Catalytically highly active PVP-protected AgAu bimetallic nanoparticles (BNPs) less than 2 nm in diameter were fabricated by simultaneous physical mixture of aqueous dispersions of Au clusters with Ag+ ions. The prepared AgAu BNPs, the dispersion of which was stably kept for more than 2 months under ambient conditions, were characterized by UV-vis, ICP, HR-TEM, and EDS in HR-STEM. The prepared BNP colloidal catalysts possessed a high activity for aerobic glucose oxidation. The highest activity of 3.77 mol-glucoses(-1) mol-metal(-1) was observed for the BNPs prepared with Ag/Au atomic ratio of 2/8, which was more than two times higher than that of Au nanoparticles with nearly the same particle sizes. (C) 2012 Elsevier B.V. All rights reserved.