College of Environmental Science and Engineering, North China Electric Power University , Beijing 102206, People's Republic of China.
CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology , Beijing 100190, People's Republic of China.
Nano Lett. 2017 Oct 11;17(10):6083-6089. doi: 10.1021/acs.nanolett.7b02583. Epub 2017 Oct 2.
Comprehension and modulation of optical activity at nanoscale have attracted tremendous interest in the past decades due to its potential application in many fields including chemical/biological sensing, artificial metamaterials, asymmetric catalysis, and so forth. As for the conventional molecular materials, magnetic field is among the most effective routes in inducing and manipulating their optical activity; whereas the magnetic optical activity at nanoscale calls for deeper understanding, especially for anisotropic noble metal nanoparticles. In this work, distinctly different magnetic circular dichroism (MCD) responses are demonstrated in gold nanorods (GNRs) with a derivative-shaped MCD signal corresponding to the transverse surface plasmon resonance (TSPR) band and a Gaussian-shaped signal at the position of the longitudinal surface plasmon resonance (LSPR) band. Furthermore, changing the aspect ratio of GNRs easily regulates such magnetoplasmonic CD response. More interestingly, GNR assemblies with different geometric configuration (end-to-end and side-by-side) show structure-sensitive magnetoplasmonic CD response. Armed with theoretical calculation, we clearly elucidate the intrinsic relationship of the resultant magnetoplasmonic CD response with the optical symmetry and geometry factor inside one-dimensional GNRs. This work not only greatly benefits our understanding toward the nature of SPR mode in anisotropic plasmonic nanostructures but also opens the way to achieve tunable magnetoplasmonic response, which will significantly advance the design and application of optical nanodevices.
在过去的几十年中，由于其在化学/生物传感、人工超材料、不对称催化等诸多领域的潜在应用，纳米尺度上的旋光理解和调控引起了极大的兴趣。对于传统的分子材料，磁场是诱导和操纵其旋光性最有效的途径之一；而纳米尺度上的磁光活性需要更深入的理解，特别是对于各向异性的贵金属纳米粒子。在这项工作中，金纳米棒（GNRs）表现出明显不同的磁圆二色性（MCD）响应，其中衍生型 MCD 信号对应于横向表面等离子体共振（TSPR）带，而高斯型信号位于纵向表面等离子体共振（LSPR）带的位置。此外，改变 GNR 的纵横比可以轻松调节这种磁等离子体 CD 响应。更有趣的是，具有不同几何构型（端到端和并排）的 GNR 组装体表现出结构敏感的磁等离子体 CD 响应。通过理论计算，我们清楚地阐明了所得磁等离子体 CD 响应与一维 GNR 内部的光学对称性和几何因子之间的内在关系。这项工作不仅极大地促进了我们对各向异性等离子体纳米结构中 SPR 模式本质的理解，而且为实现可调谐的磁等离子体响应开辟了道路，这将显著推进光学纳米器件的设计和应用。
