Single-step synthesis and catalytic activity of structure-controlled nickel sulfide nanoparticles

Article abstract of DOI:10.1039/c5ce00742a

Nanoparticle single-phase nickel sulfides such as NiS, NiS₂, Ni₃S₄, and Ni₇S₆ were prepared from elemental sulfur and nickel nitrate hexahydrate, using a temperature-controlled precursor injection method. The initial ratio of the concentrations of the sources was used to control the size and phase of the final product. Phase control was confirmed using X-ray diffraction and transmission electron microscopy. The synthesized nickel sulfide phases, which had metallic characteristics, were used to study the catalytic reduction of 4-nitrophenol. The results showed that the catalytic activity of the NiS nanoparticles in the reduction of 4-nitrophenol to 4-aminophenol was higher than those of the other nickel sulfide phases. In addition, the nanocrystals showed good separation ability and reusability for reduction of 4-nitrophenol.

Full text of DOI:10.1039/c5ce00742a

View Article Online
View Journal
CrystEngComm
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: K. Rajan, D.
Thangaraju, P. Natarajan and Y. Hayakawa, CrystEngComm, 2015, DOI: 10.1039/C5CE00742A.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/crystengcomm

Page 1 of 25
CrystEngComm
View Article Online
DOI: 10.1039/C5CE00742A
Single-Step Synthesis and Catalytic Activity of Structure-Controlled
Nickel Sulfide Nanoparticles
†
‡
†
Rajan Karthikeyan, Dheivasigamani Thangaraju, Natarajan Prakash, and Yasuhiro
†
,‡,
Hayakawa *
†
Graduate School of Science and Technology, Shizuoka University, 3ꢀ5ꢀ1 Johoku,
Nakaꢀku, Hamamatsu, Shizuoka 432ꢀ8011, Japan
‡
Research Institute of Electronics, Shizuoka University, 3ꢀ5ꢀ1 Johoku, Nakaꢀku,
Hamamatsu, Shizuoka 432ꢀ8011, Japan
*Corresponding author. Tel./Fax: +81 53 478ꢀ1310
Eꢀmail: royhaya@ipc.shizuoka.ac.jp (Yasuhiro Hayakawa)
1

CrystEngComm
Page 2 of 25
View Article Online
DOI: 10.1039/C5CE00742A
Single-Step Synthesis and Catalytic Activity of Structure-Controlled
Nickel Sulfide Nanoparticles
ABSTRACT
2 3 4 7 6
Nanoparticle singleꢀphase nickel sulfides such as NiS, NiS , Ni S , and Ni S were
prepared from elemental sulfur and nickel nitrate hexahydrate, using
a
temperatureꢀcontrolled precursor injection method. The initial ratio of the
concentrations of the sources was used to control the size and phase of the final product.
Phase control was confirmed using Xꢀray diffraction and transmission electron
microscopy. The synthesized nickel sulfide phases, which had metallic characteristics,
were used to study the catalytic reduction of 4ꢀnitrophenol. The results showed that the
catalytic activity of the NiS nanoparticles in the reduction of 4ꢀnitrophenol to
4
ꢀaminophenol was higher than those of the other nickel sulfide phases. In addition, the
nanocrystals showed good separation ability and reusability for reduction of
ꢀnitrophenol.
4
2

