Synthesis of 10 nm β‐NaYF4:Yb,Er/NaYF4 Core/Shell Upconversion Nanocrystals with 5 nm Particle Cores |
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| Authors: | Thorben Rinkel Athira Naduviledathu Raj Simon Dühnen Prof?Dr Markus Haase |
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| Affiliation: | Institute of Chemistry of New Materials, University of Osnabrück, Osnabrück, Germany |
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| Abstract: | A new method is presented for preparing gram amounts of very small core/shell upconversion nanocrystals without additional codoping of the particles. First, ca. 5 nm β‐NaYF4:Yb,Er core particles are formed by the reaction of sodium oleate, rare‐earth oleate, and ammonium fluoride, thereby making use of the fact that a high ratio of sodium to rare‐earth ions promotes the nucleation of a large number of β‐phase seeds. Thereafter, a 2 nm thick NaYF4 shell is formed by using 3–4 nm particles of α‐NaYF4 as a single‐source precursor for the β‐phase shell material. In contrast to the core particles, however, these α‐phase particles are prepared with a low ratio of sodium to rare‐earth ions, which efficiently suppresses an undesired nucleation of β‐NaYF4 particles during shell growth. |
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| Keywords: | core/shell nanocrystals lanthanides luminescence nanoparticles upconversion |
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