Synthesis of REF3 (RE = Nd, Tb) nanoparticles via a solvent extraction route

Article abstract of DOI:10.1016/j.materresbull.2009.02.001

NdF₃ and TbF₃ nanoparticles were successfully synthesized via a solvent extraction route using Cynex923 (R₃P{double bond, long}O). X-ray diffraction (XRD) study showed that pure hexagonal phase NdF₃ and pure ort

Full text of DOI:10.1016/j.materresbull.2009.02.001

Materials Research Bulletin 44 (2009) 1565–1568
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Materials Research Bulletin
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Synthesis of REF (RE = Nd, Tb) nanoparticles via a solvent extraction route
3
a,b
a
a
a
a,
Fuqiang Guo , Hongfei Li , Zhifeng Zhang , Shulan Meng , Deqian Li *
a
State Key Laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun 130022, China
b
Graduate University of Chinese Academy of Sciences, Beijing 100049, China
A R T I C L E I N F O
A B S T R A C T
Article history:
NdF3 and TbF3 nanoparticles were successfully synthesized via a solvent extraction route using
Received 3 September 2008
Received in revised form 29 January 2009
Accepted 3 February 2009
Available online 13 February 2009
Cynex923 (R
orthorhombic phase TbF
electron microscopy (TEM) and scanning electron microscopy (SEM) observations indicated that as-
obtained NdF nanoplates have a diameter of 50–80 nm and thickness of 10–20 nm and TbF products
3
P
O). X-ray diffraction (XRD) study showed that pure hexagonal phase NdF
3
and pure
3
could be obtained under the current synthetic conditions. Transmission
3
3
have sphere morphologies with diameter from 70 to 170 nm. The driving force for the growth of NdF
nanoplates could be attributed to the hexagonal crystal structure. The luminescence properties of NdF
3
3
Keywords:
A. Fluorides
and TbF
3 3
nanoparticles were investigated, which indicated that NdF nanoparticles showed typical
A. Nanostructures
B. Chemical synthesis
C. Electron microscopy
D. Optical properties
3+
emission at 888, 1064, and 1328 nm and TbF
3
nanoparticles showed characteristic emission of Tb (f–f).
ß 2009 Elsevier Ltd. All rights reserved.
1
. Introduction
2 2
the porous spherical TiO nanoparticles [32], mesoporous ZrO
powder [33] and titanium phosphate nanotubes [34] were
prepared via solvent extraction route. However, the synthesis of
The novel properties of rare earth compounds have drawn
continuous research attention to practical applications in lumi-
nescence, catalysis, and biological fields [1]. As an important rare
3
REF nanoparticles via solvent extraction route has not been
reported in the literature by now, to the best of our knowledge. In
addition, the solvent extraction route provides an opportunity for
the integration of hydrometallurgical extraction and materials
synthesis [35], which may facilitate the continuous and large-scale
production of nanomaterials.
3
earth compound, rare earth fluorides (REF ) are currently under
active investigation because of their unique optical [2,3],
optoelectronics [4], magneto-optical [5], scintillation [6,7], and
tribology properties [8,9]. These outstanding luminescent char-
acteristics are due to the lanthanide ions’ sharp absorption and
emission bands in the ultraviolet, visible and infrared wavelength
regions, originated from f–d and f–f transitions. Their high Faraday
effect with very low absorption in the visible is applicable to
optoelectronics such as an optical isolator, optical switches or
optical memory [4].
3 3
The present paper explores the synthesis of NdF and TbF
nanoparticles via a solvent extraction route and the luminescence
properties are characterized. The extractant loading with lantha-
nide ions acts as the template and metal ions source. The
lanthanide ion release and precipitation reaction rates are
controlled by the coordination capability between the extractant
and lanthanide ions. The nanoparticles were investigated using
XRD, TEM, SEM, DLS, and FTIR. Their excitation and emission
spectra were studied.
