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

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

Research output: Contribution to journalArticlepeer-review

67 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)7774-7778
Number of pages5
JournalNano letters
Volume16
Issue number12
DOIs
StatePublished - Dec 14 2016

Bibliographical note

Funding Information:
Xing C., D.V.C., L.J., and R.P.V.D. acknowledge support from the National Science Foundation Center for Chemical Innovation dedicated to Chemistry at the Space-Time Limit (CaSTL) Grant CHE-1414466. N.C., E.A.P., N.J., T.S., M.C.H., and R.P.V.D. acknowledge support from the Department of Energy Office of Basic Energy Sciences (SISGR Grant DE-FG02-09ER16109) and the National Science Foundation Materials Research Science and Engineering Center (NSF DMR-1121262). G.G., Xu C., and R.P.V.D acknowledge support from the Air Force Office of Scientific Research MURI (FA9550-14-1-0003)

Publisher Copyright:
© 2016 American Chemical Society.

Keywords

  • Ultrahigh vacuum
  • conformational isomers
  • nanoscale chemical imaging
  • single molecule spectroscopy
  • tip-enhanced Raman spectroscopy

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