Au nanoparticles embedded in mesoporous ZrO2 films: Multifunctional materials for electrochemical detection

Abstract

Multifunctional electrodes that combine the adsorption capacity of mesoporous oxides and the electrocatalytic activity of metallic nanoparticles (NPs) were designed, synthesized and tested for As (III) determination in aqueous solution. The electrodes were produced in two steps: first, mesoporous ZrO2 thin films were prepared by evaporation induced self-assembly and, afterwards, Au NPs were included within the pores by adsorption of Au (III) and subsequent chemical reduction. Different pore sizes and Au NPs loadings were explored, in order to study its effect over the sensor's performance. The obtained materials were characterized by electron microscopy, UV–vis spectrometry and X Ray Reflectometry. The electrochemical performance was studied by cyclic voltammetry. By comparison with empty ZrO2 and Au loaded SiO2 electrodes, it was possible to determine that the Au loaded ZrO2 electrodes present a synergetic effect for the As (III) detection, combining the electrocatalytic behavior of Au NPs and the adsorption capacity of mesoporous ZrO2. Moreover, a clear difference in the electrochemical performance of the material was observed depending on the pore size and the amount of incorporated Au NPs. In particular, a higher sensitivity (detection limit as low as 1.0 ppb of As (III)) was observed when small NPs (around 5 nm) were included within mesoporous films with bigger pore sizes (7 nm diameter) due to a higher accessibility.