Synthesis, characterization and optical band gap of NiO nanoparticles derived from anthranilic acid precursors via a thermal decomposition route

Article abstract of DOI:10.1016/j.poly.2010.11.020

This study focuses on the preparation and characterization of single phase NiO nano particles. Four nickel anthranilic acid complexes were synthesized by the semi-solid phase reaction method as precursors for the preparation of NiO nanoparticles via a solid-state decomposition procedure at 700 °C. Thermogravimetric analysis (TGA) was applied to determine the thermal behavior of the precursors and the temperature at which the precursors decompose leaving the oxide. The crystalline structures of the products were investigated by X-ray diffraction (XRD), the morphology of particles by SEM and TEM. The particles size was determined by STM, and the average particle size was found to be 8 nm. Electronic spectra were used to clarify qualitatively the change in absorption band positions on changing the particle size of NiO. The optical band gap of the NiO nanoparticles was calculated and indicated a direct transition. The values of the optical band gap of NiO nanoparticles increase as the particle size decreases.

Full text of DOI:10.1016/j.poly.2010.11.020

Polyhedron 30 (2011) 470–476
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, characterization and optical band gap of NiO nanoparticles derived
from anthranilic acid precursors via a thermal decomposition route
⇑
Nasser Mohammed Hosny
Chemistry Department, Faculty of Science, Port-Said University, 23 December Street, Port-Said, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 25 July 2010
Accepted 9 November 2010
Available online 1 December 2010
This study focuses on the preparation and characterization of single phase NiO nano particles. Four nickel
anthranilic acid complexes were synthesized by the semi-solid phase reaction method as precursors for
the preparation of NiO nanoparticles via a solid-state decomposition procedure at 700 °C. Thermogravi-
metric analysis (TGA) was applied to determine the thermal behavior of the precursors and the temper-
ature at which the precursors decompose leaving the oxide. The crystalline structures of the products
were investigated by X-ray diffraction (XRD), the morphology of particles by SEM and TEM. The particles
size was determined by STM, and the average particle size was found to be 8 nm. Electronic spectra were
used to clarify qualitatively the change in absorption band positions on changing the particle size of NiO.
The optical band gap of the NiO nanoparticles was calculated and indicated a direct transition. The values
of the optical band gap of NiO nanoparticles increase as the particle size decreases.
Keywords:
Nanostructures
Nickel oxide
Anthranilic acid precursors
Inorganic materials
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
uted to the different effects in terms of volume, quantum size,
surface and macroscopic quantum tunnel. NiO nanoparticles
Nanometer-sized particles have attracted extensive research
interest, mainly due to their size-dependent properties and great
potential for many applications such as non-linear optics, photo-
electrochemical cells, heterogeneous photo-catalysis, optical
switching and single electron transistors [1–7]. The morphology
of the particles, either spherical, rod, tetra-pod or hexagonal-
shaped, will have an effect on the properties and also influence
the self-assembly process [8–13]. The use of single-molecule
precursors in which a metal–chalcogenide bond is available has
proven to be a very efficient route to high-quality nanoparticles
[14–16]. One of the advantages of this technique is the shape con-
trol of the nanoparticles through variation of the experimental
conditions. The thermal decomposition approach to inorganic pre-
cursors is considered a very important method in preparing metal
oxides nanoparticles [17,18].
contain many important properties over those of bulk and
micro-NiO particles [25]. Niasari et al. have prepared NiO nano-
particles from nickel phthalate complexes using a solid-state ther-
mal decomposition route. They studied the effect of calcination
temperature on the particle size, which is found to be 29 nm
[26].
In this work we prepared NiO nanoparticles with an average
particle size of 8 nm from nickel anthranilic acid semi-solid com-
plexes by solid-state decomposition. We aimed to clarify the effect
of changing the metal anion and metal to ligand ratio on the crystal
lattice and the particle size of NiO.
