SYNTHESIS AND CHARACTERIZATION OF SILVER DOPED
ZINC OXIDE NANOPARTICLES
M.Sc. Project
Abraham Wakwaya
August 2015
Haramaya University, Haramaya
SYNTHESIS AND CHARACTERIZATION OF SILVER DOPED ZINC
OXIDE NANOPARTICLES
A Graduate Project Submitted to the Department of Physics,
School of Graduate Studies
HARAMAYA UNIVERSITY
In Partial Fulfillment of the Requirements for the Degree of
MASTER OF SCIENCE IN PHYSICS
(Nanoscale Physics)
Abraham Wakwaya
August 2015
Haramaya University, Haramaya
HARAMAYA UNIVERSITY
POSTGRADUATE PROGRAM DIRECTORATE
As project research advisor,here by certify that I have read and evaluated this project prepa
red under my guidance by ABRAHAM WAKWAYA entitled:”
Synthesis and Characterization Silver Doped Zinc Oxide Nanoparticles”.I
recommended that it be submitted as fulfilling the project requirement.
Prof. US Tandon
Major Advisor
_________________
______________
Signature
Date
As member of the board of examiners of the M.Sc. project open defense examination, we
certify that we have read and evaluated the project prepared by Abraham Wakwaya and
examined the candidate. We recommend that the project be accepted as fulfilling the
project requirement for the degree of Master of Science in Nanoscale Physics.
______________________
Chairperson
______________________
Internal Examiner
______________________
External Examiner
_________________
Signature
_________________
Signature
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Signature
_______________
Date
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Date
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Date
Final approval and acceptance of the Graduate Project is contingent up on the submission of its
final copy to the council of Graduate Studies (CGS) through the candidate’s department or school
of graduate committee (DGC or SGS).
ii
DEDICATIONS
This project manuscript is dedicated to my father Wakwaya Dube and my mother Chaltu
Ayana for nursing me with affection and love and for their dedicated partnership in the
success of my life.
iii
STATEMENT OF THE AUTHOR
By my signature below, I declare and affirm that this Graduate project is my work. I have
followed all ethical and technical principles of scholarship in the preparation, data
collection, data analysis and compilation of this graduate project. Any scholarly matter
that is included in the project has been given recognition through citation.
The Graduate project is submitted in partial fulfillment of the requirement for M.Sc.
degree at Haramaya University. The project is deposited in the Haramaya University
Library and is made available to borrowers under the rule of the library. I solemnly
declare that this Graduate project has not been submitted to any other institution anywhere
for the award of any academic degree, diploma or certificate.
Brief quotation from this Graduate project may be made without special permission
provided that accurate and complete acknowledgment of the source is made. Requests for
permission for extended quotations from or reproduction of this Graduate project in whole
or in part may be granted by the Head of the School or Department when in his or her
judgment the proposed use of material is in the interest of scholarship. In all other
instance, however, permission must be obtained from the author of the Graduate project.
Name: Abraham Wakwaya
Date:
Signature: _________
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School/Department: ______________
iv
LIST OF ABBREVIATIONS
AAS
Atomic Absorption Spectroscopy
Ag/ZnO
Silver Doped Zinc Oxide
CVD
Chemical Vapor Deposition
eV
Electron volt
FTIR
Fourier Transforms Infrared Spectroscopy
FWHX
Full Width at Half Maximum
DI
Dionized
MHA
Mueller Hinton Agar
NPs
Nanoparticles
RT
Room temperature
UV-Vis
Ultra violet visible Spectroscope
Zc
Zinc calcined
v
BIOGRAPHICAL SKETCH
The author was born in June 1979 E.C in Ebantu Woreda oromia Administrative Zone. He
attended Hinde Elementary school, and completed his secondary education at Gidda
Ayana Senior Secondary School in June 1994 E.C. Just after completion of his secondary
education, he joined the Robe College of Teachers Education in September 1995 E.C. and
graduated with diploma in physics in June 1996 E.C. After completion of his diploma, he
was employed by the Oromia Regional Bureau of Education to Horro Guduru Wollega
Zone as a Physics teacher in Finchaa Senior Secondary School. He then joined Jimma
University in summer program in June 1998 E.C and graduate with a B.E.d. degree in
Physics in September 2001. After completion of his B.E.d., he thought at Agemsa General
Secondary School. He had been serving as a Physics teacher till he joined the school of
Graduate Studies of the Haramaya University to pursue his M.Sc. degree in June 2011.
vi
ACKNOWLEDGEMENT
Above all, I praise the Almighty God for giving me health, strength and endurance so as
to successfully under take the courses, research work, and to compile this manuscript.
Thank you God!
I am highly grateful to my advisor Professor U.S.Tandon, for his guidance,
encouragement and critical remarks while developing the proposal, and for giving me
constructive and valuable comments and suggestions that shaped this project.
I am very thankful to Dr. Abdisa Bakala and Lemi Wakjira for their unreserved
cooperation and fruitful assistance which invariably helped me a lot during this research
work. My sincere thanks also go to Mr. Fituma Diriba for rendering me technical
assistance d u r i n g the course of this research work and successful and timely accomplis
hment of this study would have been difficult without his cooperation. My thanks also
goes to Dr. Kalid Ahimed department head of Material Science Engineering of Adama
Science and Technology University for helping me to characterize ZnO and Ag/ZnO.
My thanks and special appreciation also go to my sisters Almaz Wakwaya,Rumane
Wakwaya and my brothers Daniel wakwaya and Amanuel Wakwaya for their support in
providing me with the necessary assistance and information and for their encouragement.
I would also like pass a heartfelt gratitude to my mother Chaltu Ayana , my father
Wakwaya Dube for their moral support and invaluable encouragement throughout my
life.
Last but not least I would like to appreciate and support provided to me by the university
in general and the department of physics in particular.
vii
TABLE OF CONTENTS
DEDICATIONS
III
STATEMENT OF THE AUTHOR
IV
LIST OF ABBREVIATIONS
V
BIOGRAPHICAL SKETCH
VI
VII
ACKNOWLEDGEMENT
LIST OF TABLES
X
LIST OF FIGURES
XI
LIST OF TABLES IN THE APPENDIX
XII
LIST OF FIGURES IN THE APPENDIX
XIII
ABSTRACT
XIV
1.
INTRODUCTION
1
2.
