Mechanistic studies on the galvanic replacement reaction between multiply twinned particles of Ag and HAuCl4 in an organic medium
Mechanistic studies on the galvanic replacement reaction between multiply twinned particles of Ag and HAuCl4 in an organic medium
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DOI：
10.1021/ja067800f
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发表时间：
2007-02-14
影响因子：
15
通讯作者：
Xia, Younan
中科院分区：
文献类型：
--
作者：
Lu, Xianmao;Tuan, Hsing-Yu;Xia, Younan
本文研究了11 ~ 14nm Ag和HAuCl4的多孪晶颗粒（MTPs）在氯仿中电取代反应的机理。随着HAuCl4与Ag的摩尔比的增加，我们监测了形貌和光谱的变化。反应的细节与以往在单晶银纳米立方体和立方体上观察到的不同。由于Au和Ag在富含空位和晶界缺陷的小MTPs内快速形成合金，因此在每个Ag模板表面没有形成完整的Au壳。取而代之的是，取代反应导致十面体或二十面体形状的银MTPs形成合金纳米环和纳米笼。对于由11 nm Ag MTPs制备的纳米纳米片和纳米笼，表面等离子体共振（SPR）峰可以在400 ~ 616 nm之间连续移动。当Ag mtp的尺寸增加到14 nm时，SPR峰可以进一步移动到740 nm，这是生物医学应用所寻求的波长。我们还研究了盖层配体和AgCl沉淀物对取代反应的影响。虽然通常由油胺包覆的Ag MTPs生成空心结构，但通过使用油酸或氧化三辛基膦（TOPO）等更强的包覆配体，我们获得的空心结构很少。研究发现，由于在AgCl和油胺之间形成了一种可溶配合物，额外添加的油胺对于形成控制良好、均匀且不受AgCl污染的中空结构至关重要。
This article presents a mechanistic study on the galvanic replacement reaction between 11- and 14-nm multiply twinned particles (MTPs) of Ag and HAuCl4 in chloroform. We monitored both morphological and spectral changes as the molar ratio of HAuCl4 to Ag was increased. The details of reaction were different from previous observations on single-crystal Ag nanocubes and cuboctahedrons. Because Au and Ag form alloys rapidly within small MTPs rich in vacancy and grain boundary defects, a complete Au shell did not form on the surface of each individual Ag template. Instead, the replacement reaction resulted in the formation of alloy nanorings and nanocages from Ag MTPs of decahedral or icosahedral shape. For the nanorings and nanocages derived from 11-nm Ag MTPs, the surface plasmon resonance (SPR) peak can be continuously shifted from 400 to 616 nm. When the size of Ag MTPs was increased to 14 nm, the SPR peak can be further shifted to 740 nm, a wavelength sought by biomedical applications. We have also investigated the effects of capping ligands and AgCl precipitate on the replacement reaction. While hollow structures were routinely generated from oleylamine-capped Ag MTPs, we obtained very few hollow structures by using a stronger capping ligand such as oleic acid or tri-n-octylphosphine oxide (TOPO). Addition of extra oleylamine was found to be critical to the formation of well-controlled, uniform hollow structures free of AgCl contamination thanks to the formation of a soluble complex between AgCl and oleylamine.