Controlling Three-Color Förster Resonance Energy Transfer in an Optical Fabry–Pérot Microcavity at Low Mode Order

Abstract

We study three-color Förster resonance energy transfer (triple FRET) between three spectrally distinct fluorescent dyes, a donor and two acceptors, which are embedded in a single polystyrene nanosphere. The presence of triple FRET energy transfer is confirmed by selective acceptor photobleaching. We show that the fluorescence lifetimes of the three dyes are selectively controlled using the Purcell effect by modulating the radiative rates and relative fluorescence intensities when the nanospheres are embedded in an optical Fabry–Pérot microcavity. The strongest fluorescence intensity enhancement for the second acceptor can be observed as a signature of the FRET process by tuning the microcavity mode to suppress the intermediate dye emission and transfer more energy from donor to the second acceptor. Additionally, we show that the triple FRET process can be modeled by coupled rate equations, which allow to estimate the energy transfer rates between donor and acceptors. This fundamental study has the potential to extend the classical FRET approach for investigating complex systems, e.g., optical energy switching, photovoltaic devices, light-harvesting systems, or in general interactions between more than two constituents.

Thin Films of Conjugated Chalcogenadiazole: Growth, Structure, and Optical Properties of Substituted Selenadiazoloquinoxaline

“…Photoluminescence spectra were recorded with a Labram HR 800 spectrometer (Horiba Jobin Yvon, France) with a CCD 1024 × 256 pixel 2 detector and a frequency-doubled Nd:YAG excitation laser with a wavelength of 532 nm. Temperature-dependent PL spectra were obtained with a cooling CryoVac system with liquid nitrogen in the range from 80 to 290 K. Fluorescence lifetime measurements were performed at 77 K in an optical cryostat (SVT-200, Janis) with a custom-built confocal microscope 42 equipped with an air objective lens (NA = 0.85, Newport), a spectrometer (Shamrock, Andor Technology, U.K.) with a thermoelectrically cooled (203 K) CCD camera, and a single photon avalanche diode (SPAD, PDM series, Micro Photon Devices, Italy). Samples were excited by a 485 nm pulsed laser diode (PicoQuant GmbH, Germany) with a pulse width of <100 ps at a repetition rate of 40 MHz with linear polarization.…”