LITERTURE REVIEW
4
2.1 Nanotechnology
4
2.2 Use Of Zinc Oxide And Silver Doped Zinc Oxide
5
2.3. Zinc Oxide Nanocomposites
7
2.3.1 Methods of Synthesizing ZnO and Ag/ZnO Nnanomaterial
8
2.3.1.1 Precipitation method
8
2.3.1.2 Sol-gel methods
8
2.3.1.3 Pulse Mode
9
2.3.1.4 Hydrothermal Synthesis Of Zno Nanoparticless
viii
10
3
12
MATERIALS AND METHODS
3.1
Experimental Site
12
3.2
Material and Apparatus
12
3.3
Chemicals and Reagents
12
3.4
Methods of Synthesis and Characterizations
12
3.4.1 Synthesis of ZnO Nanoparticles
12
3.4.1.1 Preparation of Ag doped ZnO nanoparticles
13
3.4.2 Methods of Characterization of synthesized Nanoparticles
4
13
3.4.2.1 UV-visible absorpion
13
3.4.2.2 X-Ray diffraction
14
RESULTS AND DISCUSSION
15
4.1 Characterization
15
4.1.1 UV-visible absorption study
15
4.1.2 XRD Analysis
18
5.
5.1
SUMMARY AND RECOMMENDATIONS
Summary and Conclusion
20
Error! Bookmark not defined.
6.
REFERENCES
21
7.
APPENDICES
26
ix
LIST OF TABLES
Page
1: Band gap energy of pue ZnO and Ag /doped ZnO nanoparticles at a temperature of
500℃
18
2: The calculated average crystallite size (D) of the nanoparticles
19
x
LIST OF FIGURES
Page
1: Optical absorption spectra of undoped ZnO nanoparticles at nanoparticles at 500℃ 16
2: Optical absorption spectra of Ag:ZnO nanoparticles at nanoparticles at 500℃
17
3: XRD spectra of ZnO and Ag-doped ZnO nanoparticles.
18
xi
LIST OF TABLES IN THE APPENDIX
Page
1.Uv data of ZnO nanoparticles
26
2.Uv Data of Ag/ZnO
29
xii
LIST OF FIGURES IN THE APPENDIX
1XRD-data of ZnO nanoparticles
32
2 XRD-data of Ag/ZnO nanoparticles
33
xiii
SYNTHESIS AND CHARACTERIZATION OF SILVER DOPED
ZINC OXIDE NANOPARTICLES
ABSTRACT
Zincoxide (ZnO) and Silver doped zincoxide(Ag:ZnO) nanoparticles have been
synthesized by the precipitation method. Ag:ZnO nano material was prepared from the
already prepared ZnO aqueous solution of silver nitrate. The nanoparticles and composites
were characterized by powder X-ray diffraction (XRD). The resulted Ag:ZnO
nanocomposite was structurally and optically characterized using XRD and Uv-vis
techniquees. The X-ray Diffraction (XRD) pattern clearly showed the presence of
crystalline Ag:ZnO particles. Further, UV-Vis spectrophotometer results have shown the
presence of Ag:ZnO nanocomposite at specific wavelengths.
Key words: Synthesis, Uv-vis and XRD.
xiv
1. INTRODUCTION
Nano sized particles of semiconductor materials have gained much more interest in recent
years due to their desirable properties and applications in different areas such as catalysts,
sensors, photoelectron devices, functional and drug delivery devices. These nanomaterials
have novel electronic, structural, and thermal properties which are of high scientific
interests in basic and applied fields. Zinc oxide (ZnO) nanocomposite is a wide band gap
semiconductor with an energy gap of 3.4 eV at room temperature. It has been used
frequently for its catalytic, electrical, optoelectronic, and photochemical properties. Zinc
oxide is an inorganic compound with the formula ZnO. It is a white powder that is
insoluble in water, and it is widely used as an additive in numerous materials and products
including rubbers, plastics, ceramics, glass, cement, lubricants (Hernandezbattez, et al.,
2008), paints, ointments, adhesives, sealants, pigments, foods (source of Zn nutrient),
batteries, ferrites, fire retardants, and first-aid tapes. It occurs naturally as the mineral
zincite, but most zinc oxide is produced synthetically.
ZnO nanostructures have a great advantage to apply to a catalytic reaction process due to
their large surface area and high catalytic activity. ZnO is a wide band gap (3.4 eV at
room temperature) compound semiconductor that is appropriate for short wavelength
optoelectronics applications. The large exciton binding energy (60 meV) in ZnO crystal
allows efficient excitonic emission at room temperature. Therefore, ZnO nanostructures
have had a wide range of high technology applications like surface acoustic wave filters,
photonic crystals, gas sensors, photo catalysis. Metal silver is also a significant visible
light photosensitizer, which is stable and nontoxic. Ag is also relatively cheap; thus Ag
modification of ZnO nanoparticles has great significance for industrial practice.
Nanoparticles are of interest because of their high reactivity due to the large surface area
to volume ratio. It has been observed that nanomaterials display significantly different
properties compared to the properties of the same bulk material and that the properties of
the materials are size and shape-dependent at nanoscale range (Zhu.et al., 2002).
2
Nanoparticles are becoming key components in wide range applictations in engineering,
medicine, Pharmaceutical molecular science, medical engineering toxicology, cosmetics,
energy, food technology, environment and health diseases. As we enter to the twenty first
century, semiconductor nanostructures are revolutnalizing many areas of electronics,
optoelectronics and photonics. ZnO nanoparticles are very important in the category of
semiconductor nanoparticles. It is an intrinsic n-type semiconductor material that
crystallizes in the hexagonal crystal system; it is relatively inexpensive, presents low
toxicity, and is very effective in protecting against UV rays. Many research groups
concentrate on doping ZnO with transition metal ions (Al, Cu, Ag, Ni). As transition
metal elements have close ionic radius parameter to that of Zn2+, these elements can easily
penetrate into ZnO crystal lattice or substitute Zn2+ position in crystal, these are widely
used in spintronics, photonics and optoelectronics device applications.
Silver is soft, white, lustrous transition metal it possesses the highest electrical
conductivity, thermal conductivity and reflectivity of any metal. It is also good for
producing a shallow acceptor level in ZnO as it is a soft more over ZnO doped with Ag
can improve the distribution of surface charges, accept a conduction band generated by
solar light irradiation during photoreaction, prevent the recombination of the photo
generated electron-hole. Ag/ZnO has received considerable attention. Ag doped ZnO
Nanomaterials enhances ultraviolet emission and improves electrical and optical
properties ( Chauhan et al., 2010).
