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Research on Chemical Intermediates ISSN 0922-6168Volume 41Number 1 Res Chem Intermed (2015) 41:357-363DOI 10.1007/s11164-013-1197-x
Preparation and characterization of nickeloxide nanoparticles via solid state thermaldecomposition of dinuclear nickel(II) Schiffbase complex [Ni2(Brsal-1,3-ph)2] as a newprecursorAliakbar Dehno Khalaji, MahsaNikookar & Debasis Das
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Preparation and characterization of nickel oxidenanoparticles via solid state thermal decompositionof dinuclear nickel(II) Schiff base complex [Ni2(Brsal-1,3-ph)2] as a new precursor
Aliakbar Dehno Khalaji • Mahsa Nikookar •
Debasis Das
Received: 26 February 2013 / Accepted: 10 April 2013 / Published online: 25 April 2013
� Springer Science+Business Media Dordrecht 2013
Abstract The synthesis and characterization of nickel oxide nanoparticles via
solid state thermal decomposition of a dinuclear nickel(II) complex, [Ni2(Brsal-1,3-
ph)2] as a new precursor is reported. [Ni2(Brsal-1,3-ph)2] complex is characterized
by elemental analyses and Fourier transform infrared (FT-IR) spectroscopy. Ther-
mogravimetric analysis reveals its thermal stability and decomposition pattern.
Solid state thermal decomposition of the complex at 450 �C for 3 h produces nickel
oxide nanoparticles which are characterized by FT-IR spectroscopy, X-ray powder
diffraction, scanning electron microscopy (SEM), and transmission electron
microscopy (TEM). SEM and TEM images demonstrate the square shape of the NiO
nanoparticles of between 10 and 15 nm.
Keywords Ni(II) Schiff base complex � Nanoparticles � XRD � SEM � TEM
Introduction
In recent years, the preparation of transition metal oxide nanoparticles have been
widely studied due to their versatile applications, such as chemical sensors, catalysts,
antistatic coating, radioactive waste management, etc. [1, 2]. The synthesis and
characterization of different transition metal oxide nanoparticles with specific sizes
and morphology have been reported [3–7]. Amongst them, NiO nanoparticles have
received much attention because of their application in battery cathodes, gas sensor
materials, photovoltaic devices, etc. [8–10]. NiO nanoparticles as p-type semicon-
ductors having a stable wide band gap (3.6–4.0 eV) have been studied for their wide
A. D. Khalaji (&) � M. Nikookar
Department of Chemistry, Faculty of Science, Golestan University, Gorgan, Iran
e-mail: [email protected]
D. Das
Department of Chemistry, The University of Burdwan, Burdwan, West Bengal, India
123
Res Chem Intermed (2015) 41:357–363
DOI 10.1007/s11164-013-1197-x
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application in magnetic materials [11]. Thus, the size, shape, and morphology of NiO
nanoparticles are important for their technological applications. To date, NiO
nanoparticles having various morphologies have been prepared by different techniques,
such as sol–gel, thermal decomposition, evaporation, etc. [12–17]. However, thermal
decomposition techniques are considered as the most promising [18–21] because one
can control the process conditions, particle size, particle crystal morphology, and
purity. Moreover, it requires a short time, and has high yields, low costs and low power
consumption. Very recently, Salavati-Niasari and co-workers [10, 12, 18, 19, 21, 22]
have synthesized NiO nanoparticles using thermal decomposition of Ni(II) complexes.
They have a calcined tetrahedral nickel(II) complex [Ni(acta)2] in the temperature
range of 300–900 �C to get NiO nanoparticles with a size of about 24 nm [21]. Farhadi
and Roostaei-Zaniyani [20] have synthesized NiO nanoparticles by solid state thermal
decomposition of octahedral nickel(II) complexes in the temperature range of
200–400 �C to obtain NiO nanoparticles having a size about 13–15 nm.
