Controlled synthesis and morphology evolution of nickel sulfide micro/nanostructure

Article abstract of DOI:10.1016/j.jallcom.2010.10.178

A facile hydrothermal method has been developed for synthesis of nickel sulfide micro/nanostructure using Ni(NO₃)₂·6H ₂O as nickel source, SC(NH₂)₂ as sulfur source and 1,2-ethylenediamin/sodium dodecyl sulfate as surfactant. Different morphologies such as petal-, urchin- and sphere-like nickel sulfide structures have been synthesized by tuning the reaction time, reaction temperature, and the surfactant. The as-prepared products were characterized by X-ray diffraction, Field-emission scanning electron microscope, and Photoluminescence spectra. The relationship of the fluorescence properties with their morphology and phase was studied, and the possible growth mechanism of nickel sulfide structure was proposed based on the morphology evolution of nickel sulfide.

Full text of DOI:10.1016/j.jallcom.2010.10.178

Journal of Alloys and Compounds 509 (2011) 2170–2175
Contents lists available at ScienceDirect
Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jallcom
Controlled synthesis and morphology evolution of nickel sulfide
micro/nanostructure
Wenjun Donga,b,∗, Lina Ana, Xuebin Wanga, Bingjie Lia, Benyong Chena, Weihua Tanga,
Chaorong Lia,∗, Ge Wangb
a Department of Physics, Center for Optoelectronics Materials and Devices, Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Ministry of Education,
Engineering Research Center for Eco-Dyeing & Finishing of Textiles, Ministry of Education of China, Zhejiang Sci-Tech University, Hangzhou 310018, People’s Republic of China
b School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 26 July 2010
Received in revised form 25 October 2010
Accepted 28 October 2010
Available online 9 November 2010
A facile hydrothermal method has been developed for synthesis of nickel sulfide micro/nanostructure
using Ni(NO3)2·6H2O as nickel source, S C(NH2)2 as sulfur source and 1,2-ethylenediamin/sodium dode-
cyl sulfate as surfactant. Different morphologies such as petal-, urchin- and sphere-like nickel sulfide
structures have been synthesized by tuning the reaction time, reaction temperature, and the surfac-
tant. The as-prepared products were characterized by X-ray diffraction, Field-emission scanning electron
microscope, and Photoluminescence spectra. The relationship of the fluorescence properties with their
morphology and phase was studied, and the possible growth mechanism of nickel sulfide structure was
proposed based on the morphology evolution of nickel sulfide.
Keywords:
Nickel sulfide
Nanostructure
Morphology
© 2010 Elsevier B.V. All rights reserved.
Growth mechanism
1. Introduction
successfully prepared hexagonal structured ␤-NiS hollow spheres
by a dodecanethiol-assisted hydrothermal process [28]. However,
Chalcogenide nanostructure has attracted considerable atten-
tion owing to the unique optical, electrical, and magnetic properties
[1–9]. As a family member of the chalcogenide nanomaterial, nickel
sulfide has shown excellent application in catalysts [10–13], photo-
conduction [14], rechargeable lithium ion battery cathode [15–17],
and solar storage [18]. Up to now, three main approaches includ-
ing solid-state reactions, vapor phase reactions and soft chemistry
method have been developed successfully to fabricate nickel sul-
fide nanostructures [19–22], and different morphologies of nickel
sulfide nanostructures such as nanoneedles [23], nanorods [24],
nanotubes [25] and core-shell structures [26] have been synthe-
sized successfully. In particular, the hydro-/solvothermal method
has been used widely, because the high purity, good dispersed,
and size-controlled nickel sulfide nanostructures can be easily
obtained. For example, Wang et al. have prepared hexagonal phase
NiS nanobelts by hydrothermally, which were 50 nm in thickness,
70–200 nm in width and about 10 nm in length [27]; Zhao et al. have
a rational method to synthesize the morphology-controlled nickel
sulfide still remains as a challenge.
In this paper, different morphologies such as petal-, urchin- and
sphere-like nickel sulfide structures have been successfully syn-
thesized by a simple hydrothermal method. The reaction effects,
such as reaction time, reaction temperature, and the surfactant on
the morphologies of the as-prepared products were systematically
investigated. The growth mechanism of the morphology-controlled
nickel sulfide has been supposed based on experiment results.
2. Experimental
2.1. Materials and physical measurements
All chemicals were analytical grade purity and used as purchased without fur-
ther purification. The X-ray diffraction (XRD) pattern of the products was recorded
on a Bruker AXS D8 Discover diffraction system with a Cu K␣ radiation source
(ꢀ = 0.15405 nm) at a scanning rate of 0.02◦/s in the 2ꢁ range of 15–60◦. The images
of the as-prepared product were obtained on a HITACHI S-4800 field emission scan-
ning electron microscope (FE-SEM) at 1.0 kV. The photoluminescence (PL) spectra
were obtained on a Hitachi fluorescence spectrometer (F-7000) with a Xenon laser
at room temperature.
∗
Corresponding authors at: Department of Physics, Center for Optoelectronics
Materials and Devices, Key Laboratory of Advanced Textile Materials and Man-
ufacturing Technology, Ministry of Education, Engineering Research Center for
Eco-Dyeing & Finishing of Textiles, Ministry of Education of China, Zhejiang Sci-Tech
University, Hangzhou 310018, People’s Republic of China. Tel.: +86 571 8684587;
fax: +86 571 86843587.
2.2. Micro/nanostructure nickel sulfide prepared by hydrothermal method
Experimental details for petal-, urchin- and sphere-like nickel sulfide products
were as following: Ni(NO3)2·6H2O (0.5 g), S C (NH2)2 (0.6525 g) and 0.2 ml of 1,2-
ethylenediamine (or/and 2.0 g of sodium dodecyl sulfate) were added into 50 ml of
E-mail addresses: wenjundong@zstu.edu.cn (W. Dong), crli@zstu.edu.cn (C. Li).
0925-8388/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2010.10.178