There are many advantages in this work as it uses a green chem-
istry solvent technique, is a simple method, saves time, uses cheap
available chemicals, has crystalline products and provides smaller
nanoparticles of NiO.
Nanostructured NiO has a wide range of applications as a p-type
semiconductor with a stable wide band gap (3.6–4.0 eV) [19],
although bulk NiO is an antiferromagnetic insulator [20]. Nano-
sized NiO is also used in alkaline batteries [21], electrochemical
capacitors [22], smart windows [23] and as an active layer for
gas sensors [24].
2. Experimental
All the chemicals used were of analytical grade and used with-
out further purification.
High surface area metal oxides with a size of 1–100 nm are
desirable absorbents, carriers and catalysts. The catalytic activity
of NiO nanoparticles in pyrolyzing biomass components are attrib-
2.1. Technique
Carbon and hydrogen contents were determined at the Micro-
analytical Unit of Mansoura University. The metal analyses were
carried out by standard methods [27]. Infrared spectra were mea-
sured using KBr discs on a Mattson 5000 FTIR spectrometer. Cali-
bration with the frequency reading was made with polystyrene
⇑
Tel.: +20 128013556.
E-mail address: Nasserh56@yahoo.com
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.11.020

N.M. Hosny / Polyhedron 30 (2011) 470–476
471
film. Electronic spectra were recorded on UV2 Unicam UV–Vis
2.3. Synthesis of NiO nanoparticles
spectrometer using 1 cm Stoppard silica cells. Thermal analysis
measurements (TGA and DTG) were recorded on a Schimadzu
model 50 instrument using 20 mg samples. The nitrogen flow rate
and heating were 20 cm3/min and 10 °C/min, respectively. XRD
patterns were recorded using Philips X’PERT-PRO materials re-
search diffractometer. Scanning electron microscopy and scanning
tunneling microscopy (SEM and STM) images of the products were
obtained with a JEOL electron microscope, JEM-1230, Japan. Trans-
mission electron microscope (TEM) images of the products were
obtained with a JEOL JEM-1200EXII electron microscope.
The as-prepared Ni–anthranilic acid complexes were ignited in
a muffle furnace at a rate of 50 °C/min in air. NiO nanoparticles
were synthesized at 700 °C.
3. Results and discussion
The most important infrared bands of anthranilic acid and its
nickel complexes are collected in Table 1. The IR spectrum of
anthranilic acid shows several bands in the region 2564–
2709 cmꢁ1, indicating its presence in the zwitter ionic form. The
spectrum also shows bands at 1664, 1630 and 1459 cmꢁ1 assigned
2.2. Synthesis of the precursors
to
of all the precursors (Fig. 1) show bands in the region 1685–
1693 cmꢁ1, assigned to as(COOꢁ) of a coordinated carboxyl group
m m
as(COOꢁ), d(NH3þ) and s(COOꢁ), respectively [28]. The spectra
1:1 and 1:2 M ratios of the hydrated nickel acetate and/or chlo-
ride with anthranilic acid (C7H7NO2) were mixed and ground in
5 ml distilled water. The mixture was ground for 20 min in a mor-
tar. The resultant semi-solid mixture was dried at 100 °C for 2 h,
whereupon a green powder was obtained for all four metal
complexes.
