Synthesis of nickel nanocrystallites with hexagonal flake-like morphology from nickel dimethylglyoximate

Article abstract of DOI:10.1246/cl.2004.1564

Nickel nanocrystallites with hexagonal flake-like morphology with a side length of 200-400 nm and a thickness of 20-30 nm were prepared by reduction of nickel dimethylglyoximate with hydrazine hydrate in a solution. Selected area electron diffraction (SAED) pattern revealed that the flakes were single crystals. It was found that the precursor, nickel dimethylglyoximate, played an important role for the formation of these flakes. Magnetic properties of the product were measured by a vibration sample magnetometer (VSM). Copyright

Full text of DOI:10.1246/cl.2004.1564

1564
Chemistry Letters Vol.33, No.12 (2004)
Synthesis of Nickel Nanocrystallites with Hexagonal Flake-like Morphology
from Nickel Dimethylglyoximate
Xiaomin Ni, Lifu Chen, Huagui Zheng,ꢀ Dongen Zhang, Qingbiao Zhao, and Jimei Song
Department of Chemistry, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China
(Received July 26, 2004; CL-040876)
Nickel nanocrystallites with hexagonal flake-like morpholo-
adjusted above 12 using the solution of sodium hydroxide. Then
the red mixture was transformed into a 50-mL Teflon-lined au-
toclave. The clave was sealed, maintained at 110 ꢁC for 10 h
and then allowed to cool to room temperature. The resulting
black powders were collected and washed, and finally dried in
a vacuum at 50 ꢁC for 4 h.
The X-ray diffraction (XRD) patterns were collected on a
Japan Rigaku Damax ꢀA diffractometer with graphite mono-
chromized Cu Kꢁ radiation (ꢂ ¼ 0:15418 nm). Transmission
electron microscope (TEM) was performed by a Hitachi model
H-800 transmission electron microscope with an accelerating
voltage of 200 kV. The M–H hysteresis loop was recorded by
a model BHV-55 vibrating sample magnetometer.
X-ray diffraction (XRD) was used to examine the phase
composition of the product. Figure 1 was a typical XRD pattern
of the sample. Three peaks at 2ꢃ ¼ 44:6ꢁ, 51.8ꢁ, 76.2ꢁ could be
indexed to the face-centered cubic nickel and the corresponding
Miller indices were marked for each diffraction peak. No peaks
of metal hydroxides or other impurities were detected, suggest-
ing the complete reduction of nickel dimethylglyoximate. The
strong and sharp peaks revealed that nickel particles were well
crystalline.
gy with a side length of 200–400 nm and a thickness of 20–30 nm
were prepared by reduction of nickel dimethylglyoximate with
hydrazine hydrate in a solution. Selected area electron diffrac-
tion (SAED) pattern revealed that the flakes were single crystals.
It was found that the precursor, nickel dimethylglyoximate,
played an important role for the formation of these flakes. Mag-
netic properties of the product were measured by a vibration
sample magnetometer (VSM).
Considerable attention has been drawn to the morphology
control of nanocrystals because of the intimate relationship be-
tween the property and morphology of nanomaterials.1 A lot
of methods have been exploited to fabricate nanoparticles with
various morphologies, such as anode aluminium oxide (AAO),
mesoporous silica, carbon nanotubes, microemulsion, surfac-
tants, and polymers.2–7 In addition to these techniques, recently
coordination chemistry method, avoiding complicated process
and special instruments, has been widely used to control the
morphology of nanomaterials.8 For example, Xiong and co-
workers succeeded in preparing Cu2O nanowires employing
the linear complex of [Cu3(dmg)2Cl2]n2nþ; Stibnite boundle rods
were synthesized by thermal decomposition of Sb(DDTC)3;
Hollow spheres of ZnO and nanotubes of Sb were both created
using organic metal complexes as reactants.9–12 In this synthetic
route, morphology of the desired materials showed close associ-
ation with the structure and shape of the complex precursors.
Nanosized nickel crystals show wide applications in the
fields of magnetic recording, medical diagnosis, catalysis, elec-
tronics, and conduction.13–15 Because of its highly symmetric cu-
bic lattices, the anisotropic growth of nickel has been a challeng-
ing issue. Although several morphologies of nickel nanoparticles
have been achieved by template-based methods, such as nano-
wires templated by AAO, hollow spheres resulted from micro-
emulsion and nanorods assisted by mixed surfactants.16–18 How-
ever, there have been seldom reported on the synthesis of hexag-
onal nickel nanoflakes to the best of our knowledge.
2000
(111)
1800
1600
1400
1200
1000
800
(200)
600
400
200
0
(222)
30
40
50
60
θ / degree
70
80
2
Figure 1. XRD pattern of the sample.
Here, we put forward a facile method to prepare single crys-
talline nickel nanoflakes by reduction of nickel dimethylglyoxi-
mate. The role of the precursor for the formation of nanoflakes
was investigated. Compared with other template methods, this
synthetic route proved to more simple and convenient.
All reagents were analytical grade. A typical experimental
process could be described as following. First, 8 mmol of diace-
tyldioxime was dissolved into 13-mL of ethanol to give a homo-
genous solution. Then this solution was added dropwise into 25-
mL of aqueous solution containing 4 mmol of NiCl2. Red floccu-
lates emerged in the system, indicating the formation of nickel
Morphology and size of the product were studied by TEM.
Figure 2a showed that as-prepared sample mainly consisted of
hexagonal flakes with the side length of 200–400 nm. From some
standing nanoflakes shown on the TEM image, the thickness of
the flakes was estimated to be 20–30 nm. Figure 2b gave a typi-
cal hexagonal nanoflake and the corresponding SAED pattern
(inset in Figure 2b). The diffraction spots suggested that the flake
was single crystalline. ED patterns recorded on each individual
nanoflake were essentially the same, implying the single crystal-
line nature of these flakes.
dimethylglyoximate. Subsequently, 2-mL of N2H4 H2O (80%)
It was known that Ni2þ could be coordinated by dimethyl-
glyoxime and formed nickel dimethylglyoximate, which had a
.
was added under continuous stirring and pH of the system was
Copyright Ó 2004 The Chemical Society of Japan

