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Probing the electromagnetic field of a 15-nanometre hotspot by single molecule imaging


When light illuminates a rough metallic surface, hotspots can appear, where the light is concentrated on the nanometre scale, producing an intense electromagnetic field. This phenomenon, called the surface enhancement effect1,2, has a broad range of potential applications, such as the detection of weak chemical signals. Hotspots are believed to be associated with localized electromagnetic modes3,4, caused by the randomness of the surface texture. Probing the electromagnetic field of the hotspots would offer much insight towards uncovering the mechanism generating the enhancement; however, it requires a spatial resolution of 1–2 nm, which has been a long-standing challenge in optics. The resolution of an optical microscope is limited to about half the wavelength of the incident light, approximately 200–300 nm. Although current state-of-the-art techniques, including near-field scanning optical microscopy5, electron energy-loss spectroscopy6, cathode luminescence imaging7 and two-photon photoemission imaging8 have subwavelength resolution, they either introduce a non-negligible amount of perturbation, complicating interpretation of the data, or operate only in a vacuum. As a result, after more than 30 years since the discovery of the surface enhancement effect9,10,11, how the local field is distributed remains unknown. Here we present a technique that uses Brownian motion of single molecules to probe the local field. It enables two-dimensional imaging of the fluorescence enhancement profile of single hotspots on the surfaces of aluminium thin films and silver nanoparticle clusters, with accuracy down to 1.2 nm. Strong fluorescence enhancements, up to 54 and 136 times respectively, are observed in those two systems. This strong enhancement indicates that the local field, which decays exponentially from the peak of a hotspot, dominates the fluorescence enhancement profile.

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Figure 1: The principle of Brownian motion single molecule super-resolution imaging.
Figure 2: Hotspots on an aluminium film.
Figure 3: A hotspot on silver nanoparticle clusters.


  1. Kneipp, K. et al. Single molecule detection using surface-enhanced Raman scattering (SERS). Phys. Rev. Lett. 78, 1667–1670 (1997)

    Article  ADS  CAS  Google Scholar 

  2. Nie, S. & Emory, S. R. Probing single molecules and single nanoparticles by surface-enhanced Raman scattering. Science 275, 1102–1106 (1997)

    Article  CAS  Google Scholar 

  3. Shalaev, V. M. & Stockman, M. I. Fractals: optical susceptibility and giant Raman scattering. Z. Phys. D 10, 71–79 (1988)

    Article  ADS  CAS  Google Scholar 

  4. Stockman, M. I., Faleev, S. V. & Bergman, D. J. Localization versus delocalization of surface plasmons in nanosystems: can one state have both characteristics? Phys. Rev. Lett. 87, 167401 (2001)

    Article  ADS  CAS  Google Scholar 

  5. Betzig, E. & Trautman, J. K. Near-field optics: microscopy, spectroscopy, and surface modification beyond the diffraction limit. Science 257, 189–195 (1992)

    Article  ADS  CAS  Google Scholar 

  6. Nelayah, J. et al. Mapping surface plasmons on a single metallic nanoparticle. Nature Phys. 3, 348–353 (2007)

    Article  ADS  CAS  Google Scholar 

  7. Vesseur, E. J. R., de Waele, R., Kuttge, M. & Polman, A. Direct observation of plasmonic modes in Au nanowires using high-resolution cathodoluminescence spectroscopy. Nano Lett. 7, 2843–2846 (2007)

    Article  ADS  CAS  Google Scholar 

  8. Kubo, A., Jung, Y. S., Kim, H. K. & Petek, H. Femtosecond microscopy of localized and propagating surface plasmons in silver gratings. J. Phys. At. Mol. Opt. Phys. 40, S259–S272 (2007)

    Article  ADS  CAS  Google Scholar 

  9. Jeanmaire, D. L. & Van Duyne, R. P. Surface Raman spectroelectrochemistry: Part I. Heterocyclic, aromatic, and aliphatic amines adsorbed on the anodized silver electrode. J. Electroanal. Chem. 84, 1–20 (1977)

    Article  CAS  Google Scholar 

  10. Albrecht, M. G. & Creighton, J. A. Anomalously intense Raman spectra of pyridine at a silver electrode. J. Am. Chem. Soc. 99, 5215–5217 (1977)

    Article  CAS  Google Scholar 

  11. Fleischmann, M., Hendra, P. J. & McQuillan, A. J. Raman spectra of pyridine adsorbed at a silver electrode. Chem. Phys. Lett. 26, 163–166 (1974)

    Article  ADS  CAS  Google Scholar 

  12. Creighton, J. A., Blatchford, C. G. & Albrecht, M. G. Plasma resonance enhancement of Raman scattering by pyridine adsorbed on silver or gold sol particles of size comparable to the excitation wavelength. J. Chem. Soc. Faraday Trans. 2 75, 790–798 (1979)

    Article  CAS  Google Scholar 

  13. Moskovits, M. Surface roughness and the enhanced intensity of Raman scattering by molecules adsorbed on metals. J. Chem. Phys. 69, 4159–4161 (1978)

