Ambitions to reach atomic resolution with light have been a major force in shaping nano-optics, whereby a central challenge is achieving highly localized optical fields. A promising approach employs plasmonic nanoantennas, but fluorescence quenching in the vicinity of metallic structures often imposes a strict limit on the attainable spatial resolution, and previous studies have reached only 8 nm resolution in fluorescence mapping. Here, we demonstrate spatially and spectrally resolved photoluminescence imaging of a single phthalocyanine molecule coupled to nanocavity plasmons in a tunnelling junction with a spatial resolution down to ∼8 Å and locally map the molecular exciton energy and linewidth at sub-molecular resolution. This remarkable resolution is achieved through an exquisite nanocavity control, including tip-apex engineering with an atomistic protrusion, quenching management through emitter–metal decoupling and sub-nanometre positioning precision. Our findings provide new routes to optical imaging, spectroscopy and engineering of light–matter interactions at sub-nanometre scales.
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The data that support the findings of this study are available from the corresponding authors on reasonable request.
The MATLAB codes used for the electromagnetic calculations in this study are available from the corresponding authors on reasonable request.
Lewis, A., Isaacson, M., Muray, A. & Harootunian, A. Scanning optical spectral microscopy with 500 Å spatial resolution. Biophys. J. 41, 405a (1983).
Pohl, D. W., Denk, W. & Lanz, M. Optical stethoscopy: image recording with resolution λ/20. Appl. Phys. Lett. 44, 651–653 (1984).
Betzig, E. & Chichester, R. J. Single molecules observed by near-field scanning optical microscopy. Science 262, 1422–1425 (1993).
Michaelis, J., Hettich, C., Mlynek, J. & Sandoghdar, V. Optical microscopy using a single-molecule light source. Nature 405, 325–328 (2000).
Frey, H. G., Witt, S., Felderer, K. & Guckenberger, R. High-resolution imaging of single fluorescent molecules with the optical near-field of a metal tip. Phys. Rev. Lett. 93, 200801 (2004).
Anger, P., Bharadwaj, P. & Novotny, L. Enhancement and quenching of single-molecule fluorescence. Phys. Rev. Lett. 96, 113002 (2006).
Kühn, S., Håkanson, U., Rogobete, L. & Sandoghdar, V. Enhancement of single-molecule fluorescence using a gold nanoparticle as an optical nanoantenna. Phys. Rev. Lett. 97, 017402 (2006).
Ma, Z., Gerton, J. M., Wade, L. A. & Quake, S. R. Fluorescence near-field microscopy of DNA at sub-10 nm resolution. Phys. Rev. Lett. 97, 260801 (2006).
Höppener, C., Lapin, Z. J., Bharadwaj, P. & Novotny, L. Self-similar gold-nanoparticle antennas for a cascaded enhancement of the optical field. Phys. Rev. Lett. 109, 017402 (2012).
Mauser, N. & Hartschuh, A. Tip-enhanced near-field optical microscopy. Chem. Soc. Rev. 43, 1248–1262 (2014).
Weisenburger, S. & Sandoghdar, V. Light microscopy: an ongoing contemporary revolution. Contemp. Phys. 56, 123–143 (2015).
Hermann, R. J. & Gordon, M. J. Nanoscale optical microscopy and spectroscopy using near-field probes. Annu. Rev. Chem. Biomol. Eng. 9, 365–387 (2018).
Park, K.-D., Jiang, T., Clark, G., Xu, X. & Raschke, M. B. Radiative control of dark excitons at room temperature by nano-optical antenna-tip Purcell effect. Nat. Nanotechnol. 13, 59–64 (2018).
Gerton, J. M., Wade, L. A., Lessard, G. A., Ma, Z. & Quake, S. R. Tip-enhanced fluorescence microscopy at 10 nanometer resolution. Phys. Rev. Lett. 93, 180801 (2004).
Agio, M. & Alù, A. Optical Antennas (Cambridge Univ. Press, 2013).
Matsuzaki, K. et al. Strong plasmonic enhancement of biexciton emission: controlled coupling of a single quantum dot to a gold nanocone antenna. Sci. Rep. 7, 42307 (2017).
Chikkaraddy, R. et al. Mapping nanoscale hotspots with single-molecule emitters assembled into plasmonic nanocavities using DNA origami. Nano Lett. 18, 405–411 (2018).
Groß, H., Hamm, J. M., Tufarelli, T., Hess, O. & Hecht, B. Near-field strong coupling of single quantum dots. Sci. Adv. 4, eaar4906 (2018).
Chen, X. et al. Modern scattering-type scanning near-field optical microscopy for advanced material research. Adv. Mater. 31, 1804774 (2019).
Park, K.-D. et al. Tip-enhanced strong coupling spectroscopy, imaging, and control of a single quantum emitter. Sci. Adv. 5, eaav5931 (2019).
Becker, S. F. et al. Gap-plasmon-enhanced nanofocusing near-field microscopy. ACS Photon. 3, 223–232 (2016).
Zhang, R. et al. Chemical mapping of a single molecule by plasmon-enhanced Raman scattering. Nature 498, 82–86 (2013).
Lee, J., Crampton, K. T., Tallarida, N. & Apkarian, V. A. Visualizing vibrational normal modes of a single molecule with atomically confined light. Nature 568, 78–82 (2019).
Zhang, Y. et al. Visually constructing the chemical structure of a single molecule by scanning Raman picoscopy. Natl Sci. Rev. 6, 1169–1175 (2019).
