Department of Applied Chemistry, Tokyo University of Science Yamaguchi, SanyoOnoda-shi, Yamaguchi 756-0884, Japan.
J Colloid Interface Sci. 2011 Feb 1;354(1):131-8. doi: 10.1016/j.jcis.2010.10.036. Epub 2010 Oct 21.
PVP-protected Ag(core)/Au(shell) bimetallic nanoparticles of enough small size, i.e., 1.4nm in diameter were synthesized in one-vessel using simultaneous reduction of the corresponding ions with rapid injection of NaBH(4), 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 2months under ambient conditions. The highest activity (16,890mol-glucoseh(-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 2.0nm, 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 NaBH(4) into the starting solution and having the large mean particle size, showed a low catalytic activity.
采用一步法在一个容器中，通过快速注入 NaBH4 还原相应的离子，合成了足够小尺寸的 PVP 保护的 Ag（核）/Au（壳）双金属纳米粒子，粒径为 1.4nm，并用高分辨透射电子显微镜（HR-TEM）进行了表征。Ag（核）/Au（壳）双金属纳米粒子对有氧葡萄糖氧化表现出高且持久的催化活性，在环境条件下可稳定保持 2 个月以上。对于 Ag/Au 原子比为 2/8 的双金属纳米粒子，观察到最高的活性（16890mol-葡萄糖h-1mol-金属-1），其 TOF 值比具有几乎相同粒径的 Au 纳米粒子高几倍。与通常的 Au 纳米粒子相比，所制备的双金属纳米粒子具有更高的催化活性，这归因于：（1）较小的平均粒径，通常小于 2.0nm；（2）相邻 Ag 原子和保护 PVP 向 Au 活性位的电子电荷转移效应。相比之下，通过将 NaBH4 逐滴加入起始溶液中合成的具有较大平均粒径的 Ag-Au 合金纳米粒子表现出较低的催化活性。
