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and monodisperse truncated octahedral YF
nanocrystals in large
3
2+
quantities [97, 98]. Significant activity of Eu
was observed in the
aqueous solution at low temperature (ca. 100
°
C), and so the Eu
2+
.
synthesized YOF nanoparticles by the decomposition of a single-
source precursor, namely, sodium yttrium fluorocarbonate, under
mild hydrothermal conditions, followed by thermal treatments [99].
Li
emission was observed in the Eu-doped YF
products. Zeng
et al
3
(R =Eu,
Tb, Yb/Er, and Yb/Tm) submicroprism crystals in hexagonal phase
with good uniformity [100]. RECl
et al
. reported the hydrothermal synthesis of NaYF
:R
3+
4
, sodium citrate, and NaF were used
as starting materials, and the ratio of sodium citrate and RE
3
3+
was
found to have strong influence on the shape and size of the products
(Fig. 1.9). They also
submicrocrystals with
different phase and morphologies, including
synthesized NaYbF
4
β
-NaYbF
microdisks,
4
β
microprisms,
microtubes,
-NaLuF
microprisms, microdisks,
4
microtubes,
β
-NaLuF
sub-microplates,
α
-NaYbF
submicrospheres,
4
4
α
and
employed an
EDTA modified hydrothermal method to prepare prismatic NaHoF
-NaLuF
submicrospheres [101-103]. Wu
et al.
4
4
microtubes and NaSmF
nanotubes [104].
4
Figure 1.9
SEM images for β-NaYF
:5%Tb
3+
samples prepared with
different molar ratios of sodium citrate and RE
3+
: (a) without
sodium citrate, (b) 1:2, (c) 1:1, (d) 2:1, (e) 4:1, (f) 8:1. Insets are
higher-magnification images for the corresponding samples.
4
