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Large single-molecule fluorescence enhancements produced by a bowtie nanoantenna

Nature Photonics volume 3, pages 654–657 (2009)Cite this article

Abstract

Owing to the size mismatch between light and nanoscale objects such as single molecules, it is important to be able to control light–molecule interactions1,2,3,4. Plasmonic nanoantennas create highly enhanced local fields when pumped resonantly, leading to increased Raman scattering5, but whether fluorescence enhancement occurs depends upon a variety of factors. Although sharp metal tips6 and colloids7,8 can enhance fluorescence, the highly enhanced optical fields of lithographically fabricated bowtie nanoantennas9 provide a structure that is more controllable and amenable to integration. Using gold bowties, we observe enhancements of a single molecule's fluorescence up to a factor of 1,340, ten times higher than reported previously7,8,10,11,12,13,14,15,16,17,18,19,20,21,22. Electromagnetic simulations reveal that this is a result of greatly enhanced absorption and an increased radiative emission rate, leading to enhancement of the intrinsic quantum efficiency by an estimated factor of nine, despite additional non-radiative ohmic effects. Bowtie nanoantennas thus show great potential for high-contrast selection of single nanoemitters.

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Figure 1: Experimental set-up.
Figure 2: Measurement of fF for single fluorescent molecules (SMs) as a function of bowtie gap size.
Figure 3: Electromagnetic simulations of single fluorescent molecule fluorescence near a gold bowtie nanoantenna.
Figure 4: Fluorescence decay lifetime measurements of single fluorescent molecules (SMs) enhanced by bowtie nanoantennas.

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Acknowledgements

This work was supported in part by National Science Foundation (NSF) grant DMR-0507296 and by Center for Probing the Nanoscale (CPN) through NSF grant PHY-0425897 (W.E.M.) and by an Air Force Office of Scientific Research (AFOSR) Multidisciplinary University Research Initiative (MURI) program no. FA9550-04-1-0437 (S.F.). Work was performed in part at the Stanford Nanofabrication Facility supported by NSF grant ECS-9731293.

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Authors and Affiliations

  1. Department of Chemistry, Stanford University, Stanford, 94305, California, USA

    Anika Kinkhabwala & W. E. Moerner

  2. Department of Electrical Engineering, Stanford University, Stanford, 94305, California, USA

    Zongfu Yu & Shanhui Fan

  3. Max-Planck Institute for Polymer Research, Mainz, D-55128, Germany

    Yuri Avlasevich & Klaus Müllen

Authors
  1. Anika Kinkhabwala
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  3. Shanhui Fan
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  6. W. E. Moerner
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Contributions

A.K. and W.M. performed experiments and data analysis of experimental data. Z.Y. and S.F. simulated bowtie nanoantennas using FDTD. Y.A. and K.M. synthesized the TPQDI fluorophore.

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Correspondence to W. E. Moerner.

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Kinkhabwala, A., Yu, Z., Fan, S. et al. Large single-molecule fluorescence enhancements produced by a bowtie nanoantenna. Nature Photon 3, 654–657 (2009). https://doi.org/10.1038/nphoton.2009.187

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