Several approaches involving modified precipitation [10,11],
microemulsion [8,12–16], polyol [17,18], and hydrothermal
methods [19–26] have been used to synthesize a variety of
3
REF . Some other novel methods such as ultrasound assisted route
[
27], microwave synthesis [28], polymer-involved arc discharge
2
. Experimental
method [29], single-source precursor (SSP) route [30], and liquid–
solid–solution (LSS) phase transfer synthesis [31] are also used for
2.1. Synthesis
3
the synthesis of REF . As an alternative method, the solvent
extraction route is of considerable interest owing to its efficient,
economical, and environmentally friendly characteristics. So far,
Cyanex923 is a mixture of tri-alkyl phosphine oxides, alkyl
being n-hexyl and n-octyl, which is a commercially available
extractant kindly supplied by Cytec Canada Inc. 4-(1,1,3,3-
Tetramethylbutyl)phenyl-polyethylene glycol (Triton X-100) was
purchased from Sigma–Aldrich.
*
Corresponding author. Tel.: +86 431 85262036; fax: +86 431 85698041.
E-mail address: ldq@ciac.jl.cn (D. Li).
0025-5408/$ – see front matter ß 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.materresbull.2009.02.001

1
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F. Guo et al. / Materials Research Bulletin 44 (2009) 1565–1568
In a typical synthesis, a total of 20 ml of the organic phase
containing Cyanex923 at 0.7 mol/l in n-heptane and 10 ml of the
aqueous phase (0.5 mol/l Nd(NO or Tb(NO ) were mixed in a
0-ml separating funnel, and then shaken for 30 min with a
3
)
3
3 3
)
3
mechanical shaker. The organic and aqueous phases were
separated by centrifugation for 5 min. The obtained organic phase
loading with Nd(NO
3 3 3 3
) or Tb(NO ) was added dropwise into a 50-
ml conical flask containing 10 ml mixing solution of 1.5 mol/l NH
4
F
and 0.5% Triton X-100. The conical flask was then exposed to an
ultrasonic bath under ambient air for 20 min. White precipitates
were obtained, and the used Cyanex923 could be recycled. The as-
obtained precipitates were centrifuged and washed with deionized
water and acetone in sequence. The final product was dried in
vacuum at 60 8C for 5 h.
Bulk NdF
stoichiometric amounts of 0.5 mol/l Nd(NO
.14 mol/l HF aqueous solutions.
3
(or TbF
3
) particles were prepared by mixing
3
)
3
(or Tb(NO ) and
3 3
)
1
2.2. Methods
3 3
Fig. 1. XRD patterns of (a) NdF and (b) TbF nanoparticles.
˚
˚
The samples were characterized on a Rigaku D/MAX-2500 X-ray
˚
lattice constants a = 7.0202 A and c = 7.1912 A (JCPDS 78-1858).
Fig. 1b shows typical XRD patterns for TbF nanoparticles. The
diffraction pattern of the product can be indexed to a pure
orthorhombic phase (space group: Pnma (no. 62)) of TbF with
powder diffractometer with Cu K
a
radiation (
l
= 1.5406 A) and a
3
scanning rate of 158/min. The operation voltage and current were
maintained at 40 kV and 150 mA, respectively. Scanning electron
microscopy (SEM) images were taken on a Hitachi-S4800 electron
microscope. Samples for SEM observation were prepared by
dropping a diluted suspension of the sample powders on silicon
substrate. The samples were spraycoated with a thin layer of
platinum before observation. Transmission electron microscopy
3
˚
˚
˚
lattice constants a = 6.3349 A, b = 6.8121 A and c = 4.3580 A, which
is in good agreement with the literature (JCPDS 37-1487). A
thorough XRD characterization indicates that pure phase of the
rare earth fluorides could be obtained under the current synthetic
conditions.
