Infrared spectroscopy is a powerful tool widely used in research and industry for a label-free and unambiguous identification of molecular species. Inconveniently, its application to spectroscopic analysis of minute amounts of materials, for example, in sensing applications, is hampered by the low infrared absorption cross-sections. Surface-enhanced infrared spectroscopy using resonant metal nanoantennas, or short “resonant SEIRA”, overcomes this limitation. Resonantly excited, such metal nanostructures feature collective oscillations of electrons (plasmons), providing huge electromagnetic fields on the nanometer scale. Infrared vibrations of molecules located in these fields are enhanced by orders of magnitude enabling a spectroscopic characterization with unprecedented sensitivity. In this Review, we introduce the concept of resonant SEIRA and discuss the underlying physics, particularly, the resonant coupling between molecular and antenna excitations as well as the spatial extent of the enhancement and its scaling with frequency. On the basis of these fundamentals, different routes to maximize the SEIRA enhancement are reviewed including the choice of nanostructures geometries, arrangements, and materials. Furthermore, first applications such as the detection of proteins, the monitoring of dynamic processes, and hyperspectral infrared chemical imaging are discussed, demonstrating the sensitivity and broad applicability of resonant SEIRA.

中文翻译：

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使用共振纳米天线的表面增强红外光谱

红外光谱法是一种功能强大的工具，广泛用于研究和工业中，以无标记且明确地鉴定分子种类。不便的是，其在微量材料的光谱分析中的应用，例如在传感应用中，受到低红外吸收横截面的阻碍。使用共振金属纳米天线或简称“共振SEIRA”的表面增强红外光谱技术克服了这一限制。这种金属纳米结构被共振激发，具有电子（等离激元）的集体振荡，在纳米级提供巨大的电磁场。位于这些场中的分子的红外振动增强了几个数量级，从而能够以前所未有的灵敏度进行光谱表征。在这篇评论中，我们介绍了共振SEIRA的概念，并讨论了潜在的物理原理，尤其是分子和天线激发之间的共振耦合，以及增强的空间范围及其随频率的缩放。基于这些基本原理，对最大化SEIRA增强效果的不同途径进行了综述，包括纳米结构的几何形状，排列和材料的选择。此外，讨论了诸如蛋白质检测，动态过程监测和高光谱红外化学成像等首次应用，证明了共振SEIRA的灵敏度和广泛的适用性。基于这些基本原理，对最大化SEIRA增强效果的不同途径进行了综述，包括纳米结构的几何形状，排列和材料的选择。此外，讨论了诸如蛋白质检测，动态过程监测和高光谱红外化学成像等首次应用，证明了共振SEIRA的灵敏度和广泛的适用性。基于这些基本原理，对最大化SEIRA增强效果的不同途径进行了综述，包括纳米结构的几何形状，排列和材料的选择。此外，讨论了诸如蛋白质检测，动态过程监测和高光谱红外化学成像等首次应用，证明了共振SEIRA的灵敏度和广泛的适用性。