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Structural characterization and photoluminescenceproperties of zinc oxide nano particles synthesizedby chemical route method
P.B. Taunk a,*, R. Das b, D.P. Bisen c, Raunak kumar Tamrakar b
a Department of physics, Govt. Digvijay College, Rajnandgaon, C.G, Indiab Department of Applied Physics, Bhilai Institute of Technology (Seth Balkrishan Memorial), Near Bhilai House, Durg,
C.G 491001, Indiac School of Studies in Physics and Astrophysics, Pt. Ravishankar Shukla University, Raipur, C.G 492010, India
a r t i c l e i n f o
Article history:
Received 11 December 2014
Received in revised form
9 March 2015
Accepted 16 March 2015
Available online 1 April 2015
Keywords:
Zinc oxide
Chemical route method
Nano particles
XRD
SEM
TEM
* Corresponding author.E-mail addresses: pritibalataunk@gma
(R.k. Tamrakar).
Peer review under responsibility of The Ehttp://dx.doi.org/10.1016/j.jrras.2015.03.0061687-8507/Copyright© 2015, The Egyptian Socopen access article under the CC BY-NC-ND l
a b s t r a c t
Nanostructures, crystalline Zinc oxide powder were synthesized by mixing Zinc chloride
(0.04M) and sodium hydroxide (0.08M) using chemical route method. 0.001M molar con-
centrations of TEA (Tri ethanolamine) in aqueous solution used to the growing reaction
solution. The powder samples are annealed at 190 �C. The experimental results indicate a
successful growth of Zinc oxide in solid form which is not observed ever before. XRD, SEM,
TEM and PL were performed to characterize the morphology, growth and optical nature of
the samples. The some Rod and particle like morphology of zinc oxide has been examined
by transmission electron microscopy. The particle size was found to vary from 7 to 21 nm.
The room temperature PL spectra exhibits low intensity UV emission peak at 407 nm and
blue emission band around 484 nm.
Copyright © 2015, The Egyptian Society of Radiation Sciences and Applications. Production
and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
1. Introduction
In recent, ZnO has emerged as one of the most studied ma-
terial. This is a wide band gap semiconductor having wurtzite
structure (Islam & Podder, 2008). ZnO nanostructures have
attracted a lots of research interest due to their unique
structure and size dependent electrical, optical and mechan-
ical properties. It has promising applications such as an
inexpensive, anticorrosive n-type semiconductor, transparent
conductive contacts, solar cells, gas sensors, short-
il.com (P.B. Taunk), d
gyptian Society of Radiat
iety of Radiation Sciencesicense (http://creativecom
wavelength laser diode, light-emitting diodes and thin film
transistor (Vijayan et al., 2008). ZnO have attracted consider-
able attention because they can be tailored to possess high
electrical conductivity, high infrared reflectance and high
visible transmittance by applying different coating tech-
niques. Consequently it is added into various material and
product, including plastic ceramic, glass cement rubber lu-
bricants, paints, ointment, sealant pigment, foods, batteries,
fire retardant etc (Widiyastuti et al., 2014; Zhiwei et al., 2010).
As compared to other oxide material such as ZrO2, Y2O3,
[email protected] (D.P. Bisen), [email protected]
ion Sciences and Applications.
andApplications. Production and hosting by Elsevier B.V. This is anmons.org/licenses/by-nc-nd/4.0/).
J o u r n a l o f R a d i a t i o n R e s e a r c h and A p p l i e d S c i e n c e s 8 ( 2 0 1 5 ) 4 3 3e4 3 8434
Gd2O3, CeO2, Y2SiO5 and etc; ZnO material is much cheap and
easily available material (Dubey, Agrawal & Kaur, 2015;
Tamrakar, Upadhyay, Bisen, 2014; Tamrakar, Bisen,
Upadhyay & Bramhe, 2014; Tiwari, Kuraria & Tamrakar,
2014; Tamrakar, 2013; Tamrakar & Bisen, 2013; Tamrakar,
Bisen, Robinson, Sahu, & Brahme, 2014).
In the form of one dimensional nano wires/nano rods/
nanotubes or two dimensional nano plates/nano sheets, it has
been widely accepted as the building blocks for nanodevices.
In view of this point, controlled growth of nanostructure in
term of size, shape and orientation is a prerequisite, and a
large amount of intensive research has been conducted to
prepare desired ZnO architectures (Cao & Cal, 2008).
