Many of its multiple applications are related to its oxygen transfer and storage ability: electrochemical redox couple for mediator-less glucose sensor and control of automotive emissions [19]; electrolyte material [20]; and promotion of CO oxidation in direct alcohol fuel cells by supplying oxygen ions to the Pt catalyst [21�C23], among others. Electrochemical (bio)sensors based on CeO2-nanostructured-modified electrodes with enhanced electrocatalytic activity may facilitate the determination of many biomolecules. For example, some analytes determined by using CeO2-nanostructured-modified electrodes are: uric acid [24], ascorbic acid (AA) [25] and their mixture [12] at modified glassy carbon electrodes, dopamine [26] at a based carbon fiber microbiosensor, and urea [27] at an indium tin oxide (ITO)-coated glass substrate.
However, their analytical applications are not much extended despite of the good selectivity, sensitivity, reproducibility and stability obtained for many of these devices, what make them promising voltammetric sensors for real sample analysis. The reason for this fact is usually attributed to the poor electrical conductivity of the electrodes based on this metal oxide, which limits their applications.To overcome this shortage, the formation of nanocomposites, where at least one of the constituents possesses remarkable conductivity, may be a solution to increase sensitivity. In the literature it is possible to find many examples of these nanocomposites: Cu nanoparticles/ZnO [28], metal oxide/carbon nanotubes [29] and graphene/metal oxide core-shell nanostructures [30].
As far as we know there are only a few electroanalytical applications of similar CeO2-based nanostructures used as bi- or multi-functionalized Entinostat electrocatalysts: TiO2/CeO2 nanoparticles [27] and Pd nanoparticles/CeO2 nanoparticles [31].The present work reports the study of the electrocatalytic activity of CeO2 nanoparticles and AuSNPs/CeO2 nanocomposites. Both kinds of nanomaterials were deposited on the surface of a Sonogel-Carbon (SNGC) matrix by a simple drop-casting method and the sensing devices built with them were applied to the determination of AA, used as benchmark analyte. Different SNGC electrode configurations (CeO2 concentration and AuSNPs/CeO2 proportion used for the modification of the sensors) were tested. The advantages of employing CeO2 nanoparticles and AuSNPs/CeO2 nanocomposites in SNGC supporting material are also described. The electrochemical performance of the sensors was characterized by Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV). Up to the extent of our knowledge, this is one of the first electrochemical applications of AuSNPs/CeO2 nanocomposites as bi-functionalized electrocatalysts in (bio)sensors.