Page 3 of 25
CrystEngComm
View Article Online
DOI: 10.1039/C5CE00742A
INTRODUCTION
Inorganic nanoparticle synthesis has received much attention for optical,
electrical, and magnetic applications due to its rich physicoꢀchemical properties.
Environmental friendly transition metal chalcogenide nanoparticle synthesis is the
1
–4
current interest in energy applications
.
Nickle sulfides have potential applications in
5–7
lithium ion batteries, supercapacitors, and dyeꢀsensitized solar cells . The different
phases of nickle sulfide has more complex phases such as NiS (αꢀNiS and βꢀNiS), Ni S ,
3
2
2 3 4 9 8 7 6
NiS , Ni S , Ni S , and Ni S make synthesis of singleꢀphase nickel sulfide complicated.
The phase diagram of nickel sulfide has a large number of sulfurꢀrich and nickelꢀrich
phases at low temperatures. The synthesis of sulfurꢀrich phases is less complex than that
of nickelꢀrich phases. NiS shows two different phase types, depending on the synthesis
temperature. Kullerud and Yund reported that the phase transformation from αꢀNiS to
8
βꢀNiS occurs at 282 °C .
Nickel sulfides with different phases and morphologies, such as layerꢀrolled
9
10–13
14
NiS , hexagonal NiS
rhombohedral NiS, and dodecahedral NiS
methods, for various applications; for example, NiS
for photocatalytic hydrogen production and in supercapacitors . Several methods for
2
, NiS cuboids, NiS nanobelts , threeꢀdimensional flowerꢀlike
15
2
have been synthesized, using different
cubic nanoparticles have been used
2
1
6
1
3,17
the synthesis of selenide and sulfide
nanocrystals have been investigated.
1
8
Solvothermal and wetꢀchemical methods , which involve highꢀtemperature solidꢀstate
and vaporꢀphase reactions, have been used to synthesize nickel sulfides. However,
controlledꢀphase nickel sulfide synthesis is difficult using these methods. In
hydrothermal or solvothermal synthesis, concentration control leads to the formation of
3

CrystEngComm
Page 4 of 25
View Article Online
DOI: 10.1039/C5CE00742A
19
other phases within the synthesized product . The synthesis of nickel sulfide phases
2
0
3 4
such as Ni S requires a twoꢀstep reduction process to control the phase and
morphology. We have developed a singleꢀstep injection process, using oleylamine as
both the solvent and the reducing agent, to obtain the desired phases in the nickel
sulfide binary phase diagram. We described the synthesis and evolution of hierarchical
1
9
nickel sulfide architectures in our previous communication .
Temperatureꢀcontrolled injection reactions have several advantages in the
2
1
synthesis of nanoparticles, such as low cost and better productivity . Shape control of
sulfurꢀbased nanocrystals by injecting a molecular precursor into highꢀboilingꢀpoint
2
2
solvents was reported by Lee et al . Recently, many groups have focused on using
different amines for the sizeꢀ and structureꢀcontrolled synthesis of individual metal
2
,23–25
sulfide phases
. The use of oleylamine–metal complexes has been well studied by
Joo et al.; they reported the synthesis of various sizeꢀcontrolled metal sulfides such as
2
6
PbS, ZnS, CdS, and MnS, with particle sizes of 6−13 nm . Sulfur–oleylamine
interactions lead to the formation of H S, which reacts with a metal precursor to form
2
24
metal sulfide nanoparticles .
In this paper, we describe the singleꢀstep, structureꢀcontrolled synthesis of
nickel sulfide nanoparticles with different phases, using a precursor hotꢀinjection
method with oleylamine as the sole solvent. The catalytic properties of the different
phases of nickel sulfide were investigated.
EXPERIMENTAL
Materials
4