W. Dong et al. / Journal of Alloys and Compounds 509 (2011) 2170–2175
2171
Table 1
SEM images of the as-prepared products with different surfactant at 160 ◦C in 24 h.
Surfactant
Results
Morphology
SEM image
Low magnification
High magnification
1,2-Ethylenediamin
Petal-like
Sodium dodecyl sulfate
Urchin-like
1,2-Ethylenediamin and sodium dodecyl sulfate
Sphere-like
distilled water with vigorous stirring. Then the mixed solution was transferred into
a 100 ml Teflon-lined autoclave with 60% capacity of the total volume. The autoclave
was sealed and maintained at 160 ◦C for 24 h. Finally, the autoclave was cooled to
room temperature naturally. The precipitates were collected by centrifugation and
washed with distilled water and alcohol for 3 times, respectively. Then the products
were dried under vacuum at 60 ◦C for 10 h.
tion of 1,2-ethylenediamine effect on the morphology evolution of
the petal-like structure were systematically investigated.
The effect of reaction temperature on the morphology was
shown in Fig. 1. When the reaction temperature was in the range
of 120–140 ◦C, about 2 ␮m nanosheet nickel sulfide spheres were
obtained, and the nanosheet is 50 nm in thickness (Fig. 1(a)). When
the temperature was 160 ◦C, perfect petal-like structures were
obtained (Fig. 1(b)) and the petal shows a zigzag surface. When
reaction temperature was 180 ◦C, the petal surface became smooth
(Fig. 1(c)). XRD patterns of petal-like structures prepared at dif-
ferent temperature show that the morphology of nickel sulfide
has close relationship to the phase (Fig. 1(d)). When the temper-
ature was in the range of 120–140 ◦C, the sphere structure was
pure Ni3S4 phase. When the temperature increased to 160 ◦C, the
petal-like structure with zigzag surface was NiS phase. Higher reac-
tion temperature such as 180 ◦C can convert all Ni3S4 phase to NiS
phase, and then the zigzag surfaces were developed into smooth
ones.
The reaction time effect on the morphology of the petal-like
structure was likewise studied at 160 ◦C (as shown in Table 2). After
2 h reaction, the nanosheets microspheres were prepared, and the
nanosheet is about 200 nm in thickness. When the reaction time
extended to 8 h, petals structures were formed. It seems that the
petals grow up on the surfaces of spheres. When the reaction time
increased to 24 h, zigzag structured petals were formed, and scarce
bumps appeared on the surface of the petals. When the reaction
time was 48 h, the bumps were disappeared and the zigzag surfaces
were developed into smooth.
3. Results and discussion
3.1. Morphologies and structures of the as-prepared nickel sulfide
products
The FE-SEM images of as-prepared products using 0.5 g
of Ni(NO3)2·6H2O, 0.6525 g of S C(NH2)2, and 0.2 ml of 1,2-
ethylenediamine (or/and 2.0 g of sodium dodecyl sulfate) were
shown in Table 1. The micrometer-sized self-assembled structures
products were synthesized successfully on a large scale (Table 1(a)).
The petal-like nickel sulfide structures were uniform, and most of
them were around 5 ␮m in diameter (as shown in Table 1(b)). The
petals with a zigzag surface were around 2 ␮m in length. Table 1(c)
and (d) show the nanorod urchin-like nickel sulfide structure, and
the nanorods around 500 nm in diameter radiated from the cen-
ter of urchin-like crystals. Table 1(e) shows the sphere-like nickel
sulfide pattern with 10 ␮m in diameter. The detail information of
the surface shows that the surface of the sphere is composed by
dendrite-like nanostructures (Table 1(f)).
3.2. Morphology evolution of the petal-like nickel sulfide
structure
To substantially understand the effect of 1,2-ethylenediamine
on the morphology of the nickel sulfide structures, different
amounts of 1,2-ethylenediamine was used in the experiments
(as shown in Table 2). Only NiS nanotubes were obtained in the
The petal-like nickel sulfide structures were prepared when
1,2-ethylenediamine was used as surfactant. The influence factors
including reaction temperature, reaction time and the concentra-