Chemistry Letters Vol.33, No.12 (2004)
1565
46.2
23.1
0
-23.1
-46.2
-10000
-5000
0
5000
10000
H(Oe)
Figure 2. a) TEM images of the sample. b) A typical hexagonal
nickel nanoflake and the corresponding ED pattern (inset in
Figure 2b). C) TEM image of the precursor of nickel dimethyl-
glyoximate.
Figure 3. M–H (Magnetization–Hysteresis) loops of as-
prepared nickel nanoflakes measured at room temperature.
for further applications in the magnetic, photonic, catalysis,
and electronic fields.
square planar structure. We proposed that the flake-like mor-
phology of our product related to the planar structure of the pre-
cursor. To illustrate the puzzle, we attempted to replace the li-
gands with other N-complexing agents such as ethylenediamine,
hydrazine, and pyridine which all combined with Ni2þ in a octa-
hedral structure, keeping the other reaction conditions equal. Re-
sults showed that no flake-like particles could be obtained and
the products were only nickel nanocrystallites with no definite
geometric shapes, proving the unique role of nickel dimethyl-
glyoximate for the formation of nickel nanoflakes. To examine
further the effect of precursor on the shape of the final product,
we studied the morphology of nickel dimethylglyoximate. The
TEM image of Figure 2c showed that the precursor was rib-
bon-like with a diameter of 300–500 nm and length of dozens
of microns, which exhibited a characteristic of planar morphol-
ogy. On the basis of the above facts, we deduced that the forma-
tion of nanoflakes was related to the template effects of the com-
plex precursor.19 During the reaction, it was possible that the re-
duced nickel atoms were confined on a plane by the specially
shaped precursor, inducing the oriented growth of nickel nano-
crystals. As a result, flake-like single crystals of nickel were ob-
tained. It was likely that the planar ribbon-shaped precursor pro-
vided orientation for the growth of nickel particles. Meanwhile,
the slow release of Ni2þ from the complex precursor may also be
favorable for the growth of single crystalline nickel particles.20
However, why these flakes appeared at a hexagonal shape was
still not clear and the related research was under way.
References
1
2
A. P. Alivisatow, Science, 271, 933 (1996).
H. O. Cao, Z. Xu, H. Sang, D. Sheng, and C. Y. Tie, Adv.
Mater., 13, 121 (2001).
3
K. S. Napolsky, A. A. Eliseev, A. V. Knotko, A. C. Lukahsin,
A. A. Vertegel, and Y. D. Tretyakov, Mater. Sci. Eng., C, 23,
151 (2003).
4
5
Y. Zhang and H. Dai, Appl. Phys. Lett., 77, 3015 (2000).
S. Mishima, M. Kawamura, S. Matsukawa, and T. Nakajima,