m
[28]. This band is shifted to higher wavenumbers in comparison
with its position in the free ligand. The spectra also show two
bands in the regions 3122–3144 and 3305–3314 cmꢁ1, assigned
to m(NH2). These bands are shifted to lower wavenumbers com-
Anal. Calc. for [Ni(Anth)Acꢀ2H2O] (1): NiC9H13NO6: C, 37.27; H,
4.48; N, 4.83; Ni, 20.26. Found: C, 37.40; H, 4.10; N, 5.10; Ni,
20.50%. Anal. Calc. for [Ni(Anth)2ꢀ2H2O] (2): Ni(C7H8NO3)2: C,
45.81; H, 4.36; N, 7.63; Ni, 16.0. Found: C, 45.72; H, 4.40; N, 8.0;
Ni, 16.40%. Anal. Calc. for [Ni(Anth)Cl2ꢀ2H2O]4H2O (3): NiC7H17-
NO8Cl2: C, 22.40; H, 4.53; N, 3.73; Ni, 15.7; Cl, 18.94. Found: C,
22.60; H, 4.90; N, 4.0; Ni, 16.0; Cl, 19.20%. Anal. Calc. for
[Ni(Anth)2ꢀ2H2O]Cl2 (4): Ni(C7H9NO3Cl)2: C, 38.20; H, 4.10; N,
6.63; Ni, 13.4; Cl, 16.14. Found: C, 38.40; H, 3.80; N, 6.30; Ni,
13.80; Cl, 16.50%. Scheme 1 represents the formation of the precur-
sors and NiO nanoparticles.
pared with the position for anthranilic acid, indicating the partici-
pation of the amino nitrogen in bonding. The difference between
m
as(COOꢁ) and s(COOꢁ) of all the precursors (Table 1) is greater
m
than 200 cmꢁ1, indicating that the carboxyl group is coordinated
in a monodentate manner [28,29]. A shoulder band is observed
at 1643 cmꢁ1 in the spectrum of precursor (1), which may be as-
signed to
(3) and (4) show bands in the regions 3459–3488 and 1356–
1360 cmꢁ1, which could be assigned to
(OH) and d(OH) of an un-
m
as(COOꢁ) of the acetate group. The spectra of precursors
m
ionized carboxyl group, respectively. The IR spectrum of the NiO
nanoparticles shows a band at 430 cmꢁ1, characteristic of NiO
O
OH2
O
O
Ni(Ac) 2.2H 2O
Ni
CH3
N
O
H2
OH2
O
H2
N
O
2 Ni(Ac) 2.2H2O
NiCl2.6H2O
H2
O
N
Ni
OH2
O
H2
O
700 oC
O
OH
O
OH2
NH2
OH
Ni
Cl
NiO
N
Cl
H2
OH2
O
H2
OH
Ni
N
H2O
N
2NiCl2.6H2O
Cl2
OH2
H2
HO
O
Scheme 1. Formation of precursors and NiO nanoparticles.

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N.M. Hosny / Polyhedron 30 (2011) 470–476
Table 1
Some IR spectral bands of anthranilic acid (Anth) and its nickel complexes.
Precursors
m
(NH2)
d(NH2)
mas(COO)
ms(COO)
m
(M–N)
m(M–O)
Anthranilic acid
3324s,3239s
3124m,3305s
3122s,3305s
3144m,3311s
3120s,3314s
1630m
1615sh
1614sh
1617sh
1614m
1664m
1685sh
1693w
1683sh
1685m
1483m
1456m
1457m
1463m
1450m
[Ni(Anth)Acꢀ2H2O] (1)
[Ni(Anth)2ꢀ2H2O] (2)
[Ni(Anth)Cl2ꢀ2H2O]4H2O (3)
[Ni(Anth)2ꢀ2H2O]Cl2 (4)
470w
467w
490w
499w
411w
418w
420w
415w
(e)
(d)
(c)
(b)
(a)
4000
3500
3000
2500
2000
1500
1000
500
Wavenumber(cm-1
)
Fig. 1. IR spectra of: (a) NiO, (b) [Ni(Anth)Acꢀ2H2O] (1), (c) [Ni(Anth)2ꢀ2H2O] (2), (d) [Ni(Anth)Cl2ꢀ2H2O]4H2O (3), (e) [Ni(Anth)2ꢀ2H2O]Cl2 (4).
[26]. Also, the spectrum of NiO shows the disappearance of any
bands assigned to the organic moiety, indicating the complete
decomposition of the precursor at 700 °C.