However, various precursors have been used for the preparation of NiO
nanoparticles via the thermal decomposition method, but there are few reports on
the Ni(II) Schiff base complexes [23–25]. Recently, our group has been synthesized
NiO nanoparticles via thermal decomposition method of Ni(II) Schiff base complexes
[24, 25]. Here, we have prepared NiO nanoparticles from dinuclear nickel(II) Schiff
base complex, [Ni2(Brsal-1,3-ph)2], as a new precursor (Scheme 1). The product is
identified by FT-IR spectroscopy, XRD, SEM, and TEM studies.
Experimental
Materials and methods
All reagents and solvents for synthesis and analysis were commercially available
and used as received without further purification. Elemental analyses were carried
NH2 NH2
O
OHBrN
OH
N
OH
Br Br
NiCl2
CH3OH+
N
O
N
O
N
O
N
ONi Ni
Br
BrBr
Br
Scheme 1 Synthesis of dinuclear nickel(II)complex, [Ni2(Brsal-1,3-ph)2]
358 A. D. Khalaji et al.
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out using a Heraeus CHN–O-Rapid analyzer, and the results agreed with calculated
values. Fourier transform infrared spectra were recorded as a KBr disk on a FT-IR
Perkin–Elmer spectrophotometer. XRD pattern of the nanoparticles was recorded on
a Bruker AXS diffractometer D8 ADVANCE with Cu-Ka radiation with nickel beta
filter in the range 2h = 10�–80�. Scanning electron microscopy (SEM) images were
obtained on a Philips XL-30ESEM. Transmission electron microscopy (TEM)
images were obtained on a Zeiss-EM10C transmission electron microscope with an
accelerating voltage of 80 kV.
Synthesis of [Ni2(Brsal-1,3-ph)2] precursor
To a stirring solution of 5-bromosalicysilaldehyde (0.2 mmol, in 5 ml of methanol)
was added 1,3-phenylenediamine (0.2 mmol) in 10 ml of methanol and the mixture
was stirred for 30 min in air at room temperature. Then, the methanolic solution of
NiCl2�6H2O (0.2 mmol in 10 ml) was added dropwise and the mixture was stirred
for 1.5 h in air at room temperature. Microcrystals of [Ni2(Brsal-1,3-ph)2] were
obtained after the solvent was evaporated slowly for several days at room
temperature, then the products were collected by filtration and dried in vacuum. The
yield was 79 %. Anal. calc. for C40H28N4Ni2O4: C, 45.25; H, 2.28; N, 5.28 %.
Found: C, 44.95; H, 2.41; N, 5.36 %. FT-IR (KBr pellet cm-1): 3,058 (CH
aromatic), 1,611 (C=N), 1,534, 1,464, 1,444 (C=C aromatic).
Preparation of NiO nanoparticles
The dinuclear nickel(II) Schiff base complex, [Ni2(Brsal-1,3-ph)2], was loaded into
a platinum crucible and then placed in an oven and heated at a rate of 10 �C/min in
air. Nanoparticles of nickel oxide were synthesized at 450 �C after 3 h. The final
products were washed with ethanol at least three times to remove impurities, if any,
and dried at r.t. for 3 days. The synthesized NiO nanoparticles were characterized
by FT-IR, XRD, and SEM. FT-IR (KBr pellet cm-1): 435 (Ni–O).
Results and discussion
Figure 1 shows the FT-IR spectra of the dinuclear [Ni2(Brsal-1,3-ph)2] complex and
nickel oxide nanoparticles. In the complex, a strong band at 1,611 cm-1is due to the
C=N stretching vibration. The peak was 435 cm-1 in the FT-IR spectra of NiO
nanoparticles assigned to Ni–O stretching [10, 12, 18, 19, 21, 22]. The existence of a
free precursor is ruled out due to the absence of stretching vibrations of CH, C=N
and other groups of the ligand.