Photocatalytic and photoluminescence properties, (Nguyen Va et al., 2012) Micro leakage
and antibacterial properties ( Shayani Rad et al., 2013). Since the physical and chemical
properties of ZnO nanoparticles are influenced both by their shape and size, a control of
morphology of ZnO structures is needed for their commercial usage. ZnO with various
nano-sized structures can made using simple fabrication methods including solvothermal,
hydrothermal, chemical vapor deposition (CVD), laser ablation, oxidation process,
precipitation, Pulse mode, gelcombustion, and sol–gel. Precipitation is used to synthesize
pure and silver doped nanoparticles. The particles further characterized using X-Ray
diffraction, Scanning Electron Microscopy (SEM) and Fourier transform infrared (FTIR)
to investigate the effect of Silver on structural ,morphological and optical properties of
zinc oxide nanoparticles.
3
Nanomaterials are considered as excellent adsorbents, catalysts and sensors due to their
large specific surface area and high reactivity. In recent years, the application of
nanoparticles have expanded considerably in various fields such as cell labelling, drug
targeting gene delivery, micro electronics, solar cells, electroluminescent devices,
detergent and cosmetics. For instance nanoparticles have been examined for their ability to
reduce microbial infections and to prevent bacterial colonization. Hence the nanoparticles
are called “a wonder of modern medicine”. Zinc oxide (ZnO) nanoparticles have received
considerable attention in recent years, because of their stability under harsh processing
conditions and moreover they are safe materials to human beings and animals. Food and
Drug Administration (USA) recognized “Ag/ZnO nanoparticles as safe”.
Objectives
General Objective
 To undertake synthesis and characterization of silver doped zinc oxide (Ag/ZnO)
nanoparticles.
Specific Objectives
 To synthesize ZnO and Ag/ZnO nanoparticles.
 To estimate the band gap energy and crystal size of nanoparticles of Pure Zinc
Oxide and silver doped zinc oxide nanoparticles from UV/vis spectrophotometer
 To characterize the synthesized silver doped zinc oxide nano material using XRD.
4
2. LITERTURE REVIEW
2.1 Nanotechnology
Nanotechnology is the creation and exploitation of nanomaterials with structural features
in between those of atoms and their bulk materials. In order words, nanotechnology is a
technology of design and applications of nanoscale materials with their fundamentally
new properties and functions. When the dimensions of materials are in nanoscales the
properties of the materials are significantly different from those of atoms as well as those
of bulk materials.
Moreover, when the size of materials is in the nanoscale regime the large surface area to
volume ratio exhibited by nanomaterials, improves the high surface reactivity with the
surrounding surface, which makes nanomaterials ideally suitable candidates for many
types of sensor applications. Therefore, nanomaterials has opened up possibilities for new
innovative functional devices and technologies (Roco et al.,2011)The importance of
nanotechnology was pointed out by Richard Feynman in his lecture delivered at an
international forum in the meeting of the American Physical Society at California Institute
of Technology (CalTech) entitled ‘‘There is plenty of room at the bottom’’ on December
1959 (Kaur et al., 2014).
Currently, nanotechnology has been recognized as a revolutionary field of science and
technology and have been applied in many applications, including environmental
applications, medical applications, biomedical applications, healthcare and life sciences,
agricultures, food safety, security, energy production and conversion applications, energy
storage, consumer goods, infrastructure, building and construction sector, and aerospace.
Moreover, the new nanotechnology applications provide very fast response, low-cost,
long-life time, easy to use for unskilled users, and high efficiency of devices and it also
provides a new approaches to diagnosis and treatment of diseases, effective environmental
monitoring and alternative ways for substantial energy development for a better world.
We can say that, nanotechnology is applied almost in every aspect of our modern world
( Boisseau and Loubaton, 2011).
5
In this regard, the development of new methods to synthesize nanomaterials have paved
the way in creating new opportunities for the development of innovative nanostructures
based devices. In particular, the ability to synthesize nanostructures materials with
controllable shape, size and structure and enhance the properties of nanomaterials
provides excellent prospects for designing nanotechnology based devices.
2.2 Use Of Zinc Oxide And Silver Doped Zinc Oxide
In recent years, nanomaterial-based sensors have attracted much attention from both
scientific research communities and from industrial applications points-of-view. For
sensor applications, the fabrication processes are on economic oriented approach, use of
inexpensive materials by economical synthesis methods and the sensor system should
presents low power consumption, ease of fabrication, high accuracy, fast response time,
high compatibility, portable and easy to use for unskilled users are the most important
factors for the developmentof new sensors based devices. In the response to above
requirements, metal oxide semiconductor nanomaterials have attracted high interest due to
their promising applications in a diversity of technological areas, including sensors area.
In the fields of nanotechnology based sensors, metal oxides nanostructures stand out as
being among the most versatile nanomaterials because of their excellent physical and
chemical properties (Wang and Song, 2006).
Among metal oxide nanomaterials, ZnO nanostructures are of the most promising metal
oxides due to their attractive physical and chemical properties. From these properties,
ZnO nanostructures are highly attractive from research communities in the applications of
sensing. ZnO nanomaterials have attracted huge attention in sensing areas due to its
relatively large surface area to volume ratio, larger band gap (3.4 eV at room
temperature), high exciton binding energy (60 meV) high transparency, its high iconicity
and biocompatibility. Also, ZnO is an important multifunctional material suitable for
many different applications in transparent electronics, optoelectronics, transparent
electronics, solar cell, smart windows, biodetection, piezoelectric devices (Chen et al.,
2008).
In addition, the performance of the sensors can be improved by doping ZnO
nanostructure with different metals or by alloyed ZnO with other metal oxides. This is due
to the dopant influenced on the properties ZnO nanostructures such as the band gap,
optical property and electrical conductivity. Furthermore, room temperature ferromagnetic
6
properties are also achieved by doping with transition metals into ZnO nanostructures,
which shows potential for increasing performance of sensing device and for future
spintronics applications .