From the above findings it could be concluded that anthranilic
acid binds to Ni in a mono-negative bidentate manner through
the carboxylate oxygen, after deprotonation, and the amino nitro-
gen in the case of precursors (1) and (2). While in precursors (3)
and (4) it acts as a neutral bidentate ligand, coordinating to Ni
13
12
11
10
9
8
through the carboxyl group in the protonated form and the amino
7
6
5
4
3
2
1
nitrogen. The molar conductivities values in DMF (10ꢁ3 M) at 25 °C
are 5.0, 7.0, 10 and 90
X
ꢁ1 cm2 molꢁ1 for precursors (1), (2), (3)
and (4), respectively. These values suggest that precursors (1), (2)
and (3) are non-electrolytic, while precursor (4) has a 1:2 electro-
lytic nature [30]. Precursor (3) reacts with AgNO3 in HNO3 solution,
and this fact is taken as evidence that the chloride ions are bonded
to nickel in the complex.
The magnetic moment values of all the precursors lie in the
range 3.20–3.30 B.M. Also, the electronic spectra of all the precur-
0
200
400
600
800
sors in nujol show two bands around 14 000 and 24 000 cmꢁ1
,
Temperature (C)
assigned to 3A2g ? 3T1g 2) and 3A2g ? 3T1g(P) (
(m m3) transitions,
respectively. These findings suggest the presence of a six coordi-
nated Ni(II) center [31,32].
Fig. 2. TGA of [Ni(Anth)2ꢀ2H2O] (2).
then the anthranilic acid decomposes. Precursor (2) decomposes
completely at 400 °C, while the others completely decompose at
ca 600 °C, leaving NiO as a residue. From the above findings, the
calcination temperature was chosen to be 700 °C for preparing
NiO nanoparticles. It is expected that calcination of precursor (2)
at a lower temperature of ca 400 °C may lead to a smaller particle
size of the NiO nanoparticles. As precursor (2) was calcined above
the decomposition temperature, there should be sudden decompo-
sition of the precursor leading to rapid nucleation and growth of
the crystals [14,26].
3.1. Thermal analyses
The results of thermogravimetric analyses of the precursors (2)
and (3) are given in Figs. 2 and 3. The TGA curves serve as a guide in
deciding the calcination temperature for the precursors. The ther-
mal analyses (TGA and DTG) curves of the complexes were carried
out within a temperature range from room temperature up to
800 °C. The estimated mass loss was computed based on the TGA
results and the calculated mass loss is computed using the results
of the microanalyses (Table 2). The thermograms indicate that pre-
cursors (1), (2) and (4) are stable up to 200 °C. Precursor (3) loses
four molecules of water of hydration in the temperature range
25–103 °C, indicating that it has not been dried enough. All the
precursors lose coordinated water, followed by acetate or chloride,
3.2. XRD and electron microscope (SEM, STM and TEM) patterns
Fig 4 shows the XRD pattern of NiO derived from precursors
(1)–(4) after calcination at 700 °C. The crystallite size of NiO was

N.M. Hosny / Polyhedron 30 (2011) 470–476
473
calculated from the major diffraction peak of NiO using Debye–
6
5
4
3
2
1
Scherrer formula D = 0.89k/b cos h [33], where k is the wavelength
of the X-rays (1.5406 ÅA for Cu Ka radiation), b is the full width at
0
half maximum and h is the peak position. The estimated particle
size was found to be 25, 20, 19 and 17 for samples of NiO which
resulted from the ignition of the precursors (1), (2), (3) and (4),
respectively. All the peaks are well indexed to a rhombohedral lat-
tice for NiO obtained from precursors (1), (2) and (4). The bunse-
nite syn lattice is well indexed for NiO obtained from precursor
(3). This variation in lattice of NiO may result from the effect of
the anion, where in the case of NiO derived from precursors (1),
(2) and (4) the suggested active sites which coordinate to Ni are
O and N of the anthranilic acid only, while in the case of precursor
(3), the active sites are O, N of the anthranilic acid and Cl donors.
