Journal of Modern Physics, 2013, 4, 1022-1026 Published Online July 2013 (
An Analysis of Structural and Optical Prop erties Undoped
ZnS and Doped (with Mn, Ni) ZnS Nano Particles
Apurba Kr. Das1*, Apurba Kr. Buzarbaruah2, Santanu Bardaloi3
1Arya Vidyapeeth College, Guwahati, India
2Dimoria College, Khetri, India
3Gauhati University, Guwahati, India
Email: *
Received January 2, 2013; revised February 4, 2013; accepted March 1, 2013
Copyright © 2013 Apurba Kr. Das et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
The behavior of nano-particles finds a wide application in opto-electronic and semi-conductor devices. ZnS nano-crys-
tals were grown into poly-vinyl alcohol matrix by chemical route at different weight percentage. Optical properties of
both un-doped and doped with ZnS nano-crystalline compounds were studied. The nano structure was characterized
with the help of X-ray diffraction (XRD) and Hi-resolution Transmission Electron Microscopy (HRTEM). Surface
morphology was studied with the help of Scanning Electron Microscopy (SEM). The average particle sizes of ZnS,
ZnS-Ni and ZnS-Mn were found to be 6.51, 7.3 and 12 nm respectively in TEM and that obtained from Debye-Scherrer
formula is about 2.3 and 2.5 nm for undoped and doped ZnS respectively. Peak of Photo-luminescence (PL) emission
spectra was obtained at 375 nm at room temperature and another peak at 433 nm for Ni. Again the peak of Photo-lu-
minescence (PL) emission spectra was obtained at 334 nm at room temperature for Mn, Mn dependant emission was
found at 580 nm. These data showed successful doping. PL studies also confirmed presence of dopant in the nano crys-
tallites. Optical absorption studies were carried out with UV-VIS Spectrophotometer and showed a strong absorbance at
wavelength 400 nm with a tendency towards blue shift. Selected area electron diffraction (SAED) shows a set of four
well defined rings corresponding to diffraction from different planes of the nano crystallites. HRTEM image showed a
well crystalline ZnS doped with Ni and Mn. Both Raman spectra and XRD studies confirmed the well crystalline states
of ZnS.
Keywords: Nano-Particle; PVA; XRD; SEM; TEM; HRTEM; SAED
1. Introduction
The physical and chemical properties of nano materials
like optical absorbance, fluorescence, catalytic activity,
electrical and thermal conductivity etc. are significantly
different from the corresponding bulk materials. The
special properties of nano particles are due quantum size
confinement in nano structure and extremely large sur-
face to volume ratio relative to bulk materials and there-
fore it is possible to keep high percentage of atoms or
molecules in lower reactive boundaries.
The synthesis and characterization of nano crystals
grown with different chemicals have created interest
among the researchers. Low-dimensional semiconductors,
like ZnS composite nano-structured have attracted much
interest because of their valuable photoluminescence pro-
perties [1]. Chemical growth process is a very simple,
economical, efficient, and convenient method among the
various researchers. In optical sensors, electrolumines-
cence devices, digital displays, etc. doped ZnS nano ma-
terials are being used extensively. Photo luminescent
properties and efficiency of ZnS depend on intrinsic sur-
face states of the particles, and nature of the chemicals
treatment employed in their fabrication. Research is also
noticed on the application of these types of films in
light-emitting materials as well as on their optical prop-
erties [2]. The optical light emission in blue-red spectral
region is characterized by blue shift at smaller crystallite
dimension. We are trying to characterize the properties of
ZnS with different doping agents (Ni and Mn) with the
help of instrument like X-ray Powder Diffractometer
(XRD), Scanning Electron Microscopes (SEM), High
Resolution Transmission Electron Microscopes (HRTEM),
Photo-luminescence spectrometer (PL), UV visible spec-
trophotometer (UV-VIS), etc.
*Corresponding author.
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A. K. DAS ET AL. 1023
Experimental The synthesisation ZnS nano-particles
were done by using Polyvinyl Alcohol (PVA) as a matrix.
