Department of Chemistry, University, Houston, Texas 77005, USA.
ACS Nano. 2010 Aug 24;4(8):4657-66. doi: 10.1021/nn1011144.
We have explored the consequences of symmetry breaking on the coupled surface plasmon resonances in individual dimers of gold nanorods using single-particle dark-field scattering spectroscopy and numerical simulations. Pairs of chemically grown nanorods can exhibit wide variation in sizes, gap distances, and relative orientation angles. The combination of single-particle spectroscopy and theoretical analysis allowed us to discern the effects of specific asymmetry-inducing parameters one at a time. The dominant influence of symmetry breaking occurred for longitudinal resonances in strongly coupled nanorods in linear end-to-end configurations. In particular, we found that the normally dark antibonding dimer mode becomes visible when the sizes of the two nanorods are different. In addition, we observed a conductively coupled plasmon mode that was red-shifted by at least 250 nm from the bonding plasmon mode for the corresponding nontouching geometry. Gaining detailed insight into how symmetry breaking influences coupled surface plasmon resonances of individual nanorod dimers is an important step toward the general understanding of the optical properties of assemblies of chemically synthesized nanorods with unavoidable irregularities in size and orientation.
我们使用单粒子暗场散射光谱和数值模拟研究了对称破缺对金纳米棒单体中耦合表面等离子体共振的影响。通过化学方法生长的纳米棒对可以表现出尺寸、间隙距离和相对取向角的广泛变化。单粒子光谱学和理论分析的结合使我们能够一次辨别出特定非对称诱导参数的影响。在线性端到端配置中，强耦合纳米棒的纵向共振发生了主要的对称破缺影响。具体来说，我们发现当两个纳米棒的尺寸不同时，通常为暗的非键合二聚体模式变得可见。此外，我们观察到一个导电耦合等离子体模式，其相对于相应的非接触几何形状的键合等离子体模式红移了至少 250nm。深入了解对称破缺如何影响单个纳米棒二聚体的耦合表面等离子体共振，是朝着理解化学合成纳米棒组装体的光学性质迈出的重要一步，因为这些组装体在尺寸和取向方面不可避免地存在不规则性。