Precursors prepared from a 1:2 Ni:anthranilic acid ratio provide a
good coating of the central Ni atom. So, a smaller particle size of
NiO was obtained after the removal of the organic moieties by
calcination.
0
200
400
600
800
Temperature (C)
The SEM image (Fig. 5) shows the NiO nanoparticles are spheri-
cal in shape. The STM image (Fig. 6) shows the average diameter of
the spherical NiO nanoparticles is 8 nm. This value is relatively
smaller than that calculated from XRD data. In Table 3, the
size of the NiO nanoparticle is compared with results of several
previous reports. According to these results, it is clear that the
NiO obtained from [Ni(Anth)2ꢀ2H2O]Cl2 is the smallest in size, com-
pared to the other precursors [26,34,35]. The TEM image (Fig. 7)
indicates that uniform spherical particles were prepared from
[Ni(Anth)2ꢀ2H2O].
Fig. 3. TGA of [Ni(Anth)Cl2ꢀ2H2O]4H2O (3).
Table 2
Thermo analytical results (TG) of precursors (1), (2), (3) and (4).
Precursor
T
Mass loss
estim.
(Calcd %)
Assignment of
fragment lost
range
(°C)
[Ni(Anth)Acꢀ2H2O] (1)
355–
470
471–
621
200–
360
47.5 (47.9)
31.3 (32.1)
9.8 (9.2)
2H2O, CO, NH2 and Ac
Anthranilic acid without
CO and NH3
2H2O
3.3. Electronic spectra and optical band gap
[Ni(Anth)2ꢀ2H2O] (2)
361–
400
71.0 (70.5)
20.0 (19.2)
18.1 (18.9)
37.4 (38.4)
55.0 (55.5)
2 Anthranilic acid without
one O
4H2O of hydration
The variation of absorbance of NiO nanoparticles resulting from
precursors (1), (2), (3) and (4) with wavelength is shown in (Fig. 8).
The absorption edges are seen to be shifted slightly towards lower
wavenumber (blue shift). This shift indicates an increase in the
band gap, which can be attributed to a decrease in particle size
[36].
[Ni(Anth)Cl2ꢀ2H2O]4H2O 24–
(3)
103
104–
391
392–
560
210–
470
Cl2
Anthranilic acid
The optical band gap was estimated using Tuac’s equations
[Ni(Anth)2ꢀ2H2O]Cl2 (4)
2H2O, 1 anthranilic acid
and Cl2
1 Anthranilic acid
[37,38]:
a
h
m
= A(hy ꢁ Eg)n, where n is equal to 1/2 and 2 for direct
and indirect transitions respectively,
A is an energy independent constant. The plots of (
a is the absorption coefficient.
471–
570
31.0
(31.15)
ahm
ah )
)2 and ( m 1/2
versus hm have been produced, from which a direct band gap was
(d)
(c)
(b)
(a)
0
20
40
60
80
100
2 Theta (degree)
Fig. 4. XRD patterns of: (a) [Ni(Anth)Acꢀ2H2O] (1), (b) [Ni(Anth)2ꢀ2H2O] (2), (c) [Ni(Anth)Cl2ꢀ2H2O]4H2O (3), and (d) [Ni(Anth)2ꢀ2H2O]Cl2 (4).

474
N.M. Hosny / Polyhedron 30 (2011) 470–476
Fig. 5. SEM image of NiO derived from precursor (2).
Fig. 6. STM image of NiO derived from precursor (2).
Table 3
Comparison of NiO particle size using different methods.
