Ultrafast fluorescent decay induced by metal-mediated dipole-dipole interaction in two-dimensional molecular aggregates

摘要

Two-dimensional molecular aggregate (2DMA), a thin sheet of stronglyinteracting dipole molecules self-assembled at close distance on an orderedlattice, is a fascinating fluorescent material. It is distinctively differentfrom the single or colloidal dye molecules or quantum dots in most previousresearch. In this paper, we verify for the first time that when a 2DMA isplaced at a nanometric distance from a metallic substrate, the strong andcoherent interaction between the dipoles inside the 2DMA dominates itsfluorescent decay at picosecond timescale. Our streak-camera lifetimemeasurement and interacting lattice-dipole calculation reveal that themetal-mediated dipole-dipole interaction shortens the fluorescent lifetime toabout one half and increases the energy dissipation rate by ten times thanexpected from the noninteracting single-dipole picture. Our finding can enrichour understanding of nanoscale energy transfer in molecular excitonic systemsand may designate a new direction for developing fast and efficientoptoelectronic devices.