The creation of artificial enzymes that mimics the complexity and function of natural systems has been a major challenge for the past two decades. The use of nanomaterials as peroxidase mimetic systems have recently been of great importance since it has been shown the intrinsic peroxidase activity of Fe2O3 magnetic nanoparticles. Subsequently, other nanomaterials including gold nanoparticles (AuNPs), FeS nanosheets, CoFe2O4, CuO, Co3O4, V2O5, carbon nanomaterials, Ru2O and CeO2 were applied as enzyme mimics for peroxidase. Compared with the natural enzymes, these nanoparticles are low cost, stable against denaturation at high concentration of substrate, easily stored and prepared. Recently, the application of cerium oxide nanoparticles (CeNPs) as an enzyme mimic was based on its antioxidant activity, which is directly related to a lower energy conversion of his redox Ce4+/ Ce3+ pair. The functionalization of its surface with gold nanoparticles (AuNPs) increases its stability, conductivity, and biocompatibility, being more effective for biomolecules immobilization and a desirable interface for electrochemical biosensing. The strong interest on semiconductor oxides decorated with metal nanoparticles emerged from their optical properties. A greatly increased performance and selectivity of these devices in the degradation of organic dyes, alcohols oxidation and gas sensing is based on the strong surface plasmon resonance band (SPR) presented by metallic nanoparticles. By manipulating size, morphology and composition of these particles, the SPR maximum can be adjusted throughout the visible and in infrared region, allowing the construction of a more versatile and less expensive sensor to be applied in one specific wavelength. In this context, a new term "Plasmonic Photocatalysis" arise, which is considered a promising technology for high performance photocatalysis. In this sense, it is emphasized that the plasmonic activity of hybrid CeO2/Au systems as enzyme mimetic systems have not been investigated for biological molecules monitoring and it will be one of the main objectives of this present work. A detailed study of interfacial semiconductor oxide/metal nanoparticle synergistic effects will be held in order to understand how the energy transfer process from metallic nanoparticle to semiconductor oxide will be able to modify the Ce4+/Ce3+ rate and, therefore, influencing its biosensing performance.
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