Modification of Förster Resonance Energy Transfer using Plasmonic Nanogaps

Förster resonance energy transfer (FRET) is a fundamental phenomenon in photosynthesis,  organic photovoltaics and biosensing. FRET is a non-radiative energy transfer process from an  excited molecular donor into a nearby... [ view full abstract ]

Förster resonance energy transfer (FRET) is a fundamental phenomenon in photosynthesis,  organic photovoltaics and biosensing. FRET is a non-radiative energy transfer process from an  excited molecular donor into a nearby molecular acceptor and its efficiency is dependent on  the inverse sixth power of the distance between donor and acceptor pair. The rate and range of FRET processes between two quantum emitters can be enhanced by controlling the photonic environment defined by the local density of optical states (LDOS). Successful control over   such energy transfers can open the way to range of applications in integrated nano-photonic devices and nano-sensors.

In thiswork, we present a silver nano-gap, consisting of a sliver nanoparticle coupled to an extended silver film, designed to enhance Förster resonance energy transfer. We considered nanoparticles of diameters 100 and 200 nm to form nano-gaps of width 30 nm doped with the laser dye Uranin LC 5520 and the molecular dye Rhodamine 6G as the donor-acceptor pair. Experimentally, up to 14-fold enhancement in acceptor fluorescence emission intensity and 3.6-fold enhancement in the FRET rate were observed in the presence of nano-gaps. To support the experimental observations, the optical properties of the plasmonic nano-gaps were studied using FDTD calculations giving deeper insight in the energy transfer in the presence of plasmonic nanogaps.