Page 5 of 25
CrystEngComm
View Article Online
DOI: 10.1039/C5CE00742A
Ni(NO
NaBH
3
)
2
·6H
2
O (purity 98%), elemental sulfur, ethanol (99.95%), 4ꢀnitrophenol,
4
, and acetone (purity 99.9%) were purchased from Wako Pure Chemical
Industries, Ltd., Japan. Oleylamine (70%) was purchased from Sigma Aldrich. The
reagents were used without further purification.
Synthesis of Nickel Sulfide Nanoparticles
A typical procedure for nickel sulfide particle synthesis was as follows. Ni(NO
3
)
2
2
·6H O
(1 mmol) was mixed with oleylamine (10 mL) in a 100 mL threeꢀnecked flask (A). The
2
solution was heated at 100 °C for 1 h to remove moisture and O in the oleylamine.
Elemental sulfur (1 mmol) and oleylamine (10 mL) were placed in a separate 100 mL
threeꢀnecked flask (B) and heated at 70 °C for 30 min to form a sulfur–amine mixture.
The transparent yellow sulfur–oleylamine solution (B) was loaded into a glass syringe
and injected into the nickel–oleylamine solution mixture (A). This mixture of the
sources in a concentration ratio of 1:1 gave the NiS phase. The temperature was raised
2
to 210 °C and the mixture was continually stirred for 1 h under a N atmosphere to
initiate the reaction. After cooling, the particles were collected by centrifugation,
washed with ethanol, and dried under vacuum for 1 h. The particles were dispersed in
an organic solvent and stored in a tightly closed container.
When the temperature was raised to 210 °C, the sulfur–amine mixture released
2
H S, which reacted with the metal–oleylamine complex to form a nickel sulfide
21
3 2 2
product . These procedures were repeated using Ni(NO ) ·6H O:elemental sulfur
concentration ratios of 1:2, 3:4, and 3:2 to synthesize nickel sulfide nanoparticles with
different phases. The oleylamine acted as both a solvent and a capping agent. Table 1
5

CrystEngComm
Page 6 of 25
View Article Online
DOI: 10.1039/C5CE00742A
shows details of the phases present in the synthesized products with respect to
concentration.
Catalytic Study
The catalytic activities of the synthesized nickel sulfide nanoparticles were investigated
as follows. Aqueous solutions of 4ꢀnitrophenol (10 mg in 50 mL of distilled water) and
NaBH
NaBH
4
4
(750 mg in 200 mL of distilled water) were freshly prepared. 4ꢀNitrophenol and
in a concentration ratio of 1:10 were mixed with nickel sulfide nanoparticles
(4.0 mg). The mixture was placed in a quartz cuvette and the reaction was monitored
using UVꢀvis spectroscopy. This step was repeated several times to study the stability of
the nanoparticles.
Characterization
The crystalline phases of the final precipitates were identified by powder Xꢀray
−
1
diffraction (XRD) performed at a scan rate of 0.04 s in the 2
θ range 10° to 80°
(
RINTꢀ2200 diffractometer, Rigaku, Japan, CuKα radiation, = 1.54178 Å). The
λ
particle sizes and morphologies of the final precipitates were determined using
transmission electron microscopy (TEM) and highꢀresolution TEM (HRTEM; JEOL
JEM 2100F) at an accelerating voltage of 200 kV. Binding energies were investigated
using Xꢀray photoelectron spectroscopy (XPS; Shimadzu ESCA 3100).
Fourierꢀtransform infrared spectroscopy (FTIR) was performed using a JEOL
JIRꢀWINSPEC 50 spectrometer.
6

Page 7 of 25
CrystEngComm
View Article Online
DOI: 10.1039/C5CE00742A
RESULTS AND DISCUSSION
NiS Phase
A typical XRD pattern of the nickel sulfide particles prepared using the
temperatureꢀdependent injection method is shown in Figure 1(a). The pattern shows that
the sample is crystalline. The pattern in Figure 1(a) corresponds to the αꢀNiS phase. The
use of a 1:1 concentration ratio of nickel to sulfur in the presence of oleylamine resulted
in formation of a nickel monosulfide phase. JCPDS reference 01ꢀ075ꢀ0613, i.e., αꢀNiS,
matched the synthesized sample well. Figure 1(b) and (c) show TEM and HRTEM
images of the NiS nanoparticles. The TEM image shows that the sizes of the spherical
nanoparticles ranged from 8 to 10 nm. The highꢀmagnification image shows that the
distance between the atomic layers was 2.94 Å, which matches the dꢀspacing of the
(100) plane of the NiS phase (Figure 1a). A single phase with good crystallinity was
obtained in a single step at 210 °C. Oleylamine helped to make the particle size
distribution uniform.
2
NiS Phase
The XRD pattern shown in Figure 2(a) matched JCPDS reference 00ꢀ011ꢀ0099, i.e., the
NiS phase. A source material concentration ratio of 1:2 resulted in formation of nickel
2
disulfide nanoparticles. Figure 2(b) and (c) show the sample morphology. The TEM
image shows that the cubic particles were well distributed, and of size 6–8 nm. The
distance between the atomic layers of the cubic nanoparticles was 2.77 Å (Figure 2c),
2
which matches that of the (200) plane of the NiS phase.
3 4
Ni S Phase
7

