Förster resonance energy transfer in a nanoscopic system on a dielectric interface

We investigate picosecond-resolved energy transfer between a quantum dot (donor) and an organic molecule (acceptor) in the proximity of a reflecting metallic/non-metallic surface. We demonstrate experimentally that the Förster resonance energy transfer (FRET) is significantly influenced by the proximity of the mirror. Locating a cadmium selenide quantum dot (donor: D) attached to an organic dye merocyanine (acceptor: A) at well-defined positions from the reflecting silver/silicon surface allows the transfer rate to be determined as a function of distance from the surface. An attempt to fit the experimental data to a model relying upon the change of the apparent energy transfer rate due to interference of direct and reflected light waves reveals reasonably good results. The results show that the observed FRET rate in a D-A pair on the mirror surface is oscillating in nature, providing information for the measured energy transfer, which could be potentially different from that of the actual transfer due to optical interference.