Among ZnO nanostructures, 1-D ZnO nanostructures such as nanorods, nanowires,
nanobelts, and nanotube are becoming a major focus in nanoscience research and are of
interest for many different applications due to their important physical properties and
application prospects. The key factors for the great interest in 1-D ZnO nanostructures in
sensing applications arises for many reasons. The electron transport in 1-D ZnO
nanostructures are directly in contact with the surrounding environment and high surface
area to volume ratio which is mandatory for fast reaction kinetics. Their high electronic
conductance, minimum power consumption, relatively simple preparation methods and
large-scale production can achieved. 1-D ZnO nanostructures have superior stability due
to high crystallinity, ultrahigh sensitivity, and the potential for the integration of
addressable arrays on a mass production scale. It also exhibits as semiconducting
properties
and also
piezoelectric properties
which can form the basis
for
electromechanically coupled sensors and transducers, it is relatively biocompatible and
they can be relatively easily incorporated into microelectronic devices (Wang et al.,
2006).
The unique properties of 1-D ZnO nanostructures provide promising combination for
chemical selectivity, an electronically and chemically tunable platform crucial for tailored
sensor response. Therefore, 1-D ZnO nanostructures are important potential candidates for
the realization of sensor applications. So far, 1-D ZnO nanostructures, especially ZnO
NRs/NWs are extensively applied in various sensing applications fields, e.g. biosensors,
biomarker, drug delivery, chemical sensors, gas sensors , pH sensors, humidity sensor,
UV sensors temperature sensors, and pressure/force/mass/load sensors.
Also, the high performances of several types of sensors have been enhanced by utilizing
different metals doped ZnO nanorods, e.g. high performance of sensors can be achieved
by Ag-doped ZnO nanorods for UV sensors. The controlled preparation of 1-D ZnO
nanostructures is considered to play a significant role in exploring the prospects and future
challenges for the development of sensing devices. Therefore, this dissertation aims to
provide a novel route to the low temperature hydrothermal synthesis of 1-D ZnO and Agdoped ZnO nanostructures with fast, low cost, controllable size, shape, uniform
7
distribution and structure orientation with desirable properties for higher sensor’s
performances and multifunctional sensing devices (Yang et al., 2010).
2.3.
Zinc Oxide Nanocomposites
Zinc oxide nanoprticle is a unique and key inorganic material that has attracted an
extensive research due to its characteristic features and novel applications in wide areas of
science and technology. It has multiple properties like semiconducting, piezoelectric,
pyroelectric, catalysis, optoelectronics and powder metallurgy. In addition, the optical
properties of ZnO nanoparticles play a very important role in optoelectronic, catalytic and
photochemical properties (Djurisic and Leung, 2006).
Recently, the material scientists all over the world have used different methods such as
chemical
vapor
deposition
(CVD),
electro
deposition
(ED),
hydrothermal,
electrochemical, solution combustion, sol–gel, vapor–liquid–solid process, pulsed laser
deposition and precipitation method for the preparation of ZnO nanocomposite. Due to
these special criteria, the ZnO has an edge for applications of semiconductor including
transparent electronics, ultraviolet (UV) light emitters, piezoelectric device, and chemical
gas sensor, transistors, solar cells, catalysts and spin electronics . Among all methods,
precipitation and sol-gel technique provides suitable control of nucleation, ageing and
growth of particles in solution. The direct precipitation is also one of the simple and cost
effective methods for bulk production of ZnO nano materials (Olivera et al., 2011).
Among several oxides semiconductor ZnO nanostructures is considered to be the best, it
is clearly demonstrated in many studies that nanoparticles of ZnO have significantly an
important industrial material, because it has an inorganic and semiconducting material
with inherent properties that share its structure as wurtzite .
ZnO mean that it can be used as a sensor, converter, energy generator and photocatalyst in
hydrogen production. Because of its hardness, rigidity and piezoelectric constant it is an
important material in the ceramics industry, while its low toxicity, biocompatibility and
biodegradability make it a material of interest for biomedicine and in pro-ecological
systems (Ludi et al., 2009 ).
8
2.3.1. Methods of Synthesizing ZnO and Ag/ZnO Nnanomaterial
2.3.1.1 Precipitation method
This strategy involves the simultaneous occurrence of nucleation, growth, coarsening and/
or agglomeration processes. These sub-processes that participate in the whole reaction
are modulated by a stabilizing agent. ZnO NPs with average crystallite size, 20 nm,
have been produced by application of this strategy. In typical procedure, polyethylene
glycol solution syringed into a three-neck flask. Then, zinc acetate dihydrates and
ammonium carbonate aqueous solutions were dropped into the flask at the same time with
vigorous stirring. After reacting for 2 hours at room temperature, the precipitates were
washed and filtered with ammonia solution (pH=9) and anhydrous ethanol for several
times, and dried under vacuum for 12 h. Finally, the precursors were calcined at 500°C for
3 h and milled to obtain ZnO nanoparticles (Hong et al., 2009).
2.3.1.2 Sol-gel methods
The Sol gel process used for synthesis of nanoparticles is very simple, cost effective and
environment friendly. The chemicals used by the authors are of Zinc chloride (ZnCl2),
Sodium Hydroxide (NaOH), silver Nitrate Ag (NO)3 and Ethanol (C2H6O) were
purchased and used without any purification. The procedure for preparing un doped and
Ag doped Nanoparticles is as follows. To synthesize Pure ZnO Nanoparticles, 0.5 M
aqueous ethanol solution of Zinc Nitrate was kept under constant stirring using magnetic
stirrer to dissolve completely Zinc Nitrate for one hour and 0.5 M aqueous ethanol
solution of NaOH was also prepared in the same way with stirring of one hour. After
complete dissolution of ZnCl2, 0.5 M NaOH aqueous solution was added under high speed
constant stirring, drop by drop (slowly for 45 min) touching the walls of the vessel
(Lin et al., 2011).
The reaction was allowed to proceed for 2 hrs after complete addition of NaOH. The
beaker was sealed at this condition for 2 h. After the completion of reaction, the solution
was allowed to settle for overnight further, the supernatant solution was separated
carefully. The remaining solution was centrifuged for 10 min and the precipitate was
removed. Thus, precipitated ZnO NPs cleaned three times with deionised water and
ethanol to remove the byproducts which were bound with the nanoparticles. The solution
then dried in an oven at about 60℃. After drying Zn(OH)2 is completely converted to into
ZnO. For the synthesis of Ag doped ZnO nanopowder 0.5 M concentration of silver
9
Nitrate Ag(NO)3 was added into the zinc solution before sodium hydroxide NaOH
solution and the same procedure was repeated to obtain the Ag doped ZnO nanoparticles
(Ruby et al, 2010) .
