TY - GEN A1 - Würth, Christian T1 - Systematic characterization of Upconversion nanoparticles: Effect of size, microenvironment, Energy transfer, shells N2 - Solid state multi-band emitters like lanthanide doped up-conversion nanoparticles (UCNPs) are promising materials for energy and biotechnologies. These materials are excitable in the near infrared (NIR) and show emission bands from UV to SWIR with excellent photostability, and long luminescence lifetimes in the µs range. The efficiency of these materials, i.e. the multiphoton absorption processes, the excitation power dependent population, and deactivation dynamics are strongly influenced by the particle size, structure, doping concentration, surface chemistry, and microenvironment. For applications UCNPs have to be optimized to meet the application relevant optical properties like the upconversion quantum yield (UC) and downshifting quantum yield (PL), luminescence lifetime and emission spectra. We investigated ß-NaYF4 NPs co-doped with Yb3+ and Er3+ in aqueous and organic media and as powder. For the later, bulk and nanomaterial is compared. For dispersed particles the influence of surface chemistry (ligands), microenvironment (solvent) and size (10 to 43 nm) was studied. Especially for bioapplications the Förster-Resonance-Energy-Transfer (FRET) efficiency from UCNPs to organic dye molecules (rose bengal and sulforhodamine B) was optimized with respect to the UCNP size. T2 - UpCon 2018 CY - Valencia, Spanien DA - 02.04.2018 KW - Nanoparticle KW - Upconversion KW - Quenching PY - 2018 UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/44762 AN - OPUS4-44762 AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany