Sonochemical synthesis, characterization and optical analysis of some metal oxide nanoparticles (MO-NP; M=Ni, Zn and Mn)

Article abstract of DOI:10.1016/j.physb.2010.06.041

Some nanosized metal oxide (MO) such as ZnO, NiO and MnO were successfully synthesized by sonochemistry method in solutions at room temperature. The reactants used are (M(Ac)₂·2H₂O) and sodium hydroxide (NaOH), and H₂O/EtOH as a carrier in polyethylene glycol (PEG) template. Some of parameters such as effect concentration of NaOH solution, ultrasound power and sonicating time in growth and morphology of the nanostructures were investigated. The best morphology with smaller particles size and good distribution was obtained by using 0.025 M solution of NaOH and 45 W ultrasound powers in 1 h sonicating time. The particle size of the nanosized metal oxide powders synthesized at room temperature is approximately between 40 and 80 nm. The resulting nanosized powder was characterized by X-ray diffraction (XRD) measurements, Raman, BET, solid state UVvis and scanning electron microscopy (SEM).

Full text of DOI:10.1016/j.physb.2010.06.041

Physica B 405 (2010) 3972–3976
Contents lists available at ScienceDirect
Physica B
journal homepage: www.elsevier.com/locate/physb
Sonochemical synthesis, characterization and optical analysis of some metal
oxide nanoparticles (MO-NP; M¼Ni, Zn and Mn)
Alireza Aslani a,n, Alireza Bazmandegan-Shamili a, Karim Kaviani b
a Department of Chemistry, Faculty of Science, Vali-E-Asr University, Rafsanjan, PO BOX 77176, Islamic Republic of Iran
b Department of Nanotechnology, Kimya Javid Company, Gitipasand Industrial Group, Isfahan, PO BOX 16315-585, Islamic Republic of Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Some nanosized metal oxide (MO) such as ZnO, NiO and MnO were successfully synthesized by
sonochemistry method in solutions at room temperature. The reactants used are (M(Ac)2 ꢀ 2H2O) and
sodium hydroxide (NaOH), and H2O/EtOH as a carrier in polyethylene glycol (PEG) template. Some of
parameters such as effect concentration of NaOH solution, ultrasound power and sonicating time in
growth and morphology of the nanostructures were investigated. The best morphology with smaller
particles size and good distribution was obtained by using 0.025 M solution of NaOH and 45 W
ultrasound powers in 1 h sonicating time. The particle size of the nanosized metal oxide powders
synthesized at room temperature is approximately between 40 and 80 nm. The resulting nanosized
powder was characterized by X-ray diffraction (XRD) measurements, Raman, BET, solid state UV–vis
and scanning electron microscopy (SEM).
Received 27 April 2010
Received in revised form
17 June 2010
Accepted 21 June 2010
Keywords:
Nanosized MO
PEG
ZnO
NiO
& 2010 Elsevier B.V. All rights reserved.
MnO
Sonochemistry
1. Introduction
of the bubble. Since this collapse occurs in less than a nanosecond
[2,3], very high cooling rates, in excess of 1011 K/s, are also
obtained. This high cooling rate hinders the organization and
crystallization of the products. For this reason, in all cases dealing
with volatile precursors where gas phase reactions are predomi-
nant, amorphous nanoparticles are obtained. While the explana-
tion for the creation of amorphous products is well understood, the
reason for the nanostructured products is not clear. One explana-
tion is that the fast kinetics does not permit the growth of the
nuclei, and in each collapsing bubble a few nucleation centers are
formed whose growth is limited by the short collapse. However
sonochemistry is one of the earliest techniques used to prepare
nanosized compounds. Nanomaterials are at the leading edge of
rapidly developing field of nanotechnology [4–7]. A reduction in
particle size to nanometer scale results in various special and
interesting properties compared to their bulk properties.
In recent years, metal oxide (MO) nanoparticles as a kind of
functional material has attracted extensive interests due to its
novel optical, electronic, magnetic, thermal and mechanical
properties and potential application in catalyst, battery
electrodes, gas sensors, electrochemical films, photo-electronic
devices and so on. In these applications, it is still needed for
synthesizing high-quality and ultra-fine powders with required
characteristics in terms of their size, morphology, microstructure,
composition purity, crystallizability, etc., which are the most
essential factors which eventually determine the microstructure
and performance of the final products. Therefore, it is very
Sonochemistry is the research area in which molecules
undergo a chemical reaction due to the application of powerful
ultrasound radiation (20 kHz–10 MHz). The physical pheno-
menon responsible for the sonochemical process is acoustic
cavitations. Let us first address the question of how 20 kHz
radiation can rupture chemical bonds (the question is also related
to 1 MHz radiation), and try to explain the role of a few
parameters in determining the yield of a sonochemical reaction,
and then describe the unique products obtained when ultrasound
radiation is used in materials science. A number of theories have
been developed in order to explain how 20 kHz sonic radiation
can break chemical bonds. They all agree that the main event in
sonochemistry is the creation, growth, and collapse of a bubble
that is formed in the liquid. The stage leading to the growth of
the bubble occurs through the diffusion of solute vapor into the
volume of the bubble. The last stage is the collapse of the bubble,
which occurs when the bubble size reaches its maximum
value. From here we will adopt the hot spot mechanism, one of
the theories that explain why, upon the collapse of a bubble,
chemical bonds are broken. This theory claims that very high
temperatures (5000–25,000 K) [1] are obtained upon the collapse
n Corresponding author. Tel.: +98 391 3202441; fax: +98 391 3202429.
E-mail address: a.aslani@vru.ac.ir (A. Aslani).
0921-4526/$ - see front matter & 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.physb.2010.06.041