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W. Dong et al. / Journal of Alloys and Compounds 509 (2011) 2170–2175
Fig. 1. SEM images of the as-prepared nickel sulfide products at different temperatures (a) 120–140 ◦C; (b) 160 ◦C; (c) 180 ◦C; and (d) XRD pattern of the as-prepared petal-like
pattern nickel sulfide at different temperature (ꢀ indicates ␣-NiS peaks; ᭹ indicates Ni3S4 peaks; ꢂ indicates ␤-NiS peaks).
Ni(NO3)2·6H2O (0.5 g) and S C (NH2)2 (0.6525 g) solution were
used without surfactant. The protrudent corners were grown on
the surface of the spheres when 0.05 ml of 1,2-ethylenediamine
was used, which is similar with the tendency of orientation growth
mechanism [29,30]. When the 1,2-ethylenediamine increased to
0.15 ml, the protrudent corners grow to petal structures obvi-
ously. When 0.2 ml of 1,2-ethylenediamine was used, petal-like
structures with zigzag surface were generated, and scarce bumps
were grown on the zigzag surfaces. Under similar conditions, when
1,2-ethylenediamine increased from 0.05 ml to 0.2 ml, an obvi-
Table 2
FE-SEM images of the as-prepared samples under different reaction conditions.
Time
1, 2-Ethylenediamine
0 ml
0.05 ml
0.15 ml
0.2 ml
2 h
8 h
–
–
–
–
–
–
24 h
48 h
–
–
–

W. Dong et al. / Journal of Alloys and Compounds 509 (2011) 2170–2175
2173
Fig. 2. FE-SEM images of the as-prepared urchin-like nickel sulfide products at different reaction times (a) 4 h; (b) 12 h; (c) 24 h.
Fig. 3. FE-SEM images of the as-prepared sphere-like pattern nickel sulfide products at different temperatures (a) 120 ◦C; (b) 140 ◦C; (c) 160 ◦C.
ous morphology evolution from sphere to petal-like structure was
observed.
as the surfactant, the NiS2 phase was easily obtained. Therefore, the
surfactants showed that which significantly effected on the phase
composition. Interestingly, the broad diffraction lines existed in all
samples indicated that the assembled microstructures were com-
posed by very small particles [32] (Fig. 4). The particle size was
evaluated by Scherrer formula [33]:
3.3. Morphology evolution of the urchin- and sphere-like nickel
sulfide structures
The urchin- and sphere-like nickel sulfide structures were pre-
pared with different surfactant at 160 ◦C for 24 h. The urchin-like
nickel sulfide was prepared with sodium dodecyl sulfate, and the
sphere-like nickel sulfide was prepared with the co-existence of
1,2-ethylenediamin and sodium dodecyl sulfate.
As to the morphology of urchin-like nickel sulfide, the reaction
time shows more profound effect than that of the reaction tem-
perature. When the reaction time was 4 h, nanorods clusters were
formed (Fig. 2(a)). When reaction time was 12 h, imperfect urchin-
like structures were formed, and the nanorods radiated from the
center of crystals (Fig. 2(b)). When the hydrothermal treatment
time was prolonged to 24 h, entire urchin-like nickel sulfide struc-
tures were generated. The nanorods around 500 nm in diameter
radiated from the center developed into the complex urchin-like
structures (Fig. 2(c)).
Kꢀ
D =
ˇ cos ꢁ
where D is the averaged dimension of crystallites; K is the Scher-
rer constant, (K = 0.89); ꢀ is the wavelength of the CuK␣1 radiation
(0.15405 nm), ꢁ is the Bragg angle of the peak and ˇ is the cor-
rected half-width of the diffraction peak. The average crystalline
size of petal-, urchin- and sphere-like product is about 46.0 nm,
23.9 nm, and 54.6 nm, respectively, and these small particles were
assembled into the microstructures.
In addition, the reaction temperature shows profound effect on
the morphology of the sphere-like nickel sulfide. When the reac-
tion temperature was 120 ◦C, scarce nanoparticles around 200 nm
in diameter were appeared (Fig. 3(a)). When the temperature
increased to 140 ◦C, particles around 200 nm in diameter were
formed (Fig. 3(b)). Perfect sphere-like structures about 5 ␮m in
diameter constructed by nanorods were obtained in the range of
160–180 ◦C. High resolution SEM image shows that the surface of
the sphere is pinaster-like structure (Fig. 3(c)).
3.4. Phase control of the microcrystal
XRD patterns of as-prepared products were shown in Fig. 4.
When 1, 2-ethylenediamin was added into the solution, NiS (␣-
and ␤-) and Ni3S4 were obtained. When sodium dodecyl sulfate
was used, the products were composed of NiS2, ␤-NiS and Ni3S4.
It confirmed that Ni3S4 is always presented in the samples [31].
When 1,2-ethylenediamine was used as the surfactant, pure NiS
phase was easily obtained. When sodium dodecyl sulfate was used
Fig. 4. XRD patterns of the as-prepared products (a) petal-like; (b) sphere-like; (c)
urchin-like. (ꢂ indicates ␣-NiS peaks; ᭹ indicates NiS2 peaks; ꢀ indicates Ni3S4
peaks; the ␤-NiS was not marked).

