Particle-Size-Dependent Förster Resonance Energy Transfer from Upconversion Nanoparticles to Organic Dyes.
Upconversion nanoparticles (UCNPs) are attractive candidates for energy transfer-based analytical applications. In contrast to classical donor-acceptor pairs, these particles contain many emitting lanthanide ions together with numerous acceptor dye molecules at different distances to each other, strongly depending on the particle diameter. UCNPs with precisely controlled sizes between 10 and 43 nm were prepared and functionalized with rose bengal and sulforhodamine B by a ligand-exchange procedure. Time-resolved studies of the upconversion luminescence of the UCNP donor revealed a considerable shortening of the donor lifetime as a clear hint for Förster resonance energy transfer (FRET). FRET was most pronounced for 21 nm-sized UCNPs, yielding a FRET efficiency of 60%. At larger surface-to-volume ratios, the FRET efficiency decreased by an increasing competition of nonradiative surface deactivation. Such dye-UCNP architectures can also provide an elegant way to shift the UCNP emission color, since the fluorescence intensity of the organic dyes excited by FRET was comparable to that of the upconversion emission of smaller particles.
University of Regensburg , Institute of Analytical Chemistry, Chemo- and Biosensors, 93040 Regensburg, Germany.
Verena
V
Muhr
BAM Federal Institute for Materials Research and Testing , Division 1.10 Biophotonics, 12489 Berlin, Germany.
Christian
C
Würth
BAM Federal Institute for Materials Research and Testing , Division 1.10 Biophotonics, 12489 Berlin, Germany.
Marco
M
Kraft
University of Regensburg , Institute of Analytical Chemistry, Chemo- and Biosensors, 93040 Regensburg, Germany.
Markus
M
Buchner
University of Regensburg , Institute of Analytical Chemistry, Chemo- and Biosensors, 93040 Regensburg, Germany.
Antje J
AJ
Baeumner
BAM Federal Institute for Materials Research and Testing , Division 1.10 Biophotonics, 12489 Berlin, Germany.
Ute
0000-0002-0944-1115
U
Resch-Genger
University of Regensburg , Institute of Analytical Chemistry, Chemo- and Biosensors, 93040 Regensburg, Germany.
Thomas
0000-0002-4224-4762
T
Hirsch