Nanophotonic Enhancement of the Förster Resonance Energy-Transfer Rate with Single Nanoapertures

Abstract

Tailoring the light-matter interaction and the local density of optical states (LDOS) with nanophotonics provides accurate control over the luminescence properties of a single quantum emitter. This paradigm is also highly attractive to enhance the near-field Förster resonance energy transfer (FRET) between two fluorescent emitters. Despite the wide applications of FRET in nanosciences, using nanophotonics to enhance FRET has remained a debated and complex challenge. Here we demonstrate enhanced energy transfer within single donor-acceptor fluorophore pairs confined in single gold nanoapertures. Experiments monitoring both the donor and the acceptor emission photodynamics clearly establish a linear dependence of the FRET rate on the LDOS in nanoapertures, demonstrating that nanophotonics can be used to intensify the near-field energy transfer. Strikingly, we observe a significant six-fold increase in the FRET rate for large donor-acceptor separations exceeding 13 nm. Exciting opportunities are opened to investigate biochemical structures with donor-acceptor distances much beyond the classical Förster radius. Importantly, our approach is fully compatible with the detection of single biomolecules freely diffusing in water solution under physiological conditions.

FRET Enhancement in Aluminum Zero‐Mode Waveguides

“…linear dependence with Γ D , confirming the possibility to control FRET with nanophotonics [23,48]. Another remarkable feature of FRET in ZMWs is the larger FRET rate enhancement in the case of increased D-A separations (Fig.…”

“…A similar trend was reported for circular aluminum ZMWs but without quantitative data [33], while another study quantified a reduction of the FRET efficiency by 15% induced by the ZMWs [34]. Recently, our group has investigated FRET in ZMWs milled in gold films, reported a linear dependence of the FRET rate on the LDOS and quantified a slight variation of the FRET efficiency with the aperture diameter [48].…”

“…For short D-A distances (on the order of the Förster radius or below), the direct dipole-dipole energy transfer dominates and the LDOS has a moderate effect on the FRET rate, especially for nanophotonic structures of the size of a half wavelength with limited field gradients [31]. However, for larger D-A distances and structures with more pronounced field confinement, a supplementary contribution from the energy transfer mediated by the nanostructure can further enhance the apparent FRET rate [24,48].…”

“…Here, we build on our previous methodology [48] to investigate the role of aluminum ZMWs on the FRET process between individual donor-acceptor fluorophore pairs on double stranded DNA linkers. ZMWs milled in aluminum are by far the most widely used structures as compared to other metals such as gold or copper [8][9][10][11][12][13][14][15][16][17][18][19][20][32][33][34], thanks to their commercial availability, low chemical reactivity and the availability of surface passivation protocols [36].…”

Energy Transfer between Spatially Separated Entangled Molecules

“…Many factors can affect these types of energy transfer such as the local photonic mode density1, 2, 3, 4, 5, 6 which can be controlled in the weak light–matter interaction regime. This is typically achieved by placing the quantum emitters in a resonant cavity.…”