Single molecule photophysics near metallic nanostructures.

Metal-enhanced fluorescence (MEF) is useful in single molecule detection (SMD) by increasing the photostability, brightness and increase in radiative decay rates of fluorophores. We have investigated MEF from an individual fluorophore tethered to a single silver nanoparticle and also a single fluorophore between a silver dimer. The fluorescence lifetime results revealed a near-field interaction mechanism of fluorophore with the metal particle. Finite-difference time-domain (FDTD) calculations were employed to study the distribution of electric field near the metal monomer and dimer. The coupling effect of metal particles on the fluorescence enhancement was studied. We have also investigated the photophysics of FRET near metal nanoparticles and our preliminary results suggest an enhanced FRET efficiency in the presence of a metal nanoparticle. In total, our results demonstrate improved detectability at the single molecule level for a variety of fluorophores and quantum dots in proximity to the silver nanoparticles due to the near-field metal-fluorophore interactions.