Nano Vision, Vol.

3 (1), 37-43 (2013)

Synthesis of Nickel Nanoparticles Using Polyol Process

M. SRISUDHAa, K. KARTHIKb and S. PONNUSWAMYa
a

PG and Research Department of Chemistry,

Government Arts College (Autonomous),
Coimbatore, Tamilnadu, INDIA.
b
Department of Chemistry,
Kumaraguru College of Technology (Autonomous),
Coimbatore, Tamilnadu, INDIA.
(Received on: February 8, 2013)
ABSTRACT
Nickel nanoparticles (NiNPs) have been synthesized by the
reduction of nickel acetate, Ni(CH3COO)2, with polyethylene
glycol 400(PEG 400) without adding any surfactant or capping
agent. PEG 400 served as a reducing agent as well as a solvent.
Rod like nickel nanoparticles were obtained by the reduction of
nickel acetate with PEG 400 at 100C followed by centrifugation,
washed with acetone and upon drying in air at room temperature.
The synthesized nickel nanoparticles have been characterized by
X-ray diffraction (XRD), Scanning Electron Microscopy (SEM),
High Resolution Transmission Electron Microscopy (HRTEM)
and Energy Dispersive X-ray analysis (EDAX) techniques. The
average crystallite size of the nickel nanoparticles were calculated
from the XRD pattern using Scherrers formula. EDAX analysis
confirmed the presence nickel nanoparticles. The effect of reaction
time, reaction temperature and concentration of the chemical on
the size of the nickel nanoparticles formed have also been studied.
Keywords: Polyol process, PEG 400, nickel nanoparticles,
HRTEM, EDAX.

1. INTRODUCTION
The field of nanoparticle research
covers a wide range of interest in the fields
of chemistry, physics and materials science.

Nickel nanoparticles can exist in two

crystalline structures, fcc and hcp. Most of
the nickel powders are ferromagnetic
substances. Nickel nanoparticles are found
more useful in catalysis, conducting inks,

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M. Srisudha, et al., Nano Vision, Vol.3 (1), 37-43 (2013)

ferrofluids and magnetic

materials1.
Nanostructured nickel particles have
received more attention because of their
magnetic properties, which make them
suitable for applications in magnetic sensors,
memory
devices
and
biomolecular
separations2-8. Control of the nanoscale
morphology enables precise control of the
properties of the end product. The particle
size, morphology and composition can be
manipulated to produce materials of
different properties9-10. In this present work,
nickel nanoparticles have been synthesized
using the polyol11 process without adding
any surfactant or capping agents and the
particles were analyzed using XRD, SEM,
HRTEM and EDAX. The effect of reaction
time, reaction temperature and the
concentration of the chemicals over the size
of the particles have been studied.
EXPERIMENTAL
In a typical nickel nanoparticle
(NiNP) preparation, 2g of nickel acetate was
dissolved in appropriate amount of PEG-400
in a round bottom flask and allowed to
reflux. The colour of the solution changed
to black indicated the formation of NiNPs.
After that the resultant solution was cooled
to room temperature. The residue was
separated by centrifugation followed by
washing with acetone and dried in air at
room temperature.
The resulting NiNPs were further
characterized by XRD, SEM, HRTEM and
EDAX. In order to study the effect of
reaction time, reaction temperature and
concentration of the chemicals over the size
of the NiNPs, the reactions were performed
at different reaction conditions. In order to

