Gold nanoparticle dimer plasmonics: finite element method calculations of the electromagnetic enhancement to surface-enhanced Raman spectroscopy
Gold nanoparticle dimer plasmonics: finite element method calculations of the electromagnetic enhancement to surface-enhanced Raman spectroscopy
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DOI：
10.1007/s00216-009-2738-4
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发表时间：
2009-08-01
影响因子：
4.3
通讯作者：
Schatz, George C.
中科院分区：
文献类型：
--
作者：
McMahon, Jeffrey M.;Henry, Anne-Isabelle;Schatz, George C.
有限元方法进行计算，以确定消光光谱和电磁（EM）的贡献，表面增强拉曼光谱（Sers）的90纳米Au纳米粒子二聚体后，实验nanotags建模。计算结果表明，EM性能显着依赖于结区，特别是间距小于1 nm的纳米颗粒之间的距离。对于消光光谱，低于1 nm的间距导致从与孤立的纳米颗粒相关的600 nm等离子体激元最大值强烈红移的最大值。这一结果同意定性以及与实验透射电子显微镜图像和局部表面等离子体共振光谱，也提出。计算进一步表明，低于0.5纳米的间距，尤其是纳米颗粒轻微融合以产生微小缝隙，会导致EM增强10（10）或更大。假设在两个纳米颗粒周围都有均匀的Sers分子涂层，我们确定，无论分离如何，最高的EM场总是主导Sers信号。此外，我们确定，对于小的分离，小于3%的分子总是贡献大于90%的信号。
Finite element method calculations were carried out to determine extinction spectra and the electromagnetic (EM) contributions to surface-enhanced Raman spectroscopy (SERS) for 90-nm Au nanoparticle dimers modeled after experimental nanotags. The calculations revealed that the EM properties depend significantly on the junction region, specifically the distance between the nanoparticles for spacings of less than 1 nm. For extinction spectra, spacings below 1 nm lead to maxima that are strongly red-shifted from the 600-nm plasmon maximum associated with an isolated nanoparticle. This result agrees qualitatively well with experimental transmission electron microscopy images and localized surface plasmon resonance spectra that are also presented. The calculations further revealed that spacings below 0.5 nm, and especially a slight fusing of the nanoparticles to give tiny crevices, leads to EM enhancements of 10(10) or greater. Assuming a uniform coating of SERS molecules around both nanoparticles, we determined that regardless of the separation, the highest EM fields always dominate the SERS signal. In addition, we determined that for small separations less than 3% of the molecules always contribute to greater than 90% of the signal.