CrystEngComm
Page 8 of 25
View Article Online
DOI: 10.1039/C5CE00742A
A concentration ratio of 3:4 (nickel source 1.5 mmol, 0.435 g; sulfur source 2 mmol,
.064 g) gave the sulfurꢀrich phase Ni . The XRD pattern, shown in Figure 3(a)
matched JCPDS reference 00ꢀ047ꢀ1739 well. The TEM and HRTEM images in Figure
(b) and (c) show that the particles had a bulging spherical morphology. The dꢀspacing
observed from the HRTEM image, 2.78 Å, was close to that of the (311) plane (see
0
3 4
S
3
3 4
Figure 3a). The dꢀspacing value of 2.33 Å corresponded to the (220) plane of the Ni S
phase.
7 6
Ni S Phase
The XRD pattern of the material synthesized using a source concentration ratio of 3:2
matched that of the nickelꢀrich phase Ni (Figure 4a; JCPDS reference 00ꢀ014ꢀ0364).
Figure 4(b) and (c) show the TEM and HRTEM images of Ni . The TEM image
7 6
S
7 6
S
shows that the wellꢀdistributed particles consisted of spherical and elongated spherical
particles of size 8–20 nm. The broad particle size distribution is caused by the high
nickel concentration in the source. The HRTEM image shows that the distances
between the atomic layers in spherical and elongated spherical nanoparticles were
different. The spherical nanoparticle dꢀspacing, 2.85 Å, corresponds to the (121) plane
and the elongated spherical particle dꢀspacing, 3.12 Å, corresponds to the (042) plane.
FTIR Analysis
Figure 5 shows the FTIR spectra of the synthesized nickel sulfide nanoparticles with
different phases. The peaks from the C–H stretching modes are observed at 2921 and
−1, 27–30
−1
31
2852 cm
, the broad peak at 3400 cm corresponds to the N–H stretching of
−
1
free amines, and the peak at 1653 cm is related to N–H rocking vibrations. The
8

Page 9 of 25
CrystEngComm
View Article Online
DOI: 10.1039/C5CE00742A
−1
7 6
absence of the peaks at 1389 and 3400 cm in the spectrum of the Ni S sample
31
indicates lower reactivities of the C–N and N–H bonds in organic ligands .
XPS Analysis
The XP spectra of the different phases of the synthesized nanoparticles are shown in
Figure 6. Table 2 show the binding energies of the synthesized phases. The binding
energy of 852.8 eV (Ni 2p 3/2) for the NiS and Ni
7
S
6
samples matched the reported
, i.e., 852.5 and 853.1 eV, respectively,
were close to the reported values of 852.85 and 854.3 eV. All the Ni 2p1/2 binding
32
2 3 4
values . The binding energies for NiS and Ni S
24,33,34
energies matched the reported values
. The difference between the binding
energies of Ni 2p1/2 and Ni 2p3/2 is approximately equal to the standard value for nickel
35
doublet peaks (17.4) , but this difference is 18.4 eV in the case of NiO bonds. This
confirms that the materials are protected from oxidation by oleylamine capping of the
particles. Doublet peaks of S 2p3/2 and S 2p1/2 for NiS
2
, i.e., 161.2 and 162.8 eV,
data . These values are similar to those for the nickelꢀrich
. The other phases such as NiS and Ni had sulfur doublet peaks
3
3
matched the reported NiS
phase Ni
consistent with the reported values .
2
7
S
6
3 4
S
3
2
The different materials obtained using different molar concentrations of the
source materials (Table 1) show that the availability of the nickel source for reaction
with the sulfur–amine mixture is very important in synthesizing singleꢀphase nickel
sulfides. The local nickel concentration increased during the reaction to form the more
stable Ni
3
S
4
phase. In this case, all the sulfur source molecules reacted with the metal
and
phases
precursor. The complex phases in the nickel sulfide phase diagram, such as Ni
3 4
S
Ni
7
S , were obtained without sulfur impurities. The results for the NiS and NiS
6 2
9