    Article  ADS  CAS  Google Scholar 

  14. Gersten, J. & Nitzan, A. Electromagnetic theory of enhanced Raman scattering by molecules adsorbed on rough surfaces. J. Chem. Phys. 73, 3023–3037 (1980)

    Article  ADS  CAS  Google Scholar 

  15. Sarychev, A. K., Shubin, V. A. & Shalaev, V. M. Anderson localization of surface plasmons and nonlinear optics of metal-dielectric composites. Phys. Rev. B 60, 16389–16408 (1999)

    Article  ADS  CAS  Google Scholar 

  16. Seal, K. et al. Coexistence of localized and delocalized surface plasmon modes in percolating metal films. Phys. Rev. Lett. 97, 206103 (2006)

    Article  ADS  CAS  Google Scholar 

  17. Hutchison, J. A. et al. Subdiffraction limited, remote excitation of surface enhanced Raman scattering. Nano Lett. 9, 995–1001 (2009)

    Article  ADS  CAS  Google Scholar 

  18. Betzig, E. et al. Imaging intracellular fluorescent proteins at nanometer resolution. Science 313, 1642–1645 (2006)

    Article  ADS  CAS  Google Scholar 

  19. Rust, M. J., Bates, M. & Zhuang, X. W. Sub-diffraction-limit imaging by stochastic optical reconstruction microscopy (STORM). Nature Methods 3, 793–796 (2006)

    Article  CAS  Google Scholar 

  20. Sharonov, A. & Hochstrasser, R. M. Wide-field subdiffraction imaging by accumulated binding of diffusing probes. Proc. Natl Acad. Sci. USA 103, 18911–18916 (2006)

    Article  ADS  CAS  Google Scholar 

  21. Wu, D., Liu, Z., Sun, C. & Zhang, X. Super-resolution imaging by random adsorbed molecule probes. Nano Lett. 8, 1159–1162 (2008)

    Article  ADS  CAS  Google Scholar 

  22. Hell, S. W. in Single Molecule Spectroscopy in Chemistry, Physics and Biology (eds Gräslund, A., Rigler, R. & Widengren, J. ) 365–398 (Springer Series in Chemical Physics, Springer, 2009)

    Google Scholar 

  23. Roeffaers, M. et al. Super-resolution reactivity mapping of nanostructured catalyst particles. Angew. Chem. 121, 9449–9453 (2009)

    Article  Google Scholar 

  24. Mortensen, K. I., Churchman, L. S., Spudich, J. A. & Flyvbjerg, H. Optimized localization analysis for single-molecule tracking and super-resolution microscopy. Nature Methods 7, 377–381 (2010)

    Article  CAS  Google Scholar 

  25. Chang, C. C. et al. Aluminum oxidation in water. J. Electrochem. Soc. 125, 787–792 (1978)

    Article  CAS  Google Scholar 

  26. Wokaun, A., Lutz, H. P., King, A. P., Wild, U. P. & Ernst, R. R. Energy transfer in surface enhanced luminescence. J. Chem. Phys. 79, 509–514 (1983)

    Article  ADS  CAS  Google Scholar 

  27. Chance, R. R., Prock, A. & Silbey, R. Comments on the classical theory of energy transfer. J. Chem. Phys. 62, 2245–2253 (1975)

    Article  ADS  CAS  Google Scholar 

  28. Anger, P., Bharadwaj, P. & Novotny, L. Enhancement and quenching of single-molecule fluorescence. Phys. Rev. Lett. 96, 113002 (2006)

    Article  ADS  Google Scholar 

  29. Taminiau, T. H., Stefani, F. D., Segerink, F. B. & van Hulst, N. F. Optical antennas direct single-molecule emission. Nature Photon. 2, 234–237 (2008)

    Article  CAS  Google Scholar 

  30. Kinkhabwala, A. et al. Large single-molecule fluorescence enhancements produced by a bowtie nanoantenna. Nature Photon. 3, 654–657 (2009)

    Article  ADS  CAS  Google Scholar 

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We thank G. Bartal and A. Niv for discussions. This research was supported by the US Department of Energy Office of Science, Basic Energy Sciences and Lawrence Berkeley National Laboratory under contract no. DE-AC02-05CH11231.

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Authors and Affiliations



H.C., A.L., X.Y. and X.Z. designed the experiments; H.C., A.L., C.G. and M.L. conducted experiments; C.L. and Y.L. conducted computer simulations and theoretical analysis; H.C., A.L., X.Y. and X.Z. wrote the paper.

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Correspondence to Xiang Zhang.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains details of Supplementary Movie 1, Supplementary Information sections 1-8 (see Table of Contents for details) and additional references. (PDF 1043 kb)

Supplementary Movie 1

This movie illustrates the principle of our Brownian motion single molecule super-resolution technique (see Supplementary Information file for full details). (MOV 5380 kb)

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Cang, H., Labno, A., Lu, C. et al. Probing the electromagnetic field of a 15-nanometre hotspot by single molecule imaging. Nature 469, 385–388 (2011).

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