Scalable synthesis of Sb(III)Sb(V)O4 nanorods from Sb 2O5 powder via solvothermal processing

Article abstract of DOI:10.1016/j.ssc.2005.01.013

Scalable Sb(III)Sb(V)O₄ nanorods from Sb₂O ₅ powder were prepared using solvothermal route. XRD and HRTEM demonstrate that the nanorods are single-crystal orthorhombic-Sb ₂O₄ phase with several micrometers long and 200-300 nm diameter size. XPS result further shows that the antimony cations in the nanorods are composed of three valence and five valence antimony ions. The emission of the nanorods appears around 450 nm wavelength. The formation mechanism of the Sb(III)Sb(V)O₄ nanorods was discussed in detail.

Full text of DOI:10.1016/j.ssc.2005.01.013

Solid State Communications 133 (2005) 765–769
www.elsevier.com/locate/ssc
Scalable synthesis of Sb(III)Sb(V)O nanorods from Sb O powder
4
2 5
via solvothermal processing
*
Tianhao Ji , Maoyu Tang, Lin Guo, Xingyi Qi, Qinglin Yang, Huibin Xu
Applied Chemistry Department, School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics,
Beijing 100083, People’s Republic of China
Received 13 December 2004; accepted 10 January 2005 by C.N.R. Rao
Available online 25 January 2005
Abstract
Scalable Sb(III)Sb(V)O4 nanorods from Sb O powder were prepared using solvothermal route. XRD and HRTEM
demonstrate that the nanorods are single-crystal orthorhombic-Sb O phase with several micrometers long and 200–300 nm
2
5
2
4
diameter size. XPS result further shows that the antimony cations in the nanorods are composed of three valence and five
valence antimony ions. The emission of the nanorods appears around 450 nm wavelength. The formation mechanism of the
Sb(III)Sb(V)O nanorods was discussed in detail.
4
q 2005 Elsevier Ltd. All rights reserved.
PACS: 68.37.Lp; 76.67.Kn; 81.07.Kb
Keywords: A. Nanostructures; B. Nanofabrications; C. Transmission electron microscopy
Nanometer-sized semiconductor oxides of nanowires or
nanorods have stimulated intensive research activities due to
their high stability and potential values for fundamental
studies of dimensionality and size in the physical properties
as well as for the application in optoelectronic nanodevices
oxide has been reported to exhibit high proton conductivity,
so it has potential application in humidity-sensing material
[10]. Herein we utilized the Sb
O powder directly and
2 5
simply to synthesize a large scale of Sb(III)Sb(V)O
4
(denoted as SSO) nanorods under mild condition by
solvothermal method. General SSO powder material can
[
1]. Recently, the nanowires or nanorods of several binary
be prepared using Sb
or at high temperature and high pressure (300–500 8C, 100–
800 atm) by the mixture of Sb with Sb in NaOH and
aqueous solutions [12], whereas the synthesis and
2 5
O at about 750 8C for a long time [11]
oxides, such as In [2], Ga [3], SnO [4], ZnO [5] or
3
2
O
2
O
3
2
TiO [6], have been successfully prepared. However, until
2
1
2
O
3
2 5
O
now, a large scale of nanorods or nanowires of antimony
oxides have not been obtained yet.
2 2
H O
characterization of the SSO nanorods have hardly been
studied except for the microemulsion preparation of only
single low-quality SSO nanowire (shown in TEM image)
reported in the literature [13].
2 3 2 5
The antimony oxides of Sb O and Sb O have been
widely used in many applications. They are additive
materials of flame retardant [7,8] and they are also used as
an optical materials due to its high refractive index and high
abrasive resistance [8]. As a kind of Lewis acid catalyst, the
2 5
In this communication, ball-milled Sb O powder was
chosen as starting compound to synthesis the SSO nanorods,
since it can be easily bought and long-time stored as well as
considered on the basis of structural transformation from
general powder to special shape materials which have
special applications in many fields. Additionally, more
importance is that it can slowly dissolve in warm alkali
Sb
2 5
O has shown good active for the transformation of
propene into acrylonitrile [9]. Recently, hydrous antimony
*
Corresponding author. Tel./fax: C86 1082314436.
E-mail address: tianji@buaa.edu.cn (T. Ji).
0038-1098/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.ssc.2005.01.013

