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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,

pbisen@rediffmail.com (D.P. Bisen), raunak.ruby@gmail.com

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)

2

Zn (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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