(
TEM) images were acquired by a JEOL JEM-1011 transmission
Transmission electron microscopy (TEM) and scanning electron
microscopy (SEM) provide further insight into the morphology and
electron microscope at 100 kV. Samples for TEM observation were
prepared by evaporating a drop of diluted particle dispersion on a
carbon coated 300 mesh copper grid. The dynamic light scattering
microstructural details of NdF
3
and TbF
3
nanoparticles. As shown
products
in the TEM image in Fig. 2a and b, the as-obtained NdF
3
(
DLS) experiments were performed on a particle size analyzer,
are block-like particles consisting of several round nanoplates. The
diameter and thickness of the plates are estimated to range from
50 to 80 nm and 10 to 20 nm, respectively. In TEM images, the
plate-built nanoparticles exhibit the morphology of particles made
up of rods, for the edges of the stacked plates tend to lie on the
substrate [26]. However, some of nanoplates or stacked nanoplates
cannot lie on the substrate. They exhibit round or ellipse
morphology in the TEM image (Fig. 2b). The SAED of a single
plate-like nanoparticle (inset of Fig. 2a) has revealed the
model Zetasizer 1000HS (Malvern instruments, UK). FTIR spectra
were taken on a BRUKER Vertex 70 FTIR spectrometer (BRUKER
OPTICS, Germany) in the range 400–4000 cm . All spectra were
ꢀ
1
ꢀ1
recorded at a resolution of 2 cm
excitation and emission spectra of TbF
500 spectrophotometer equipped with a 150 W xenon lamp as
the excitation source. The luminescence spectra of NdF were
with 32-sample scans. The
3
were taken on a Hitachi F-
4
3
recorded on a JY FL-3 spectrophotometer equipped with a 450 W
Xe arc lamp and a liquid nitrogen cooled R5509 NIR PMT.
polycrystalline nature of NdF
stacked nanoplates can be clearly seen in SEM image (Fig. 2c). Fig. 3
shows typical images of TbF nanoparticles, from which it can be
3 3
products. NdF nanoplates and
3
. Results and discussion
3
seen that most of the samples dispersed on the substrate have
sphere morphologies with diameter from 70 to 170 nm. Based on
The crystalline phases of the as-obtained products were
identified by X-ray diffraction (XRD). As shown in Fig. 1a, the
reflections of the XRD pattern can be readily indexed to a pure
3
the results, the driving force for the growth of NdF nanoplates
could be attributed to the hexagonal crystal structure, which is
well known to exhibit anisotropic growth [36].
3
hexagonal phase (space group: P63cm (no. 185)) of NdF with
Fig. 2. (a) TEM image of NdF
3
3
nanoparticles (inset: SAED patterns taken from a single rodlike nanoparticle); (b) magnified TEM image of NdF nanoparticles (inset: a single
plate-built nanoparticle); (c) SEM image of NdF
3
nanoparticles.

F. Guo et al. / Materials Research Bulletin 44 (2009) 1565–1568
1567
3 3
Fig. 3. (a) TEM images of TbF nanoparticles; (b) SEM images of TbF nanoparticles.
3 3
Fig. 4. Particle size distribution using dynamic light scattering: (a) NdF and (b) TbF nanoparticles.
3
+
Dynamic light scattering studies (Fig. 4) show the particle size
distribution of the samples. As shown in Fig. 4a, there are two
peaks located in the range of 17–25 nm and 40–70 nm, respec-
J = 9/2, 11/2, 13/2). The excitation spectrum (Fig. 6c) of Tb
contains an intense band at 219 nm, which are due to the
7
3+
8
transitions from the ground state ( F
6
)
of the Tb
(4f)
7
tively. It is attributed to the partial agglomeration of NdF
nanoplates. The size distribution of TbF nanoparticles tends to
be a little broader (Fig. 4b). The particles in the range of 130–
00 nm were detected. In addition, the size observed is larger than
3
configuration to the different excited states of the (4f) 5d
configuration. The forbidden f–f excited transitions of Tb can
also be observed clearly in the excitation spectrum. Upon
3+
3
2
3
excitation at 219 nm, the TbF nanoparticles give characteristic
5
7
0
5
7
obtained by TEM [37].
blue emission
(J = 3, 4, 5, 6) of Tb , of which the D
is the most prominent one (Fig. 6d).
