A rational complexing-reduction route to antimony nanotubes

Article abstract of DOI:10.1039/b303712f

Antimony nanotubes with inner diameters of 15-80 nm, wall thickness of 10-30 nm and lengths of up to several micrometers have been successfully prepared by a rational complexing-reduction route using zinc powder as reductant at low temperature (80-140°C).

Full text of DOI:10.1039/b303712f

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A rational complexing-reduction route to antimony nanotubes
b
Hanmei Hu, Maosong Mo, Baojun Yang, Mingwang Shao, Shuyuan Zhang, Qiaowei Li
b
b
b
a
b
ab
and Yitai Qian*
a
Structure Research Laboratory, University of Science and Technology of China, Hefei,
Anhui 230026, P. R. China
Department of Chemistry, University of Science and Technology of China, Hefei,
Anhui 230026, P. R. China. E-mail: ytqian@ustc.edu.cn; Fax: +86 551 363 1760
L e t t e r
b
Received (in Montpellier, France) 2nd April 2003, Accepted 4th June 2003
First published as an Advance Article on the web 2nd July 2003
Antimony nanotubes with inner diameters of 15–80 nm, wall
thickness of 10–30 nm and lengths of up to several micrometers
have been successfully prepared by a rational complexing-reduc-
value is about 5 after completion of the chemical reaction.
Hence, a possible chemical reaction pathway may be described
as follows:
2
0
tion route using zinc powder as reductant at low temperature
ꢀ
SbCl3 þ 3 CH3COCH2COCH3 ! SbðCH3COCHCOCH3Þ3
(
80–140 C).
þ 3 HCl ð1Þ
3
Zn þ SbðCH3COCHCOCH3Þ þ 6 Hþ ! SbH3 þ 3 Zn2þ
1
3
Since the discovery of carbon nanotubes, much attention has
been focused on nanotube materials due to their novel proper-
þ 3 CH3CO CH2COCH3 ð2Þ
2
ties and promising applications in nanodevices. Many types of
2þ
Zn þ 2 CH3COCH2COCH3 ! ZnðCH3COCHCOCH3Þ
3
4
2
nanotubes such as MX
2
(M ¼ Mo or W, X ¼ S or Se), BN,
þ
5
6
7
8
9
þ 2 H
ð3Þ
ð4Þ
2 2 2 3
NiCl, vanadium oxide, InS, NbS and TaS , Bi S , and
1
0
organic nanotubes have been reported. There has been a
steadily increasing interest in the study of metallic nanotubes
in recent years. Generally, template-based techniques have
2
SbH3 ! 2 Sb þ 3 H2
Fig. 1 shows a typical XRD pattern of the as-synthesized
antimony products. All of the strong and sharp reflection
peaks can be readily indexed to a pure rhombohedral lattice
structure of antimony with calculated lattice constants a ¼
1
1
12
been used to prepare metallic nanotubes such as Au, Ni,
1
3
Fe and Co. Metallic Bi nanotubes have been prepared by
a controlled hydrothermal reduction method, which suggests
that the formation of Bi nanotubes may be associated with
˚
˚
4
.286 A and c ¼ 11.256 A, which is in agreement with the lit-
1
4
its layered structure. Similar to the a-Bi structure, a-Sb also
has a pseudolayered structure. In the same layer, each Sb atom
is coordinated with three other Sb atoms by covalent bonds,
thus forming a trigonal pyramid. These pyramids further form
a puckered antimony layer with shared vertices. At the same
time, each Sb atom contact three other Sb atoms in the adja-
cent layer via weak van der Waals forces. The above observa-
tions stimulated us to consider the possibility of preparing
nanotubes of antimony with a layered structure.
˚ ˚
erature values of a ¼ 4.307 A and c ¼ 11.27 A (JCPDS 05-0562).
No impurity peaks were detected. Energy-dispersive X-ray
(EDX) analysis of the nanotubes indicates that they are pure
antimony (Fig. 2).
On the basis of TEM observations, the yield of Sb nano-
tubes is ca. 50%. Figs. 3(a) and 3(b) show the tubular morphol-
ogies of the as-prepared Sb products. They have inner
diameters of 15–80 nm, wall thickness of 10–30 nm and lengths
of up to several micrometers with obvious open ends. Most of
the nanotubes are flexible and tend to bend. Fig. 3(c) shows
a typical bent nanotube. One Sb nanotube was characterized
by its SAED pattern [inserted in Fig. 3(b)]. Diffuse diffraction
spots are due to the cylindrical structure of the sample. The
HRTEM image of an individual Sb nanotube, shown in
Fig. 3(e), unambiguously reveals the multiwalled structure. The
Antimony is a semimetal whose energy overlap between the
1
5
conduction and valence bands is about 180 meV at 4.2 K. As
in Bi, electronic transport phenomena in Sb occur via both
electrons and holes. Amorphous or polycrystalline antimony
nanowires have been prepared in porous anodic alumina tem-
plates using the vapor phase deposition technique and their
1
6–18
particular transport properties have been also studied.
Recently, single-crystalline antimony nanowire arrays have
been prepared by pulsed electrodeposition in anodic alumina
˚
average distance between the neighboring fringes is ca. 3.107 A,
1
9
membranes. However, studies of the rational synthesis, phy-
sical properties and potential application of antimony nano-
tubes are still a challenge for chemical and material science
researchers.
Herein, a rational complexing-reduction route was devel-
oped to synthesize Sb nanotubes under controlled solvother-
mal conditions. In our synthetic system, acetylacetone was
selected as both solvent and complexing agent. Antimony
chloride, taken as the antimony source, was coordinated with