Thermal behavior (TG) of the complex has been studied under N2 atmosphere
from room temperature to 800 �C with the heating rate of 20 �C/min. The TG/DTA
plot is presented in Fig. 2. Temperature-dependent mass losses (experimental and
calculated) are summarized in Table 1.
Figure 3 shows the XRD pattern (10 \ 2h\ 80) of the NiO nanoparticles. The
diffraction peaks can be indexed to the pure NiO cubic phase [21, 22]. The
Preparation of nickel oxide via dinuclear nickel(II) Schiff base complex 359
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crystallite size (Dc) is calculated using the Debye–Scherre formula Eq. (1) from the
major diffraction peak of the NiO nanoparticles.
Dc ¼ 0:89k=bcosh ð1Þ
Where k is the X-ray wavelength used in XRD (here 1.5418 A), b is the pure
diffraction broadening of a peak at half-height, and h is the Bragg angle. Thus, the
average diameter of the NiO nanoparticles is found as 15 nm.
Fig. 1 FT-IR spectra of Ni(II) complex (a) and NiO nanoparticles (b)
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The morphology and microstructure of the NiO nanoparticles were further
investigated using SEM and TEM. Figure 4 shows the SEM and TEM images of the
NiO nanoparticles obtained from dinuclear nickel(II) Schiff base complex,
[Ni2(Brsal-1,3-ph)2], using solid state thermal decomposition at 450 �C for 3 h.
Studies show the particle size of NiO nanoparticles is about 5–15 nm. The particles
are both spherical and cubic.
Fig. 2 The TG/DTA graph of the Ni(II) complex
0
1000
2000
3000
4000
5000
6000
20 30 40 50 60 70 80
Fig. 3 XRD patterns of NiO nanoparticles obtained from [Ni2(Brsal-1,3-ph)2]
Table 1 Mass loss as a function of temperature of the Ni(II) complex
Steps T (�C) TG mass loss (%) calcd. (found) Assignments
Step 1 29–391 14.18 (12.06) C6H6
Step 2 391–665 71.65 (74.56) C14H10N2OBr2
Residual 665–744 14.02 (13.36) NiO
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The choice of complexes as precursor is a key step in the preparation of NiO
nanoparticles [9, 20, 23–25]. In Table 2, some of the precursors used in this method
are compared with the present work. According to these results, NiO nanoparticles
were synthesized successfully with suitable conditions and small size.
Fig. 4 a SEM and b TEM images of NiO nanoparticles
Table 2 Comparison of particle size of NiO nanoparticles by thermal decomposition method of Ni(II)
Schiff base complexes
Sample Precursor T (�C) Reaction time (h) Particle size (nm)
according to XRD results
Ref
1 [Ni(salen)] 500 5 15–20 [23]
2 [Ni(Brsalph)(NO3)] 550 3.5 55 [24]
3 [Ni(Salophen)] 550 3.5 35 [25]
4 [Ni(Me-salophen)] 550 3.5 70 [25]
5 [Ni(NH3)6](NO3)2 200–400 1 12 [20]
6 [Ni(en)3](NO3)2 200–400 1 15 [9]
7 [Ni2(Brsal-1,3-ph)2] 450 3 5–10 This work
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Conclusion
Pure and nanosized NiO nanoparticles with an average size of 5–10 nm have been
successfully prepared by solid state thermal decomposition (at 450 �C for 3 h) of
dinuclear [Ni2(Brsal-1,3-ph)2] complex as a new precursor. We have been able get
uniform NiO nanoparticles with narrow size. This method is facile, inexpensive,
nontoxic, and can be extended for the preparation of other transition metal oxide
nanoparticles. To the best of our knowledge, this is a rare report on the synthesis of
NiO nanoparticle from asymmetric dinuclear Ni(II) Schiff base complex.
Acknowledgments A. D. Khalaji and M. Nikookar are grateful to the Council of Iran National Science
Foundation and Golestan University for financial support.
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