Benz, F. et al. Single-molecule optomechanics in “picocavities”. Science 354, 726–729 (2016).
Barbry, M. et al. Atomistic near-field nanoplasmonics: reaching atomic-scale resolution in nanooptics. Nano Lett. 15, 3410–3419 (2015).
Dulkeith, E. et al. Fluorescence quenching of dye molecules near gold nanoparticles: radiative and nonradiative effects. Phys. Rev. Lett. 89, 203002 (2002).
Huang, Y. P. et al. Shell-isolated tip-enhanced Raman and fluorescence spectroscopy. Angew. Chem. 130, 7645–7649 (2018).
Zhang, F. L. et al. Elucidating molecule–plasmon interactions in nanocavities with 2 nm spatial resolution and at the single-molecule level. Angew. Chem. 131, 12261–12265 (2019).
Kinkhabwala, A. et al. Large single-molecule fluorescence enhancements produced by a bowtie nanoantenna. Nat. Photon. 3, 654–657 (2009).
Russell, K. J., Liu, T.-L., Cui, S. & Hu, E. L. Large spontaneous emission enhancement in plasmonic nanocavities. Nat. Photon. 6, 459–462 (2012).
Belacel, C. et al. Controlling spontaneous emission with plasmonic optical patch antennas. Nano Lett. 13, 1516–1521 (2013).
Faggiani, R. M., Yang, J. & Lalanne, P. Quenching, plasmonic, and radiative decays in nanogap emitting devices. ACS Photon. 2, 1739–1744 (2015).
Kongsuwan, N. et al. Suppressed quenching and strong-coupling of purcell-enhanced single-molecule emission in plasmonic nanocavities. ACS Photon. 5, 186–191 (2018).
Qiu, X., Nazin, G. & Ho, W. Vibrationally resolved fluorescence excited with submolecular precision. Science 299, 542–546 (2003).
Zhang, Y. et al. Visualizing coherent intermolecular dipole–dipole coupling in real space. Nature 531, 623–627 (2016).
Imada, H. et al. Real-space investigation of energy transfer in heterogeneous molecular dimers. Nature 538, 364–367 (2016).
Kuhnke, K., Grosse, C., Merino, P. & Kern, K. Atomic-scale imaging and spectroscopy of electroluminescence at molecular interfaces. Chem. Rev. 117, 5174–5222 (2017).
Doppagne, B. et al. Electrofluorochromism at the single-molecule level. Science 361, 251–255 (2018).
Kimura, K. et al. Selective triplet exciton formation in a single molecule. Nature 570, 210–213 (2019).
Doppagne, B. et al. Single-molecule tautomerization tracking through space-and time-resolved fluorescence spectroscopy. Nat. Nanotechnol. 15, 207–211 (2020).
Haroche, S. & Raimond, J.-M. Exploring The Quantum: Atoms, Cavities, and Photons (Oxford Univ. Press, 2006).
Zhang, Y. et al. Sub-nanometre control of the coherent interaction between a single molecule and a plasmonic nanocavity. Nat. Commun. 8, 15225 (2017).
Chen, C., Chu, P., Bobisch, C., Mills, D. & Ho, W. Viewing the interior of a single molecule: vibronically resolved photon imaging at submolecular resolution. Phys. Rev. Lett. 105, 217402 (2010).
Neuman, T. S., Esteban, R., Casanova, D., García-Vidal, F. J. & Aizpurua, J. Coupling of molecular emitters and plasmonic cavities beyond the point-dipole approximation. Nano Lett. 18, 2358–2364 (2018).
Rendell, R. & Scalapino, D. Surface plasmons confined by microstructures on tunnel junctions. Phys. Rev. B 24, 3276–3294 (1981).
Savage, K. J. et al. Revealing the quantum regime in tunnelling plasmonics. Nature 491, 574–577 (2012).
Schmaus, S. et al. Giant magnetoresistance through a single molecule. Nat. Nanotechnol. 6, 185–189 (2011).
Kalkbrenner, T. et al. Optical microscopy via spectral modifications of a nanoantenna. Phys. Rev. Lett. 95, 200801 (2005).
Novotny, L. & Hecht, B. Principles of Nano-Optics (Cambridge Univ. Press, 2012).
Hecht, B., Bielefeldt, H., Inouye, Y., Pohl, D. & Novotny, L. Facts and artifacts in near-field optical microscopy. J. Appl. Phys. 81, 2492–2498 (1997).
We thank B. Wang for helpful discussions. This work was supported by the National Key R&D Program of China (grant numbers 2016YFA0200600 and 2017YFA0303500), the National Natural Science Foundation of China, the Strategic Priority Research Program of the Chinese Academy of Sciences (grant number XDB36000000) and the Anhui Initiative in Quantum Information Technologies. J.A. acknowledges project IT1164-19 of the consolidated university groups from the Basque Government.
The authors declare no competing interests.
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Extended Data Fig. 1 Schematic drawing of our custom-built experimental setup for TEPL measurements.
This setup is composed of four sub-systems: a laser source for light excitation, a dark-box for optical filtering, polarization control and alignment, a low-temperature UHV STM for sample preparation and characterization with a built-in lens for both light excitation and collection, and a photon detection sub-system containing a SPAD for PL intensity measurements and a spectrometer equipped with a highly sensitive CCD detector for PL spectral measurements.
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Yang, B., Chen, G., Ghafoor, A. et al. Sub-nanometre resolution in single-molecule photoluminescence imaging. Nat. Photonics 14, 693–699 (2020). https://doi.org/10.1038/s41566-020-0677-y