An easy method to prepare nanowire

Article abstract of DOI:10.1246/cl.2003.594

SrCO₃ nanowires and BaCO₃ nanowires with single crystal structure and aspect ratio of about 1000 were prepared by a simple reaction without template. Preferentially assembling-reconstruction of colloidal particles was supposed as the formation mechanism.

Full text of DOI:10.1246/cl.2003.594

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Chemistry Letters Vol.32, No.7 (2003)
An Easy Method to Prepare Nanowire
Li Wang and Yongfa Zhu
Department of Chemistry, Tsinghua University, Beijng, 100084, P. R. China
(Received April 9, 2003; CL-030308)
SrCO3 nanowires and BaCO3 nanowires with single crystal
tern showed that the nanowires had uniform diameters of about
10 nm and was single crystal. The aspect ratios of SrCO3 nano-
wires reached more than 1000 (average length of 10 mm and
diameter of 10 nm).
structure and aspect ratio of about 1000 were prepared by a sim-
ple reaction without template. Preferentially assembling-recon-
struction of colloidal particles was supposed as the formation
mechanism.
Nanowires are of fundamental importance to the study of
size- and dimensionality-dependent chemical and physical phe-
1
{5
nomena,
nanostructure materials is still a major challenge. Porous mate-
but how to rationally synthesize one-dimensional
6
{8
9
rials and carbon nanotubes are generally used as hard tem-
plates and surfactant micelles are usually used as soft
templates
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0{13
to synthesize nano-wires.
Here report an easy method to prepare SrCO3 and BaCO3
nanowire by a simple reaction. It will pioneer a new field in
the synthesis of carbonate nanowires and related materials using
assembling of colloidal particles. On the basis of the decompo-
sition of carbonates, this new method can be extended to
synthesize other nanowire materials such as salt, oxide and met-
al. Besides, on the basis of the unique performance of SrCO3
and BaCO3 material in low-temperature catalytic oxidation of
VOC (volatile organic compound)and chemiluminescence
sensor, the related study on SrCO3 nanowires was performed.
The results reveal that SrCO3 nanowires show lower catalyzing
temperature, higher stability, higher activity and longer life, in-
dicating its importance in development of low-temperature
combustion catalyst and chemiluminescence sensors.
Figure 2. Effect of condition on nanowire growth A: react for
10 min; B: react for 60 min without heating; C: react with lower
pH value.
Further characterization on composition and structure of the
nanowires was performed using EDX (energy disperse X-ray
analysis), LRS (laser Raman spectroscopy) and XRD (X-ray
diffraction). EDX results indicated nanowires were consisted
of strontic species, and LRS spectrum of the nanowires was
the same with standard SrCO3 powder. The XRD patterns of na-
nowire sample, as shown in Figure 1B, indicated that these
peaks are attributed to the pure strontianite-type crystal accord-
ing to the XRD standard spectrum of SrCO3 powder.
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The effects of time, temperature and pH on the growth of
SrCO3 nanowires were investigated systemically. As shown in
Figure 2A, the nanowires showed a particle-particle-like discon-
tinuous morphology when the reaction time was only 10 min,
indicating nanowires were formed by assembling of particles.
The particles were most ellipsoid with the long axis along the
nanowires, indicating that the growth and assembling of colloi-
dal particles were in certain direction.
Prolonging reaction time to 60 min at room temperature, the
nanowires were apparently continuous and coarse, as shown in
Figure 2B. The corresponding electron diffraction pattern of a
nanowires bundle revealed a typical diffraction pattern due to
a preferentially oriented fibrous texture. The diffraction pattern
identified that the SrCO3 nanowires are crystals of orthorhom-
bic structure and only (00l)spots can be observed along the fi-
ber axis, indicating that each wire is a single crystal with a pre-
ferential growth direction along the c axis.
Figure 1. Characterization of typical SrCO3 nanowires A:
TEM micrograph along with the electron diffraction pattern;
B: XRD patterns of SrCO3 nanowires.
SrCO3 nanowires were obtained by exposing fresh satu-
rated Sr(OH)2 solution to air, based on Sr(OH)2 + CO2 !
SrCO3#+ H2O reaction. A typical SrCO3 nanowire sample,
which was prepared by exposing fresh Sr(OH)2 solution to air
The pH value of Sr(OH)2 solution also has great influence
on the formation of nanowires. Compared with the typical
SrCO3 nanowire sample, the aspect ratio of nanowire decreased
dramatically from 1000 to 4 with pH value of solution decreas-
ing from 14 to 12, as seen in Figure 2C. This revealed the role
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for 0.5 hour then being dried at 60 C for 16 h, was shown in
Figure 1. Figure 1A showed the TEM micrograph with electron
diffraction pattern and a magnified part of the sample. TEM
photo indicated that most of SrCO3 nanowires aggregated as
regular bundles. The magnified part and electron diffraction pat-
À
of OH in adsorb predacious growth and assembling process.
Copyright ꢀ 2003 The Chemical Society of Japan