CrystEngComm
Page 10 of 25
View Article Online
DOI: 10.1039/C5CE00742A
clearly show that any stable phase of nickel sulfide can be synthesized by singleꢀstep
temperatureꢀcontrolled synthesis with the help of oleylamine.
Catalytic Activities of Nickel Sulfide Catalysts
We investigated the reduction of 4ꢀnitrophenol to 4ꢀaminophenol to help us to
36,37
understand the catalytic activities of the synthesized nickel sulfide phases
. No
reduction was observed without the presence of nickel sulfide catalysts. Figure 7 shows
photographs of 4ꢀnitropheneol reduction and the chemical equation. Figure 8 shows the
UVꢀvis absorbance spectra with respect to time. During the reaction, hydrogen species
were first transferred to the surface of the synthesized products and then 4ꢀnitrophenol
38
was reduced to 4ꢀaminophenol . In Figure 8, the absorption peak at 400 nm represents
the 4ꢀnitrophenolate ion and the peak at 293 nm is related to 4ꢀaminophenol. When NiS
nanoparticles were added to the solution, reduction to 4ꢀaminophenol was complete in
about 300 s (Figure 8a). The catalytic activities of the sulfurꢀrich phases were lower
2 3 4
than that of the NiS phase. The reduction times using NiS and Ni S were both 400 s
(
Figure 8b and c). For the Ni phase, reduction was complete in 500 s. The NiS phase
7 6
S
had much higher catalytic activity. Figure 9 shows the reduction rates with different
nickel sulfide phases. The reaction rate increased linearly with respect to time. The
reduction rate constant (Kobs) was calculated using the absorption vales for the
39,40
4ꢀnitrophenol reduction reaction
.
ꢅ − ꢅ
ꢆ
ꢇ
ln ꢄ
ꢉ
ꢅꢆ − ꢅꢈ
ꢀꢁꢂꢃ
=
ꢊ
1
0

Page 11 of 25
CrystEngComm
View Article Online
DOI: 10.1039/C5CE00742A
where A
0
, A
t
, and A
∞
are the initial absorbance, absorbance at time t, and absorbance at
, Ni , and Ni
infinite time, respectively. The calculated Kobs values for NiS, NiS
2
S
3 4
7 6
S
−
3
−3
−3
−3 −1
are 8.949 × 10 , 3.030 × 10 , 3.728 × 10 , and 2.737 × 10 s , respectively. Among
the four synthesized nickel sulfide phases, NiS gave the highest rate of degradation of
11
4
ꢀnitrphenol because of its higher metallic nature . To study the structural change after
its catalytic reduction, nanoparticles of NiS phase were collected by centrifugation and
investigated the structure by XRD analysis. Fig.10 shows the XRD pattern of NiS phase
after its catalytic activity. The corresponding JCPDS reference 00ꢀ001ꢀ1286 was well
matched with the NiS phase. No phase change was observed even after its catalytic
reduction but the crystal system was changed from hexagonal to rhombohedral of NiS
phase. The repeated catalytic activity of NiS phase was well matched with the initial
experiment of Figure.8 (a) and its reduction time of 4ꢀnitrophenol to 4ꢀaminophenol is
300 sec.
CONCLUSIONS
We successfully synthesized nickel sulfide nanoparticles with different phases via a
simple temperatureꢀcontrolled injection method in oleylamine solvent. The products
were uniformꢀsized nanocrystals. The injection method enabled the sulfur ions to react
slowly with the wellꢀdispersed nickel ions in the presence of oleylamine, to form nickel
sulfide nanoparticles. This enabled formation of the desired phase instead of mixed
3 4
phases. The complications in the synthesis of Ni S were overcome by adjusting the
source concentrations. XRD and TEM analyses confirmed the presence of singleꢀphase
nanoparticles of sizes less than 15 nm for all the synthesized products. The presence of
sulfur and nickel and the peak shifts with respect to phase formation were observed
11