Precursor
Method
Calcination temp. (°C)
Calcination time (h)
Particle sizea
Nickel citrate [34]
ultrasonic spray pyrolysis
thermal decomposition
solid-state decomposition
solid-state decomposition
700
700
700
700
2
2
2
2
54
70
29
17
Nickel dimethylglyoximate [35]
Nickel phthalate [Ni(pht)2] [26]
Nickel anthranalate [Ni(Anth)2ꢀ2H2O]Cl2
a
According to XRD.

N.M. Hosny / Polyhedron 30 (2011) 470–476
475
Fig. 7. TEM image of NiO derived from precursor (2).
A1
A2
A3
A4
EA1 = 2.45 eV
EA3= 2.82 eV
EA2= 2.93 eV
EA4= 3.12 eV
400
1.6
1.4
1.2
430
416
458
300
438
200
A1
A2
A3
A4
100
0
400
500
2.5
3.0
3.5
Wavelength (nm)
hν (eV)
Fig. 8. Absorption spectra of NiO nanoparticles A1 = NiO derived from precursor
(1), A2 = NiO derived from precursor (2), A3 = NiO derived from precursor (3), and
A4 = NiO derived from precursor (4).
Fig. 9. Optical band gap of NiO nanoparticles A1 = NiO derived from precursor (1),
A2 = NiO derived from precursor (2), A3 = NiO derived from precursor (3), and
A4 = NiO derived from precursor (4).
found (Fig. 9) by extrapolating the linear portion of the curve to
(ahm
)
1/2 = 0. The curves indicate that the values of the direct band
4. Conclusion
gap (Eg) are equal to 2.45, 2.82, 2.93 and 3.12 eV for NiO derived
from precursors (1), (2), (3) and (4), respectively. The band gap val-
ues suggest that NiO nanoparticles are semi-conductors. Also,
these values of (Eg) are in the same range as that of highly efficient
photovoltaic materials. So, the present compounds could be con-
sidered as potential materials for harvesting solar radiation in solar
cell applications [39].
Metal complexes derived from anthranilic acid have been used
as new precursors for synthesizing NiO nanoparticles. The NiO
nanoparticles are spherical with a nanosize range from 17 to
25 nm, as deduced from the results of XRD data. The particle size
and the crystal form of NiO are affected by the anion of the nickel
salts and the ratio of Ni to anthranilic acid. The solid-state decom-

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N.M. Hosny / Polyhedron 30 (2011) 470–476
[20] C.D. Guerra, A. Remn, J.A. Garcia, J. Piqueras, Phys. Stat. Sol. 163 (1997)
497.
[21] J. Bahadur, D. Sen, S. Mazumder, S. Ramanathan, J. Solid State Chem. 181
(2008) 1227.
position method provides a simple method of obtaining nanoparti-
cles. Also, a green chemistry solvent technique and smaller parti-
cles of NiO have been obtained in this study.
[22] T. Nathan, A. Aziz, A.F. Noor, S.R.S. Prabaharan, J. Solid State Electrochem. 12
(2008) 1003.
[23] C.G. Granqvist (Ed.), Handbook of Inorganic Electrochromic Materials, Elsevier,
Amsterdam, 1995.
[24] I. Hotovy, J. Huran, L. Spiess, S. Hascik, V. Rehacek, Sens. Actuators B 57 (1999)
147.
[25] J. Li, R. Yan, B. Xiao, D.T. Liang, D.H. Lee, Energy Fuels 22 (2008) 16.
[26] M. Salavati-Niasari, F. Mohandes, F. Davar, M. Mazaheri, M. Monemzadeh, N.
Yavarinia, Inorg. Chim. Acta 362 (2009) 3691.
[27] A.I. Vogel, A Text Book of Quantitative Inorganic Analyses, 2nd ed., Longman,
London, 1961.
[28] K. Nakamoto, Infrared Spectra of Inorganic and Coordination Compounds, John
Wiley, New York, 1970.
[29] S. Cakir, E. Coskun, P. Naumov, E. Bicer, J. Mol. Struct. 608 (2001) 101.
