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首页> 外文期刊>Chemistry: A European journal >From Discrete Particles to Spherical Aggregates:A Simple Approach to the Self-Assembly of Au Colloids
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From Discrete Particles to Spherical Aggregates:A Simple Approach to the Self-Assembly of Au Colloids

机译：从离散粒子到球形聚集体：金胶体自组装的简单方法

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Here we demonstrate a simple,template-free approach to the formation of spherical gold aggregates through the reduction of HAuCl_4 by NaBH_4,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>=1:0.5) very loosely linked aggregates are formed;however,at very high Cys ratios (Au:Cys<=l: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)-contain-ing 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.
机译：在此我们展示了一种简单，无模板的方法，该方法在半胱氨酸（Cys）作为封端剂存在的情况下，通过NaBH_4还原HAuCl_4来减少HAuCl_4形成球形金聚集体。溶液和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。在弱碱性pH（7-10）下，Au：Cys比率为1：0.5至1：2，呈球形形成30-80 nm的金聚集体。在较低的Cys比率（Au：Cys> = 1：0.5）下形成非常疏松的团聚体;但是在非常高的Cys比率（Au：Cys <= l：3）下形成获得了2-4 nm的分散Au粒子，与原始胶体形式几乎没有区别。聚集体尺寸受组分浓度显着影响;标准水平增加3倍导致Au球形聚集体尺寸增大，200- 500 nm。此外，我们将Cys和赖氨酸（Lys）的组合用作封端剂/并发现通过调节封端剂/交联剂混合物中Cys和Lys的比例，可以很容易地将Au胶体聚集体的形态从线性变成球形，引入巯基（SH）-包含有机酸会降低Cys的交联能力，特别是在长链酸的情况下。完全破坏球形聚集体本身就凸显了Cys的重要性。对此有序自组装过程的解释提出了，在已知的金胶体表面化学的背景下。

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