Directing Single-Molecule Emission with DNA Origami-Assembled Optical Antennas

Abstract

We demonstrate the capability of DNA selfassembled optical antennas to direct the emission of an individual fluorophore, which is free to rotate. DNA origami is used to fabricate optical antennas composed of two colloidal gold nanoparticles separated by a predefined gap and to place a single Cy5 fluorophore near the gap center. Although the fluorophore is able to rotate, its excitation and far-field emission is mediated by the antenna, with the emission directionality following a dipolar pattern according to the antenna main resonant mode. This work is intended to set out the basis for manipulating the emission pattern of single molecules with selfassembled optical antennas based on colloidal nanoparticles.

Recent advances in plasmonic nanocavities for single-molecule spectroscopy

“…65 Finally, with this technique, a single-photon emitter can be routinely placed in the hotspots of MNPs with nanometer precision, a key factor in controlling the coupling between single molecules and nanocavities. 66,67 These advantages were initially exploited to revisit experiments on uorescence-enhanced spectroscopy 68,69 and SERS [70][71][72] using dimer nanocavities made of Au or Ag, achieving enhancement values outperforming in some cases those obtained by using nanocavities fabricated with more complex top-down lithographic techniques. 73 While most DNA origami based dimer nanocavities are based on spherical MNPs, anisotropic geometries such as gold nanorods were also demonstrated.…”

Efficient Generation of Two-Photon Excited Phosphorescence from Molecules in Plasmonic Nanocavities

“…Selective positioning and orienting can be achieved with DNA origami directed-assembly. 47 − 50 Superradiance and other cooperative effects are expected within the NPoM due to the small mode volume; however, we keep the occupancy per excitation low (<10 –6 to reduce these effects). 51 − 53 Our results show that NPoMs are excellent nanophotonic constructs to explore nonlinear interactions at the nanoscale.…”

Nanoscale control of single molecule Förster resonance energy transfer by a scanning photonic nanoantenna

“…An additional effect of the coupling between photonic antennas and emitters is the modification of the spatial emission and directionality of the fluorescence emission [30][31][32][33]. When in resonance, the emitter couples to the nanoantenna so that the radiation proceeds from the coupled system, giving rise to changes in the angular emission.…”

“…However, experiments aimed to validate these simulations have been performed on diffusing emitters, where there is no control over the position or orientation of the emitters with respect to the antenna. This drawback can be partially overcome by making use of DNA origamis to immobilize the FRET pair at designed positions with respect to the antenna [20,33,35]. Yet, such approach is static, and only one relative position can be probed on a specific origami construct.…”