acetylacetone to form Sb-acetylacetone complexes, which were
then reduced in situ to antimony products by zinc powder
under certain conditions. The pH value of the reaction system
is 1–2 before the reductive reaction takes place, while the pH
Fig. 1 XRD pattern of the as-synthesized antimony products.
DOI: 10.1039/b303712f
New J. Chem., 2003, 27, 1161–1163
1161
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oxygen atoms, which can complex with almost every metal in
2
4
the periodic table to form coordination complexes. When
anhydrous SbCl was added to acetylacetone, the solution
3
gradually turned from colorless to yellow at room tempera-
ture, which implies that Sb-acetylacetone complexes might be
formed in the solution. Fig. 4 shows the IR spectra of pure
3
+
acetylacetone and of an acetylacetone solution containg Sb
ions, respectively. In spectrum a, the two absorption bands
at 1729 and 1710 cm can be assigned to the normal carbonyl
ꢁ
1
ꢁ1
frequencies. The broad band at 1622 cm is due to the conju-
gated, hydrogen-bonded carbonyl group characteristic of the
2
5
Fig. 2 EDX spectrum of an individual antimony nanotube.
enolic form of the b-diketone. Although there are some dis-
turbances of the free solvent molecules in spectrum b, some
differences are apparent between spectra a and b. In spectrum
ꢁ1
corresponding to the (012) plane lattice distance in rhombohe-
dral antimony. Moreover, the Sb nanotubes always coexist
with sheets and structures with an unfinished tube-like mor-
phology [indicated by the arrow in Fig. 3(d)]. The observed
rolling phenomenon suggests that the formation of Sb nano-
tubes really has a close relation with its pseudolayered struc-
ture. Similar results have been previously reported in the
b, the absorption bands at 1606 and 1558 cm can be assigned
to chelated carbonyl and the C=C stretch, respectively. The
2
5
ꢁ
1
two bands at 1721 and 1685 cm may result from the coop-
eration of free solvent molecule and chelated carbonyl. The
lowering of the carbonyl frequency can be attributed to acetyl-
acetone coordinating with metal to form the coordination
complexes. Production of the complexes could reduce the con-
3
+
preparation of WS
2
nanotubes and a ‘‘rolling mechanism’’
was proposed. Remskkar and coworkers have obtained
direct evidence for the derivation of MoS tubules from the
centration of free Sb ions in solutions, making the reaction
mainly proceed in situ at the complexes and providing enough
time and opportunity for the growth of Sb nanotubes. More-
over, the adsorption of the solvent to specific surfaces of the
crystals may also affect the morphology of the final product.
Although we cannot yet put forward a reliable model for
the structure of the Sb-acetylacetone complexes, the present
experimental results reveal that the complexes may be essential
for the formation of Sb nanotubes. It is possible that the Sb-
acetylacetone complexes serve as an intermediate or a molecu-
lar template in the control of the growth of Sb nanotubes.
More in-depth studies are still needed to explore the effects
of the complexing solvent on the growth processes of the anti-
mony nanotubes.
2
1
2
2
2
bending of platelets. Li suggested a rolling of layered struc-
tures to achieve Bi nanotubes and proposed a 3-D model for
1
4
Bi nanotubes. Here, our experimental results also suggest
that the formation of Sb nanotubes may be the result of the
rolling of the layered structure. Further study of its mechanism
is in progress.
Surely, the layer structure of antimony is indispensable for
the formation of its nanotubes. And yet, the solvothermal
treatment should provide a possible driving force for the
nucleation and growth of antimony nanotubes. We speculate
that the acetylacetone solvent not only may act as a complex-
2
3
ing agent but also may play the same role as amines, which
act as a structure-directing agent for the growth of Sb
nanotubes. Acetylacetone is a bidentate ligand with two anchor
The effects of the temperature and solvent on the morphol-
ogy of the Sb products have been investigated. It was found
that higher or lower temperatures are not favorable for the
Fig. 3 TEM images showing (a) and (b) several Sb nanotubes, SAED pattern inserted in (b); (c) a typical bent nanotube; (d) the coexistence of
well-defined nanotubes, unfinished tubular structures and sheets; (e) HRTEM image of the Sb nanotubes; (f) chain-like morphology obtained at
ꢀ
1
80 C.
1
162
New J. Chem., 2003, 27, 1161–1163

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HRTEM images and EDX analysis were taken with a JEOL-
2
010 transmission electron microscope with an accelerating
voltage of 200 kV. FT-IR spectra were measured on a Bruker
Vector-22 FT-IR spectrophotometer in the region of 4000–
ꢁ
1
00 cm .
4
Acknowledgements
Financial support from the National Natural Science Founda-
tion of China and the 973 Projects of China is gratefully
acknowledged.
3+
Fig. 4 IR spectra of (a) pure acetylacetone and (b) Sb -containing
acetylacetone solution.
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New J. Chem., 2003, 27, 1161–1163
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