Au@Ag core-shell nanocubes with finely tuned and well-controlled sizes, shell thicknesses, and optical properties.
Au@Ag core-shell nanocubes with finely tuned and well-controlled sizes, shell thicknesses, and optical properties.
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DOI：
10.1021/nn102237c
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发表时间：
2010-11-23
期刊：
影响因子：
17.1
通讯作者：
Xia Y
中科院分区：
文献类型：
--
作者：
Ma Y;Li W;Cho EC;Li Z;Yu T;Zeng J;Xie Z;Xia Y
本文介绍了一种制备Au@Ag核壳纳米立方体的简便方法，其边长在13.4 ~ 50 nm范围内可控。合成涉及使用单晶，球形Au纳米晶体的大小为11 nm的种子在水溶液中，与抗坏血酸作为还原剂和十六烷基三甲基氯化铵（CTAC）作为封端剂。通过改变AgNO 3前体与Au种子的比例，可以从1.2到20 nm微调Ag壳层的厚度。我们还研究了生长机制，通过检查种子（由CTAC或CTAB封端）和封端剂（CTAC与CTAB）对所得核壳纳米晶体的尺寸和形状的影响。我们的研究结果清楚地表明，CTAC作为封端剂在Au种子和Au@Ag核-壳纳米立方体的合成中的效果比CTAB好得多。我们进一步研究了Au@Ag纳米立方体的局域表面等离子体共振特性随Ag壳层厚度的变化。通过与理论计算得到的消光光谱的比较，我们推导出了一个临界值，即壳层厚度在3 nm左右，此时Au核的等离子体激元激发将被Ag壳层完全屏蔽。此外，这些Au@Ag核-壳纳米立方体可以通过电置换反应转化为内部含有原始Au种子的Au基中空纳米结构。
This paper describes a facile method for generating Au@Ag core-shell nanocubes with edge lengths controllable in the range of 13.4 to 50 nm. The synthesis involved the use of single-crystal, spherical Au nanocrystals of 11 nm in size as the seeds in an aqueous system, with ascorbic acid serving as the reductant and cetyltrimethylammonium chloride (CTAC) as the capping agent. The thickness of the Ag shells could be finely tuned from 1.2 to 20 nm by varying the ratio of AgNO3 precursor to Au seeds. We also investigated the growth mechanism by examining the effects of seeds (capped by CTAC or CTAB) and capping agent (CTAC vs. CTAB) on both size and shape of the resultant core-shell nanocrystals. Our results clearly indicate that CTAC worked much better than CTAB as a capping agent in both the syntheses of Au seeds and Au@Ag core-shell nanocubes. We further studied the localized surface plasmon resonance properties of the Au@Ag nanocubes as a function of the Ag shell thickness. By comparing with the extinction spectra obtained from theoretical calculations, we derived a critical value around 3 nm for the shell thickness at which the plasmon excitation of the Au cores would be completely screened by the Ag shells. Moreover, these Au@Ag core-shell nanocubes could be converted into Au-based hollow nanostructures containing the original Au seeds in the interiors through a galvanic replacement reaction.
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