Xu Haiyan, Wang Jianping
Beijing National Laboratory for Molecular Sciences, Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China.
University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
Phys Chem Chem Phys. 2023 Nov 1;25(42):29042-29049. doi: 10.1039/d3cp03880g.
The detection performance of traditional infrared spectroscopy can be very limited in the case of molecular vibrational modes with low absorption cross-sections. On account of its electric field enhancement, plasmonic antenna can be combined with infrared spectroscopy to realize surface enhanced infrared detection and characterization of molecules. In this work, a super asymmetric cross antenna structure with tunable dual-frequency resonance and a high enhancement factor is designed. By systematically studying the transmission spectrum and charge distribution of this super asymmetric cross antenna structure, the physical origin of the dual-frequency resonance and its tunability are characterized in detail. In addition, in order to target desired molecular ensembles, the relationship between the resonance frequency and electric-field intensity of the two resonance modes and the parameters of structure and incident light are examined, yielding an enhancement factor close to 100 in the desired frequency region. Finally, the experimental results show that the proposed super asymmetric cross antenna structure can indeed generate dual-frequency resonances, agreeing reasonably with the theoretical results. It is believed that the super asymmetric cross antenna structure can be widely used to sensitively detect trace molecules, and in monolayered chemistry and bio-molecules, allowing their structures and dynamics to be studied using nonlinear infrared spectroscopy.
在分子振动模式具有低吸收截面的情况下，传统红外光谱的检测性能可能非常有限。由于其电场增强作用，等离子体天线可与红外光谱相结合，以实现表面增强红外检测和分子表征。在这项工作中，设计了一种具有可调双频共振和高增强因子的超不对称交叉天线结构。通过系统地研究这种超不对称交叉天线结构的透射光谱和电荷分布，详细表征了双频共振的物理起源及其可调性。此外，为了针对所需的分子集合，研究了两种共振模式的共振频率与电场强度以及结构和入射光参数之间的关系，在所需频率区域产生了接近100的增强因子。最后，实验结果表明，所提出的超不对称交叉天线结构确实可以产生双频共振，与理论结果合理吻合。相信这种超不对称交叉天线结构可广泛用于灵敏检测痕量分子，以及单层化学和生物分子，从而能够使用非线性红外光谱研究它们的结构和动力学。
