Department of Chemistry, University of Illinois at Chicago , Chicago, Illinois 60607, United States.
J Am Chem Soc. 2017 Dec 27;139(51):18664-18669. doi: 10.1021/jacs.7b10645. Epub 2017 Dec 12.
Ultrahigh vacuum tip-enhanced Raman spectroscopy (UHV-TERS) combines the atomic-scale imaging capability of scanning probe microscopy with the single-molecule chemical sensitivity and structural specificity of surface-enhanced Raman spectroscopy. Here, we use these techniques in combination with theory to reveal insights into the influence of intermolecular interactions on the vibrational spectra of a N-N'-bis(2,6-diisopropylphenyl)-perylene-3,4:9,10-bis(dicarboximide) (PDI) self-assembled monolayer adsorbed on single-crystal Ag substrates at room temperature. In particular, we have revealed the lifting of a vibrational degeneracy of a mode of PDI on Ag(111) and Ag(100) surfaces, with the most strongly perturbed mode being that associated with the largest vibrational amplitude on the periphery of the molecule. This work demonstrates that UHV-TERS enables direct measurement of molecule-molecule interaction at nanoscale. We anticipate that this information will advance the fundamental understanding of the most important effect of intermolecular interactions on the vibrational modes of surface-bound molecules.
超高真空针尖增强拉曼光谱（UHV-TERS）将扫描探针显微镜的原子尺度成像能力与表面增强拉曼光谱的单分子化学灵敏度和结构特异性结合在一起。在这里，我们结合理论使用这些技术揭示了分子间相互作用对室温下吸附在单晶 Ag 衬底上的 N-N'-双（2,6-二异丙基苯基）-苝-3,4:9,10-二羧酸二酰亚胺（PDI）自组装单层的振动光谱的影响的深入了解。特别是，我们揭示了 PDI 在 Ag(111) 和 Ag(100)表面上的振动简并的消除，其中受扰最强的模式是与分子外围最大振动幅度相关的模式。这项工作表明，UHV-TERS 能够直接测量纳米尺度上的分子间相互作用。我们预计，这些信息将推动对分子间相互作用对表面结合分子振动模式的最重要影响的基础理解。