CrystEngComm
Page 12 of 25
View Article Online
DOI: 10.1039/C5CE00742A
using XPS. The catalytic activities of the synthesized nickel sulfide nanoparticles were
investigated; the NiS phase had the best activity and the phase was stable even after its
catalytic reduction experiment.
ACKNOWLEDGMENTS
This work was financially supported by a GrantꢀinꢀAid for Japan Society for the
Promotion of Science (JSPS) Fellows, related to the JSPS Postdoctoral Fellowship for
Foreign Researchers (No. 26 04050) from the Ministry of Education, Culture, Sports,
Science, and Technology (MEXT) of Japan, and a cooperative research project of the
Research Institute of Electronics, Shizuoka University. The authors would like to thank
Mr. T. Koyama and Mr. W. Tomada for their help with XRD and XPS analyses. R.
Karthikeyan thanks MEXTꢀJapan for the award of a research fellowship.
REFERENCES
1.
2.
3.
4.
X. Peng, L. Manna, W. Yang, J. Wickham, E. Scher, a Kadavanich, and A.
Alivisatos, Nature, 2000, 404, 59–61.
Q. Liu, A. Díaz, A. Prosvirin, Z. Luo, and J. D. Batteas, Nanoscale, 2014, 6,
8
935–8942.
C. J. Barrelet, Y. Wu, D. C. Bell, and C. M. Lieber, J. Am. Chem. Soc., 2003, 125,
1498–9.
1
Y. Hasegawa, M. Afzaal, P. O’Brien, Y. Wada, and S. Yanagida, Chem.
Commun. (Camb)., 2005, 1, 242–3.
1
2

Page 13 of 25
CrystEngComm
View Article Online
DOI: 10.1039/C5CE00742A
5.
6.
7.
L. Mi, Q. Ding, W. Chen, L. Zhao, H. Hou, C. Liu, C. Shen, and Z. Zheng,
Dalton Trans., 2013, 42, 5724–30.
T. Zhu, H. Bin Wu, Y. Wang, R. Xu, and X. W. D. Lou, Adv. Energy Mater.,
2
012, 2, 1497–1502.
W. S. Chi, J. W. Han, S. Yang, D. K. Roh, H. Lee, and J. H. Kim, Chem.
Commun. (Camb)., 2012, 48, 9501–9503.
8
.
.
G. Kullerud and R. a. Yund, J. Petrol., 1962, 3, 126–175.
9
X. Jiang, Y. Xie, J. Lu, L. Zhu, W. He, and Y. Qian, Adv. Mater., 2001, 13,
1
278–1281.
1
1
1
1
1
0. J. T. Sparks and T. Komoto, J. Appl. Phys., 1963, 34, 1191.
1. J. Sparks and T. Komoto, Phys. Lett., 1967, 25, 5–6.
2. J. Sparks and T. Komoto, Rev. Mod. Phys., 1968, 40, 752–754.
3. J. and J. P. R. A. S. Barker, Phys. Rev. B, 1974, 10, 987–994.
4. L. Wang, Y. Zhu, H. Li, Q. Li, and Y. Qian, J. Solid State Chem., 2010, 183,
2
23–227.
15. S. Chen, K. Zeng, H. Li, and F. Li, J. Solid State Chem., 2011, 184, 1989–1996.
16. H. Pang, C. Wei, X. Li, G. Li, Y. Ma, S. Li, J. Chen, and J. Zhang, Sci. Rep.,
2
014, 4, 3577, 1–8.
1
3