Chem. Lett., 2002, 1092.
6
X. Zheng, Y. Xie, L. Zhu, X. Jiang, and A. Yan, Ultrason.
Sonochem., 9, 311 (2002).
7
8
L. Qi, J. Li, and J. Ma, Adv. Mater., 14, 300 (2002).
K. Soulantica, A. Maisonnat, F. Senocq, M. C. Fromen,
M. J. Casanove, and B. Chaudret, Angew. Chem., Int. Ed.,
40, 2984 (2001).
9
Y. Xiong, Z. Li, R. Zhang, Y. Xie, J. Yang, and C. Wu,
J. Phys. Chem. B, 107, 3679 (2003).
10 C. H. An, K. B. Tang, Q. Yang, and Y. T. Qian, Inorg. Chem.,
42, 8081 (2003).
11 Z. Li, Y. Xie, Y. Xiong, and R. Zhang, New J. Chem., 27, 1518
(2003).
12 H. Hu, M. Mo, B. Yang, M. Shao, S. Zhang, Q. Li, and
Y. Qian, New J. Chem., 27, 1161 (2003).
13 V. F. Puntes, K. M. Krishnan, and A. P. Alivisatos, Science,
291, 2115 (2001).
Magnetic measurements on thus-prepared nanoflakes were
conducted and the M–H hysteresis loop was presented in
Figure 3. The coercivity reached 198.8 Oe, much enhanced com-
pared with that of bulk nickel (100 Oe), possibly for their novel
morphology and nanosize.21 Owing to that the particle size ex-
ceeded the single magnetic domain size of nickel, the product
did not show superparamagnetization.22 The saturation magnet-
ization (Ms) and remnant magnetization (Mr) were 48.4 and
14.86 emu gꢂ1, respectively.
In conclusion, hexagonal nickel flakes with a side length of
200–400 nm and a thickness of 20–30 nm were prepared via the
reaction between nickel dimethylglyoximate and hydrazine hy-
drate. The planar precursor showed a significant influence on
the formation of flake-like nickel nanocrystals. To the best of
our knowledge, this is the first report of the preparation of single
crystalline nickel with hexagonal flake-like morphology. The re-
sultant nickel nanoflakes may provide interesting possibilities
14 M. P. Pileni, Adv. Funct. Mater., 11, 323 (2001).
15 W. X. Zhang, C. B. Wang, and H. L. Lien, Catal. Today, 40,
387 (1998).
16 J. Bao, C. Tie, Z. Xu, Q. Zhou, D. Shen, and Q. Ma, Adv.
Mater., 13, 1631 (2001).
17 J. Bao, Y. Liang, Z. Xu, and L. Si, Adv. Mater., 15, 1832
(2003).
18 N. Coydente, M. Respaud, F. Secocq, M. J. Casanove, C.
Amiens, and B. Chaudret, Nano Lett., 1, 565 (2001).
19 C. Chen, C. Zhu, L. Hao, Y. Hu, and Z. Chen, Chem. Lett., 33,
898 (2004).
20 Z. Liu, S. Li, Y. Yang, S. Peng, Z. Hu, and Y. Qian, Adv.
Mater., 15, 1946 (2003).
21 J. H. Hwang, V. P. Dravid, M. H. Teng, J. J. Host, B. R.
Elliott, D. L. Johnson, and T. O. Mason, J. Mater. Res., 12,
1076 (1997).
22 D. H. Chen and S. H. Wu, Chem. Mater., 12, 1354 (2000).
Published on the web (Advance View) November 6, 2004; DOI 10.1246/cl.2004.1564