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Carl, Frederike; Birk, Leonie; Grauel, Bettina; Pons, Monica; Würth, Christian; Resch-Genger, Ute; Haase, Markus

LiYF4:Yb/LiYF4 and LiYF4:Yb,Er/LiYF4 core/shell nanocrystals with luminescence decay times similar to YLF laser crystals and the upconversion quantum yield of the Yb,Er doped nanocrystals

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  • Medientyp: E-Artikel
  • Titel: LiYF4:Yb/LiYF4 and LiYF4:Yb,Er/LiYF4 core/shell nanocrystals with luminescence decay times similar to YLF laser crystals and the upconversion quantum yield of the Yb,Er doped nanocrystals
  • Beteiligte: Carl, Frederike; Birk, Leonie; Grauel, Bettina; Pons, Monica; Würth, Christian; Resch-Genger, Ute; Haase, Markus
  • Erschienen: Springer Science and Business Media LLC, 2021
  • Erschienen in: Nano Research
  • Sprache: Englisch
  • DOI: 10.1007/s12274-020-3116-y
  • ISSN: 1998-0124; 1998-0000
  • Schlagwörter: Electrical and Electronic Engineering ; General Materials Science ; Condensed Matter Physics ; Atomic and Molecular Physics, and Optics
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  • Beschreibung: <jats:title>Abstract</jats:title><jats:p>We developed a procedure to prepare luminescent LiYF<jats:sub>4</jats:sub>:Yb/LiYF<jats:sub>4</jats:sub> and LiYF<jats:sub>4</jats:sub>:Yb,Er/LiYF<jats:sub>4</jats:sub> core/shell nanocrystals with a size of approximately 40 nm revealing luminescence decay times of the dopant ions that approach those of high-quality laser crystals of LiYF<jats:sub>4</jats:sub>:Yb (Yb:YLF) and LiYF<jats:sub>4</jats:sub>:Yb,Er (Yb,Er:YLF) with identical doping concentrations. As the luminescence decay times of Yb<jats:sup>3+</jats:sup> and Er<jats:sup>3+</jats:sup> are known to be very sensitive to the presence of quenchers, the long decay times of the core/shell nanocrystals indicate a very low number of defects in the core particles and at the core/shell interfaces. This improvement in the performance was achieved by introducing two important modifications in the commonly used oleic acid based synthesis. First, the shell was prepared via a newly developed method characterized by a very low nucleation rate for particles of pure LiYF<jats:sub>4</jats:sub> shell material. Second, anhydrous acetates were used as precursors and additional drying steps were applied to reduce the incorporation of OH<jats:sup>−</jats:sup> in the crystal lattice, known to quench the emission of Yb<jats:sup>3+</jats:sup> ions. Excitation power density (<jats:italic>P</jats:italic>)-dependent absolute measurements of the upconversion luminescence quantum yield (<jats:italic>Φ</jats:italic><jats:sub>UC</jats:sub>) of LiYF<jats:sub>4</jats:sub>:Yb,Er/LiYF<jats:sub>4</jats:sub> core/shell particles reveal a maximum value of 1.25% at <jats:italic>P</jats:italic> of 180 Wcm<jats:sup>−2</jats:sup>. Although lower than the values reported for NaYF<jats:sub>4</jats:sub>:18%Yb,2%Er core/shell nanocrystals with comparable sizes, these <jats:italic>Φ</jats:italic><jats:sub>UC</jats:sub> values are the highest reported so far for LiYF<jats:sub>4</jats:sub>:18%Yb,2%Er/LiYF<jats:sub>4</jats:sub> nanocrystals without additional dopants. Further improvements may nevertheless be possible by optimizing the dopant concentrations in the LiYF<jats:sub>4</jats:sub> nanocrystals. </jats:p>