CrystEngComm
Page 14 of 25
View Article Online
DOI: 10.1039/C5CE00742A
17. V. G. Pol, S. V Pol, and A. Gedanken, Adv. Mater., 2011, 23, 1179–90.
1
8. C. N. R. Rao, S. R. C. Vivekchand, K. Biswas, and a Govindaraj, Dalton Trans.,
007, 3728–49.
2
19. Y. H. R.Karthikeyan, M. Navaneethan, J. Archana, D. Thangaraju, M.
Arivanandhan, Dalton Trans., 2014, 43, 17445–17452.
2
2
2
0. A. Ghezelbash and B. a Korgel, Langmuir, 2005, 21, 9451–6.
1. B. Wu, N. Zheng, and G. Fu, Chem. Commun. (Camb)., 2011, 47, 1039–1041.
2. S. M. Lee, Y. W. Jun, S. N. Cho, and J. Cheon, J. Am. Chem. Soc., 2002, 124,
1
1244–11245.
2
2
2
3. A. Lut, M. A. Malik, P. O. Brien, and F. Tuna, 2012, 2253–2259.
4. J. W. Thomson, K. Nagashima, P. M. Macdonald, and G. a Ozin, 2011, 3–5.
5. A. Dyal, K. Loos, M. Noto, S. W. Chang, C. Spagnoli, K. V. P. M. Shafi, A.
Ulman, M. Cowman, and R. a Gross, J. Am. Chem. Soc., 2003, 125, 1684–5.
26. S. H. Choi, K. An, E. G. Kim, J. H. Yu, J. H. Kim, and T. Hyeon, Adv. Funct.
Mater., 2009, 19, 1645–1649.
27. L. Polavarapu and Q.ꢀH. Xu, Nanotechnology, 2009, 20, 185606, 1–7.
28. J. He, P. Kanjanaboos, N. L. Frazer, A. Weis, X. M. Lin, and H. M. Jaeger, Small,
2
010, 6, 1449–1456.
1
4

Page 15 of 25
CrystEngComm
View Article Online
DOI: 10.1039/C5CE00742A
29. A. Khare, A. W. Wills, L. M. Ammerman, D. J. Norris, and E. S. Aydil, Chem.
Commun., 2011, 47, 11721–11723.
30. M. Klokkenburg, J. Hilhorst, and B. H. Erné, Vib. Spectrosc., 2007, 43, 243–248.
31. L. Zhang, L. Wang, Z. Jiang, and Z. Xie, Nanoscale Res. Lett., 2012, 7, 312, 1–6.
32. M. SalavatiꢀNiasari, F. Davar, and M. Mazaheri, Mater. Res. Bull., 2009, 44,
2
246–2251.
33. S.ꢀL. Yang, H.ꢀB. Yao, M.ꢀR. Gao, and S.ꢀH. Yu, CrystEngComm, 2009, 11,
1
383–1390.
34. L. Sangaletti, T. Thio, and J. W. Bennett, 1997, 55, 9514–9519.
3
5. C. D. Wagner, W. M. Riggs, L. E. Davis, and J. F. Moulder, Handbook of X-ray
Photoelectron Spectroscopy, 1979.
36. T. Yu, J. Zeng, B. Lim, and Y. Xia, Adv. Mater., 2010, 22, 5188–92.
37. F. H. Lin and R. A. Doong, J. Phys. Chem. C, 2011, 115, 6591–6598.
38. N. Pradhan, A. Pal, and T. Pal, Colloids Surfaces A Physicochem. Eng. Asp.,
2
002, 196, 247–257.
39. S. Gu, S. Wunder, Y. Lu, M. Ballauff, R. Fenger, K. Rademann, B. Jaquet, and A.
Zaccone, J. Phys. Chem. C, 2014, 118, 18618–18625.
1
5

