  We report an experimental study of the plasmon-assisted spontaneous emission
and the F\"orster resonance energy transfer between organic molecules and
semiconductor colloidal quantum dots. The localized plasmonic field in the
nanogap between a gold nano-popcorn's tips and a 5-nm separated gold film
supports high photonic density of states and provides pathways for the
light-matter interaction mechanisms. We demonstrate that, besides the total
spontaneous emission rate enhancement factor up to 66 for quantum dots and
molecules, the F\"orster resonance energy transfer efficiency and rate constant
are simultaneously modified. While the energy transfer efficiency is reduced
from 84 to 35 per cent due to the non-radiative quenching effect and fast donor
spontaneous emission rate, the energy transfer rate constant is significantly
increased from 4 to 20 ns-1. Our results have quantitatively elucidated decay
mechanisms that are important toward understanding and controlling of the
light-matter interaction at the nanoscale.
