Chemical Identification of Single Ultrafine Particles Using Surface-Enhanced Infrared Absorption
Chemical Identification of Single Ultrafine Particles Using Surface-Enhanced Infrared Absorption
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DOI：
10.1103/physrevapplied.11.014036
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发表时间：
2019-01-18
影响因子：
4.6
通讯作者：
Pucci, Annemarie
中科院分区：
文献类型：
--
作者：
Huck, Christian;Tzschoppe, Michael;Pucci, Annemarie
在过去的十年中，表面增强红外吸收（SEIRA）已被证明是一种强有力的方法，以增强薄分子层的振动信号。到目前为止，很少有人注意到使用SEIRA检测和表征纳米尺寸颗粒（如超细灰尘颗粒）的可能性。在这里，我们报告的SEIRA测量表明，即使是一个深亚波长尺寸小于100 nm的单个粒子可以检测到和化学特征与标准红外显微光谱。我们的方法是基于蝴蝶结形状的Au孔的等离子体共振，这些孔被设计成极大地增强纳米尺寸的二氧化硅颗粒的材料特定的声子激发。我们表明，蝴蝶结的几何形状是特别适合于单粒子光谱，因为它结合了一个强烈的电磁热点的优势，其大小可以调整到粒子的尺寸，很容易定位的超细尘埃粒子内的热点。与数值计算一致，我们表明，可以实现的检测限方面的颗粒直径小于20 nm，这对应于低于0.002的直径的真空波长的比率。我们的方法提供了从最微小的颗粒中分析红外波段的可能性，从而为基于SEIRA的设备能够感知超细灰尘铺平了道路。
In the past decade, it has been demonstrated that surface-enhanced infrared absorption (SEIRA) is a powerful method to enhance vibrational signals of thin molecular layers. Much less attention has so far been given to the possibility of using SEIRA for the detection and characterization of nanometer-sized particles, such as ultrafine dust particles. Here, we report on SEIRA measurements demonstrating that even one single particle with a deeply subwavelength dimension of less than 100 nm can be detected and chemically characterized with standard infrared microspectroscopy. Our approach is based on plasmonic resonances of bowtie-shaped Au apertures that are designed to extraordinarily enhance the material-specific phononic excitations of a nanometer-sized silica particle. We show that the bowtie geometry is especially suited for single-particle spectroscopy, as it combines the advantage of an intense electromagnetic hot spot, the size of which can be adjusted to the particle dimension, with easy positioning of ultrafine dust particles inside that hot spot. In agreement with numerical calculations, we show that a detection limit in terms of a particle diameter of less than 20 nm can be achieved, which corresponds to a ratio of the diameter to the vacuum wavelength below 0.002. Our approach offers the possibility of analyzing infrared bands from tiniest particles and thus paves the way toward SEIRA-based devices that can sense ultrafine dust.