Optical properties of coupled metallic nanorods for field-enhanced spectroscopy
Optical properties of coupled metallic nanorods for field-enhanced spectroscopy
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DOI：
10.1103/physrevb.71.235420
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发表时间：
2005-06-01
影响因子：
3.7
通讯作者：
Mallouk, T
中科院分区：
文献类型：
--
作者：
Aizpurua, J;Bryant, GW;Mallouk, T
研究了耦合金属纳米棒的光学性质，以探讨耦合等离子体结构在场增强光谱学中的应用。耦合纳米棒的光散射计算与边界元法，包括延迟。耦合纳米棒系统的模式计算的边界电荷方法，并讨论其对称性。孤立纳米棒和成对纳米棒的类似散射行为可以掩盖产生近场增强的非常不同的局部响应。孤立棒的响应随棒长的增加而红移，因为棒内恢复力减小。近场和远场响应随着杆长度的增加而单调增加（沿杆沿着增加极化）。对于耦合的纳米棒，耦合将电荷定位在棒端之间的差距处并分裂简并模式。局部电荷去极化的intrarod响应，并提供了一个额外的红移。此外，纳米棒之间的差距中的近场增强通过差距处的耦合诱导电荷局部化而显著增加。对于短纳米棒，耦合系统中的近场响应由限定差距的棒端的几何形状决定。对于较长的纳米棒，耦合系统中的响应由棒长度决定。改变纳米棒的尺寸和几何形状以修改棒间耦合对局部场增强具有主要影响。环境和实际金属材料的影响对场增强没有那么大的影响。
The optical properties of coupled metallic nanorods are studied to investigate the use of coupled plasmonic structures in field-enhanced spectroscopies. Light scattering by coupled nanorods is calculated with the boundary element method, including retardation. The modes of coupled nanorod systems are calculated by the boundary charge method and discussed in terms of their symmetry. Similar scattering behavior for isolated nanorods and pairs of nanorods can mask the very different local responses that produce near-field enhancement. The response of isolated rods redshifts with increasing rod length because intrarod restoring forces are reduced. The near- and far-field responses increase monotonically with increasing rod length (increasing polarization along the rod). For coupled nanorods, coupling localizes charge at the gap between the rod ends and splits degenerate modes. The localized charge depolarizes the intrarod response and provides an additional redshift. Moreover, the near-field enhancement in the gap between the nanorods is dramatically increased by coupling-induced charge localization at the gap. For short nanorods, the near-field response in coupled systems is determined by the geometry of the rod ends that define the gap. For longer nanorods, the response in coupled systems is determined by the rod length. Changing the dimensions and geometry of the nanorods to modify the interrod coupling has a major effect on the local-field enhancement. The effects of the environment and the actual metallic material do not have as big an influence on the field enhancement.