Different weight% solutions of PVA and ZnCl2 in deion-
ized water were taken and stirred at 200 rpm in a mag-
netic stirrer at temperature 70˚C for 3 hours. The solution
was kept overnight for complete dissolution and found to
be transparent. A 2 weight% Na2S solution was added till
the whole solution appears milky. The solution was kept
over night inside a dark chamber. As soon as the nano-
structure formed, it embedded into the gap. The chemical
reaction took place as follows
ZnClNa SZnS 2NaCl
To make different % of ZnS:Ni solution, NiCl2·6H2O
was mixed by weight% with deionized water. Solution so
obtained was mixed with another solution of PVA and
ZnCl2. Then the solution was stirred at 200 rpm in a
magnetic stirred at constant temperature 70˚C. 0.08 M
weight% Na2S solution was added to the solution. Pre-
cipitation found was washed with deionized water and
taken for study.
To make different % of ZnS:Mn solution, MnCl2·4H2O
was mixed by weight% with deionized water. Solution so
obtained was mixed with another solution of PVA and
ZnCl2. Then the solution was stirred at 200 rpm in a
magnetic stirrer at constant temperature 70˚C. 0.08 M
weight% Na2S solution was added to the solution. Pre-
cipitation found was washed with deionized water and
taken for study.
2. Microstructure Studies
2.1. XRD Studies
The XRD studies shown in Figures 1(a) and (b) were ob-
tained from powder. Diffractogram was obtained from a
Philips X’pert Pro Powder diffractometer using Cu Kα
radiation with the operating voltage 40 kV and current 20
mA. The pattern observed was found to be within the
nano range [3,4]. XRD patterns revealed the films to be
polycrystalline [5]. Planes (111), (220) and (311) were
found to present which tallied well with the JCPDS card
No. 05-0566. The average particle size corresponding to
the FWHM was calculated with the Scherrer formulae
in case of undoped ZnS, which is also in good agree-
0 1020304050607080
and found to be 2.3 nm [6].
2.2. Electron Diffraction Studies
Selected area electron diffraction (SAED) was done with
the help of HRTEM. Photo of SAED of undoped ZnS
(Figures 2(a)-(c)) also showed a set of three well defined
rings corresponding to the planes (111), (220) and (311)
(o %)
(in Degrees)
0 102030405060708090100
Int e ns ity
Wave length in nm
1% Mn
1% Ni
Figure 1. (a) XRD diffractogram of ZnS; (b) XRD diffrac-
togram of ZnS-Mn.
(a) (b)
Figure 2. (a) SAED of ZnS; SAED of ZnS-Ni; (c) SAED
of ZnS-Mn. (b)
Copyright © 2013 SciRes. JMP
ment with that of XRD data.
2.3. SEM Studies
Photographs of the nano-crystalline thin film were taken
crystalline doped
ptical Absorbance Study
f ZnS was recorded
with (JEOL, JSM-6360) SEM and shown in Figure 3.
The surface morphology of the film prepared at 70˚C
with PVA was observed and found that all the particles
formed not exactly spherical. Study showed that the sur-
face of the film was smooth, uniform and without any
crack. The particle sizes of ZnS-Ni, ZnS-Mn were found
to be 7 - 16 and 7 - 15 nm respectively.
2.4. Photo Luminescence Studies
The photo luminescence studies of nano
& un-doped (Figure 4) were done at room temperature
by using F-2500 FL Spectrophotometer. In all the meas-
urement the excitation wavelength was 240 nm. Emis-
sion spectra showed a broad peak at 378 nm and another
small broad peak at 451 nm for ZnS while 375 nm and
433 nm for ZnZ-Ni (0.5%) and at 382 nm for ZnS-Ni.
For Mn the emission spectra showed a broad peak at 346
nm and another small broad peak at 468 nm. PL in this
region is due to the presence of S vacancies in the lattice.
PL spectra of ZnS:Mn thin film revealed yellow-orange
emissions. Mn dependent yellow emission was found at
580 nm which was also a confirmation successful Mn
doping. Starting with the blue emission (at 468 nm), in-
tensity decreases towards the orange emission (at 580 nm)
[7]. PL spectra of ZnS:Ni revealed yellow-orange emis-
2.5. O
The optical absorbance (Figure 5) o
at room temperature using a Double Beam Automated
Spectrophotometer (Hitachi-U3210) where the meas-
urement of optical absorbance was done in the range 200
- 800 nm. The wavelength showed strong absorption.
The peak of the absorption showed at 287 nm for ZnS.
