Synthesis of indium hollow spheres and nanotubes by a simple template-free solvothermal process

Article abstract of DOI:10.1016/j.inoche.2003.12.010

Indium hollow spheres and nanotubes were successfully synthesized via a simple template-free solvothermal route at different temperatures. The products were characterized by X-ray powder diffraction and transmission electron microscopy.

Full text of DOI:10.1016/j.inoche.2003.12.010

Inorganic Chemistry Communications 7 (2004) 344–346
www.elsevier.com/locate/inoche
Synthesis of indium hollow spheres and nanotubes
by a simple template-free solvothermal process
*
Yunxia Zhang , Guanghai Li, Lide Zhang
Institute of Solid State Physics, Chinese Academy of Sciences, P.O. Box 1129, Hefei 230031, People’s Republic of China
Received 28 November 2003; accepted 8 December 2003
Published online: 8 January 2004
Abstract
Indium hollow spheres and nanotubes were successfully synthesized via a simple template-free solvothermal route at different
temperatures. The products were characterized by X-ray powder diffraction and transmission electron microscopy.
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: Indium; Hollow spheres; Nanotubes; Solvothermal
In recent years, metal nanoparticles have attracted
extensive attention for their potential applications in
optics, electronics, photoelectronics, catalysis, sensing,
clinical diagnostics, surface-enhanced Raman scattering
(SERS), information storage, and energy conversion/
storage [1,2]. While metal nanoparticles with hollow
structures are particularly interesting due to their low
density, large specific area, mechanical and thermal
stability, and surface permeability [3,4]. A variety of
hollow spheres have been successfully fabricated by
various methods, such as template-assisted process (by
coating the template with a thin shell of the desired
materials and subsequently removing the template by
calcination or solvent etching), including polystyrene
latex spheres [5], resin spheres [6], microemulsions [7],
polymer micelles [8], polymer-surfactant complex mi-
celles [9], ultrasonication [10], and etc. However, very
few approaches have achieved practical significance
owing to very high cost of the methods. It is very im-
portant to explore a simple and cheap access to pre-
paring inorganic hollow spheres.
tors, and also used to improve some dental alloys [11]. It
is easily alloyed and converted. Indium semiconductor
compounds such as InP [12] and InAs [13], are used in
infrared detectors, high-efficiency photovoltaic devices
and high-speed transistors. In addition, Indium is easily
oxidized to In2O3, which has been widely employed as a
microelectronic device material in solar cells, flat-panel
displays, sensors, and architectural glasses [14]. Indium
nanoparticles is expected to have better catalytic and
recording properties than coarse-grained indium parti-
cles. Nevertheless, the studies on the fabrication of in-
dium nanoparticles are very few. Kimoto and Nishida
[15] produced nanocrystalline indium powder by vac-
uum deposition techniques. Zhao et al. [16] prepared
indium nanoparticles via a novel solution route. Liu
et al. [17] reported the preparation of nanocrystalline
indium powders by c-irradiation. Katerina [18] adopted
the organometallic route to synthesize indium nano-
particles. In this study, we report the preparation of
indium hollow spheres adopting a simple solvothermal
route without using any template for the first time.
All the reagents were of analytical grade and were
used without further purification. In a typical process,
0.221 g anhydrous InCl3 and 0.098 g Zn powder (the
mol ratio of InCl3 to Zn is 1/1.5) were added to a 50 ml
Teflon-lined stainless steel autoclave. Then the autoclave
was filled with 90% absolute ethanol and the solution
Indium is widely used in the field of electronics for
semiconductor devices, thermistors and optical devices,
electronics soldering (alloys), for control rods in reac-
* Corresponding author. Tel.: +865515591437; fax: +865515591434.
E-mail address: zyxqm@263.net (Y. Zhang).
1387-7003/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2003.12.010

Y. Zhang et al. / Inorganic Chemistry Communications 7 (2004) 344–346
345
was constantly stirred for 30 min. The autoclave was
sealed and maintained at 120 °C for 20 h, then cooled to
room temperature naturally. The dark grey products
were filtered, washed several times with distilled water
and absolute ethanol to remove the impurities, and then
dried at 70 °C for 4 h.
The purity and composition of the products were
characterized by powder X-ray diffraction (XRD) using
a Rigaku D/Max cA X-ray diffractometer with Cu Ka
ꢀ
radiation (k ¼ 1:54178 A). The morphologies of the
samples were observed with a transmission electron
microscope (TEM, Hitachi H-800) performed at 200 kV.
And the microstructures of the samples were analyzed
with a high-resolution transmission electron microscope
(HRTEM, JEOL-2010).
The X-ray diffraction (XRD) pattern of the samples
prepared at 120 °C is shown in Fig. 1. All the peaks can
be indexed to the body-centered tetragonal Indium
(JCPDS 72-1184), and no characteristic peaks of impu-
rities, such as unreacted Zn and In2O3, were observed
which substantiates that our as-prepared products are
very pure. It can be easily seen that the peaks are fairly
broad, indicating the small particle size. According to
the ScherrerÕs equation, the size of these particle com-
posing indium hollow spheres was about 8 nm.
Fig. 2 is several typical transmission electron mi-
croscopy (TEM) images of the samples prepared at
120 °C. The strong contrast between the dark edge and
the brighter center of indium nanospheres revealed their
hollow features. The outer diameter of these nano-
spheres is about 100–150 nm, as shown in Fig. 2(a).
TEM images at higher magnification (shown in Fig. 2(b)
and (c)) clearly indicate that these nanospheres are
composed of very small indium nanoparticles, which is
in agreement with the results of XRD. The corre-
sponding selected area electron diffraction (shown in the
inset in Fig. 2(c)) exhibits diffuse ring pattern indicated
that these indium hollow spheres are polycrystalline.
Fig. 2. Several typical TEM images of samples prepared at 120 °C.
The HRTEM image in the Fig. 2(d) further confirmed
the hollow nature of these indium nanospheres.
Fig. 3 is a typical TEM image of the samples prepared
at 150 °C. Unfortunately, it is difficult to obtain clearer
TEM image of indium nanotubes due to their high
sensitive to the electron beam. From Fig. 3 (a), it can be
seen that the diameter of indium nanotubes is about in
the range of 80–120 nm. Fig. 3(b) is a typical TEM
image of a single nanotube in which the opening and
1200
JCPDS 85-1409
1000
800
600
400
200
0
30
40
50
60
70
2
θ
(degree)
Fig. 1. XRD pattern of as-prepared indium nanospheres.
Fig. 3. Two typical TEM images of samples prepared at 150 °C.

346
Y. Zhang et al. / Inorganic Chemistry Communications 7 (2004) 344–346
obvious contrast in the terminal fully display the char-
acter of the nanotubes.
Acknowledgements
In the solvothermal process, the solvent played an
important role in the formation of indium. In our ex-
periment, absolute ethanol was chosen as a solvent. As a
control experiment, when water was used as the solvent,
the products contained In2O3 besides indium. Of course,
the reaction temperature also affects the morphology
of the as-prepared samples. The yield of indium hollow
spheres was lower at lower temperature, such as 90 °C.
On the other hand, indium nanotubes were the main
product besides the hollow spheres at 150 °C. These
indicate that the growth kinetics affects the morphology
of the final product.
This work was supported by National Major Project
of Fundamental Research: Nanomaterials and Nano-
structures (Grant No. G19990645).
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powder as raw materials by a simple solvothermal pro-
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simple compared with other methods for synthesizing
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