766
T. Ji et al. / Solid State Communications 133 (2005) 765–769
solution, so in soft template of the mixture of ethylenedia-
mine (EA) with ethylene glycol (EG) and part reduction of
5C
3C
the Sb to Sb cations by the EA, a large scale of the SSO
nanorods can be obtained. Under high temperature of
solvothermal process, the reductive property of the EA has
been confirmed [14].
Fig. 1 is the schematic illumination of the SSO nanorods
and metal antimony particles prepared from the ball-milled
Sb O5 powder. The SSO nanorods were obtained in the
2
mixture solution of the EA and EG with a little bit oleic acid
and water at 200 8C for reaction time of 24 h, whereas over
reaction time of 65 h, metal antimony particles were
prepared due to the completely reduction of precursor
2 5
Sb O . The SSO nanorods were also obtained when the
reaction temperature was decreased to 150 8C, but reaction
time needs much longer than that at 200 8C. This is because
at low temperature the dissolution and part reduction of the
Fig. 2. XRD patterns of (a) the orthorhombic Sb(III)Sb(V)O
nanorods, (b) the hexagonal metal Sb particles and (c) the used
precursor Sb powder.
4
2 5
used Sb O powder are relative slower and the formation of
2 5
O
the SSO nanorods needs the longer time. Many experiments
for the preparation of the SSO nanorods and the metal Sb
pattern c of the Fig. 2, the crystallinity of the SSO nanorods
and Sb particles is very high. It demonstrates that the
2 5
particles using Sb O powder were performed by changing
reaction conditions, such as reaction temperature and time,
and the mixture of the nanorods and the metal Sb could also
be prepared, but any core-shell structural Sb-coated SSO
nanorods could not be observed.
2 5
reaction processing from Sb O powder to the products SSO
and metal Sb phases is not only phase and shape
transformation processing, but also a kind of crystalline
processing.
X-ray diffraction (XRD) analyses was used to determine
the phases of the SSO and metal antimony (Fig. 2). The
pattern a in the Fig. 2 is the XRD pattern of the SSO phase.
All the peaks could be indexed to SSO compound according
to the reported data (JCPDS No. 11-694) [12] of bulk
Representative scanning electron microscopy (SEM) of
the SSO nanorods and metal Sb particles are shown in Fig.
3. A majority of the SSO nanorods with smooth surface were
observed (Fig. 3(a)). Typically they have several
micrometers long and 200–300 nm diameter size. Their
atomic ratio of O/Sb measured on SEM-energy-dispersive
X-ray analyses is about 2.1, close to the chemical
composition ratio of the SSO (O/SbZ2). The excess of
oxygen atoms may be caused by the surfactant oleic acid on
the surface of the SSO. In Fig. 3(b), the metal Sb particles
with several micrometers can also be observed.
2 4
orthorhombic-Sb O . No peaks of any other phase were
detected, indicating that the main product is the SSO phase.
It is noted that the relative intensities of some diffraction
peaks are greatly changed comparing with the standard
values. Its strongest diffraction peak is indexed to (202)
plane, not reported (112) plane of bulk Sb O , indicating
2
4
that the nanorods may have a preferential [101] growth
direction. The pattern b in the Fig. 2 is the XRD pattern of
the metal antimony material. It could be indexed to
A high-resolution transmission microscope (HRTEM)
image provides an insight into the structure of the prepared
SSO nanorods (Fig. 4). Generally Sb
structures of orthorhombic [12] and monoclinic [15] which
are also called as a-Sb O and b-Sb O , respectively.
2 4
O has two types of
hexagonal lattice of metal Sb with cell constants aZbZ
˚
4
.30, cZ11.27 A, which are in excellent agreement with the
reported data (JCPDS No. 5-0562) of bulk hexagonal-Sb. In
comparison with the XRD pattern of Sb O powder in the
2
4
2 4
Herein, the prepared SSO nanorods are orthorhombic crystal
of the a-Sb . The HRTEM image (Fig. 4(b) and (c)) of the
2
5
2 4
O
end of the individual nanorods shows that it is the single
crystal with the presence of few dislocations and defects,
whereas the side surfaces of the nanorods are covered with
thin and relatively smooth amorphous layers (about 3 nm).
The amorphous layer may be resulted mainly from the
surfactant oleic acids. Perpendicular to c-axis, the layer-
periodically packed lattice with about 1.15 nm distance
corresponding to four-atom layer unit along [001] direction
can be seen. This distance is close to the c value of the cell
Fig. 1. Schematic mechanism for Sb(III)Sb(V)O
4
nanorods and
powder using
constant of the a-Sb O (aZ5.436, bZ4.810 and cZ
metal Sb particles prepared from ball-milled Sb
solvothermal processing.
2
O
5
2 4
˚
11.76 A). The corresponding selected area electron