A. Aslani et al. / Physica B 405 (2010) 3972–3976
3973
important to control the powder properties during the prepara-
tion process. There are many chemical and physical methods to
prepare nanometer metal oxide (MO), including the precipitation
of metal acetate with NaOH [8–14]. Recently, the interest
preparation of nanometer MO has been growing. However, only
few practical methods have been reported. The nanomaterials
whose synthesis was reported are ZnS [15,16], Sb2S3 [17,18], HgSe
[19], SnS2 [20], CdS [21], CdSe [22], PbX (E¼S, Se, Te, O) [23], CuS
[24], Ag2Se [25] and CdCO3 [26]. But the sonochemical method for
preparation of nanomaterials is very interesting, simple, cheap
and safe. However, in the present work we have developed a
simple physical method (sonochemical method) to prepare NiO,
MnO and ZnO nanostructures, wherein MO is synthesized by the
reaction of (CH3CO2)2M ꢀ 2H2O and NaOH in an ultrasonic device.
The MO nanoparticles have been characterized by X-ray powder
diffraction (XRD), Raman spectroscopy, solid state UV, BET and
also the morphology and size of the nanostructures have been
observed by scanning electron microscopy (SEM). We have
performed these reactions in several conditions to find out the
role of different factors such as the aging time of the reaction in
the ultrasonic device and the concentration of the metal acetate
on the morphology and size of nanostructures.
times ethanol and water. Finally, the washed solid phase was
calcinated at 500 1C for 30 min. Table 1 shows the conditions of
reactions in detail. A multiwave ultrasonic generator (Bandlin
Sonopuls Gerate-Typ: UW 3200, Germany) equipped with a
converter/transducer and titanium oscillator (horn), 12.5 mm in
diameter, operating at 30 kHz with a maximum power output of
780 W, was used for the ultrasonic irradiation. The ultrasonic
generator automatically adjusted the power level. The wave
amplitude in each experiment was adjusted as needed. X-ray
powder diffraction (XRD) measurements were performed using a
Philips diffractometer of X’pert Company with mono chromatized
CuK radiation. The samples were characterized with a scanning
a
electron microscope (SEM) (Philips XL 30) with gold coating.
Raman spectra were recorded on a Labram HR 800-Jobin Yvon
Horbiba spectrometer. UVeVis spectra were measured with an
HP 8453 diode array spectrophotometer. The specific surface area
of samples was determined using the Brunauer–Emmet–Teller
(BET) method in
a volumetric adsorption apparatus (ASAP
2010 M, Micrometritics Instrument Corp).
3. Results and discussion
The reaction between Mn, Ni and Zn acetate and sodium
hydroxide to form MO has been shown in Scheme 1.
2. Experimental
Typical procedure for preparation of MO nanoparticles: NaOH
solution with a concentration of 0.1 M (100 ml) were added to the
0.05 and 0.025 M solutions of M(CH3COO)2 ꢀ 2H2O in ethanol/
water. To investigate the role of surfactants on the size and
morphology of nanoparticles, we used 0.5 g of polyethylene glycol
(PEG) in the reaction with optimized conditions. The mixtures
were sonicated for 30–60 min, with different ultrasound powers
followed by centrifuging with a centrifuge, and separation of the
solid and liquid phases. The solid phase was washed for three
1) NaOH, H2O/EtOH
Mn(OAc)2.2H2O
Ni(OAc)2.2H2O
Zn(OAc)2.2H2O
NP-MnO
NP-NiO
in PEG template
))))
2) Calcination at 500 oC
NP-ZnO
Scheme 1. Preparation of MO nanoparticles.
Table 1
Experimental conditions for the preparation of MO nanoparticles.
Series 1
Mn(OAc)2
ꢀ
2H2O
NaOH (0.1 M)
Aging time
Ultrasound power
Template
1
2
3
4
5
6
7
8
50 ml (0.05 M)
50 ml (0.05 M)
50 ml (0.025 M)
50 ml (0.025 M)
50 ml (0.05 M)
50 ml (0.05 M)
50 ml (0.025 M)
50 ml (0.025 M)
100 ml
100 ml
100 ml
100 ml
100 ml
100 ml
100 ml
100 ml
1 h
30 W
45 W
30 W
45 W
30 W
45 W
30 W
45 W
PEG
PEG
PEG
PEG
PEG
PEG
PEG
PEG
1 h
1 h
1 h
30 min
30 min
30 min
30 min
Series 2
Ni(OAc)2
ꢀ
2H2O
NaOH (0.1 M)
Aging time
Ultrasound power
Template
1
2
3
4
5
6
7
8
50 ml (0.05 M)
50 ml (0.05 M)
50 ml (0.025 M)
50 ml (0.025 M)
50 ml (0.05 M)
50 ml (0.05 M)
50 ml (0.025 M)
50 ml (0.025 M)
100 ml
100 ml
100 ml
100 ml
100 ml
100 ml
100 ml
100 ml
1 h
30 W
45 W
30 W
45 W
30 W
45 W
30 W
45 W
PEG
PEG
PEG
PEG
PEG
PEG
PEG
PEG
1 h
1 h
1 h
30 min
30 min
30 min
30 min
Series 3
Zn(OAc)2
ꢀ
2H2O
NaOH (0.1 M)
Aging time
Ultrasound power
Template
1
2
3
4
5
6
7
8
50 ml (0.05 M)
50 ml (0.05 M)
50 ml (0.025 M)
50 ml (0.025 M)
50 ml (0.05 M)
50 ml (0.05 M)
50 ml (0.025 M)
50 ml (0.025 M)
100 ml
100 ml
100 ml
100 ml
100 ml
100 ml
100 ml
100 ml
1 h
30 W
45 W
30 W
45 W
30 W
45 W
30 W
45 W
PEG
PEG
PEG
PEG
PEG
PEG
PEG
PEG
1 h
1 h
1 h
30 min
30 min
30 min
30 min