D
3
– F
J
0
(J = 3, 4, 5) and green emission
D
4
– F
J
3
+
5
7
Fig. 5 shows the FTIR spectra of bulk TbF
3
particles and as-
4 5
– F (543 nm) green emission
ꢀ1
synthesized TbF
spectrum a: bulk TbF
3
nanoparticles. The peaks at 3292 (3431 cm in
ꢀ
1
3
particles) and 1638 cm are attributed to
the stretching vibration of –OH group and bending vibration of
adsorbed molecular water, respectively [38]. Compared with
spectrum of bulk TbF
X-100, such as carbon chain, methyl, ether C–O–C, and phenyl ring
were found in the spectrum of the as-synthesized TbF nanopar-
are assigned to the
3
particles, all groups of surfactant Triton
3
ꢀ1
ticles. The peaks at 2929 and 2858 cm
vibration of carbon chain –(CH –; the peak at 1429 cm
assigned to the asymmetric deformation mode of CH groups; the
are assigned to the symmetric
ꢀ
1
2
)
n
is
3
ꢀ1
peaks at 1081 and 1020 cm
ꢀ
1
stretching vibration of C–O–C group; and the peak at 813 cm is
assigned to the C–H out-of-plane bending vibration of the phenyl
ring. It is speculated that the surfactant molecules are associated
3
with the as-synthesized TbF nanoparticles. The as-synthesized
NdF nanoparticles are also modified by the surfactant. The FTIR
3
spectrum is not shown in this paper.
Luminescence spectra of the as-synthesized NdF
3
and TbF
3
nanoparticles are shown in Fig. 6. The excitation spectra of NdF
3
nanoparticles (Fig. 6a) were collected after emission at 1064 nm
and the emission spectra (Fig. 6b) were obtained by collecting the
3
excitation at 520 nm. The spectra of NdF nanoparticles show the
Fig. 5. FTIR spectra of (a) bulk TbF
3 3
particles and (b) as-synthesized TbF
3+
4
4
typical luminescence of Nd at 888, 1064, and 1328 nm ( F3/2– I
J
,
nanoparticles.

1
568
F. Guo et al. / Materials Research Bulletin 44 (2009) 1565–1568
nanomaterials might find applications in optics, optoelectronics,
magneto-optics, and tribology.
Acknowledgements
Many thanks are given to Cytec Canada Inc. for supplying
Cyanex923. This project was supported by the National Basic
Research Program of China (2006CB403302).
References
[
[
[
1] G.X. Xu, Rare Earths, 2nd ed., Metallurgical Industry Press, Beijing, 1995.
2] C.G. Olson, M. Piacentini, D.W. Lynch, Phys. Rev. B 18 (1978) 5740.
3] J.W. Stouwdam, G.A. Hebbink, J. Huskens, F.C.J.M. van Veggel, Chem. Mater. 15
(2003) 4604.
[
[
[
4] K. Tanaka, K. Fujita, N. Soga, J. Qiu, K. Hirao, J. Appl. Phys. 82 (1997) 840.
5] Y. Xu, M.Q. Duan, Phys. Rev. B 46 (1992) 11636.
6] K. Shimamura, E.G. V ı´ llora, S. Nakakita, M. Nicl, N. Ichinose, J. Cryst. Growth 264
(2004) 208.
[
7] K. Shimamura, E.G. V ı´ llora, S. Nakakita, M. Nicl, N. Ichinose, Nucl. Instrum.
Methods A 537 (2005) 139.
[
[
8] S.Q. Qiu, J.X. Dong, G.X. Chen, Wear 230 (1999) 35.
9] L.B. Wang, M. Zhang, X.B. Wang, W.M. Liu, Mater. Res. Bull. 43 (2008) 2220.
[
[
[
[
[
[
[
[
[
10] J. Zhou, Z. Wu, Z. Zhang, W. Liu, H. Dang, Wear 249 (2001) 333.
11] J.W. Stouwdam, F.C.J.M. van Veggel, Nano Lett. 2 (2002) 733.
12] S.Q. Qiu, J.X. Dong, G.X. Chen, Powder Technol. 113 (2000) 9.
13] H. Guo, Appl. Phys. B 84 (2006) 365.
14] H. Zhang, H.F. Li, D.Q. Li, S.L. Meng, J. Colloid Interface Sci. 302 (2006) 509.
15] H. Lian, M. Zhang, J. Liu, Z. Ye, J. Yan, C. Shi, Chem. Phys. Lett. 395 (2004) 362.
16] J.-L. Lemyre, A.M. Ritcey, Chem. Mater. 17 (2005) 3040.
17] S. Eiden-Assmann, G. Maret, Mater. Res. Bull. 39 (2004) 21.
18] Z.L. Wang, Z.W. Quan, P.Y. Jia, C.K. Lin, Y. Luo, Y. Chen, J. Fang, W. Zhou, C.J.
