Abstract
Here we investigate the energy transfer rates of a Förster resonance energy transfer (FRET) pair positioned in close proximity to a 5 nm gold nanoparticle (AuNP) on a DNA origami construct. We study the distance dependence of the FRET rate by varying the location of the donor molecule, D, relative to the AuNP while maintaining a fixed location of the acceptor molecule, A. The presence of the AuNP induces an alteration in the spontaneous emission of the donor (including radiative and non-radiative rates) which is strongly dependent on the distance between the donor and AuNP surface. Simultaneously, the energy transfer rates are enhanced at shorter D-A (and D-AuNP) distances. Overall, in addition to the direct influence of the acceptor and AuNP on the donor decay there is also a significant increase in decay rate not explained by the sum of the two interactions. This leads to enhanced energy transfer between donor and acceptor in the presence of a 5 nm AuNP. We also demonstrate that the transfer rate in the three "particle" geometry (D + A + AuNP) depends approximately linearly on the transfer rate in the donor-AuNP system, suggesting the possibility to control FRET process with electric field induced by 5 nm AuNPs close to the donor fluorophore. It is concluded that DNA origami is a very versatile platform for studying interactions between molecules and plasmonic nanoparticles in general and FRET enhancement in particular.
Highlights
Förster resonance energy transfer (FRET) is based on a welldefined distance-dependent dipole–dipole interaction within a donor–acceptor pair
We demonstrate that the transfer rate in the three “particle” geometry (D + A + AuNP) depends approximately linearly on the transfer rate in the donor–AuNP system, suggesting the possibility to control FRET process with electric field induced by 5 nm AuNPs close to the donor fluorophore
To investigate the mechanism of FRET enhancement, we looked at a simple additive model
Summary
Förster resonance energy transfer (FRET) is based on a welldefined distance-dependent dipole–dipole interaction within a donor–acceptor pair. Contradictory results about LSP enhanced FRET efficiency have been shown to depend on the spectral and geometrical properties such as size and shape of the metallic nanoparticle (MNP),[17,21] or position and orientation of the fluorophore relative to the MNP.[15,17,22] Other studies have shown that the spontaneous emission rate of the luminescent entity, including radiative and non-radiative rates, can be altered by the effect of LSP.[23,24,25] Ever since the pioneering works of Purcell and Drexhage,[26,27] different nanophotonic geometries have been developed to study how the Förster energy transfer is modified by the optical environment using microcavities,[28,29,30] nanoantennas,[31] metallic films,[32,33] microresonators,[34,35] or photonic crystals.[36] Many of these studies have argued that the FRET rate might be entirely controlled by the localized surface plasmons.[28,30,31,33,34,35] disparity in the observed results can be related to the lack of control of a multitude of experimental parameters such as donor–acceptor distance, cross-talk between neighboring FRET pairs, donor–. The origin of the observed energy transfer enhancement is discussed in terms of changes in the donor decay rates
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