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Synthesis of Hexagonal Yb 3+ ,Er 3+ ‐Doped NaYF 4 Nanocrystals at Low Temperature
Author(s) -
Schäfer Helmut,
Ptacek Pavel,
Eickmeier Henning,
Haase Markus
Publication year - 2009
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200900642
Subject(s) - oleylamine , materials science , nanocrystal , luminescence , nanoparticle , hexagonal phase , phosphor , phase (matter) , analytical chemistry (journal) , particle size , doping , photoluminescence , chemical engineering , nanotechnology , optoelectronics , organic chemistry , chemistry , engineering
Nanocrystals of NaYF 4 doped with Yb 3+ and Er 3+ are synthesized in oleylamine using Y 2 (CO 3 ) 3 , Yb 2 (CO 3 ) 3 , Er 2 (CO 3 ) 3 , Na 2 CO 3 , and NH 4 F as precursors. In contrast to other starting materials normally used for such syntheses, these precursors react even at room temperature to form hexagonal‐phase ( β ‐phase) NaYF 4 :Er,Yb nanoparticles. Cubic‐phase ( α ‐phase) NaYF 4 :Yb,Er particles are formed only at elevated temperatures (>250 °C). The formation of the cubic phase at high temperatures can be suppressed by replacing pure oleylamine with oleic acid/oleylamine mixtures. Under optimized reaction conditions, particles with an average particle size of about 7 nm are generated in 84% yield. Heat treatment (30 min, 280 °C) of the particles significantly increases the luminescence efficiency. A transparent solution of the heat‐treated, nanometer‐sized phosphor in toluene shows intense visible light emission upon excitation in the near infrared.