Stable Dispersions of PVP-Protected Au/Pt/Ag Trimetallic Nanoparticles as Highly Active Colloidal Catalysts for Aerobic Glucose Oxidation

A simple, effective method has been demonstrated to synthesize Au/Pt/Ag trimetallic nanoparticles (TNPs) with an average diameter of 1.5 nm by reduction of the corresponding ions with rapid injection of NaBH4. The prepared TNPs were characterized by UV-vis, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy, and energy dispersion X-ray spectroscopy in high-resolution scanning transmission electron microscopy. The activity of the TNPs is several times higher than that of Au NPs with nearly the same particle size. The high catalytic activities of the Au/Pt/Ag TNPs can be ascribed to the following factors: (1) the small average size, about 1.5 nm in diameter, and (2) the formed negatively charged Au atoms due to electron donation of Ag neighboring atoms and poly(N-vinyl-2-pyrrolidone) acting as catalytically active sites for aerobic glucose oxidation. The presence of the negatively charged Au atoms was supported by XPS measurements and electron density calculation with density functional theory.