NaYF4 :Yb,Er/NaYF4 Core/Shell Nanocrystals with High Upconversion Luminescence Quantum Yield.
Angew Chem Int Ed Engl
; 57(28): 8765-8769, 2018 07 09.
Article
em En
| MEDLINE
| ID: mdl-29732658
Upconversion core/shell nanocrystals with different mean sizes ranging from 15 to 45â
nm were prepared via a modified synthesis procedure based on anhydrous rare-earth acetates. All particles consist of a core of NaYF4 :Yb,Er, doped with 18 % Yb3+ and 2 % Er3+ , and an inert shell of NaYF4 , with the shell thickness being equal to the radius of the core particle. Absolute measurements of the photoluminescence quantum yield at a series of different excitation power densities show that the quantum yield of 45â
nm core/shell particles is already very close to the quantum yield of microcrystalline upconversion phosphor powder. Smaller core/shell particles prepared by the same method show only a moderate decrease in quantum yield. The quantum yield of 15â
nm core/shell particles, for instance, is reduced by a factor of three compared to the bulk upconversion phosphor at high power densities (100â
W cm-2 ) and by approximately a factor of 10 at low power densities (1â
W cm-2 ).
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2018
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Article