Unveiling the Correlation between Nanometer-Thick Molecular Monolayer Sensitivity and Near-Field Enhancement and Localization in Coupled Plasmonic Oligomers
Unveiling the Correlation between Nanometer-Thick Molecular Monolayer Sensitivity and Near-Field Enhancement and Localization in Coupled Plasmonic Oligomers
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DOI：
10.1021/nn5028714
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发表时间：
2014-09-01
期刊：
影响因子：
17.1
通讯作者：
Maier, Stefan A.
中科院分区：
文献类型：
--
作者：
Koenig, Matthias;Rahmani, Mohsen;Maier, Stefan A.
金属纳米团簇，有时被称为超分子或等离子体低聚物，表现出有趣的光学性质，如法诺共振和光手性。这些特性保证了各种实际应用，特别是在超灵敏的生化传感中。本文通过实验研究了等离子体五聚体和四聚体对自组装纳米厚烷硫醇单层吸附的敏感性。发现这种低聚物的单层灵敏度明显高于单等离子体纳米粒子，这取决于纳米簇的排列、组成纳米粒子的形状和等离子体共振波长。结合全波数值模拟结果和电磁摄动理论，揭示了每个纳米团簇中产生的等离子体“热点”的近场强度增强和空间定位与灵敏度之间的直接关系。我们的观察结果超越了传统的考虑（如优化纳米颗粒几何形状或缩小共振线宽度），以提高基于金属纳米簇的生物传感器的传感性能，并打开了使用等离子体纳米簇进行单分子检测和鉴定的可能性。
Metal nanoclusters, sometimes called metamolecules or plasmonic oligomers, exhibit interesting optical properties such as Fano resonances and optical chirality. These properties promise a variety of practical applications, particularly in ultra-sensitive biochemical sensing. Here we investigate experimentally the sensitivities of plasmonic pentamers and quadrumers to the adsorption of self-assembled nanometer-thick alkanethiol monolayers. The monolayer sensitivity of such oligomers is found to be significantly higher than that of single plasmonic nanoparticles and depends on the nanocluster arrangement, constituent nanoparticle shape, and the plasmon resonance wavelength. Together with full-wave numerical simulation results and the electromagnetic perturbation theory, we unveil a direct correlation between the sensitivity and the near-field intensity enhancement and spatial localization in the plasmonic "hot" spots generated in each nanocluster. Our observation is beyond conventional considerations (such as optimizing nanoparticle geometry or narrowing resonance line width) for improving the sensing performance of metal nanoclusters-based biosensors and opens the possibilities of using plasmonic nanoclusters for single-molecule detection and identification.