CrystEngComm
Page 16 of 25
View Article Online
DOI: 10.1039/C5CE00742A
40. E. Murugan and J. N. Jebaranjitham, J. Mol. Catal. A Chem., 2012, 365, 128–
1
35.
Figure captions
Figure 1. (a) XRD pattern, and (b) TEM and (c) HRTEM images of NiS phase.
2
Figure 2. (a) XRD pattern, and (b) TEM and (c) HRTEM images of NiS phase.
Figure 3. (a) XRD pattern, and (b) TEM and (c) HRTEM images of Ni
Figure 4. (a) XRD pattern, and (b) TEM and (c) HRTEM images of Ni
Figure 5. FTIR patterns of different nickel sulfide phases.
3
S
4
phase.
phase.
7
S
6
Figure 6. (a) Ni 2p and (b) S 2p XP spectra of different nickel sulfide phases.
Figure 7. Catalytic reduction of 4ꢀnitrophenol to 4ꢀaminophenol.
Figure 8. UVꢀvis spectra of 4ꢀnitrophenol reduction with (a) NiS, (b) NiS
2 7 6
, (c) Ni S ,
and (d) Ni phases.
3 4
S
Figure 9. Effects of different nickel sulfide phases on reduction of 4ꢀnitrophenol.
Figure. 10 XRD pattern of NiS phase after its catalytic activity
1
6

Page 17 of 25
CrystEngComm
View Article Online
DOI: 10.1039/C5CE00742A
Table 1. Different concentration ratios of nickel and sulfur sources and the
corresponding phases of synthesized materials
Name
Nickel source
g)
Sulfur source
(g)
Concentration
ratio
Phase
(
I – 1
I – 2
I – 3
I – 4
0.290
0.290
0.435
0.435
0.032
0.064
0.064
0.032
1:1
1:2
3:4
3:2
NiS
NiS
2
Ni
Ni
3
7
S
4
S
6
Table 2. XPS binding energy values
Phase
Ni 2p3/2
Ni 2p1/2
Ni 2p3/2 - Ni 2p1/2
(eV)
S 2p3/2
S 2p1/2
(eV)
(eV)
(eV)
(eV)
NiS
852.8
852.5
853.1
852.8
870.4
870
17.6
17.5
17.3
17.3
161.4
161.2
161.6
161.2
162.8
162.8
162.8
162.8
NiS
2
Ni3S4
Ni
870.4
870.1
7
S
6
1
7

CrystEngComm
Page 18 of 25
View Article Online
DOI: 10.1039/C5CE00742A
Figure 1. (a) XRD pattern, and (b) TEM and (c) HRTEM images of NiS phase.
1
8

Page 19 of 25
CrystEngComm
View Article Online
DOI: 10.1039/C5CE00742A
Figure 2. (a) XRD pattern, and (b) TEM and (c) HRTEM images of NiS
2
phase.
1
9

CrystEngComm
Page 20 of 25
View Article Online
DOI: 10.1039/C5CE00742A
Figure 3. (a) XRD pattern, and (b) TEM and (c) HRTEM images of Ni
S
3 4
phase.
2
0

Page 21 of 25
CrystEngComm
View Article Online
DOI: 10.1039/C5CE00742A
Figure 4. (a) XRD pattern, and (b) TEM and (c) HRTEM images of Ni
S
7 6
phase.
2
1

CrystEngComm
Page 22 of 25
View Article Online
DOI: 10.1039/C5CE00742A
Figure 5. FTIR patterns of different nickel sulfide phases.
2
2

Page 23 of 25
CrystEngComm
View Article Online
DOI: 10.1039/C5CE00742A
Figure 6. (a) Ni 2p and (b) S 2p XP spectra of different nickel sulfide phases.
2
3

CrystEngComm
Page 24 of 25
View Article Online
DOI: 10.1039/C5CE00742A
Figure 7. Catalytic reduction of 4ꢀnitrophenol to 4ꢀaminophenol.
Figure 8. UVꢀvis spectra of 4ꢀnitrophenol reduction with (a) NiS, (b) NiS , (c) Ni S ,
2
7 6
3 4
and (d) Ni S phases.
2
4

Page 25 of 25
CrystEngComm
View Article Online
DOI: 10.1039/C5CE00742A
Figure 9. Effects of different nickel sulfide phases on reduction of 4ꢀnitrophenol.
Figure. 10 XRD pattern for NiS phase after its catalytic activity
2
5