Plasmon-assisted Förster resonance energy transfer at the single-molecule level in the moderate quenching regime

Abstract

Metallic nanoparticles were shown to affect Förster energy transfer between fluorophore pairs. However, to date, the net plasmonic effect on FRET is still under dispute, with experiments showing efficiency enhancement and reduction. This controversy is due to the challenges involved in the precise positioning of FRET pairs in the near field of a metallic nanostructure, as well as in the accurate characterization of the plasmonic impact on the FRET mechanism. Here, we use the DNA origami technique to place a FRET pair 10 nm away from the surface of gold nanoparticles with sizes ranging from 5 to 20 nm. In this configuration, the fluorophores experience only moderate plasmonic quenching. We use the acceptor bleaching approach to extract the FRET rate constant and efficiency on immobilized single FRET pairs based solely on the donor lifetime. This technique does not require a posteriori correction factors neither a priori knowledge of the acceptor quantum yield, and importantly, it is performed in a single spectral channel. Our results allow us to conclude that, despite the plasmon-assisted Purcell enhancement experienced by donor and acceptor partners, the gold nanoparticles in our samples have a negligible effect on the FRET rate, which in turns yields a reduction of the transfer efficiency.

Extending Single-Molecule Förster Resonance Energy Transfer (FRET) Range beyond 10 Nanometers in Zero-Mode Waveguides

“…Actually, most cases consider short donor-acceptor separations (on the order or below the Förster radius) in order to ease the optical detection. 23,25,36,37,46,47,52 It should be acknowledged that long range energy transfer over distances up to several micrometers has been reported, [53][54][55][56][57][58] but these studies are based on radiative dipole-dipole coupling (i.e. energy transfer mediated by a propagating photon or plasmon in the far field).…”

Resonance energy transfer and quantum entanglement mediated by epsilon-near-zero and other plasmonic waveguide systems

“…2), which is also independent to the D-A emitter pair separation distance. Such a gigantic long-range RET enhancement has not been reported before [35][36][37][38][39], making ENZ waveguides an ideal nanophotonic environment to control and enhance RET-based applications. 10…”

A Self‐Assembled Plasmonic Substrate for Enhanced Fluorescence Resonance Energy Transfer

“…We then moved to investigate the influence of plasmonic substrates on the FRET efficiency. Contradictory results were reported regarding whether the FRET efficiency is increased or decreased by plasmonic modulation of metal nanoparticles . The inconsistency is likely due to the different spectral matching conditions between the substrate and the fluorophores in different studies.…”

“…Contradictory results were reported regarding whether the FRET efficiency is increased or decreased by plasmonic modulation of metal nanoparticles. [49,50] The inconsistency is likely due to the different spectral matching conditions between the substrate and the fluorophores in different studies. Here we choose Cy3/Cy5 as the FRET pair, as there is no crosstalk between the two channels ( Figure S8, Supporting Information).…”