Conformational Contrast of Surface-Mediated Molecular Switches Yields Ångstrom-Scale Spatial Resolution in Ultrahigh Vacuum Tip-Enhanced Raman Spectroscopy

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• 作者：Naihao Chiang ; Xing Chen ; Guillaume Goubert ; Dhabih V. Chulhai ; Xu Chen ; Eric A. Pozzi ; Nan Jiang ; Mark C. Hersam ; Tamar Seideman ; Lasse Jensen ; Richard P. Van Duyne
• 刊名：Nano Letters
• 出版年：2016
• 出版时间：December 14, 2016
• 年：2016
• 卷：16
• 期：12
• 页码：7774-7778
• 全文大小：381K
• ISSN：1530-6992

文摘

Tip-enhanced Raman spectroscopy (TERS) combines the ability of scanning probe microscopy (SPM) to resolve atomic-scale surface features with the single-molecule chemical sensitivity of surface-enhanced Raman spectroscopy (SERS). Here, we report additional insights into the nature of the conformational dynamics of a free-base porphyrin at room temperature adsorbed on a metal surface. We have interrogated the conformational switch between two metastable surface-mediated isomers of meso-tetrakis(3,5-ditertiarybutylphenyl)-porphyrin (H₂TBPP) on a Cu(111) surface. At room temperature, the barrier between the porphyrin ring buckled up/down conformations of the H₂TBPP-Cu(111) system is easily overcome, and a 2.6 Å lateral resolution by simultaneous TERS and STM analysis is achieved under ultrahigh vacuum (UHV) conditions. This work demonstrates the first UHV-TERS on Cu(111) and shows TERS can unambiguously distinguish the conformational differences between neighboring molecules with Ångstrom-scale spatial resolution, thereby establishing it as a leading method for the study of metal–adsorbate interactions.