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A. Aslani et al. / Physica B 405 (2010) 3972–3976
Fig. 1. X-ray powder diffraction pattern of MO nanoparticles (a) ZnO, (b) NiO and
(c) MnO.
Various conditions for preparation of MO nanostructures were
summarized in Table 1. The best morphology with smaller particles
and good distribution was obtained for the sample number 4 in series
1, 2 and 3. Fig. 1(a–c) shows the XRD patterns of the direct
sonochemicaly synthesized of the ZnO, NiO and MnO nanoparticles,
respectively. Sharp diffraction peaks shown in Fig. 1 indicate good
crystallinity of MO nanoparticles. No characteristic peak related to
any impurity was observed. The broadening of the peaks indicated
that the particles were of nanometer scale. The morphology, structure
and size of the samples are investigated by scanning electron
microscopy (SEM). Fig. 2 indicates that the original morphology of
the ZnO, NiO and MnO particles are approximately spherical with the
diameter varying between 40 to 80 nm. The role of PEG on the
morphology of this sample is obvious. It has been reported that
the presence of a capping molecule such as polyethylene glycol (PEG)
can alter the surface energy of crystallographic surfaces, in order to
promote the anisotropic growth of the nanoparticles. In this work PEG
adsorbs on the crystal nuclei and it helps the particles to grow
separately. To investigate the size distribution of the nanoparticles, a
particle size histogram was prepared for MO nanoparticles, (Fig. 3).
Most of the particles possess sizes in the range from 40 to 80 nm. For
further demonstration, the EDAX was performed for the MO
nanoparticles. The EDAX spectrum given in Fig. 4 shows the
presence of Zn, Ni and Mn as the only elementary component in
the ZnO, NiO and MnO nanoparticles, respectively. Raman spectra
recorded for ZnO, NiO and MnO nanoparticles at room temperature
have been depicted in Fig. 5. Several strong and weak bands are
observed in these spectra. ZnO shows 3 active Raman modes at 330,
442 and 578 cmꢁ1, NiO show 5 active Raman modes at 270, 398, 526,
577 and 655 cmꢁ1 and MnO show 4 Raman active modes at 382, 384,
690 and 783 cmꢁ1. In order to investigate the role of sonication on
the composition, size and morphology of the products, we have done
the reaction without sonication with the same conditions of the
optimized sample. The XRD pattern of the obtained product is
corresponding to CuO but the SEM images show that the particles of
the sample without using sonication have larger sizes comparing with
the samples obtained via the sonochemical route. Fig. 6 demonstrates
the UV–vis spectrum of the MO nanoparticles by ultrasonically
dispersing in absolute ethanol. Strong absorption peak in the UV
region can be observed. The absorption band gap Eg is usually
achieved with the aid of the following equation:
Fig. 2. Typical SEM micrographs of MO nanoparticles after calcinations: (a) ZnO,
(b) NiO and (c) MnO.
n indicates either 2 or 1/2 for direct transition and indirect
ð
ah
nÞn ¼ Bðh
Concretely, h
coefficient;
n
ꢁEgÞ
ð1Þ
transition, respectively. The inset of Fig. 5 gives us the typical
n
is the photo energy;
a
is the absorption
(
a
h
n
)2ꢂh
n curve for the MO samples calcinated at 500 1C. By the
B
is the constant related to the material; and
extrapolation of Eg (1), we can get the present band gaps as 4.1,