T. Ji et al. / Solid State Communications 133 (2005) 765–769
767
Fig. 3. SEM images of (a) Sb(III)Sb(V)O
4
nanorods (scale bar 1.5 mm); (b) metal Sb particles (scale bar 5 mm).
Fig. 4. Structural characterization of Sb(III)Sb(V)O
top end of Sb(III)Sb(V)O
diffraction pattern of the nanorod.
4
nanorods. (a) TEM image of Sb(III)Sb(V)O
4
nanorods. (b) and (c) HRTEM images of the
4
nanorods. In (c) image, Perpendicular to c-axis ([001] direction), a periodic layer packed can be seen. (d) Electron

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T. Ji et al. / Solid State Communications 133 (2005) 765–769
diffraction pattern (Fig. 4(d)) of the nanorod can also be
indexed as the reflections of the orthorhombic phase a-
Sb O .
simulated peaks have a slightly shift because of the different
3
C
5C
binding sites of the Sb and Sb cations of the SSO from
those of Sb O and Sb O compounds. The results also
2
4
2
3
2 5
The X-ray photoelectron spectroscopy (XPS) was used
to further examine the valence state and chemical
composition of the SSO nanorods [16]. Fig. 5 shows the
XPS survey (Fig. 5(a)) and Sb 3d5 (Fig. 5(b)) spectra of the
SSO nanorods. Antimony and oxygen peaks are clearly
resolved in the survey spectrum, which qualitatively provide
antimony atom number 31.7% and oxygen 62.3%, respect-
ively, in close agreement with the composition of
demonstrate that the prepared nanorods are Sb(III)Sb(V)O4
material.
The formation mechanism of the SSO nanorods is
suggested as follows. The existence of H O in the mixture
2
solution of organic compounds EA and EG directly leads to
K
K
the formation of OH groups. The OH first reacts with
Sb O powder to produce Sb–OH complexes (such as
2
5
K
Sb(OH) ). The complex can also react with EG or EA
6
5C
3C
Sb(III)Sb(V)O
spectrum peak is at 530.2 eV. This region was simulated two
4
. The binding energy of measured Sb 3d5
which partly reduces the Sb to Sb cations [14]. Then,
the partly reduced Sb(III)–OH further reacts with Sb(V)–
OH complex to obtain the SSO nanorods in soft template of
the EA and EG. As the dissolution of the Sb O powder is
3C
5C
regions of Sb and Sb cations which have the binding
energies of Sb 3d5 of 529.9 and 530.6 eV, respectively.
They have the similar peak area. In comparison with the
2
5
slow, it is beneficial to the formation of the SSO nanorods.
However, with further increasing the reaction time, the slow
dissolution of the nanorods in the alkali system causes the
standard binding energies of the Sb 3d5 of Sb
2 3
O (529.5 eV)
2 5
and Sb O (530.5 eV), the binding energies of the two
5C
3C
reduction of much more Sb cations to the Sb cations
and also the reduction of the Sb
3C
cations to metal
antimony, and finally all the nanorods transfer into metal
antimony particles.
The room temperature UV–vis spectra of the SSO
nanorods and the Sb
wavelength range are shown in Fig. 6. A shoulder peak
shown in arrow) of the absorption of the nanorods at
65 nm can be obviously observed due to two different
2 5
O powder in the 225–600 nm
(
3
valence antimony cations in the nanorods. For comparison,
the absorption edge of the Sb O shifts to around 275 nm.
2
5
The difference between their absorptions also demonstrates
the distinct of their bandgap. The sharp absorption edge of
Fig. 6. The room temperature UV–vis spectra of Sb(III)Sb(V)O
nanorods and ball-milled Sb powder. Arrow in Sb(III)Sb(V)O
4
4
Fig. 5. XPS spectra of Sb(III)Sb(V)O
4
nanorods: (a) survey
2 5
O
spectrum; (b) Sb 3d5 region. Sb 3d5 region has been simulated
3
absorption curve shows the shoulder peak caused by different
valence antimony cations. Inset is UV–vis emission spectra of
C
5C
two regions (dash dot) of the Sb 3d5 of Sb
which have the similar peak area.
and Sb
cations
4 2 5
Sb(III)Sb(V)O nanorods and ball-milled Sb O powder.

T. Ji et al. / Solid State Communications 133 (2005) 765–769
769
the nanorods indicates the present of a direct bandgap [17].
The photoluminescence (PL) of the SSO nanorods displays
a weak blue emission around 450 nm, whereas it is much
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In summary, we have successfully prepared
Sb(III)Sb(V)O nanorods mainly with several micrometers
2 5
O powder.
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b) S.H. Sun, G.W. Meng, Y.W. Wang, T. Gao, M.G. Zhang,
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5
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9
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