The peak of the absorption showed blue shift with re-
spect to bulk attributing quantum confinement effect on
the nano-particles. Optical absorption studies were car-
ried out with UV-VIS Spectrophotometer and showed a
(a) (b)
Figure 3. (a) SEMb) SEM micr
graph of ZnS-Mn
200 300 400 500 600 700 800
micrograph of ZnS-Ni; (
. o-
Wave length in nm
0.5% Ni
1% Ni
Figure 4. (a) PL spectra of Z, ZnS-Ni; (b) PL spectra of
Zn-S, ZnS-Mn.
ce at wavelength 400 nm with a tendency
shows clear lattice fringes of the (001)
peak of Raman spectra indicated
strong absorban
towards blue shift.
Optical absorbance spectrum of ZnS-Ni (0.5%, 1.0%)
features a strong peak around 400 nm. This spectra of
undoped and Ni doped ZnS nano crystal are distinguish-
able. This indicates that Ni doping has effect on the elec-
tronic absorption spectra of ZnS [8]. This may be possi-
ble for low doping level.
2.6. HRTEM
HRTEM image
plane indicating crystal growth along (001) direction.
The particle size obtained from HRTEM image is 6 nm
and 7.3 nm for ZnS-Ni and ZnS-Mn respectively.
2.7. Raman Studies
In Figure 6 the sharp
ZnS in well crystalline state. The peaks at 58 cm and
335 cm1, 347 cm1 are the characteristic Raman scatter-
ing of ZnS and indexed to LO phonon mode [9]. Another
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200 300 400 500
600 700
Absorbance (a.U)
Wave length in nm
400 450 500 550
Absorbance (a.u.)
Wave length in nm
0.5% Ni
700 800200 300 400 500 600
Absorbance (a. U)
Wave length in nm
0.5% Mn
1% Mn
Figure 5. (a) Absorbance spectra of ZnS; (b) Absorbanpectra of ZnS-Ni; (c) Absorbce spectra of ZnS-Mn.
ce san
Figure 6. Raman spectra.
peak at 264 cm1 corresponds to TO phonon mode [10]
of ZnS.
3. Conclusion
ZnS nano crystalline films (un-doped and doped with Ni
and Mn) have been synthesized by chemical route. The
structural and optical characterization of the films done
with the help of XRD, TEM, SEM, SAED, UV-VIS
spectrophotometer and PL reveals formation of doped as
well as un-doped nano particles. The emission bands at
377 nm, 449 nm (both for 0%), 375 nm, 433 nm (both for
0.5% Ni) and 382 nm for 1% Ni may be attributed to
impurities or defect state. Similarly the emission bands
with respect to 375 nm & 451 nm for ZnS-Mn may be
attributed to defect states. The third emission band at 496
nm may be attributed in the 3d shell transition of Mn2+.
The sharp peak of Raman spectra indicated ZnS in well
crystalline state which is in good agreement with that
obtained from XRD result.
From Photo luminescence study it has been observed that
, with the increase of doping% (from
Gauhati University for his
help in taking UV-VIS and PL data. We are also tha
g TEM and SEM facility.
Authors are also like to offer their gratitude to SAIF,
Guwahati, Department of Instrumentation & USIC, Gau-
hati University for providing XRD & XRF facility. The
authors are also like to offer their heart felt gratitude and
thanks to CIF and dept. of Nano-Science and Technology,
IITG for providing HRTEM and XRD facility. The au-
thors are also grateful to Prof. K. C. Sarma, Head, Dept.
of Instrumentation & USIC, Gauhati University for con-
stant guidance and help.
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4. Novelty Statement
in case of ZnS-Ni
0.5 - 1.0), the intensity of doping related emission spectra
is found to be increased. In case of ZnS-Mn, with the
increase of doping% (from 0.5 - 1.0), the intensity found
to be increased. It is also observed from the PL that with
the increase of doping% (from 0.5 - 1.0) of both ZnS-Ni
and ZnS-Mn, there is blue shift of doping related emis-
sion spectra due to quantum confinement effect. The
bands with respect to 375 nm & 451 nm may be attrib-
uted to defect states. The sharp peaks of Raman spectra
indicated ZnS nano particles were in well crystalline
5. Acknowledgements
The authors are very much thankful to Dr. P. K. Baruah,
Department of Chemistry,
to SAIF, Shillong for providin
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