title: Fluorescence lifetime enhancement of organic chromophores attached to gold nanoparticles.
abstract: We present for the first time experimental evidence of fluorescence lifetime enhancement of organic chromophores attached to metal nanospheres via radiative decay engineering. The hybrid system (HS) was a modified "diconjugated" molecular probe, 4-acetamido-4'-maleimidylstilbene-2,2'-dithiol (AMDT), covalently bound to the surface of 5-nm-diameter Au nanospheres by its two sulfur atoms, at a distance d < 1 nm and with its molecular axis parallel to the surface of the nanoparticle surface. We measured a fluorescence lifetime increase of a factor of 2 at room temperature (tau(AMDT) = (4.32 +/- 0.10) ns and tau(HS) = (8.73 +/- 0.23) ns) and a factor of 3.4 at 4.2 K (tau(AMDT) = (2.64 +/- 0.07) ns and tau(HS) = (7.96 +/- 0.14) ns). We also found that the fluorescence quantum yield of this hybrid system is not reduced, proof of a weak energy transfer between the molecular probe and the nanoparticle. These results demonstrate that a molecular dipole oriented parallel to the metal surface tends to be reduced by the coupling with its image.
authors.affiliation: Department of Chemistry, University of Central Florida, P.O. Box 162366, Orlando, Florida 32816-2366, USA. florenzi@mail.ucf.edu
authors.forename: Florencio E
authors.initials: FE
authors.lastname: Hernández
authors.forename: Shenjiang
authors.initials: S
authors.lastname: Yu
authors.forename: Marisol
authors.initials: M
authors.lastname: García
authors.forename: Andrés D
authors.initials: AD
authors.lastname: Campiglia