2.3.1.3 . Pulse Mode
To Synthesis Ag doped ZnO Nanocomposite 0.2 M zinc chloride (ZnCl2) and 0.001 M
silver nitrate (AgNO3) was mixed to 50 ml of distilled water. A 2 ml of 25% Ammonia
solution added drop wise until precipitation occurred and then further 10 drops of
Ammonia solution (NH4OH) added to make the solution clear. Pulse mode sonication
(PS) operated at 112.5 W, the frequency of the Sonicator maintained at 20 kHz ± 50 Hz.
PS takes place for one second then stops for one second, and the total process took two
hours to get precipitates. The initial pH of the solution was 10.2 whereas at the end, the
pH was 8.2 and the solution became clear silvery white and gradually solid suspension is
settled. The formed precipitate was washed several times with deionised water and
acetone followed by centrifugation at 3500 rpm for the complete elimination of chloride.
The precipitate were then dried at room temperature and kept overnight inside an oven at
110ºC in atmospheric pressure to obtain dry powder.
Ammonia solution (NH4OH) was used as precipitating agent during synthesis between
zinc chloride (ZnCl2) and silver nitrate (AgNO3) with water (H2O) to form Zn (OH)2,
AgOH, NH4Cl, NH4NO3 and H2O. The product was washed with deionised water for
several times to form Zn (OH)2, AgOH and H2O. Then again washed with acetone by
centrifuging in order to form Zn (OH)2 and 2AgOH. On heating at 110ºC the product
obtained was pure ZnO doped with silver like (Zn-O-Ag) which has been explained
below(Gao et al., 2005)
ZnCl2 + AgNO3 + NH4OH + H2O → Zn(OH)2 + AgOH + NH4Cl + NH4NO3 + H2O
Wash with DD H2O (3 times)....... [1]
∆
Zn(OH)2 + AgOH + H2O →Zn(OH)2 + 2AgOH → ZnO + Ag2O + H2O↑
Wash with Acetone
110℃
……………... .[2]
10
2.3.1.4 Hydrothermal Synthesis Of Zno Nanoparticless
The synthesis of ZnO and Ag-doped ZnO nanostructures via the low temperature
hydrothermal method is considered a promising technique due to low cost, environmental
friendly, simple solution process. In solution growth procedures of nanocrystals, there are
two processes: the nucleation and the growth of the nanocrystals. The growth processes of
ZnO nanorods/nanowires consists of the following procedures: preparation of substrate,
seeding, preparation of precursor solution and growth processes. ZnO nanorods were
grown on a number of thin films of metal coated glass, glass, semiconductor and polymer
coated substrates. Prior to the solution growth procedures, the substrates were sequentially
and repeatedly immersed in isopropanol under sonication for 5 minutes to eliminate
organic contaminant and unwanted particles. This cleaning step is followed each time by
rinsing the substrates in deionized water (DI water) and finally the substrates were blown
dried by nitrogen gun and dried in air at room temperature (RT).
In a typical process, the seed layer was spun coated three times with a seed solution (ZnO
nanoparticles) at 3000 revolutions per minute (rpm) for 30s and then the samples were
annealed in a preheated oven at 120oC for 10 minutes (Willander et al., 2009). The main
benefits for using ZnO nanoparticles as the seed layer in the hydrothermal growth method
is to provide nucleation sites for ZnO nanorods. Also, the ZnO seed layer was found to be a
critical factor for alignment and uniformity of the grown ZnO nanorods .The seed solution
was prepared by dissolving zinc acetate dehydrate (C4H10O6Zn) in absolute methanol
(99%) to obtain 0.01 M concentration under stirring at 60oC on a hotplate and then
followed by adding drop wise a solution containing potassium hydroxide (KOH) in
methanol under vigorous stirring for 2 hours (Yun, 2008). In the precursor solution
preparation process of ZnO nanocrystals, the most commonly used chemical agents to
synthesize of ZnO nanorods/nanowires are zinc nitrate hexahydrate (Zn(NO3)26H2O) and
hexamethylene tetramine (HMT) (C6H12N4). In general, the precursor solution prepared by
mixing equimolar of zinc nitrate hexahydrate and HMT under stirring for one hour.
The final process is the hydrothermal growth process. The ZnO seed-layers attached to the
substrates were immersed horizontally in the growth solution and kept in a preheated oven
at 90oC. Then the samples were collected after different growth durations and cleaned
with deionized water and dried at room temperature for further characterizations and
11
device fabrication processes (Udoma et al., 2013). At the end ZnO nanoparticles are
produced. The reaction processes involved in this method are described as the following
C6H12N4 +6 H2O ↔6H2CO +4NH4+ + OHNH3 + H2O → 4NH4+ + OHZn(NO3)2 →Zn2+ + 2NO3Zn2+ +4 NH3 → Zn(NH3)2+4
Zn2+ + 4OH- → Zn(OH3)2-4
Zn(NH3)2+4 +2OH- → 2OH- + ZnO +4 NH3 +H2O
Zn(OH)2-4 → ZnO + H2O + 2OH-
12
3
3.1
MATERIALS AND METHODS
Experimental Sites
The synthesis of ZnO nanocompositeSs and Ag doped ZnO nanocomposites of
the experiment and their UV-vis measurements were conducted at Haramaya Univerity
Chemistry department research laboratory. XRD characterization of the synthesized ZnO
and Ag/ZnO nanorods were conducted at Adama Science and Techinology University.
3.2 Material and Apparatus
The instruments and apparatus used include Beakers, Fanels, filter paper Measuring
cylinder, UV-VIS SPECTROPHOTOMETER, X-RAY DIFFRACTOMETER, Oven,
analaytical balance, hotplate, furnace, ceramic, crucible, agate mortar, water bath,
thermometer, volumetric flasks, pipettes, graduted cylinders, desicators and testtubes.
3.3 Chemicals and Reagents
Chemicals used include: zinc sulphate hexahydrate [Zn (SO4)2.6H2O], sodium hydroxide
(NaOH) and silver nitrate (AgNO3).
