Au@PtAg core/shell nanorods: tailoring enzyme-like activities via alloying

Abstract

Pt nanoparticles (NPs) have been reported to demonstrate four kinds of enzyme-like activity including superoxide dismutase (SOD), catalase, oxidase and peroxidase. Some of these activities interfere with each other. For instance, as antioxidant enzyme mimics, their SOD and catalase activities are very helpful in scavenging related reactive oxygen species (ROSs). However, their oxidase-like and/or peroxidase-like activities may simultaneously oxidize some natural antioxidants, thus compromising the final anti-oxidation efficacy. Fine tuning different enzyme-like activities is therefore very important to realize the optimization of their functions. In this paper, our effort is focused in this direction by tailoring the electronic structure of Pt NPs via alloying with Ag. All four enzyme-like activities are found to be weakened by an increased Ag percentage in the alloy, as witnessed by decreased values of K_cat. The variation in the electronic structure also changes the substrate affinity. Introducing silver into Pt weakens the affinity for H₂O₂, which affects the limit of detection (LOD) for H₂O₂ and products with H₂O₂ involved. In contrast to Fe₃O₄ MNPs, for peroxidase-like activity, hydroxyl radicals are not involved in the oxidation of chromogenic substrates for the alloy nanostructures.