Maximizing the peroxidase-like activity of Pd@PtxRu4-x nanocubes by precisely controlling the shell thickness and their application in colorimetric biosensors

Although the application of nanoscale artificial enzymes in various industries is an attractive way to circumvent the intrinsic drawbacks of natural enzymes, their catalytic constant (K-cat) as a critical reaction parameter is far from satisfactory. Presented here is the rational design and fabrication of a unique peroxidase mimic catalyst based upon Pd@PtxRu4-x (1 <= x <= 3) prepared by coating PtRu alloy as conformal, ultrathin shells on Pd nanocrystals. Benefiting from an optimal Pt/Ru ratio and well-defined {100} facets, together with confining the Pt-Ru alloy to a shell of averagely 3.3-atomic-layer thick (i.e. Pd@Pt-Ru-3.3L), the nanocrystals exhibit the highest catalytic activity and kinetics (1.2 x 10(6) s(-1)), resulting in a significant increase of catalytic activity compared with the classical PtRu nanozyme (3.6 x 10(3) s(-1)) and horseradish peroxidase (4.0 x 10(3) s(-1)), respectively. The following density functional theory calculations demonstrate that the origin of the superior catalytic performance could be attributed to the modulation of the adsorption behavior of the key reaction intermediates on the surface. As a proof of concept, its peroxidase mimicking ability is adopted for sensing glucose and glutathione molecules in human serum, with a long linear range and high selectivity. This work opens new horizons for the future development of advanced catalysts based upon alloy nanocrystals for various applications.