Resonant enhancement of the nanocrystals fluorescence near the plasmonic film surface

Effective enhancement of the fluorescence signal of chromophores adsorbed directly onto plasmonic films can be observed under conditions of strong spectral resonance between plasmon and chromophore absorptions. This effect seems to contradict the established mechanisms of complete quenching of the fluorescence of chromophores under their adsorbtion directly onto the metal surface. However, under certain conditions, enhancement of the fluorescence signal is observed for both inorganic and organic chromophores. To understand the effect and conditions of its observation, we propose to use the quantum concept of virtual photon exchange in the near optical field - dressed photons. This concept is borrowed from the physics of elementary particles and is already well adapted to the problems of nanophotonics by M. Otsu. In this paper, we discuss exclusively the key factors responsible for enhancement of fluorescence of CdSe/ZnS nanocrystals and the effective dressed photons exchange: the size of nanoparticles, the distance between them, and the presence of spectral overlap indicating the possibility of resonant interactions between plasmons and chromophores.

Communicated by Academician Sergei V. Gaponenko

1. Liu X., Yue Q., Yan T., Li J., Yan W., Ma J., Zhao C., Zhang X. Competition between Local Field Enhancement and Nonradiative Resonant Energy Transfer in the Linear Absorption of a Semiconductor Quantum Dot Coupled to a Metal Nanoparticle. Journal of Physical Chemistry C, 2016, vol. 120, no. 32, pp. 18220-18227. https://doi.org/10.1021/acs.jpcc.6b03637

2. Strekal N., Maskevich A., Maskevich S., Jardillier J.-C., Nabiev I. Selective enhancement of Raman or fluorescence spectra of biomolecules using specifically annealed thick gold films. Biopolymers, 2000, vol. 57, no. 6, pp. 325-328. https://doi.org/10.1002/1097-0282(2000)57:6%3C325::aid-bip10%3E3.0.co;2-7

3. Kulakovich O., Strekal N., Yaroshevich A., Maskevich S., Gaponenko S., Nabiev I., Woggon U., Artemyev M. Enhanced Luminescence of CdSe Quantum Dots on Gold Colloids. Nano Letters, 2002, vol. 2, no. 12, pp. 1449-1452. https://doi.org/10.1021/nl025819k

4. Geddes C. D. Reviews in Plasmonics. New York, Springer-Verlag, 2010. 334 p. https://doi.org/10.1007/978-1-4614-0884-0

5. Ohtsu M. Progress in Nanophotonics 1. Nano-Optics and Nanophotonics. Berlin, Heidelberg, Springer-Verlag, 2011.238 p. https://doi.org/10.1007/978-3-642-17481-0

6. Strekal N. D., Kulakovich O. S., Askirka V F., Sveklo I., Maskevich S. Features of the Secondary Emission Enhancement Near Plasmonic Gold Film. Plasmonics, 2008, vol. 4, no. 1, pp. 1-7. https://doi.org/10.1007/s11468-008-9063-1

7. Strekal N. D. Dimensional effect in the formation of secondary chromophore fluorescence spectra near the surface with plasmonic properries. Doklady Natsional’noi akademii nauk Belarusi = Doklady of the National Academy of Sciences of Belarus, 2014, vol. 58, no. 2, pp. 50-53 (in Russian).

8. Shchegrov A. V, Novikov I. V., Maradudin A. A. Scattering of Surface Plasmon Polaritons by a Circularly Symmetric Surface Defect. Physical Review Letters, 1997, vol. 78, no. 22, pp. 4269-4272. https://doi.org/10.1103/physrevlett.78.4269

9. Peng S., McMahon J. M., Schatz G. C., Gray S. K., Sun Y Reversing the size-dependence of surface plasmon resonances. Proceedings of the National Academy of Sciences, 2010, vol. 107, no. 33, pp. 14530-14534. https://doi.org/10.1073/pnas.1007524107

10. Weitz D. A., Garoff S., Gersten J. I., Nitzan A. The enhancement of Raman scattering, resonance Raman scattering, and fluorescence from molecules adsorbed on a rough silver surface. Journal of Chemical Physics, 1983, vol. 78, no. 9, pp. 5324-5338. https://doi.org/10.1063/L445486

11. Askirka V F., Motevich I. G., Filimonenko D. S., Maskevich S., Strekal N. D. Formation of the hot spots by CdSe/ZnS nanocrystalls and metal nanoparticles and their detection by near-field optical microscopy and far-field fluorescence XV International Conference on Quantum Optics and Quantum Information, Book of abstracts. Minsk, 2017, pp. 80-81.

12. Ohtsu M. Dressed Photons: Concepts of Light-Matter Fusion Technology. Berlin, Heidelberg, Springer-Verlag, 2014. 324 p. https://doi.org/10.1007/978-3-642-39569-7

13. Kobayashi K., Sangu S., Ito H., Ohtsu M. Near-field optical potential for a neutral atom. Physical Review A, 2001, vol. 63, no. 1, pp. 013806. https://doi.org/10.1103/physreva.63.013806

14. Nguyen V H., Nguyen B. H. Quantum field theory of interacting plasmon-photon system. Advances in Natural Sciences: Nanoscience and Nanotechnology, 2015, vol. 6, no. 2, pp. 025010. https://doi.org/10.1088/2043-6262/6/2/025010

15. Gaponenko S. V Effects of Photon Density of States on Raman Scattering in Mesoscopic Structures. Physical Review B, 2002, vol. 65, no. 14, pp. 140303(R). https://doi.org/10.1103/physrevb.65.140303