3.4
Methods of Synthesis and Characterizations
3.4.1 Synthesis of ZnO Nanoparticles
Zinc oxide nanoparticles were synthesized using a simple precipitation method with zinc
sulfate hexahydrate(ZnSO4.6H2O)and sodium hydroxide(NaOH) as starting materials. To
the aqueous solution of zinc sulfate, sodium hydroxide solution was added slowly drop
wise under vigorous stirring, and the stirring was continued for 12 h. The precipitate
obtained was filtered and washed thoroughly with deionized water. The precipitate was
dried in an oven at 100°C and ground to fine powder using agate mortar. The powder
obtained from the above method was calcined at 500℃ for 2h and the final result is ZnO
nanoparticles.
13
3.4.1.1 Preparation of Ag doped ZnO nanoparticles
There are different doping agents like P, N, As, Li, Sb, and Ag. Among these, we have
taken Ag as doping agent. Because the nature of Ag ions is simple link matrices, their
behaviour to surface states in nano materials where the surface are becomes prime
importance as the size decreases .
Ag doped
ZnO
were
prepared
by
the
precipitation
method.
In typical synthesis10 ml of AgNO3 (0.18M) was added to 5g of calcined zinc oxide(Zc).
The sample was agitated and heated at 110 0C for 30 minutes. After settling, filtering and
drying the precipitate, the powders were cooled to room temperature. Then it was calcined
at 500oC for 2 h and ground in agate mortar. The products obtained were labeled as silverdoped zinc oxide (AZ).
3.4.2
Methods of Characterization of synthesized Nanoparticles
The synthesized ZnO and Ag/ZnO NPs were characterized by X-Ray diffraction (XRD)
and Uv-vis spectroscopy.
3.4.2.1 UV-visible absorpion
Ultraviolet visible spectrometers have been in general use for the last 35 years and over
this period have become the most important analytical instrument in the modern day
laboratory. The UV-vis absorption spectra of ZnO and Ag:ZnO nanocomposite material
were recorded at room temperature. The synthesized nanocomposite were dispersed in
ethanol with water and the solution was used to record UV-vis spectra at wavelength
range between 350 and 550 nm. The spectra reveal a characteristic absorption peak of
ZnO nanocomposite material at 352nm and Ag:ZnO at 354nm. The absorbance increases
in the higher wavelength in the Ag:ZnO side indicating the role of metal Ag in ZnO.
More number of Ag are dispersed into ZnO and these metallic particles rest on the surface
of ZnO nanocomposite making the surface area more and showing plasmonic resonance
peak in the UV-vis spectra. The data recorded by Uv –vis spectra is used to calculate the
band the band gap energy (Eg) of ZnO nanoparticles and Ag:ZnO.
14
3.4.2.2 X-Ray diffraction
The crystalline size of ZnO NPs and Ag/ZnO NPs were analyzed by X-ray diffraction
(XRD). The dimension (D in nm) of zinc oxide and silver doped zinc oxide Ag/ZnO
nanoparticles were determined from XRD patterns of different ZnO and Ag/ZnO –NPs
nanocomposite samples according to the sherrer’s equation.
15
4
RESULTS AND DISCUSSION
4.1 Characterization
4.1.1. UV-visible absorption study
The UV–Vis spectra of ZnO nanoparticles obtained from Zinc sulfate hexahydrte and
sodium hydroxide calcined at 500 °C for 2 hr were shown in Fig. 1. Similarly, the UV–Vis
spectra of Ag/ZnO nanoparticles obtained from the synthesized ZnO and Ag/ZnO calcined
at 500 °C for 2 hr were shown in Fig 2. For recording UV–Vis spectra, the sample of ZnO
solution was prepared by ultrasonically dispersing them in ethanol. The synthesized
nanocomposite were dispersed in ethanol and the solution was used to record UV-vis
spectra at wavelength range between 350 and 550 nm for both. From figures 1 & Figure 2,
it can be seen that the excitonic absorption peak of as prepared pure and silver doped
samples appears around 352 nm and 354 nm respectively.
The band gap energy (Eg) of ZnO and Ag/ZnO nanoparticles was calculated by using the
formula
Eg=
ℎ𝑐
𝜆
Where h = Planck’s constant, c = velocity of light and λ = wavelength.
𝑚
h = 6.623𝑥10−34 Js, c=3× 𝑥108
hc =6.623𝑥10−34 JsX3× 𝑥108
𝑠
𝑚
𝑠
, Where
=19.869X10-26Jm
For any λ there is a prefix n=10-9m
Therefore , hc=19.869X10-26Jm/10-9m=19.869X10-17J.
If 1J= 6.242X1018eV
19.869X10-17J=X
It can be seen that the result is =1240eV
Now Eg =
1240
𝜆
eV[The band gap energy equation]
16
1.09
ZnO
1.08
1.07
absorbance
1.06
1.05
1.04
1.03
1.02
1.01
1
0.99
350
400
450
wavelengeth(nm)
500
550
Wave length(nm)
Figure 1: Optical absorption spectra of undoped ZnO nanoparticles at temperature of 500℃
From this Uv –vis data
The energy band gap of synthesized ZnO is:
ℎ𝑐
1240
Eg= 𝜆 eV= 352 eV=3.52eV
17
0.065
Ag/ZnO
0.06
0.055
absorbance
0.05
0.045
0.04
0.035
0.03
0.025
0.02
0.015
350
400
450
wavelength(nm)
500
550
Figure 2: Optical absorption spectra of Ag:ZnO nanoparticles at nanoparticles at 500℃
From the above figure the energy band gap of synthesized AgZnO is:
ℎ𝑐 1240
Eg= 𝜆 = 356 eV=3.48eV
It can be observed clearly from figures that the band gap energy decreases from 3.52 eV to
3.48 eV when pure zinc oxide nanoparticle doped with silver metal at temperature of 400
℃. The decrease in band gap indicate that the role of silver(A)g ZnO nanoparticless. The
metal silver(Ag) are dispersed into ZnO and these metallic particles rest on the surface of
ZnO nanocomposite increase the surface area more and this type of composite nanorods
has an important implication for various industrial applications.