[30] W.J. Geary, Coord. Chem. Res. 7 (1971) 81.
[31] A.B.P. Lever, Inorganic Electronic Spectroscopy, Elsevier, Amsterdam, 1986.
[32] F.A. Cotton, G. Wilkinson, Advanced Inorganic Chemistry, Wiley Inter Science,
New York, 1962.
References
[1] A.P. Alivisatos, Science 271 (1996) 933.
[2] G. Fasol, Science 280 (1998) 545.
[3] H. Zhao, E.P. Douglas, Chem. Mater. 14 (2003) 1418.
[4] K. Murakoshi, H. Hosokawa, M. Saitoh, Y. Wada, T. Sakata, H. Mori, M. Satoh, S.
Yanagida, J. Chem. Soc., Faraday Trans. 94 (1998) 579.
[5] U. Resch, A. Eychmuller, M. Haase, H. Weller, Langmuir 8 (1992) 2215.
[6] B. Liu, H. Li, C.H. Chew, W. Que, Y.L. Lam, C.H. Kam, L.M. Gan, G.Q. Xu, Mater.
Lett. 51 (2001) 461.
[7] J.Y. Kim, H.M. Kim, D.H. Shin, K.J. Ihn, Macromol. Chem. Phys. 207 (2006) 925.
[8] L. Manna, E.C. Scher, L. Li, A.P. Alivisatos, J. Am. Chem. Soc. 124 (2002) 7136.
[9] J. Hu, L.S. Li, L.W. Wang, L. Manna, A. Alivisatos, Science 292 (2001) 2060.
[10] X. Peng, Adv. Mater. 15 (2003) 459.
[11] Z.A. Peng, X.G. Peng, J. Am. Chem. Soc. 124 (2002) 3343.
[12] S.M. Lee, Y.W. Jun, S.N. Cho, J. Cheon, J. Am. Chem. Soc. 124 (2002) 11244.
[13] Y.W. Jun, Y.Y. Jung, J. Cheon, J. Am. Chem. Soc. 124 (2002) 615.
[14] S.N. Mlondo, N. Revaprasadu, P. Christian, M. Helliwell, P. O’Brien, Polyhedron
28 (2009) 2097.
[33] H. Klug, L. Alexander (Eds.), X-ray Diffraction Procedures, Wiley, New York,
1962, p. 125.
[34] S.W. Oh, H.J. Bang, Y.C. Bae, Y.K. Sun, J. Power Sources 173 (2007) 502.
[35] X. Li, X. Zhang, Z. Li, Y. Qian, Solid State Commun. 137 (2006) 581.
[36] V.R. Shinde, T.P. Gujar, C.D. Lokhande, Sol. Energy Mat. Sol. C 91 (2007) 1055.
[37] J. Tauc, R. Grigorovici, A. Vancu, Phys. Status Solid 15 (1966) 627.
[38] R.K. Pandey, S.N. Sahu, S. Chandra, Handbook of Semiconductor
Electrodeposition, Marcel Dekker, Inc., New York, 1996, p. 142.
[39] M.L. Fu, G.C. Guo, X. Liu, L.Z. Cai, J.S. Huang, Inorg. Chem. Commun. 8 (2005) 8.
[15] N. Revaprasadu, S.N. Mlondo, Pure Appl. Chem. 78 (9) (2006) 1691–1702.
[16] M. Salavati-Niasari, M. Reza, L. Estarki, F. Davar, Inorg. Chim. Acta 362 (2009)
3677.
[17] M. Salavati-Niasari, N. Mir, F. Davar, J. Alloys Compd. 493 (2010) 163.
[18] F. Davar, M. Salavati-Niasari, Z. Fereshteh, J. Alloys Compd. 496 (2010) 638–
643.
[19] H. Yang, Q. Tao, X. Zhang, A. Tang, J. Ouyang, J. Alloys Compd. 459 (2008) 98.