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W. Dong et al. / Journal of Alloys and Compounds 509 (2011) 2170–2175
Fig. 5. Growth mechanism of the as-prepared nickel sulfide products (EN: 1,2-ethylenediamin; SDS: sodium dodecyl sulfate).
3.5. Growth mechanism of the as-prepared products
a
b
Based on the SEM and XRD results, the growth mechanisms
of the nickel sulfide structures were proposed (Fig. 5). Amine
molecules could serve as coordinate ligand, architecture template,
and the S2− attaching reagent [34]. When 1,2-ethylenediamine was
used, the nanosheet spheres were prepared in the initial stage, and
then petals grown on the nanosheet sphere. The SDS microspherical
capsules were generated and the hydrophilic sulfonic group would
absorb on the surface of the capsules when high concentration
sodium dodecyl sulfate (SDS) was added in the solution. Due to the
electrostatic interaction of sulfonic group with Ni2+, the outer sur-
face of the capsules would be occupied by lots of Ni2+. The absorbed
Ni2+ ions were converted into nickel sulfide nanorods, and then the
nanorods grownradiately from the center of the urchin-like crys-
tals [35]. Moreover, the influence of the mixed 1,2-ethylenediamine
and sodium dodecyl sulfate solution was studied. The “cooperative
effect” of mixed solutions of surfactants could induce the growth of
pinaster-like dendrite structure [36]. Moreover, the mixed surfac-
tant solution assisted the formation of small nanoparticles in the
initial stage, and then developed into the sphere-like nickel sulfide
structure.
c
310 320 330 340 350 360 370 380 390 400 410 420
wavelength/nm
Fig. 6. Fluorescence spectra of the as-prepared products (a) petal-like pattern struc-
ture; (b) urchin-like pattern microstructure; (c) sphere-like pattern microstructure.
etc., which might be responsible for the differences in the PL spectra
[38,39].
3.6. Photoluminescence property
Previous research reported that the fluorescence spectrum was
influenced by the different phases, shapes, structural complexity,
and the surface/volume ratio [37]. The fluorescence property of
as-prepare nickel sulfide was shown in Fig. 6. Each PL spectra of
the three samples showed a sharp emission peaks at 316 nm and
a broad emission peak at 386 nm (excited at ꢀex = 277 nm), and
both of them were ultraviolet emission. The fluorescence emission
of petal- and sphere-like microcrystal had a maximum at about
316 nm, and the fluorescence emission of the urchin-like micro-
crystal had a maximum at about 386 nm (Fig. 6). It may be attributed
to NiS phase in the petal-like and sphere-like structure, and the
NiS2 phase in the urchin-like structure. So different kinds of sur-
factant could induce different phases, shapes, and defects density
4. Conclusions
In summary, petal-, urchin- and sphere-like nickel sulfide
microstructures were prepared successfully via a facile hydrother-
mal method. Thereaction parameters such asreaction temperature,
reaction time and the surfactants played critical roles in deter-
mining the morphology of nickel sulfide nanostructures. Based on
the experiment results, a possible growth mechanism of nanos-
tructures had been proposed. Moreover, the relationships of the
fluorescence properties of microcrystal with their morphologies
and phase were studied.

W. Dong et al. / Journal of Alloys and Compounds 509 (2011) 2170–2175
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