Two-Dimensional Infrared Spectroscopy with Local Plasmonic Fields of a Trimer Gap-Antenna Array
Two-Dimensional Infrared Spectroscopy with Local Plasmonic Fields of a Trimer Gap-Antenna Array
复制标题
DOI：
10.1021/acs.jpclett.8b01937
复制
发表时间：
2018-08-16
影响因子：
5.7
通讯作者：
Chuntonov, Lev
中科院分区：
文献类型：
--
作者：
Cohn, Bar;Engelman, Ben;Chuntonov, Lev
半波长等离子体天线被调谐到与分子振动激发共振，已经被证明可以增强多个数量级的2GHz信号。我们设计了对称三聚体间隙天线的双简并平面内等离子体激元正常模式，其具有由适当偏振的光激发的正交偶极矩，以将增强场局部化到天线的间隙中。振动激发充当等离子体激元场的灵敏探针。薄分子膜的2D光谱表明，发射增强信号的分子经历具有与激发激光脉冲偏振无关的方向的电场。我们的研究结果说明了大信号放大的分子靠近天线表面的共振等离子体激元，其中增强场的方向遵循金属表面边界条件，和相关的限制的偏振选择性光谱之间的权衡。由增强信号报告的超快量子动力学不受其与等离子体激元激发的相互作用的影响。
Half-wavelength plasmonic antennas tuned to resonance with molecular vibrational excitations have been demonstrated to enhance 2DIR signals by multiple orders of magnitude. We design doubly degenerate in-plane plasmonic normal modes of the symmetric trimer gap-antenna, which have orthogonal dipole moments excited by light of the appropriate polarization, to localize the enhanced field into the antenna's gap. Vibrational excitations serve as sensitive probes of the plasmonic fields. 2DIR spectroscopy of thin molecular films indicates that molecules emitting enhanced signals experience an electric field with a direction independent of the excitation laser pulse polarization. Our results illustrate the trade-off between the large signal amplification in molecules close to the antenna surface by resonant plasmons, where the direction of the enhanced fields follows metal surface boundary conditions, and the associated limitations for the polarization-selective spectroscopy. The ultrafast quantum dynamics reported by the enhanced signals is not affected by its interaction with plasmonic excitation.