Till today, many different techniques to produced nano
range phosphor such as spray pyrolysis (Santana, Vacio& et al.,
1999),plasma-enhancedchemicalvapordeposition (Kim&Kim,
1999), sol gel (Bao, Gu,& Kuang, 1988), sputtering (Subramanya,
Naidu,&Uthanna, 2000); solid state reactions (Tamrakar, Bisen,
Upadhyay & Tiwari, 2014; Tamrakar, Bisen, & Brahme, 2015;
Sahu, Bisen, Branhe, Wanjari and Tamrakar, 2015a, 2015b), co-
precipitation (Bisen, Sharma, Brahme, & Tamrakar, 2009) and
combustion (Tamrakar, Bisen and Sahu, 2014; Tamrakar, Bisen,
and Brahme 2014a, 2014b, 2014c) etc have been used, but in
recent times much interest has been generated around the
chemical route technique (Dubey et al., 2014; Ezema and
Azogwa, 2003). The technique is simple cost; effective, repro-
ducible and thematerial are readily available (Ezema, Ekwealor,
Osuji, 2007; Ezeme & Okeke, 2002; Ezema et al., 2007).
In this paper, we report that the very low concentration of
complexing agent is responsible for synthesis of nanopowder
which is not observed ever before and also reported observa-
tion of surface morphology and the result of optical charac-
terization of ZnO nanopowder The photoluminescence
studies were investigated in detail.
Fig. 1 e XRD patterns of the ZnO annealed at 190� C.
2. Experimental procedure
2.1. Synthesis of ZnO nanopowder
0.04M aqueous solution of zinc chloride mixed with 20 ml
of 0.08M aqueous solution of sodium hydroxide (All AR
grade 99.9% pure). 8 ml of 0.001M aqueous solution of TEA
added after in growing reaction solutions. Keep the reac-
tion solution for 18e24 h. The powder was washed many
times (more than 8 times) with triple distilled water,
filtered and dried in sunlight. After this it is annealed at
190 �C in a furnace. The color of powder is white. Reaction
mechanics is as follow (Eya, Ekpunob & Okeke, 2005; Eya,
Ekpuno & Okeke, 2005; Widiyastuti et al., 2014; Taunk,
Das, & Bisen, 2015).
ZnCl2 þ TEA 4 Zn (TEA)2þ 2Cl�
Zn (TEA)2þ 4 Zn2þ þ TEA
NaOH þ OH� 4 Naþ þ 2OH�
Zn2þ þ 2OH� 4 Zn (OH)
2Zn (OH)2 4 ZnO þ H2O
2.2. Measuring instruments
We have characterized by employing scanning electron
microscopy (SEM), XRD and Transmission electron micro-
scopy (TEM). SEM was used for morphological character-
ization of sample. The surface morphology of the white
precipitate was determined by scanning electron micro-
scope (SEM) JSM-7600F. The structural parameters of the
powder were determined using X-ray diffraction technique.
The XRD patterns were recorded with Bruker D8Advanced
X-ray diffractometer using a Cu Ka radiation source
(l ¼ 1.54056 A). The X-rays detected using a fast counting
detector based on Silicon strip technology (bruker Lynx
Eye detector) (Tamrakar, Kowar, Uplop, & Robinson, 2014;
Tamrakar, Bisen & Bramhe, 2014c; Tamrakar, Bisen,
Upadhyay, 2015; Tamrakar, Bisen, Sahu, & Brahme, 2014f;
Tamrakar, Tiwari, Kuraria, Dubey & Upadhyay, 2015). Par-
ticle diameter and surface morphology of ZnO were deter-
mined by Transmission Electron Microscope using Plilips
CM e200. The photoluminescence (PL) emission and exci-
tation spectra were recorded at room temperature by use of
a Shimadzu RF-5301 PC spectrofluorophotometer.
3. Result and discussion
3.1. X-ray diffraction (XRD) studies
To identify the crystal structure of ZnO, we performed XRD
analysis. Fig. 1 shows XRD pattern of the ZnO annealed at
190 �C. Eya reported that hydrated part removedwhen sample
is annealed 402 K (Eya et al., 2006). The X ray diffraction were
record in the range 20�e80�; most of the diffraction peaks can
Fig. 2 e A and B are shown morphology of ZnO at different magnification.
J o u rn a l o f R a d i a t i o n R e s e a r c h and A p p l i e d S c i e n c e s 8 ( 2 0 1 5 ) 4 3 3e4 3 8 435
be assigned to zinc oxide according to report. The diffraction
peaks are assigned using pattern COD 1011258. X-ray diffrac-
tion pattern of Zinc oxide confirms proper phase formation
and crystalline nature of the samples. The highest intensity
peak (101) plane of zinc oxide with other smaller intensity
peaks (100, 002, 101, 102, 210,103 and 212) is observed. The
particle sizewere calculated from theXRDpatternusingDebye
Sherrer's formula D ¼ kl/bcosq, where D is the crystallite size
for the (hkl) plane, l is the wavelength of the incident X-ray
radiation [CuKa (0.154 nm)], b is the full width at half
maximum (FWHM) in radiations, and q is the diffraction angle
for the (hkl) plane (Guinier, 1963; Tamrakar, 2012; Tamrakar
et al., 2013; Tamrakar, Bisen, Upadhyay, and Brahme, 2014)
The structure of prepared zinc hydroxide is hexagonal with
a¼ 3.22 A, c¼ 5.20 A and c/a¼ 1.6149. The observed spacing
data fromXRDare listed in the Table 1 (Tamrakar, Bisen, Sahu,
and Brahme, 2014g). Our experimentally observed spacing
data match with calculated data very well.
