Addressing the surface coverage of Au nano-agglomerates and the electrochemical properties of modified carbon paste...

This article shows the formation of Au nano-agglomerates when increasing amounts of gold nanoparticles (AuNP) are incorporated into carbon paste electrodes. The surface coverage by this agglomerates is related to the electro-oxidation of a widely studied redox compound, ascorbic acid (AA); by analyzing the effect on the oxidation peak potential (E_p,a) and oxidation peak current (i_p,a). The effects of pH and scan rate on the E_p,a and i_p,_a were investigated by cyclic voltammetry, and enabled to estimate the transfer coefficient and the number of electrons involved in the rate determining step (αn_α), the standard heterogeneous rate constant (k_s), and the diffusion coefficient of the redox compound, being 0.52 and 3.5 × 10^-3 cm s^-1 and 6.3 × 10^-6 cm² s^-1, respectively. On the other hand, the sensing ability of the modified electrode was evaluated, obtaining a sensitivity of (63.2 ± 2.5) μA mM^-1, a detection limit of 2.7 μM and a quantification limit of 8.9 μM. Additionally, a computational model based on lattice-gas model and Monte Carlo simulations in the Grand Canonical Ensemble was proposed in order to reproduce the behavior of the system, in terms of i_p,a and E_p,a shift with increasing surface coverage by Au nano-agglomerates.