Research Article Synthesis and Characterization of ZnO/ZnS ...downloads.hindawi.com/journals/jnm/2014/989632.pdf · Synthesis of ZnO/ZnS Core/Shell Nanoparticles. To pre-pare ZnO/ZnS

Research ArticleSynthesis and Characterization of ZnOZnSCoreShell Nanowires

Taher Ghrib12 Muneera Abdullah Al-Messiere1 and Amal Lafi Al-Otaibi1

1 Laboratory of Physical Alloys (LPA) Science Faculty of Dammam Dammam University PO Box 1982-31441Dammam Saudi Arabia

2 Laboratory of Photovoltaic Semiconductors and Nanostructures (LPSN) Technopole Borj-Cedria BP 901Hammam-Lif 2050 Tunisia

Correspondence should be addressed to Taher Ghrib taherghribyahoofr

Received 24 September 2013 Revised 11 January 2014 Accepted 15 January 2014 Published 26 February 2014

Academic Editor Yanbao Zhao

Copyright copy 2014 Taher Ghrib et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

ZnO nanowires of approximately 3 120583m length and 200 nm diameter are prepared and implanted vertically on substrate glass whichis coated with thin layer of ITOwhich is too covered with bulk ZnO thin layer via electrodeposition process by cyclic voltammetry-chronoamperometry and with a chemical process that is described later we have synthesized a ZnS nanolayer ZnOZnS coreshellnanowires are formed by ZnO nanowires core surrounded by a very thin layer of porous ZnS shell principally constituted witha crystal which is about 15ndash20 nm in diameter In the method ZnS nanoparticles were prepared by reaction of ZnO nanowireswith Na

2S in aqueous solution at low temperature and also we have discussed the growth mechanism of ZnOZnS nanowires

The morphology structure and composition of the obtained nanostructures were obtained by using X-ray diffraction (XRD)scanning electron microscopy (SEM) transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) Forthe structure SEM and XRD measurements indicated that the as-grown ZnO nanowires microscale was of hexagonal wurtzitephase with a high crystalline quality and TEM shows that the ZnS is uniformly distributed on the surface of the ZnO nanowires

1 Introduction

The physical and chemical characteristics of the materialremain the functioning soul of devices dedicated to industrialand societal needs in the information and health field Inthese last years investigations are oriented heavily in creationsof new materials The diversity of their properties is mainlydue to recent advances in technology development structur-ing emergence of new properties related to the size effectinterfaces stability and electrical and optical properties

Otherwise the surface treatment has experienced majoradvances combining scientific and technical research needsfor their industrial importance in everyday life and especiallythe deposition of thin nanostructured alloys which hasknown good success and high efficiency [1]

Many techniques have been tried to create thin nanos-tructured layers [2 3] including those that are expensivethose that are difficult and those that are very sensitiveand require a lot of very accurate monitoring equipment

which are mostly not unavailable in the majority of lab-oratories From these new composites which have gainedmuch importance we can cite ZnO nanowires that have beenrecognized as one of the most promising nanomaterials dueto their various properties and applications [4ndash7] As themostimportant semiconductor material ZnO possesses a widedirect band gap strong piezoelectric properties and a largebinding energy

Modification of ZnO properties by impurity incorpora-tion and surface coating is currently another important issuefor possible applications in ultraviolet optoelectronics andspintronics [8ndash10] For semiconductor materials doping withdifferent elements can adjust its electrical optical [11 12] andmagnetic properties [13ndash19] Surface modification has beenrecognized as one of the most advanced methods to buildtailored materials which are nanostructured effective andreliable [16ndash22]

Also ZnSmaterial is a well-knownmaterial which has animportant wide band gap semiconductor that allows it to be

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2014 Article ID 989632 8 pageshttpdxdoiorg1011552014989632

2 Journal of Nanomaterials

12 3

4

5

Figure 1 Experimental setup 1mdashworking electrode 2mdashagainst electrode 3mdashreference electrode 4mdashPotentiostat and 5mdashchemical solution

applied in several areas such as optical [10ndash12] photocatalyst[20] and photovoltaic devices [23]

Furthermore coreshell structured ZnOZnS nanowireshave been demonstrated to possess improved physical andchemical properties for electronics magnetism optics catal-ysis and other applications Therefore considerable efforthas been devoted to the design and controlled fabrication ofcoreshell structured ZnOZnS nanowires Up to now differ-ent preparationmethods have been explored for the synthesisof ZnO and ZnS nanowires and different morphologies wereobtained

In this study we report the growth of vertically well-aligned ZnO nanowires by cathodic electrodeposition inaqueous zinc chloride electrolyte moreover and after weproduce nanocomposites of ZnOZnS by partial conversionvia a sulfidation operation in surfaces ZnO nanowires whichreacts with Na

