@article{BastianRobelSchmidtetal.2021,
  author    = {Bastian, Philipp U. and Robel, Nathalie and Schmidt, Peter and Schrumpf, Tim and G{\"u}nter, Christina and Roddatis, Vladimir and Kumke, Michael U.},
  title     = {Resonance energy transfer to track the motion of lanthanide ions},
  series = {Biosensors : open access journal},
  volume    = {11},
  journal   = {Biosensors : open access journal},
  number    = {12},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2079-6374},
  doi       = {10.3390/bios11120515},
  pages     = {23},
  year      = {2021},
  abstract  = {The imagination of clearly separated core-shell structures is already outdated by the fact, that the nanoparticle core-shell structures remain in terms of efficiency behind their respective bulk material due to intermixing between core and shell dopant ions. In order to optimize the photoluminescence of core-shell UCNP the intermixing should be as small as possible and therefore, key parameters of this process need to be identified. In the present work the Ln(III) ion migration in the host lattices NaYF4 and NaGdF4 was monitored. These investigations have been performed by laser spectroscopy with help of lanthanide resonance energy transfer (LRET) between Eu(III) as donor and Pr(III) or Nd(III) as acceptor. The LRET is evaluated based on the Forster theory. The findings corroborate the literature and point out the migration of ions in the host lattices. Based on the introduced LRET model, the acceptor concentration in the surrounding of one donor depends clearly on the design of the applied core-shell-shell nanoparticles. In general, thinner intermediate insulating shells lead to higher acceptor concentration, stronger quenching of the Eu(III) donor and subsequently stronger sensitization of the Pr(III) or the Nd(III) acceptors. The choice of the host lattice as well as of the synthesis temperature are parameters to be considered for the intermixing process.},
  language  = {en}
}
@article{HesseKlierSgarzietal.2018,
  author    = {Hesse, Julia and Klier, Dennis Tobias and Sgarzi, Massimo and Nsubuga, Anne and Bauer, Christoph and Grenzer, Joerg and H{\"u}bner, Rene and Wislicenus, Marcus and Joshi, Tanmaya and Kumke, Michael Uwe and Stephan, Holger},
  title     = {Rapid Synthesis of Sub-10nm Hexagonal NaYF4-Based Upconverting Nanoparticles using Therminol((R))66},
  series = {ChemistryOpen : including thesis treasury},
  volume    = {7},
  journal   = {ChemistryOpen : including thesis treasury},
  number    = {2},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {2191-1363},
  doi       = {10.1002/open.201700186},
  pages     = {159 -- 168},
  year      = {2018},
  abstract  = {We report a simple one-pot method for the rapid preparation of sub-10nm pure hexagonal (-phase) NaYF4-based upconverting nanoparticles (UCNPs). Using Therminol((R))66 as a co-solvent, monodisperse UCNPs could be obtained in unusually short reaction times. By varying the reaction time and reaction temperature, it was possible to control precisely the particle size and crystalline phase of the UCNPs. The upconversion (UC) luminescence properties of the nanocrystals were tuned by varying the concentrations of the dopants (Nd3+ and Yb3+ sensitizer ions and Er3+ activator ions). The size and phase-purity of the as-synthesized core and core-shell nanocrystals were assessed by using complementary transmission electron microscopy, dynamic light scattering, X-ray diffraction, and small-angle X-ray scattering studies. In-depth photophysical evaluation of the UCNPs was pursued by using steady-state and time-resolved luminescence spectroscopy. An enhancement in the UC intensity was observed if the nanocrystals, doped with optimized concentrations of lanthanide sensitizer/activator ions, were further coated with an inert/active shell. This was attributed to the suppression of surface-related luminescence quenching effects.},
  language  = {en}
}