Chemistry Reference
In-Depth Information
Tb, Ho, Tm) nanowires. In a typical synthesis, rare earth hydroxides
gels are precipitated in basic solutions (KOH) at room temperature
and treated hydrothermally at 180°C to produce nanowires. The
synthesized nanowires are shown in Fig. 2.8. The pH of the solution
played a pivotal role in shape tuning. For example, at lower pH
(i.e., 6-7), Sm(OH)
nanosheets of low aspect ratio were obtained
(Fig. 2.8c), while a higher pH (i.e., 9-10) resulted in nanowires
of high aspect ratio (Fig. 2.8d). Limited mobility of Sm
3
ions in
higher pH was inferred to be responsible for the shape formation.
The simulated crystal structure of RE(OH)
3+
(Fig. 2.8b) provides a
3
better insight. Along the
c
-axis, there are 1D chains consisting of
−
3+
alternating OH
anions and RE
cations connected to each other.
With changing pH, OH
−
ligands can capture or release protons
2−
to form O
O, changing the sign and density of charges on
the growing crystal faces, which ultimately change the crystal
morphology. The synthesized nanowires are proposed to be used as
potential biolabels.
or H
2
Figure 2.8
nanowires as a representative RE-
hydroxide; inset: HRTEM image of a single La(OH)
(a) TEM image of La(OH)
3
nanowire;
(b) simulated crystal mode, TEM images of Sm(OH)
3
(c)
nanosheets (pH 6-7); (d) nanowires (pH 9-10); (e) nanorods
(high alkali volume) [64].
3;
Rare earth orthophosphates exhibit high thermal stability,
low water solubility, and high refractive index and, therefore, are
promising in ceramics applications. Kinetically controlled (i.e.,
temperature-dependent) 1D wire-like REPO
( RE = La, Ce, Pr, Nd, Sm,
4
Eu, Gd, Tb, Dy) were reported by Fang
. [65] (Fig. 2.9). At room
temperature, gel-like precipitates comprising ball-like nanoparticle
assemblies were formed, while subsequent treatment at 140-240°C
resulted in particles, rods, and wires depending on the temperature
et al
