Synthesis and characterization of strontium carbonate nanowires with a axis orientation and dendritic nanocrystals

Article abstract of DOI:10.1246/cl.2004.290

Strontium carbonate nanowires that grow along the a axis were synthesized in large scale through simple hydrothermal approach for the first time. The aspect ratio of the product is more than 1000. Dendritic nanocrystals were also generated at low temperatures. Moreover, this method is feasible to be applied in the synthesis of barium carbonate nanowires.

Full text of DOI:10.1246/cl.2004.290

290
Chemistry Letters Vol.33, No.3 (2004)
Synthesis and Characterization of Strontium Carbonate Nanowires with a Axis Orientation
and Dendritic Nanocrystals
Qing Huang, Lian Gao,ꢀ Ye Cai,y and Fritz Aldingery
State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics,
Chinese Academy of Sciences, Shanghai 200050, P. R. China
yPulvermetallurgisches Laboratorium, Max-Planck-Institut fur Metallforschung and Institut fur Nichtmetallische Anorganische
¨
¨
Materialien, Universitat Stuttgart, D-70569 Stuttgart, Germany
¨
(Received November 21, 2003; CL-031132)
Strontium carbonate nanowires that grow along the a axis
(b)
were synthesized in large scale through simple hydrothermal ap-
proach for the first time. The aspect ratio of the product is more
than 1000. Dendritic nanocrystals were also generated at low
temperatures. Moreover, this method is feasible to be applied
in the synthesis of barium carbonate nanowires.
(a)
20
40
60
80
One-dimensional (1-D) nanostructures, such as nanotubes,
nanowires, and nanorods are critically important to chemistry,
optics, magnetics, and electronics, and hence have great promise
for improving our understanding of fundamental concepts of
both dimensionality and size on physical properties, as well as
for application in nanodevices.1 Therefore, extensive efforts
have been made to synthesize these bulk 1-D nanostructure ma-
terials, especially nanowires. Many methods have been devel-
oped and reviewed elsewhere.2 But up to the present, the ad-
vance in the taking advantage of nanowires has been relatively
slow. The major problems seem to be the methods used, purity
or crystallinity of the products and control of component.3 In or-
der to resolve these synthetic challenges, many in-depth studies
should be performed. Carbonate materials are crucial raw mate-
rials to synthesize other compounds. Moreover, they are also
widely applied in the inorganic–organic hybrid composite mate-
rials as fillers. Hence, the morphology and size of carbonate are
much more significant to determine the properties of hybrid
composite materials.4 A few works have been reported to pre-
pare barium carbonate nanowires through reverse micelles or
microemulsions approach.5 However, to the best of our knowl-
edge, the strontium carbonate nanowires have not been inten-
sively studied.6 Herein, we introduce a novel simple hydrother-
mal method without surfactant to synthesis strontium carbonate
nanowires with a axis orientation for the first time. The width of
nanowires ranges from 20 to 200 nm and the length is more than
10 mm. Dendritic nanostructure is also observed in the strontium
carbonate. Moreover, this approach is also feasible for synthesis
of barium carbonate nanowires.
2 theta / degree
Figure 1. X-ray diffraction spectra of (a) strontium carbonate and
(b) barium carbonate nanowires synthesized at 160 ꢂC for 12 h.
out, washed with distilled water and ethanol in subsequence,
and later dried in a vacuum oven at 60 ꢂC for 12 h.
The products were characterized by using X-ray powder dif-
fraction (XRD, D/max 2550 V) with Cu Kꢀ radiation (ꢁ ¼
0:15406 nm). High-resolution transmission electron microscopy
(HRTEM) images were taken on JEOL 4000 FX microscope
equipped with double-tilt holder and operated at 400 kV. TEM
(JEM-2010, 200 kV) with EDX attachment was also applied to
observe the micromorphology.
The X-ray diffraction (XRD) spectra of strontium carbonate
and barium carbonate synthesized at 160 ꢂC can be indexed to
orthorhombic phase (space group: Pmcn) according to JCPDS
05-0418 and 45-1471, respectively (Figure 1). It is worth noting
that in the XRD spectrum of strontium carbonate the peak of
(200) plane is obviously strengthened, which imply the aniso-
tropic growth along identical orientation (Figure 1a).
Figure 2 visualizes the morphologies of products synthe-
sized at different temperatures. The strontium carbonate nano-
wires were successfully synthesized at 160 ꢂC for the duration
The chemicals used are of analytical grade. Typically,
0.1 mmol strontium acetate (Sr(CH3COO)2ꢁ3H2O, Shanghai
Chemical Reagent Co., Ltd), 20 mmol NaOH and 0.4 mmol 2-
aminoethanethiol (AET; HSCH2CH2NH2, ACROS ORGAN-
ICS) were added into 30-mL distilled water. After stirring for
5 min, this solution was transferred into a 35-mL Teflon-lined
stainless-steel autoclave and performed hydrothermal treatment
at 120–180 ꢂC for 12 h. Barium acetate instead of strontium ace-
tate was used when synthesizing the barium carbonate while oth-
er conditions remain the same. The final products were filtered
Figure 2. TEM images of strontium carbonate nanowires synthe-
sized at (a) 160 ꢂC for 12 h and (b) 180 ꢂC for 12 h. The inset is SA-
ED pattern of single nanowires. (c) Strontium carbonate dendritic
nanostructure synthesized at 130 ꢂC for 12 h. (d) Typical dendritic
nanocrystal and the corresponding SAED pattern of different posi-
tions.
Copyright ꢀ 2004 The Chemical Society of Japan

