Hydrothermal synthesis of tungsten oxide nanobelts
Xuchun Song
a,
⁎
, Yang Zhao
b
, Yifan Zheng
c
a
Department of Chemistry, Fujian Normal University, Fuzhou 350007, P. R. China
b
Department of Chemistry, Henan Normal University, Xinxiang, 453002, P. R. China
c
Coll Chem Engn and Mat Sci, Zhejiang Univ Technol, Hangzhou, 310014, P. R. China
Received 29 January 2006; accepted 5 March 2006
Available online 3 April 2006
Abstract
Tungsten oxide nanobelts have been hydrothermally fabricated at 180 °C for 12 h with sodium sulfite and cetyltrimethylammonium bromide
(CTAB) as assisted, respectively. X-ray diffraction (XRD) pattern indicates that the as-prepared samples are the pure orthorhombic phase WO
3
.
EDS spectra show that the ratio of W/O is about 1:3. The morphology was characterized by scanning electron microscopy (SEM) and transmission
electron microscopy (TEM) techniques. Based on a series of comparative experiments under different reaction conditions, the probable formation
mechanism of tungsten oxide nanobelts is proposed.
© 2006 Elsevier B.V. All rights reserved.
Keywords: Hydrothermal; Tungsten oxide; Nanobelts
1. Introduction
As a new family of one-dimensional (1D) nanostructures,
nanobelts have attracted increasing attention because of their
unique physical properties and potential applications [1–5].
Although some nanobelts made of semiconductors, metals, and

CTAB (0.8 g) was dissolved in 35 ml deionized water to
form a transparent solution. Then 0.3 g H
2
WO
4
powder and
5 ml HCl (3 M) were added to the above solution under con-
tinuous stirring. The resulting suspension was transferred into a
50 ml Teflon-lined stainless steel autoclave. Then 1.2 g Na
2
S
powder was added to Teflon-lined stainless steel autoclave and
sealed tightly. Hydrothermal treatments were carried out at
180 °C for 12 h. After that, the autoclave was allowed to cool
down naturally. Precipitates were collected, and washed with
deionized water several times and dried in air at 80 °C.
2.2. Characterization
The morphologies were charac terized using sca nning
electron microscopy (SEM, Hitachi S-4700 II, 25 kV) and
transmission electron microscopy (TEM, JEM200CX, 120 kV).
Materials Letters 60 (2006) 3405 – 3408
www.elsevier.com/locate/matlet
⁎
Corresponding author.
E-mail address: [email protected] (X. Song).
0167-577X/$ - see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.matlet.2006.03.022
The composition of the product was an alyzed by energy dis-
persive X-ray detector (EDX, Thermo Noran VANTAG-ESI,
120 kV). The X-ray diffraction (XRD, Thermo ARL SCINTAG

nanobelts with the molar ratio of about 3 (O/W). In Fig. 3, a represen-
tative XRD pattern for our assynthesized tungsten oxide nanobelts is
displayed. All the main peaks can be indexed undisputedly to ortho-
rhombic WO
3
(JCPDS card 20-1324). This agrees well with the SADE
results. No impurities could be detected in this pattern, which implies
that pure WO
3
could be obtained under the current synthetic route.
The morphologies of WO
3
nanocrystals synthesized in different
reaction conditions were shown in Fig. 4a–d. When 1.2 g Na
2
S and
5 ml HCl (3 M) were added into the reaction systems without addition
of CTAB, the prepared WO
3
agglomerated together severely (shown in
Fig. 4a). However, if we just added CTAB not Na
2
S, the nanolamellars
and short nanobelts in the sample were shown in the Fig. 4b. The result
indicated that nanocrystals dispersed well in the presence of CTAB and
the morphologies of WO
3
were independent of the HCl. When 1.2 g
Na
2

3
nanobelts.
The growth mechanism of crystal is determined by both the internal
structure and external conditions such as temperature, pressure, and
composition of the solution [15]. A possible mechanism has been
proposed to explain the nanobelts growth in thermal evaporation. Since
our situation is quite different from the dry method, the explanation of
the nanobelts growth mechanism in hydrothermal condition remains
speculative. It is well known that the shape of the nanocrystals can be
controlled by adding chemical capping reagents into the solution. The
selective interaction of the capping molecules on the facets of the first-
formed nanoparticles is crucial to the anisotropic growth of nano-
structures. For example, we have chosen a CTAB as the capping
molecules in our experiments, and found that the CTAB has a great
influence on the morphology of WO
3
nanostructures. In addition, it has
been known that the superposition of growth units on crystal surfaces
strongly affects the growth speed and orientation of crystals. The size
and structure for growth units depend on the hydrothermal reaction
conditions. The addition Na
2
S and proper content of HCl produced
different kinds of stable growth units (H
2
WO
4−x
S
x
). The growth units

that the WO
3
nanobelts possess orthorhombic with [200]
growth orientati on. A possi ble mechanism was proposed that
Na
2
S and CTAB acted corporately on the formation of WO
3
nanobelts. The effect should be able to be extend ed to the
synthesis of other 1D nanomaterial.
Acknowledgments
We wish to acknowledge the financial support from the
Foundation of Educational Committee of Fujian Province (No:
K04027).
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