Gold–Platinum Bimetallic Nanoclusters for Oxidase-like Catalysis

Guanosine monophosphate (GMP)-protected bimetallic nanoclusters of gold and platinum, Au–PtNCs-GMP, were prepared through an improved hydrothermal method under basic conditions, which show high catalytic activity for the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) under ambient conditions. Further systematic optimization of synthesis provides the best catalyst by feeding the materials 0.8 mM HAuCl4, 0.2 mM H2PtCl6, 4.0 mM NaOH, and 3.0 mM GMP, which reacted at 120 °C for 30 min, which show an initial maximum velocity (Vmax) of 253.8 × 10–8 M s–1 for TMB as the substrate. Such a value is at the top among the oxidase mimetics reported, which is essentially attributed to the synergistic effect between two metals in the small nanocluster. Moreover, the achieved Au–PtNCs-GMP show a short reaction time of 60 s for the oxidation of substrates, which is much faster than the previously reported ones. The in-depth mechanistic studies by 1H and 31P NMR spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy of the optimized Au–PtNCs-GMP reveal them to be of ultrasmall size with a unique ligand structure, particularly the synergistic effect between the two metals endow the product with a high catalytic performance. Therefore, the present study not only provides a novel bimetallic nanocluster as a good catalyst with highly efficient oxidase mimetics but also opens a way for the development of other oxidase mimetics.