Optical Activity Governed by Local Chiral Structures in Two-Dimensional Curved Metallic Nanostructures
Optical Activity Governed by Local Chiral Structures in Two-Dimensional Curved Metallic Nanostructures
复制标题
二维弯曲金属纳米结构中局部手性结构控制的光学活性
作者：
T. Narushima;S. Hashiyada;H. Okamoto
手性纳米结构显示出宏观的光学活性。在纳米结构中，局域光学活性及其利手性并不是均匀的，而是根据纳米结构的形状在空间上分布的。在这项研究中，我们通过将两个或多个弧形结构线性连接在一个二维平面上来制备由金制成的曲线型链状纳米结构。用近场圆二色谱(CD)成像评价了链状结构的局域光学活性的空间特征，并借助经典电磁模拟进行了分析。电磁模拟预测，局部光学活动出现在弧形结构连接的拐点处。局部旋光性的左旋性依赖于拐点处局部手性的左旋性。手性链结构具有奇数拐点，局部旋光性相对于结构中心对称分布。相反，非手性链结构具有均匀的拐点，且呈反对称分布。在制备的链状纳米结构的近场CD图像中，观察到手性和非手性链状结构的局部CD对称和反对称分布，与模拟结果一致。对于具有两个或更多拐点的所制造的链结构，发现局部旋光性的左旋性由拐点的左旋性决定。因此，局域光学活性主要由金链结构拐点的局域手性所决定。链结构中所有拐点的总和被认为是决定宏观光学活性的主要因素.手性28：540-544,2016.©2016 Wiley期刊，Inc.
Chiral nanostructures show macroscopic optical activity. Local optical activity and its handedness are not uniform in the nanostructure, and are spatially distributed depending on the shape of the nanostructure. In this study we fabricated curved chain nanostructures made of gold by connecting linearly two or more arc structures in a two‐dimensional plane. Spatial features of local optical activity in the chain structures were evaluated with near‐field circular dichroism (CD) imaging, and analyzed with the aid of classical electromagnetic simulation. The electromagnetic simulation predicted that local optical activity appears at inflection points where arc structures are connected. The handedness of the local optical activity was dependent on the handedness of the local chirality at the inflection point. Chiral chain structures have odd inflection points and the local optical activity distributed symmetrically with respect to structural centers. In contrast, achiral chain structures have even inflection points and showed antisymmetric distribution. In the near‐field CD images of fabricated chain nanostructures, the symmetric and antisymmetric distributions of local CD were observed for chiral and achiral chain structures, respectively, consistent with the simulated results. The handedness of the local optical activity was found to be determined by the handedness of the inflection point, for the fabricated chain structures having two or more inflection points. The local optical activity was thus governed primarily by the local chirality of the inflection points for the gold chain structures. The total effect of all the inflection points in the chain structure is considered to be a predominant factor that determines the macroscopic optical activity.Chirality 28:540–544, 2016. © 2016 Wiley Periodicals, Inc.