Spatial Extent of Plasmonic Enhancement of Vibrational Signals in the Infrared
Spatial Extent of Plasmonic Enhancement of Vibrational Signals in the Infrared
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DOI：
10.1021/nn5017204
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发表时间：
2014-06-01
期刊：
影响因子：
17.1
通讯作者：
Pucci, Annemarie
中科院分区：
文献类型：
--
作者：
Neubrech, Frank;Beck, Sebastian;Pucci, Annemarie
等离子体纳米天线可以将分子的红外振动提高几个数量级。基于共振激发金属纳米粒子的受限电磁近场，这种天线辅助的表面增强红外光谱能够检测到纳米级结构附近的微量分析物。在其他重要参数中，分析物的振动振荡器与纳米天线表面的距离决定了信号的增强。对于传感应用，这是一个特别重要的问题，因为由于功能层和大尺寸的生物分子，蛋白质或细菌，感兴趣的振动偶极子可能位于远离天线表面的地方。因此，距离和信号增强之间的关系是至关重要的，在这里用原位红外光谱法测量探针层的生长过程。我们的结果表明，信号增强减弱，等离子体共振位移的有效饱和超过100 nm。在超高真空条件下进行的实验得到了数值计算的支持。
Infrared vibrations of molecular species can be enhanced by several orders of magnitude with plasmonic nanoantennas. Based on the confined electromagnetic near-fields of resonantly excited metal nanoparticles, this antenna-assisted surface-enhanced infrared spectroscopy enables the detection of minute amounts of analytes localized in the nanometer-scale vicinity of the structure. Among other important parameters, the distance of the vibrational oscillator of the analyte to the nanoantenna surface determines the signal enhancement. For sensing applications, this is a particularly important issue since the vibrating dipoles of interest may be located far away from the antenna surface because of functional layers and the large size of biomolecules, proteins, or bacteria. The relation between distance and signal enhancement is thus of paramount importance and measured here with in situ infrared spectroscopy during the growth of a probe layer. Our results indicate a diminishing signal enhancement and the effective saturation of the plasmonic resonance shift beyond 100 nm. The experiments carried out under ultra-high-vacuum conditions are supported by numerical calculations.