Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China.
ACS Nano. 2010 Jun 22;4(6):3053-62. doi: 10.1021/nn100180d.
The plasmon coupling in the dimers of Au nanorods linked together at their ends with dithiol molecules has been studied. The plasmon coupling in the dimers composed of similarly sized nanorods gives antibonding and bonding plasmon modes. The plasmon wavelengths of the two modes have been found to remain approximately unchanged, with the scattering intensity ratio between the antibonding and bonding modes decaying rapidly as the angle between the nanorods is increased. This plasmon coupling behavior agrees with that obtained from both electrodynamic calculations and modeling on the basis of the dipole-dipole interaction. The electric field in the gap region is largely enhanced for the bonding mode, while that for the antibonding mode is even smaller than the far field, highlighting the importance of selecting appropriate plasmon modes for plasmon-enhanced spectroscopies. An anti-crossing-like behavior in the plasmon coupling energy diagram has further been revealed for linearly end-to-end assembled dimers composed of differently sized nanorods. This result will be useful for plasmonic applications where the plasmon wavelength is required to be controllable but without sacrificing the electric field enhancement.
我们研究了通过二硫键分子将金纳米棒的末端连接在一起形成的二聚体中的等离子体耦合。由相似大小的纳米棒组成的二聚体中的等离子体耦合产生了非键合和键合等离子体模式。发现这两种模式的等离子体波长基本保持不变，随着纳米棒之间夹角的增加，非键合和键合模式之间的散射强度比迅速衰减。这种等离子体耦合行为与基于偶极-偶极相互作用的电动力学计算和模型得到的结果一致。对于键合模式，间隙区域的电场得到了很大的增强，而对于非键合模式，电场甚至比远场还要小，这突出了选择合适的等离子体模式对于等离子体增强光谱学的重要性。对于由不同大小的纳米棒线性端到端组装而成的二聚体，我们进一步揭示了等离子体耦合能图中的类交叉行为。该结果将有助于等离子体应用，其中需要可控制的等离子体波长，而不会牺牲电场增强。
