Experimental approach to the fundamental limit of the extinction coefficients of ultra-smooth and highly spherical gold nanoparticles
Experimental approach to the fundamental limit of the extinction coefficients of ultra-smooth and highly spherical gold nanoparticles
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DOI：
10.1039/c5cp02968f
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发表时间：
2015-01-01
影响因子：
3.3
通讯作者：
Yi, Gi-Ra
中科院分区：
文献类型：
--
作者：
Kim, Dong-Kwan;Hwang, Yoon Jo;Yi, Gi-Ra
金纳米颗粒（AuNPs）的理论消光系数主要通过米氏（Mie）首先创立的理想球体麦克斯韦方程（一般称为米氏理论）的解析求解来验证。然而，原则上，特别是对于相对较大的AuNPs（即>40 nm），通过实验验证还不能直接实现，因为传统提出的合成方法不可避免地会产生多边形的、非理想的Au纳米球。在这里，按照我们最近的工作 (ACS Nano, 2013, 7, 11064) 中报道的程序制备了 40-100 nm 的单晶、超光滑和高度球形的 AuNP。使用 Beer-Lambert 定律凭经验提取 40-100 nm 的理想球形 AuNP 的消光系数，然后与通过解析和数值方法获得的理论极限进行比较。与小面或多边形AuNPs 的消光系数相比，本文获得的理想球形AuNPs 的消光系数与理论极限更加一致。此外，为了进一步阐明球形的重要性，我们系统地将理想球形金纳米粒子与多边形对应物进行了比较；从理论和实验方面有效地解决了表面形态对光谱响应的作用。
The theoretical extinction coefficients of gold nanoparticles (AuNPs) have been mainly verified by the analytical solving of the Maxwell equation for an ideal sphere, which was firstly founded by Mie (generally referred to as Mie theory). However, in principle, it has not been directly feasible with experimental verification especially for relatively large AuNPs (i.e., >40 nm), as conventionally proposed synthetic methods have inevitably resulted in a polygonal shaped, non-ideal Au nanosphere. Here, mono-crystalline, ultra-smooth, and highly spherical AuNPs of 40-100 nm were prepared by the procedure reported in our recent work (ACS Nano, 2013, 7, 11064). The extinction coefficients of the ideally spherical AuNPs of 40-100 nm were empirically extracted using the Beer-Lambert law, and were then compared with the theoretical limits obtained by the analytical and numerical methods. The obtained extinction coefficients of the ideally spherical AuNPs herein agree much more closely with the theoretical limits, compared with those of the faceted or polygonal shaped AuNPs. In addition, in order to further elucidate the importance of being spherical, we systematically compared our ideally spherical AuNPs with the polygonal counterparts; effectively addressing the role of the surface morphology on the spectral responses in both theoretical and experimental manners.