An in situ quick XAFS spectroscopy study on the formation mechanism of small gold nanoparticles supported by porphyrin-cored tetradentate passivants
An in situ quick XAFS spectroscopy study on the formation mechanism of small gold nanoparticles supported by porphyrin-cored tetradentate passivants
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DOI：
10.1039/c1cp20231f
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发表时间：
2011-01-01
影响因子：
3.3
通讯作者：
Tanaka, Tsunehiro
中科院分区：
文献类型：
--
作者：
Ohyama, Junya;Teramura, Kentaro;Tanaka, Tsunehiro
我们以前报道过一种以卟啉为核心的四齿钝化剂，它在卟啉平面的一个表面上具有两个二硫键，可以通过在DMF中一锅还原HAuCl（4）来制备单层保护的金纳米颗粒，尺寸为2-4 nm。所得的纳米颗粒小于使用相同的S/Au摩尔比的单齿钝化剂制备的那些。为了研究小的金纳米粒子的形成机制，在卟啉为核心的四齿钝化剂或结构相关的单齿钝化剂的存在下，金纳米粒子的形成进行了研究，通过时间分辨快速X射线吸收精细结构光谱。结果表明，在两种情况下，溶液中的Au离子在NaBH（4）还原HAuCl（4）后均被还原成小的Au团簇，即成核，但团簇的大小随初始S/Au摩尔比和钝化剂的结构而变化。因此，Au核的大小受钝化剂的动力学控制。有趣的是，与单齿钝化剂相比，卟啉核心的四齿钝化剂可以稳定尺寸为2-4 nm的较小的金纳米颗粒，但是其在捕获在非常早期阶段形成的Au核方面效率较低。
We previously reported that a porphyrin-cored tetradentate passivant, which has two disulfide straps over one face of the porphyrin plane, can produce monolayer-protected gold nanoparticles, 2-4 nm in size, by the one-pot reduction of HAuCl(4) in DMF. The resulting nanoparticles are smaller than those prepared using the same S/Au molar ratio of a monodentate passivant. To examine the formation mechanism of small gold nanoparticles, the formation of gold nanoparticles in the presence of porphyrin-cored tetradentate passivants or a structurally related monodentate passivant was studied by time-resolved quick X-ray absorption fine structure spectroscopy. The results demonstrated that all of Au ions in solution are reduced to compose small Au clusters, i.e. nuclei, just after the NaBH(4) reduction of HAuCl(4) in both cases, but their size varied with the initial S/Au molar ratios and structure of the passivants. Thus, the size of Au nuclei was kinetically controlled by the passivants. Interestingly, the porphyrin-cored tetradentate passivant could stabilize smaller gold nanoparticles, 2-4 nm in size, but it was less efficient in trapping the Au nuclei formed at a very early stage, in comparison to the monodentate passivant.