Letter | Published:

Chemical mapping of a single molecule by plasmon-enhanced Raman scattering

Nature volume 498, pages 8286 (06 June 2013) | Download Citation

Abstract

Visualizing individual molecules with chemical recognition is a longstanding target in catalysis, molecular nanotechnology and biotechnology. Molecular vibrations provide a valuable ‘fingerprint’ for such identification. Vibrational spectroscopy based on tip-enhanced Raman scattering allows us to access the spectral signals of molecular species very efficiently via the strong localized plasmonic fields produced at the tip apex1,2,3,4,5,6,7,8,9,10,11. However, the best spatial resolution of the tip-enhanced Raman scattering imaging is still limited to 3−15 nanometres5,12,13,14,15,16, which is not adequate for resolving a single molecule chemically. Here we demonstrate Raman spectral imaging with spatial resolution below one nanometre, resolving the inner structure and surface configuration of a single molecule. This is achieved by spectrally matching the resonance of the nanocavity plasmon to the molecular vibronic transitions, particularly the downward transition responsible for the emission of Raman photons. This matching is made possible by the extremely precise tuning capability provided by scanning tunnelling microscopy. Experimental evidence suggests that the highly confined and broadband nature of the nanocavity plasmon field in the tunnelling gap is essential for ultrahigh-resolution imaging through the generation of an efficient double-resonance enhancement for both Raman excitation and Raman emission. Our technique not only allows for chemical imaging at the single-molecule level, but also offers a new way to study the optical processes and photochemistry of a single molecule.

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Acknowledgements

We thank B. Wang, B. Ren, H. X. Xu, Z. Liu, and X. M. Yang for discussions and Unisoku Company for technical assistance. This work is supported by the National Basic Research Program of China, the Strategic Priority Research Program of the Chinese Academy of Sciences, the Natural Science Foundation of China and the Basque Government Project of Excellence (ETORTEK).

Author information

Author notes

    • R. Zhang
    •  & Y. Zhang

    These authors contributed equally to this work.

Affiliations

  1. Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China

    • R. Zhang
    • , Y. Zhang
    • , Z. C. Dong
    • , S. Jiang
    • , C. Zhang
    • , L. G. Chen
    • , L. Zhang
    • , Y. Liao
    • , Y. Luo
    • , J. L. Yang
    •  & J. G. Hou
  2. Material Physics Center CSIC-UPV/EHU and Donostia International Physics Center DIPC, Paseo Manuel de Lardizabal 5, Donostia-San Sebastián 20018, Spain

    • J. Aizpurua
  3. Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology, S-10691 Stockholm, Sweden

    • Y. Luo

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Contributions

R.Z. and Y.Z. contributed equally to this work. Z.C.D. and J.G.H. supervised the project and designed the experiments. R.Z., Y.Z., S.J., C.Z., L.G.C., L.Z., Y.L. and Z.C.D. performed experiments and analysed data. Y.Z., J.A., Y.L., J.L.Y. and Z.C.D. contributed to the interpretation of the data and theoretical simulations. Z.C.D., Y.Z., Y.L., J.A. and J.G.H. wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Z. C. Dong or J. G. Hou.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    This file contains Supplementary Figures 1-5, additional references and Supplementary Text and Data sections S1-S6 as follows: S1 Supplementary methods -experimental setup; S2 Supplementary methods - computational models; S3 Spectral comparison and spectral assignment; S4 the role of the tunneling current in the STM-controlled TERS; S5 an “analogue” to the broadband femtosecond stimulated Raman scattering and S6 containing the full Supplementary Video legend.

Videos

  1. 1.

    Molecular vibrations of a H2TBPP molecule for representative Raman modes in the calculated spectrum via DFT

    This video shows the molecular vibrations of a H2TBPP molecule for those representative Raman modes corresponding to the labeled peaks in Figure 2 for the calculated spectrum via DFT. The symmetry of each mode and a schematic of C2v point-group symmetry for H2TBPP molecule are also shown in this video.

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DOI

https://doi.org/10.1038/nature12151

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