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Synthesis of Hexagonal‐Phase NaYF 4 :Yb,Er and NaYF 4 :Yb,Tm Nanocrystals with Efficient Up‐Conversion Fluorescence
Author(s) -
Yi G. S.,
Chow G. M.
Publication year - 2006
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.200600053
Subject(s) - materials science , oleylamine , nanocrystal , nucleation , hexagonal phase , nanoparticle , transmission electron microscopy , phase (matter) , fluorescence , chemical engineering , nanotechnology , luminescence , optics , optoelectronics , organic chemistry , chemistry , physics , engineering
IR‐to‐visible up‐conversion fluorescent nanocrystals of hexagonal‐phase NaYF 4 :20 %Yb,2 %Er and NaYF 4 :20 %Yb,2 %Tm have been synthesized by decomposition of multiprecursors of CF 3 COONa, (CF 3 COO) 3 Y, (CF 3 COO) 3 Yb, and (CF 3 COO) 3 Er/(CF 3 COO) 3 Tm in oleylamine at 330 °C. The average particle size is 10.5 ± 0.7 nm (from random measurements of 200 particles from five transmission electron microscopy images) and 11.1 ± 1.3 nm (from dynamic‐light‐scattering measurements). The up‐conversion fluorescence intensity of the hexagonal nanocrystals in this work is much higher than that of other cubic‐phase NaYF 4 :Yb,Er nanocrystals, including the ones in this work (by a factor of 7.5). Mechanisms for nucleation and growth of the hexagonal‐phase nanoparticles are proposed. These nanocrystals are easily dispersed in organic solvents, producing a transparent colloidal solution. The hydrophobic surfaces of the particles are made hydrophilic using a bipolar surfactant. These nanoparticles and their dispersions in various media have potential applications in optical nanodevices and bioprobes.