study the effect of the reaction time over the

size of the particles, 2g nickel acetate and 50
ml PEG 400 were taken and a temperature
of 220C is maintained and the reactions
were carried out at 4 different time durations
viz., 4 hours, 5 hours, 6 hours and 7 hours. A
set of reactions were carried out at different
temperatures viz., 100C, 150C, 200C,
220C and 250C for duration of 5 hours by
taking 2g nickel acetate and 50ml PEG 400
to study the effect of reaction temperature
over the size of the NiNPs. The reactions
were also conducted by varying the
concentration of the chemicals to study the
effect of concentration of the chemicals over
the size of the NiNPs. The experimental
conditions are shown in Table 1. The
obtained NiNPs were analyzed using Bruker
model D8 advance X-ray diffractometer
using CuK(=1.5405A) radiation and the
XRD pattern were used to calculate the
crystallite size of the NiNPs using Scherrers
formula12. The morphology of the nickel
nanoparticles were analyzed by Scanning
Electron Microscopy (SEM). The size of the
synthesized nickel nanoparticles were
analysed by HRTEM. The elemental
composition of the nanoparticles was
estimated by Energy dispersive X-ray
(EDAX) analysis.
RESULTS AND DISCUSSION
In the present work, nickel
nanoparticles have been synthesized without
adding any surfactant or capping agent by
the polyol process. The XRD pattern of the
as synthesized NiNP 12 is shown in Fig. 1
and there are much broader and less intense
peaks, owing to particle size broadening,
which occurs when a sample is made up of
very small crystallites. Sharp peaks of nickel

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M. Srisudha, et al., Nano Vision, Vol.3 (1), 37-43 (2013)

were observed, which indicates the

crystalline nature of the product. The
characteristic peaks for NiNP, 2 = 39.18,
41.60, 44.52 and 58.49, corresponding to
the Miller indices (010) (002) (011) and
(012) were observed (JCPDS: 45 1027).
These peaks revealed the presence of
hexagonal nickel nanoparticles. The full
width at half-maximum (FWHM) of the
oriented peak can be used to calculate the
average crystallite size of the nickel

39

nanoparticles using the Scherrers formula12,

(D = 0.94 / cos), where 0.94 is a constant
value known as shape factor, is the
wavelength, is the full width at half
maximum of the diffraction peaks and is
the angle of diffraction. It reveals from the
XRD pattern that the well defined sharp and
broad peaks indicate the smaller crystallite
size and also it is found to be in good
agreement with the reported XRD pattern of
Ni nanoparticles.

Table 1 - Experimental reaction conditions and the average crystallite size of the nickel
nanoparticles (NiNPs) calculated from the XRD pattern
Sample

Time duration
(hours)

Concentration

Temperature
(oC)

Average crystallite size

(nm) from XRD data

EFFECT OF REACTION TIME

NiNP 1
NiNP 2
NiNP 3
NiNP 4

50 ml PEG-400+2g NA
50 ml PEG-400+2gNA
50 ml PEG-400+2g NA
50 ml PEG-400+2g NA

4
5
6
7

220
220
220
220

24
12
14
15

EFFECT OF TEMPERATURE
NiNP 5
NiNP 6
NiNP 7
NiNP 8
NiNP 9

50 ml PEG-400+2g NA
50 ml PEG-400+2g NA
50 ml PEG-400+2g NA
50 ml PEG-400+2g NA
50 ml PEG-400+2g NA

5
5
5
5
5

100
150
200
220
250

28
15
13
12
12

EFFECT OF CONCENTRATION
NiNP 10
NiNP 11
NiNP 12
NiNP 13

50 ml PEG-400+2g NA
100 mlPEG-400+2g NA
150 ml PEG-400+2g NA
200 ml PEG-400+2g NA

5
5
5
5

In the study on the effect of reaction

time on the size of the nickel nanoparticles,
all the reaction conditions were kept

220
220
220
220

12
14
15
37

constant except the time duration. The

crystallite sizes of the NiNPs are shown in
Table 1. The average crystallite size of the

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M. Srisudha, et al., Nano Vision, Vol.3 (1), 37-43 (2013)