Chemistry Letters Vol.33, No.3 (2004)
291
12 h (Figure 2a). The widths of nanowires range from 20 to
200 nm and the length is more than 10 mm. Aspect ratio of nano-
wires exceeding 1000 is dominant in our samples. Moreover,
these nanowires are slightly transparent in the TEM images,
which indicates the thickness of nanowires is less than the width
(ratio of width and thickness is about 5). The nanowires are all
straight and flat which shows the stiffness characteristic of nano-
wires and indicates the promising application in the inorganic–
organic hybrid composites as a strengthening phase. This mor-
phology of strontium carbonate is distinct from the previous re-
port in which the nanowires are curved and assembled by some
tiny particles.5 Figure 2b shows the TEM image of sample syn-
thesized at 180 ꢂC. Comparing these two samples, the morphol-
ogy and size of products have no obvious difference when the
reaction temperature elevates. But at lower temperature (for ex-
ample 130 ꢂC), dendritic nanocrystals other than nanowires
formed as shown in Figure 2c. The width of trunk is 80 nm,
and the branch’s width is as small as 20 nm. Figure 2d is the typi-
cal morphology of strontianite dendritic crystal. SAED analysis
shows the different orientations of trunk and branches (inset in
Figure 2d), where trunk is along the [1-1-2] orientation and
branches are along the [11-2] orientation.
Figure 4. TEM image of barium carbonate nanowires, inset is
SAED pattern along [010] zone axis and (b) its corresponding
HR-TEM image.
peaks including (002), (004), and (006) are dramatically
strengthened, which corroborate the SAED and HRTEM results.
The exact growth mechanism of the nanowires is not fully
understood. We think the AET molecules added should play
an important role. Control experiments were performed with
no AET molecules while maintaining other condition. The re-
sultant strontium carbonate or barium carbonate is irregular ag-
glomerates rather than nanowires (not show here). The thiol and
amine groups in the organic molecule are always used to bind
metal cation to form complexes. Thus, directed adsorption of
AET molecules on the specified planes is reasonably proposed
to account for the anisotropic growth phenomena. Morphology
evolution from dendritic nanostructure to nanowire also should
be due to the different adsorption ability on different planes at
varied temperatures that results in the change in the growth rate
of different planes. It is interesting that the strontium carbonate
nanowires grow along a axis instead of c axis which was the
preferential orientation of barium carbonate nanowires although
these two materials have the same crystal structure. In order to
explore in depth the formation mechanism of carbonate nano-
wires and dendritic nanostructures, further studies are now in
progress in our laboratory.
Figure 3. (a) TEM image of single strontium carbonate nanowire
obtained at 160 ꢂC for 12 h, inset is SAED pattern along [001] zone
axis and (b) its corresponding HR-TEM image.
In conclusion, we herein introduce a novel method to syn-
thesize the high aspect ratio (more than 1000) strontium carbo-
nate nanowires with a axis orientation. Dendritic nanostructures
were also controllably formed at low temperatures. Moreover,
this method is feasible to be applied in the synthesis of barium
carbonate nanowires. The formation mechanism of resultant
morphology is proposed by directed adsorption of AET mole-
cule on specific crystal planes.
The strontianite nanowires’ growth habit seems to be differ-
ent from the dendritic nanostructure. The SAED pattern inserted
in Figure 3a is taken along the [001] zone axis, which illustrates
that the nanowires prefer to grow along the [100] orientation.
This anisotropic growth is well consistent with the XRD result
that peak of (200) plane largely enhanced when comparing with
the standard XRD spectrum. High resolution TEM image is also
presented here and clearly show that the (100) plane (interplanar
spacing is 0.52 nm) is the preferential growth plane (Figure 3b).
This orientation also is different from the strontium carbonate re-
ported whose preferential orientation is along c axis.5
We acknowledge Meiling Ruan for her guidance and help
with the TEM work.
The formation of carbonate process is proposed by follow-
ing equations that are often used to fabricate methane gas:
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can also be synthesized. TEM image illustrates ultra-long nano-
wires as same as strontium carbonate nanowires were obtained.
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6
Published on the web (Advance View) February 9, 2004; DOI 10.1246/cl.2004.290