A. Aslani et al. / Physica B 405 (2010) 3972–3976
3975
Fig. 3. Particle size histogram of MnO, NiO and ZnO.
Fig. 6. Solid state UV absorption of MnO, NiO and ZnO nanoparticles.
Fig. 4. EDAX analysis of samples No. 4 of MnO, NiO and ZnO nanoparticles.
Fig. 7. BET plots of MnO, NiO and ZnO nanoparticles.
related to the average equivalent particle size by the equation
DBET ¼6000=ð SwÞðin nmÞ ð2Þ
r
where DBET is the average diameter of a spherical particle; Sw
represents the measured surface area of the powder in m2/g;
and
r
is the theoretical density in g/cm3. Fig. 7 shows BET plots of
MO nanoparticles, the specific surface area of MO nanoparticles
calculated using the multi-point BET-equation are 33, 40 and
53 m2/g (layout for NiO, ZnO and MnO), and the calculated average
equivalent particle size is 36, 42 and 51 nm (layout for NiO, ZnO
and MnO). We noticed that the particles size obtained from the
BET and the SEM methods, agree very well with the result given by
X-ray line broadening. The results of SEM observations and BET
methods further confirmed and verified the relevant results
obtained by XRD as mentioned above. Metal oxides are
important catalyst in organic chemistry, gas sensors (such as
CO2, NO, SO2, H2O and CO) and battery cathode in the course of our
research. The results of this investigation will be reported soon.
Fig. 5. Raman spectroscopy of MnO, NiO and ZnO nanoparticles.
4. Conclusion
3.7 and 3.9 Ev (layout for NiO, ZnO and MnO) indicating the small
blue shifts upon size reductions for MO nanoparticles. The surface
area analysis was carried out on MO nanoparticles by BET
method. Assuming the particles possess solid, spherical shape
with smooth surface and same size, the surface area can be
Nanosized of MnO, NiO and ZnO (MO) have been prepared by
reaction between corresponding metal acetate and NaOH under
ultrasound irradiation in solution at room temperature. Some of
parameters such as effect concentration of NaOH solution,

3976
A. Aslani et al. / Physica B 405 (2010) 3972–3976
ultrasound power and sonicating time in growth and morphology
of the nanostructures were investigated. The best morphology
with smaller particles size and good distribution was obtained
by using 0.025 M solution of metal acetate and 45 W ultrasound
powers in 1 h sonicating time. Average particle sizes of the
synthesized nanosized MO powders were between 40 and 80 nm.
Simple procedure, short reaction times, yields smaller particles
and mild reaction conditions at room temperature are noteworthy
advantages of this method. The specific surface area of MO
nanoparticles calculated using the multi-point BET-equation are
33, 40 and 53 m2/g (layout for NiO, ZnO and MnO), and the
calculated average equivalent particle size is 36, 42 and 51 nm
(layout for NiO, ZnO and MnO). We noticed that the particles size
obtained from the BET and the SEM methods, agree very well with
the result given by X-ray line broadening. The results of SEM
observations and BET methods further confirmed and verified the
relevant results obtained by XRD as mentioned above.
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Supporting of this investigation by Vali-E-Asr University
(Rafsanjan, Islamic Republic of Iran) and Kimya Javid Company,
Gitipasand industrial group, (Isfahan. Islamic Republic of Iran)
is gratefully acknowledged.