O’Connor, J. Lin, Chem. Mater. 18 (2006) 2030.
[
[
19] X. Wang, Y.D. Li, Angew. Chem., Int. Ed. 42 (2003) 3497.
20] C.Y. Cao, W.P. Qin, J.S. Zhang, Y. Wang, P.F. Zhu, G.F. Wang, G.D. Wei, L.L. Wang, L.Z.
Jin, J. Fluorine Chem. 129 (2008) 204.
[21] G. De, W.P. Qin, J.S. Zhang, J.S. Zhang, Y. Wang, C.Y. Cao, Y. Cui, J. Lumin. 122–123
(2007) 128.
[
[
22] F. Tao, Z.J. Wang, L.Z. Yao, W.L. Cai, X.G. Li, J. Phys. Chem. C 111 (2007) 3241.
23] M.F. Zhang, H. Fan, B.J. Xi, X.Y. Wang, C. Dong, Y.T. Qian, J. Phys. Chem. C 111
(
2007) 6652.
24] C.X. Li, X.M. Liu, P.P. Yang, C.M. Zhang, H.Z. Lian, J. Lin, J. Phys. Chem. C 112 (2008)
904.
25] M. Wang, Q.L. Huang, H.X. Zhong, X.T. Chen, Z.L. Xue, X.Z. You, Cryst. Growth Des.
(2007) 2106.
[
[
2
Fig. 6. Excitation (a) and emission (b) spectra of NdF
3
nanoparticles; excitation (c)
and emission (d) spectra of TbF nanoparticles.
3
7
[
[
26] F. Bao, Y.S. Wang, Y. Cheng, Y.H. Zheng, Mater. Lett. 60 (2006) 389.
27] L. Zhu, Q. Li, X.D. Liu, J.Y. Li, Y.F. Zhang, J. Meng, X.Q. Cao, J. Phys. Chem. C 111
(
2007) 5898.
4
. Conclusions
In this paper, based on a solvent extraction route, NdF
[
[
[
[
[
28] L. Ma, W.X. Chen, Z.D. Xu, Mater. Lett. 62 (2008) 2596.
29] Z.Y. Wang, Z.B. Zhao, J.S. Qiu, Chem. Mater. 19 (2007) 3364.
30] Y.W. Zhang, X. Sun, R. Si, L.P. You, C.H. Yan, J. Am. Chem. Soc. 127 (2005) 3260.
31] X. Wang, J. Zhuang, Q. Peng, Y.D. Li, Nature 437 (2005) 121.
32] J.H. Shi, G.H. Gu, X. Fu, M.Y. Wang, Z.S. Hu, Colloid Surf. A 194 (2001) 207.
[33] L.L. Yu, G.H. Gu, J.Y. Yang, H.T. Zhu, L. Chen, L.S. Feng, X. Fu, J. Colloid Interface Sci.
265 (2003) 101.
3
and TbF
3
nanoparticles have been successfully synthesized and character-
ized. The nanoparticles were formed at the organic/aqueous phase
interface during the stripping process and modified by Triton X-
[
34] Z.L. Yin, Y. Sakamoto, J.H. Yu, S.X. Sun, O. Terasaki, R.R. Xu, J. Am. Chem. Soc. 126
2004) 8882.
35] K. Osseo-Asare, Adv. Colloid Interface Sci. 37 (1991) 123.
1
00 at one time. SEM and TEM data from samples suggest that the
morphologies of nanoparticles can be predicted in terms of the
crystallographic structure. Photoluminescences of NdF and TbF
nanoparticles have also been investigated. This facile procedure
can be easily adjusted for series of rare earth fluoride
nanoparticles with different morphologies. We hope that these
(
[
[36] M.H. Huang, S. Mao, H. Feick, H.Q. Yan, Y.Y. Wu, H. Kind, E. Weber, R. Russo, P.D.
Yang, Science 292 (2001) 1897.
3
3
[
37] J. Ahmed, S. Vaidya, T. Ahmad, P.S. Devi, D. Das, A.K. Ganguli, Mater. Res. Bull. 43
2008) 264.
[38] C.P.Sibu,S.RajeshKumar,P.Mukundan,K.G.K.Warrier,Chem.Mater.14(2002)2876.
a
(