NiNP 1 synthesized at 4 hours duration time

is 24 nm and the size of NiNP 2 is 12 nm for
5 hours duration time. The crystallite size
continues to increase along with duration of
the reaction time. The crystallite size of the
NiNP 3, synthesized at 6 hours duration is
14 nm and that of 7 hours duration is 15 nm.
Hence it is concluded that the crystallite size
of the NiNPs increases with increase in the
reaction time. The particles begin to grow
and agglomerate at long time durations,
hence the crystallite size of the synthesized
nickel nanoparticles increase along with the
reaction time duration.
The reactions carried out to study
the effect of reaction temperature on the size
of the NiNPs, all the reaction conditions
were kept constant except the reaction
temperature. The reactions were carried out

at 100oC, 150oC, 200oC, 220oC and 250oC

temperatures and the average crystallite
sizes of the NiNPs calculated using
Scherrers formula are 28 nm, 15nm, 13nm,
12nm and 12 nm, respectively. Accordingly,
the average crystallite sizes of the NiNPs
decrease with increase in the reaction
temperature. This is due to the fact that the
chemical reduction of Ni2+ takes place
effectively at higher temperature and it
prevents the particle agglomeration, hence
the average crystallite size decreases. And
also some reactions were carried out by
keeping all the reaction conditions constant
except the concentration of the chemicals.
The average crystallite size of the NiNPs
increase as we increase the concentration of
PEG 400. At high concentration of the PEG
400, the formed NiNPs begins to aggregate,
hence the crystallite size increases.

Fig. 1 XRD pattern of the as synthesized NiNP 12

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M. Srisudha, et al., Nano Vision, Vol.3 (1), 37-43 (2013)

41

Fig. 2 SEM images of a) NiNP 5 showing rod like nanoparticles and b) NiNP 7

Fig. 3 HRTEM and corresponding SAED patterns of (a) NiNP 1; (b) NiNP 7; (c) NiNP 10

The microstructural characterization

was investigated by using SEM and
HRTEM, and shown in Fig. 2 and Fig. 3
respectively. SEM images of NiNP 5 (Fig.
2a) and NiNP 7 (Fig. 2b) shows a hexagonal
like morphology of the nickel nanoparticles.
In Fig. 2a, a rod like morphology was
observed with different arrangement. In Fig.
2b, sphere like morphology was observed.
HRTEM and Selected Area Electron
Diffraction (SAED) (inset) patterns of
synthesized NiNP 1, NiNP 7 and NiNP 10
are shown in Fig. 3(a-c) respectively. It is
observed that the nanoparticles are

encapsulated with the polymers in order to

prevent agglomeration. It was observed that
the temperature has an influence on the
morphology of the nickel nanoparticles. A
rod like nickel nanorods was formed at a
temperature of 100C, but at higher
temperatures the rod like structures were
disappeared.
Energy dispersive X-ray (EDAX)
analysis on various regions confirmed the
presence of nickel ,with energy bands
centered at 7.5 and 8.3 kev (K lines) and 0.8
kev (L lines)13. The oxygen detected could
be attributed to partial oxidation of the

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M. Srisudha, et al., Nano Vision, Vol.3 (1), 37-43 (2013)

nanoparticles during the handling of the

sample or to the presence of some residual

solvent. The EDAX spectrum of the NiNP 4

is shown in Fig. 4.

Fig. 4 - EDAX spectrum of NiNP 4

CONCLUSIONS
The NiNPs have been prepared
using polyol process without adding any
surfactant or capping agent and they were
analyzed using XRD, SEM, TEM and
EDAX analysis techniques. The crystallite
size of the as synthesized NiNPs calculated
using XRD pattern are in good agreement
with the TEM results. The crystallite size of
the NiNPs was reduced when we increase
the time duration of the reaction. Nickel
nanorods were observed at a temperature of
100C, however, at higher temperatures the
rod like structures were disappeared. It was
observed that the crystallite size of the
NiNPs decreases as we increase the reaction
temperature and it is minimum at 220o C.
The concentration does have an influence on

the size of the nanoparticles. Thus,

controlling the concentration of constituent
chemicals can control the size of the nickel
nanoparticles synthesized.
ACKNOWLEDGEMENTS
The authors thank Sophisticated
Test and Instrumentation Centre (STIC),
Cochin for recording XRD and EDAX and
PSG College of Technology, Coimbatore for
recording XRD, SEM and HRTEM.
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