Opt Lett. 2018 May 15;43(10):2332-2335. doi: 10.1364/OL.43.002332.
We have numerically demonstrated the feasibility and possibility to achieve broadband surface-enhanced Raman scattering (SERS) enhancement in the visible and near-infrared wavelength range using single nanoparticle (NP) dimer hotspot systems. Instead of the conventionally reported sub-100 nm, we find that the optimal NP size is as large as 200 nm in diameter for both Ag and Au. The key lies in the continuous arising of the bonding dipole plasmon mode and higher-order resonances at shorter wavelengths. Further, it is revealed that the near- and far-field optical responses of these hotspot systems correlate well with each other, despite the intrinsic enormous near- to far-field redshift for individual large NPs. The physical principles demonstrated here benefit significantly the fundamental understanding and engineering optimization of broadband SERS substrates.
我们已经通过数值方法证明了使用单个纳米粒子（NP）二聚体热点系统在可见光和近红外波长范围内实现宽带表面增强拉曼散射（SERS）增强的可行性和可能性。与传统报道的亚 100nm 不同，我们发现对于 Ag 和 Au，最佳 NP 尺寸为直径 200nm 左右。关键在于在较短波长下连续出现键合偶极子等离子体模式和高阶共振。此外，尽管单个大 NP 的近场到远场的固有红移非常大，但这些热点系统的近场和远场光学响应彼此之间很好地相关。这里展示的物理原理极大地有助于对宽带 SERS 基底的基础理解和工程优化。