Chemistry Letters Vol.32, No.7 (2003)
595
On the basis of above results, a formation mechanism of
SrCO3 nanowires was supposed as a directional assembling-re-
construction of colloidal particles. Firstly, some Sr(OH)2 re-
of MOE, P.R.China.
References and Notes
1
À
acted with CO2 to form SrCO3 colloidal particles, and OH an-
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ion intended to be adsorbed on the crystal faces parallelling to
the c axis of the primary nuclei, resulting in the anisometric pri-
mary SrCO3 colloidal particles. Then, the colloidal particles as-
sembled in a certain direction through their c axes to form the
particle-particle-like nanowires. The particle-particle-like nano-
wires tended to recombine in solution, and continuous nano-
wires formed as a consequence. Nanowires grew to perfect sin-
gle crystalline when appropriate reconstruction condition was
provided, such as suitable temperature and time.
Since no template was used in the preparation nanowires,
the preferential growth of SrCO3 crystal can be attributed to
the high chemical potential along c axis. On the basis of the in-
fluence of chemical potential on the shape evolution of nano-
crystal elucidated by Peng et al., in the case of one-dimensional
2
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9
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5;16
pH value in our work as shown in Figure 2C.
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BaCO3 nanowires prepared by the same method showed the
similar morphology, length and diameter with SrCO3 nano-
wires, as shown in Figure 3. This revealed the potential applica-
tion of this method in preparation of other nanowire materials.
The SrCO3 nanowire showed good catalytic performance
for catalytic oxidation of formaldehyde. Its start and complete
ꢀ
ꢀ
combustion temperature was 80 C and 100 C lower than that
of SrCO3 nanoparticle when the initial concentration was
8
ꢀ
00 ppm. Its complete combustion temperature was 140 C low-
er than that of SrCO3 nanoparticle at high concentration
7000 ppm)and it did not lost activity, indicating its great ad-
vantages in the catalytic oxidation of VOC. Besides, its catalytic
15 Z. A. Peng and X. G. Peng, J. Am. Chem. Soc., 123, 1389
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17 Since hydrolyzing of SrAl2O4 can be easily controlled, it
was used as source of fresh Sr(OH)2 solution. After SrAl2O4
powder dispersed in distilled water by ultrasonic bath for
(
14
luminescence based on catalytic oxidation of ethanol was in-
ꢀ
tensified linearly with temperature below 360 C and kept con-
stant at higher temperature, indicating the advantages in the per-
formance as chemical luminescence sensor.
1
0 min, the by-produced Al(OH)3 was removed by centrifu-
This work was partly supported by Chinese National
Science Foundation (20071021), Trans-Century Training Pro-
gram Foundation for the Talents by the Ministry of Education,
P.R.C. and supported by the Excellent Young Teacher Program
gation. Then Sr(OH)2 exposed to air at deferent temperature
for desired time. Finally, the product was washed with 10%
NaOH solution and distilled water by turn to removed the
residual Al(OH)3. The TEM analysis was obtained in a Hi-
tachi H-800 system, with accelerating voltage for electron
beam of 200 kV. The preparation of sample for LRS analy-
sis was the same as that for TEM, except for the substrate
was glass. LRS was carried out on Renishaw 2000 system.
XRD experiments were carried out using a Rigaku DMAX-
2
400 diffractometer with Cu Kꢀ radiation. Characterization
of electron diffraction is based on R ¼ K=d (R is the dis-
tance between spot and (000), K is camera constant and d
is the distance between crystal faces)and an important ref-
erence (J. Phys. Chem. B, 101, 3460 (1997)). The important
ꢀ
data were listed as following. Lttice constants a ¼ 5:10 A,
ꢀ
ꢀ
b ¼ 8:40 A,
c ¼ 6:02 A,
and
camera
constant
ꢀ
K ¼ 20:08 mmꢁA. The standard d from JCPDS (84-1778)
Figure 3. As-prepared BaCO3 nanowire.
was applied to calibrate the diffraction spots.
Published on the web (Advance View)June 10, 2003; DOI 10.1246/cl.2003.594