Lifetime imaging of radiative and non-radiative fluorescence decays on nanoplasmonic surface

We report the fluorescence lifetime imaging and quantum yield measurement of five different fluorescence dyes spanning different quantum yield and excitation wavelength ranges in solution as well as on irregular nanoplasmonic substrate surface. Due to a distribution of dye molecules at random distances and orientation to the metal nanoplasmonic structure, the dyes showed multi-component lifetime decays on the surface. We have simulated the distribution of lifetime on the surface based on fractional intensity relative to steady-state value and derived an average lifetime with species fraction. From the quantum yield and fluorescence lifetime measurements we calculated the modified radiative and non-radiative decay rates for the dyes due to energy coupling on the substrate. We measured up to 100 fold fluorescence enhancement on nanoplasmonic substrate, and all molecule fluorescence showed not only considerably higher radiative decay rate but also higher non-radiative decay rate.