PVP-protected Ag-core/Au-shell bimetallic nanoparticles of enough small size, i.e., 1.4 nm in diameter were synthesized in one-vessel using simultaneous reduction of the corresponding ions with rapid injection of NaBH4, and characterized by HR-TEM. The Ag-core/Au-shell bimetallic nanoparticles show a high and durable catalytic activity for the aerobic glucose oxidation, and the catalyst can be stably kept for more than 2 months under ambient conditions. The highest activity (16,890 mol-glucose h(-1) mol-metal(-1)) was observed for the bimetallic nanoparticles with Ag/Au atomic ratio of 2/8, the TOF value of which is several times higher than that of Au nanoparticles with nearly the same particle size. The higher catalytic activity of the prepared bimetallic nanoparticles than the usual Au nanoparticles can be ascribed to: (1) the small average diameter, usually less than 2.0 nm, and (2) the electronic charge transfer effect from adjacent Ag atoms and protecting PVP to Au active sites. In contrast, the Ag-Au alloy nanoparticles, synthesized by dropwise addition of NaBH4 into the starting solution and having the large mean particle size, showed a low catalytic activity. (C) 2010 Elsevier Inc. All rights reserved.