18
Table 1: Band gap energy of pure ZnO and Ag /doped ZnO nanoparticles at a
temperature of 500℃
Band Gap( eV )
Temperature(℃)
500℃
4.1.2
Pure ZnO
Ag doped ZnO
3.52
3.48
XRD Analysis
The XRD patterns of calcined pure ZnO and Ag/ZnO nanoparticles are shown in Figure
3.The diffraction peaks observed at scattering angle 2θ of 320, 34.6o, 36.319o, 47.8o, 56.8o,
63o and 68.5o represent typical hexagonal wurtzite structure of ZnO corresponds to
e reflection from (100), (002), (101), (102), (110), (103) and (001) crystal planes for all
synthesized powders suggesting pure hexagonal wurtzite structure of ZnO (Chen et al.,
2008)
Figure 3: XRD spectra of ZnO and Ag-doped ZnO nanoparticles.
19
The XRD pattern of Ag-ZnO also showed similar peak with the undoped ZnO. This
indicates that the crystals structure of Ag/ZnO exhibits the wurtzite structure as well.
Moreover, additional peak is observed at 2θ of 38.1o evidencing the presence of Ag in the
doped ZnO case. The diffraction peak patterns in both ZnO and Ag-ZnO were identical in
respect of their position. (Tesfaye et al.,2013).
The average crystallite size can be determined through Full-width at Half Maximum
(FWHM) of X-Ray diffraction peak by using Debye-Scherer’s equation as.
𝐷=
0.9𝜆
𝛽𝐶𝑂𝑆Ө
Where D is the average crystal size, λ is the wave length of X-ray =0.15406 nm for copper
(Cu) target Kα radiation, β is the full width at half –maximum of XRD peak and Ө is the
Bragg’s diffraction angle. The most intense peaks occurred at 2Ө=36.262o, 36.319o for
ZnO and Ag/ZnO respectively. The respective average crystallite sizes (D) of the
nanoparticles were calculated based on the most intense peaks and the values are given in
table 2.
Table 2: The calculated average crystallite size (D) of the nanoparticles
Samples
2⍬(degree)
β (radian)
D(nm)
ZnO
36.262
0.0072256662
20.19
Ag/ZnO
36.319
0.0064053611
22.78
It can be seen that the average size of nanoparticles decreased when pure ZnO
nanoparticles doped with silver metal. It also indicates that the nano crystal size of
synthesized silver doped zinc oxide nanoparticle is in the range of naano sized( i.e
between 1nm – 100nm). The calculated values of particles size are presented in Table- 3
for pure ZnO and Ag:ZnO doped at 500℃. The particles size at 500℃ is about 20.19 nm
for undoped ZnO; while 22.78 nm for Ag doped ZnO respectively.
20
5.
SUMMARY AND CONCLUSION
Zinc oxide (ZnO) nanoparticles were synthesized using a precipitation method
using
a
reaction between [ZnSO4.6H2O] and [NaOH] in aqueous solutions with proper
concentration
of
the reactants.
Ag/ZnO nanoparticle was synthesized by mixing the
synthesized ZnO nanoparticles and aqueous solution of silver nitrate. The prepared
nanoparticles were characterized by X-ray diffraction and UV-visible absorption. From
the XRD data the nano crystal size of Ag:ZnO is 22.78 nm which is between 1- 100nm.
From this result we conclude that the synthesized Ag:ZnO was a nanoparticle. The XRD
results indicate that all compositions of the synthesized nanoparticles give pure hexagonal
wurtzite crystalline structure. The incorporation of Ag+ in the site of Zn2+ provoked an
increase in the size of nanocrystals as compared to pure ZnO.
21
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26
7. APPENDICES
Table1.UV-Vis data of ZnO nanoparticles
Wavelength Scan 1
Scan Wavelength: 350.0 nm - 550.0 nm Test Mode: Abs Mode
Peak/Valley Data Record
No. Wavelength(nm) Abs
Trans(%T) Energy
Energy(100%T) Energy(0%T)
No Peak/Valley Data.
Wavelength Scan Data Record
No. Wavelength(nm)
1
550
2
548
3
546
4
544
5
542
6
540
7
538
8
536
9
534
10
532
11
530
12
528
13
526
14
524
15
522
16
520
17
518
18
516
19
514
20
512
21
510
22
508
23
506
24
504
25
502
26
500
27
498
28
496
29
494
30
492
31
490
Trans(%T) Energy
Energy(100%T Energy(0%T)
0.991
10.2
2711
25897
0.992
10.2
2665
25467
0.992
10.2
2595
24779
0.994
10.2
2461
23567
0.994
10.1
2313
22151
0.995
10.1
2149
20571
0.996
10.1
1997
19071
0.996
10.1
3687
35453
0.997
10.1
3473
33405
0.998
10.1
3311
31873
0.998
10
3199
30765
0.999
10
3145
30333
1.001
10
3139
30359
1.002
10
3141
30487
1.003
9.9
3123
30403
1.004
9.9
3095
30159
1.005
9.9
3061
29829
1.005
9.9
3015
29455
1.006
9.9
2977
29061
1.006
9.9
2933
28643
1.007
9.8
2875
28211
1.008
9.8
2835
27783
1.009
9.8
2789
27341
1.009
9.8
2741
26921
1.01
9.8
2695
26505
1.011
9.8
2651
26085
1.011
9.7
2607
25671
1.011
9.7
2571
25279
1.012
9.7
2525
24833
1.012
9.7
2477
24373
1.012
9.7
2439
23925
27
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
488
486
484
482
480
478
476
474
472
470
468
466
464
462
460
458
456
454
452
450
448
446
444
442
440
438
436
434
432
430
428
426
424
422
420
418
416
414
412
410
408
406
404
402
400
398
1.013
1.013
1.014
1.015
1.015
1.015
1.016
1.017
1.018
1.018
1.019
1.02
1.021
1.022
1.023
1.023
1.024
1.024
1.024
