Northwestern University , Department of Chemistry, 2145 Sheridan Road, Evanston, IL 60208, United States.
J Am Chem Soc. 2014 Mar 12;136(10):3881-7. doi: 10.1021/ja411899k. Epub 2014 Feb 26.
Tip-enhanced Raman spectroscopy (TERS) provides chemical information for adsorbates with nanoscale spatial resolution, single-molecule sensitivity, and, when combined with scanning tunneling microscopy (STM), Ångstrom-scale topographic resolution. Performing TERS under ultrahigh-vacuum conditions allows pristine and atomically smooth surfaces to be maintained, while liquid He cooling minimizes surface diffusion of adsorbates across the solid surface, allowing direct STM imaging. Low-temperature TER (LT-TER) spectra differ from room-temperature TER (RT-TER), RT surface-enhanced Raman (SER), and LT-SER spectra because the vibrational lines are narrowed and shifted, revealing additional chemical information about adsorbate-substrate interactions. As an example, we present LT-TER spectra for the rhodamine 6G (R6G)/Ag(111) system that exhibit such unique spectral shifts. The high spectral resolution of LT-TERS provides intramolecular insight in that the shifted modes are associated with the ethylamine moiety of R6G. LT-TERS is a promising approach for unraveling the intricacies of adsorbate-substrate interactions that are inaccessible by other means.
尖端增强拉曼光谱（TERS）提供了具有纳米级空间分辨率、单分子灵敏度的吸附物的化学信息，并且当与扫描隧道显微镜（STM）结合使用时，还具有埃级的形貌分辨率。在超高真空条件下进行 TERS 实验可以保持原始的、原子级平滑的表面，而液氦冷却则最小化了吸附物在固体表面上的扩散，从而可以直接进行 STM 成像。低温 TERS（LT-TER）光谱与室温 TERS（RT-TER）、RT 表面增强拉曼（SER）和 LT-SER 光谱不同，因为振动线变窄和移动，揭示了吸附物-基底相互作用的额外化学信息。例如，我们展示了 Rhodamine 6G（R6G）/Ag（111）系统的 LT-TER 光谱，该光谱表现出这种独特的光谱位移。LT-TERS 的高光谱分辨率提供了分子内的洞察力，因为位移模式与 R6G 的乙胺部分有关。LT-TERS 是一种很有前途的方法，可以揭示其他方法无法揭示的吸附物-基底相互作用的复杂性。
