From discrete particles to spherical aggregates: a simple approach to the self-assembly of Au colloids.
From discrete particles to spherical aggregates: a simple approach to the self-assembly of Au colloids.
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DOI：
10.1002/chem.200400529
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发表时间：
2005-02
期刊：
影响因子：
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通讯作者：
Z. Zhong;Alamelu Suriya Subramanian;J. Highfield;K. Carpenter;A. Gedanken
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文献类型：
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作者：
Z. Zhong;Alamelu Suriya Subramanian;J. Highfield;K. Carpenter;A. Gedanken
在这里，我们展示了一种简单的，无模板的方法，通过NaBH4还原HAuCl4，在半胱氨酸（Cys）作为封盖剂的存在下形成球形金聚集体。所得的聚集体在溶液中相当稳定。溶液的pH值和Au:Cys的摩尔比是形成这种高度有序聚集体的两个关键经验因素。在微碱性pH值（7-10）和Au:Cys比值为1:0.5 ~ 1:2的条件下，形成30-80 nm的球形Au聚集体。在较低的Cys比率（Au:Cys>或=1:0.5）下，形成非常松散连接的聚集体；然而，在非常高的Cys比率（Au:Cys<或=1:3）下，获得高度分散的2-4 nm的Au颗粒，与原始胶体形式几乎无法区分。骨料粒度受组分浓度的显著影响；标准水平增加3倍，导致尺寸更大的金球形聚集体，200-500纳米。此外，我们使用了Cys和赖氨酸（Lys）的组合作为封盖剂/交联剂，并发现通过调整封盖剂/交联剂混合物中Cys和赖氨酸的比例，可以很容易地将金胶体聚集体的形态从线性变为球形。引入含硫醇（SH）有机酸降低了Cys的交联能力，特别是在长链酸的情况下。球形聚集体的完全破坏突出了Cys本身的重要性。在已知的金胶体表面化学背景下，提出了这种有序自组装过程的解释。
Here we demonstrate a simple, template-free approach to the formation of spherical gold aggregates through the reduction of HAuCl4 by NaBH4, in the presence of cysteine (Cys) as a capping agent. The resulting aggregates are quite stable in solution. The pH of the solution and the molar ratio of Au:Cys are two key empirical factors in the formation of such highly ordered aggregates. At slightly alkaline pH (7-10) and with Au:Cys ratios ranging from 1:0.5 to 1:2, spherical Au aggregates of 30-80 nm are formed. At lower Cys ratios (Au:Cys> or =1:0.5) very loosely linked aggregates are formed; however, at very high Cys ratios (Au:Cys< or =1:3), highly dispersed Au particles of 2-4 nm are obtained, which are virtually indistinguishable from the original colloidal form. Aggregate size is influenced markedly by component concentration; a 3-fold increase in standard levels resulted in Au spherical aggregates of a larger size, 200-500 nm. In addition, we used a combination of Cys and lysine (Lys) as a capping agent/cross-linker and found that the morphology of the Au colloid aggregates can be easily manipulated from a linear to a spherical form by adjusting the proportions of Cys and Lys in the capping agent/cross-linker mixture. The introduction of mercapto (SH)-containing organic acids reduced the cross-linking ability of Cys, especially in the case of long-chain acids. Complete disruption of the spherical aggregates highlights the importance of Cys per se. An explanation of this ordered self-assembly process is proposed, in the context of the known surface chemistry of Au colloids.