Single-Molecule and Single-Particle-Based Correlation Studies between Localized Surface Plasmons of Dimeric Nanostructures with ∼1 nm Gap and Surface-Enhanced Raman Scattering
Single-Molecule and Single-Particle-Based Correlation Studies between Localized Surface Plasmons of Dimeric Nanostructures with ∼1 nm Gap and Surface-Enhanced Raman Scattering
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DOI：
10.1021/nl4034297
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发表时间：
2013-12-01
期刊：
影响因子：
10.8
通讯作者：
Nam, Jwa-Min
中科院分区：
文献类型：
--
作者：
Lee, Haemi;Lee, Jung-Hoon;Nam, Jwa-Min
了解等离子体耦合纳米结构内部的详细电磁场分布，特别是等离子体间隙接近1 nm的结构，是控制和利用等离子体纳米结构强光学特性的基础。使用多步 AFM 针尖匹配策略，使我们能够获得具有最佳信噪比和高可靠性的光谱。相关：局域表面等离子体（LSP）和表面增强拉曼散射（SEAS）之间的测量，在二聚体结构中检测到耦合的纵向偶极和高阶多极LSP，其中单个拉曼染料通过两个不同尺寸的Au-Ag核壳颗粒之间的单DNA杂交进行定位。在每个LSP分量的表征的基础上，首次观察到横向和纵向区域之间由于不同数量的激发四极LSP而产生的明显相位差。通过评估偶极和四极LSP的相对比例，我们发现这些间隙接近1 nm的二聚体LSP同时被激发，需要大的纵向键合偶极LSP/纵向键合四极LSP值才能产生高SERS信号强度。有趣的是，所检查的二聚体中的一小部分不仅沿着二聚体轴而且沿着耦合的横向偶极和纵向键合四极LSP之间的相互作用产生的方向表现出强烈的SERS强度。总体而言，我们的高精度相关测量策略采用具有纳米间隙的等离子体异二聚体，可以观察具有最佳信噪比的特征光谱特征以及具有明显SEAS行为的等离子体二聚体亚群，这些亚群被大多数二聚体群体隐藏，并且该方法和结果可用于了解SEAS增强因子值的整体分布和设计等离子体纳米天线结构。
Understanding the detailed electromagnetic field distribution inside a plasmonically coupled nanostructure, especially for structures with similar to 1 nm plasmonic gap, is the fundamental basis for the control and use of the strong optical properties of plasmonic nanostructures. Using a multistep AFM tip-matching strategy that enables us to gain the optical spectra with the optimal signal-to-noise ratio as well as high reliability. in correlation :measurement between localized surface plasmon (LSP) and surface-enhanced Raman scattering (SEAS), the coupled longitudinal dipolar and high-order multipolar LSPs were detected within a dimeric structure, where a single Raman dye is located via a single-DNA hybridization between two differently sized Au-Ag core-shell particles. On the basis of the characterization of each LSP component, the distinct phase differences, attributed to different quantities of the excited quadrupolar LSPs, between the transverse and longitudinal regimes were observed for the first time. By assessing the relative ratio of dipolar and quadrupolar LSPs, we found that these LSPs of the dimer with similar to 1 nm gap were simultaneously excited, and large longitudinal bonding dipolar LSP/longitudinal bonding quadrupolar LSP value is required to generate high SERS signal intensity. Interestingly, a minor population of the examined dimers exhibited strong SERS intensities along not only the dimer axis but also the direction that arises from the interaction between the coupled transverse dipolar and longitudinal bonding quadrupolar LSPs. Overall, our high-precision correlation measurement strategy with a plasmonic heterodimer with nm gap allows for the observation of the characteristic spectral features with the optimal signal-to-noise ratio and the subpopulation of plasmonic dimers with a distinct SEAS behavior, hidden by a majority of dimer population, and the method and results can be useful in understanding the whole distribution of SEAS enhancement factor values and designing plasmonic nanoantenna structures.