1.025
1.027
1.028
1.028
1.029
1.029
1.03
1.031
1.031
1.032
1.033
1.033
1.034
1.035
1.036
1.037
1.038
1.039
1.04
1.041
1.042
1.042
1.043
1.044
1.045
1.047
1.048
9.7
9.7
9.7
9.7
9.7
9.7
9.6
9.6
9.6
9.6
9.6
9.6
9.5
9.5
9.5
9.5
9.5
9.5
9.5
9.4
9.4
9.4
9.4
9.4
9.3
9.3
9.3
9.3
9.3
9.3
9.3
9.2
9.2
9.2
9.2
9.2
9.1
9.1
9.1
9.1
9.1
9.1
9
9
9
9
2389
2347
2299
2257
2209
2175
2137
2087
2039
1991
1947
1895
3633
3511
3407
3293
3185
3067
2951
2837
3515
1835
1887
1935
1969
1989
2001
2013
2019
2017
2011
1997
1981
1951
1925
1885
1843
1797
3467
3369
3271
3161
3055
2943
2817
2705
23511
23083
22651
22249
21775
21377
20991
20575
20127
19657
19205
18681
36209
35069
33977
32847
31711
30471
29243
28163
35457
18397
19029
19513
19877
20143
20341
20481
20573
20583
20527
20421
20275
20037
19769
19395
18989
18535
36093
35087
34029
32907
31761
30611
29345
28193
28
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
396
394
392
390
388
386
384
382
380
378
376
374
372
370
368
366
364
362
360
358
356
354
352
350
1.049
1.051
1.053
1.054
1.057
1.059
1.06
1.061
1.062
1.056
1.057
1.061
1.064
1.066
1.067
1.069
1.071
1.072
1.073
1.074
1.078
1.091
1.092
1.061
8.9
8.9
8.9
8.8
8.8
8.7
8.7
8.7
8.7
8.7
8.8
8.9
9
9.2
9.3
9.4
9.5
9.6
9.7
9.8
9.8
9.9
9.9
10
2581
2471
2339
2217
2081
1955
1827
3431
3217
3031
2865
2741
2609
2489
3661
3789
3891
3949
3973
3951
3911
3849
3757
3673
26877
25669
24333
23039
21617
20323
18963
35461
32941
30745
28575
26749
24867
23267
31795
32793
33451
33685
33563
33175
32531
31743
30705
29691
29
Table 1 UV –Vis Data of Ag/ZnO
Wavelength Scan 1
Scan Wavelength: 350.0 nm - 550.0 nm Test Mode: Abs Mode
Peak/Valley Data Record
No. Wavelength(nm) Abs
Trans(%T) Energy
Energy(100%T) Energy(0%T)
No Peak/Valley Data.
Wavelength Scan Data Record
No. Wavelength(nm)
1
550
2
548
3
546
4
544
5
542
6
540
7
538
8
536
9
534
10
532
11
530
12
528
13
526
14
524
15
522
16
520
17
518
18
516
19
514
20
512
21
510
22
508
23
506
24
504
25
502
26
500
27
498
28
496
29
494
30
492
31
490
32
488
Trans(%T) Energy
Energy(100%T) Energy(0%T)
0.014
96.8
24993
25807
0.014
96.8
24547
25347
0.014
96.8
23845
24629
0.014
96.8
22723
23469
0.014
96.8
21287
21993
0.014
96.8
19759
20415
0.014
96.8
18343
18951
0.014
96.7
17023
17593
0.014
96.7
32149
33227
0.014
96.7
30627
31661
0.015
96.7
29571
30587
0.015
96.7
29191
30193
0.015
96.6
29239
30251
0.015
96.6
29353
30379
0.015
96.6
29237
30267
0.015
96.6
28981
29999
0.015
96.6
28663
29667
0.015
96.6
28291
29285
0.015
96.6
27933
28919
0.015
96.6
27513
28489
0.015
96.5
27075
28041
0.015
96.5
26659
27623
0.016
96.5
26225
27177
0.016
96.5
25835
26779
0.016
96.4
25411
26353
0.016
96.4
24991
25923
0.016
96.3
24591
25525
0.016
96.4
24201
25111
0.016
96.3
23771
24681
0.017
96.2
23319
24225
0.017
96.2
22917
23807
0.017
96.2
22479
23363
30
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
486
484
482
480
478
476
474
472
470
468
466
464
462
460
458
456
454
452
450
448
446
444
442
440
438
436
434
432
430
428
426
424
422
420
418
416
414
412
410
408
406
404
402
400
398
396
0.017
0.017
0.017
0.017
0.018
0.018
0.018
0.018
0.018
0.018
0.019
0.019
0.019
0.019
0.019
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.021
0.021
0.021
0.021
0.021
0.022
0.022
0.022
0.022
0.022
0.022
0.022
0.022
0.023
0.023
0.023
0.023
0.024
0.024
0.025
0.025
0.026
0.026
0.026
96.2
96.1
96.1
96.1
96
96
96
95.9
95.9
95.8
95.8
95.7
95.7
95.7
95.6
95.6
95.5
95.5
95.5
95.5
95.4
95.4
95.3
95.3
95.2
95.2
95.2
95.1
95.2
95.2
95.1
95.1
95
95
95
94.9
94.9
94.8
94.8
94.7
94.6
94.5
94.4
94.3
94.2
94.1
22049
21643
21235
20805
20397
20035
19615
19163
18713
18257
17771
17221
16697
32237
31217
30047
28833
27689
26601
32031
16605
17157
17579
17875
18109
18257
18365
18405
18395
18335
18209
18051
17833
17571
17247
16851
16453
31927
31073
30051
29051
27949
26941
25765
24691
23531
22921
22509
22089
21655
21239
20875
20435
19977
19515
19047
18549
17985
17445
33683
32633
31431
30179
28975
27857
33529
17397
17977
18445
18753
19007
19167
19285
19339
19325
19263
19149
18985
18765
18497
18157
17751
17333
33659
32767
31719
30701
29571
28529
27317
26201
24987
31
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
394
392
390
388
386
384
382
380
378
376
374
372
370
368
366
364
362
360
358
356
354
352
350
0.027
0.027
0.028
0.029
0.029
0.03
0.031
0.031
0.032
0.033
0.034
0.034
0.035
0.037
0.038
0.049
0.058
0.062
0.065
0.068
0.062
0.058
0.052
94
93.9
93.8
93.6
93.5
93.4
93.2
93
92.9
92.7
92.6
92.5
92.3
91.9
91.7
91.4
91.1
90.6
90.1
89.5
88.8
88
87.1
22397
21223
20021
18781
17575
16405
30549
28387
26397
24541
22871
21289
19839
27323
28119
28535
28601
28343
27835
27105
26235
25181
24073
23805
22589
21335
20049
18789
17559
32753
30491
28395
26435
24679
22995
21459
29677
30601
31153
31339
31223
30831
30223
29469
28533
27527
32
*
figure1 1XRD-data of ZnO nanoparticles
33
figure1 2 XRD-data
of Ag/ZnO nanoparticles