3.2. Scanning electron microscopy (SEM) studies
Scanning electron microscopy [SEM] is a convenient tech-
nique to study the morphology of the nanostructures. Fig. 1 A
& B show that ZnO posses powder like morphology of zinc
oxide at different magnification (see Fig. 2).
Table 1 e Miller index and crystal plane distance andparticle size of zinc oxide.
Line AssignedIndices (hkl)
Calculatedspacing
Observedspacing
Particlesize (nm)
1 100 2.79 2.80 8.5
2 002 2.60 2.60 10.8
3 101 2.46 2.46 10.6
4 102 1.90 1.91 13.8
5 210 1.61 1.62 9.2
6 103 1.47 1.48 3.8
7 212 1.37 1.37 12.6
3.3. Transmission Electron Microscope (TEM) studies
Fig. 3(AeD) shows the TEM micrographs of the zinc oxide
powder along with the selected area electron diffraction
SAED pattern. The crystalline nature of the material is
clear from the SAED pattern. From the image it is also
clearly visible that crystallite presents in the powder ma-
terial are highly agglomerated. The selected area electron
diffraction pattern [SAED] shows the bright spots indicating
the high crystalline nature of the material (Fig. 3A). Trans-
mission electron microscopy [TEM] is used to determine
actual particle sizes. The TEM image shows that the parti-
cles diameter is 7e21 nm matched with XRD data. Rod like
structure is also seen in TEM images (Fig .3B,C & D). The
prepared material shows the existence of nano-rod with
spherical particles. It is apparent that the diameter of the
smallest rod is equal to the diameter of spherical particle
because the rods have been grown by nucleation growth of
smaller particles.
3.4. Photoluminescence studies
Photoluminescence spectroscopy is an important tool to
study the optical properties of semiconducting materials.
The room temperature excitation and emission PL spectra of
ZnO nanopowder sample was recorded (Figs. 4 and 5). The
excitation spectra were recorded under 500 nm wavelength
and the spectra have broad excitation peak at 235 nm. The
emission spectra was recorded under a UV light of 235 nm
wavelength as the excitation source. The PL spectra show
peaks in blue region around 407 nm and in broad blue region
around 484 nm. The peak at 407 nm originates from the
recombination of free excitons through an excitoneexciton
collision process (Parganiha, Kaur, Dubey, & Murthy, 2015;
Yang, Wang, Sun, & Li, 2009) or because of intrinsic
defects such as oxygen and zinc interstitials (Singh,
Viswanath, & Janu, 2009). The broad blue emission band
around 484 nm is generally attributed to the radiative
recombination of a photo-generated hole with an electron
Fig. 3 e A, B, C and D are shown TEM images of zinc oxide nanopowder.
Excitation
Fig. 4 e Excitation Spectra of ZnO powder. Fig. 5 e Emission Spectra of ZnO nanopowder.
J o u r n a l o f R a d i a t i o n R e s e a r c h and A p p l i e d S c i e n c e s 8 ( 2 0 1 5 ) 4 3 3e4 3 8436
occupying the oxygen vacancy. However, surface states
have also been identified as a possible cause of the visible
emission in the ZnO nanomaterials. It is known that the PL
emission is caused by the recombination of excited elec-
trons and holes, and the lower PL intensity may indicate the
lower recombination rate of electrons and holes under light
irradiation. The PL intensity is highest as prepared sample
S1 indicating the highest recombination of electrons and
holes. It is reasonable that there are some defects in the ZnO
nanostructures at the surface and subsurface due to their
fast reaction formation process and large surface-to volume
ratio (Zhiwei, et al., 2010; Shinde et al., 2014; Widiyastuti
et al., 2014).
J o u rn a l o f R a d i a t i o n R e s e a r c h and A p p l i e d S c i e n c e s 8 ( 2 0 1 5 ) 4 3 3e4 3 8 437
4. Conclusion
This study is focus on the synthesis and structural charac-
terization of zinc oxide nano particle. Zinc oxide nano particle
have a hexagonally crystalline structure. XRD study reveals
better crystallization of the powder. The particle size varies
from 7 to 21 nm. The PL spectra show peaks in blue region
around 407 nm and in blue region around 484 nm. The peak at
407 nm originates from the recombination of free excitons
through an excitoneexciton collision process. The broad blue
emission band around 484 nm is generally attributed to the
radiative recombination of a photo-generated hole with an
electron occupying the oxygen vacancy.
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