNPs, chemically synthesized and supported onto an ITO electrode (0.126 ± 0.006 cm2) was electrochemically quantified. To do this, a copper monolayer is formed onto AuNPs, due to Cu upd, when the AuNPs-modified ITO electrode is immersed in an aqueous solution containing Cu(II) ions. From both cyclic voltammetry and potentiostatic current transients recorded in the Cu upd region, corresponding to a full monolayer, it was possible to calculate the associated electric charge. From these values and those related with the charge density corresponding to a full monolayer of Cu ions onto the Au surface, the Asa of the AuNPs-modified ITO electrode was estimated. Regardless of the electrochemical method used, the Asa was practically the same, namely: (0.285 ± 0.046) cm2 and (0.265 ± 0.043) cm2 from potentiostatic and potentiodynamic experiments, respectively. After Asa evaluation the AuNPs-modified ITO remains free from Cu atoms. AFM measurements of Asa indicated that the values were comparable with those obtained by electrochemical means.

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