2S that is used as sulphur source By this simple

chemical method ZnO nanowires can be partially con-verted to ZnOZnS nanocomposites The structural electri-cal morphological and optical properties of ZnO nanowiresand ZnOZnS nanocomposites are studied in detail whichshowed the production of a material that is more efficientthan that produced in other works

2 Experimental Study

21 Materials The experimental setup used to synthe-size ZnO nanowires consists of the following elements(Figure 1) Auto Lab PGSTAT-30 (potentiostatgalvanostat)which involves three electrodes such as a platinum rodserved as against electrode a saturated silversilver chloride(AgAgCl in saturated KCl) was used as a reference electrodeand a polycrystalline glass coated with Sn-doped In

2O3

(ITO) was used as a substrate named working electrodeTheelectrolyte was an aqueous solution of ZnCl

2(5 times 10minus4M)

and KCl (01M) saturated with oxygen bubbled for 45minbefore and remains there during the experience Ultrapure

water (18MΩsdotcm) was provided by a Millipore setup Anhy-drous ZnCl

2salt (Aldrich purity gt 980) was used as the

Zn2+ precursor KCl (Aldrich purity gt 995) served as asupporting electrolyte Sodium sulfide (Na

2Ssdot119909H2O) used

for sulfidation conversion of ZnO Nanowires to ZnOZnScoreshell nanocomposites The chemicals were purchasedfrom Aldrich Chemical Corporation and used without fur-ther purification

22 Used Devices for Characterizations The morphologyof the produced ZnO nanowires and ZnOZnS coreshellnanocomposites was studied by transmission electronmicroscopy (TEM) performed on a JEOL 2100F microscopeoperating at 200 kV

The structures of the produced ZnO nanowires wascharacterized by X-ray diffraction (XRD) using a PANalyticalEmpyrean equipped with a multichannel detector (Pixel 3D)using (CuK120572 45 kV-40mA) radiation in the 20ndash90∘ 2120579 rangewith a scan step of 0026∘ for 297 s A five-axe cradle withmotorized movements is used to obtain a perfectly plannedposition of the sample and amirror with a 116∘ slit is installedin the incident path to form a parallel beam necessary toanalyze the samples in grazing incident beam (GIXRD)

The microstructure was analyzed using a Supra40 ZEISSfield emission gun scanning electronmicroscope (FEG-SEM)operating at 5 kV We observed samples with an in-lensdetectorThe composition of the coating was analyzed using aJeol 6510 scanning electronmicroscope (SEM) equippedwithan SDD (Silicon Drift Diode) detector and operating at 10 kVThe software to obtain the EDX spectrum is IridiumUltra TMSpectra with constant time of 16 and a preset time of 50

The UV-visible diffuse reflectance spectra of ZnOnanowires and ZnOZnS coreshell nanocomposites wererecorded on a Perkin Elmer-Lambda 1050 spectrophotometerequipped with a PTFE coated integration sphere

Surface composition was further investigated by X-rayphotoelectron spectroscopy (XPS) measurements using

Journal of Nanomaterials 3

O

O ZnOOxygen

adsorptionOxygen

reductionO2

minusH2O

+Zn2+

OH

minusO

Hminus

Figure 2 ZnO forming process

Curr

ent (

mA

)

Electrodeposition duration (times103 s)

05

00

minus05

minus10

minus15

minus20

minus25

minus30

minus35

0 1 2 3 4 5 6 7 8 9

Figure 3 Current variation versus the electrodeposition duration

a Thermo VG ESCALAB 250 instrument equipped witha microfocused monochromatic Al K120572 X-ray source(14866 eV) and a magnetic lens The X-ray spot size was500120583m (15 kV 150W) The spectra were acquired in theconstant analyzer energy mode with pass energy of 150and 40 eV for the general survey and the narrow scansrespectively The sample was fixed on holder using adhesivetapes with double sides and rapidly returned in the airlockfor at least 5 hours at 2 times 10minus7mbar or better The ldquoAvantagerdquosoftware version 467 was used for data acquisition andprocessing

23 Synthesis of ZnO Nanowires Before electrodepositionITO substrates were cleaned by a chemical product suchas the trichlorethylene acetone isopropanol alcohol andpure water under the ultrasonic treatment and ITO is set asworking electrode

In our technique the first necessary step (Figure 2) isto reduce oxygen that is fully filled in the solution Theelectrochemical reduction of oxygen depends on the pH ofthe solution [24] At pH gt 6 there is formation of OHminusaccording to the following reaction (1)

O2+ 2H2O + 4eminus 997888rarr 4OHminus (1)

These OHminus ions are absorbed by the working electrodesurface ZnCl

2dissociates in several species such as Zn2+ and

Zn(OH)119909Cl119910[25] which react with the OHminus adsorbed on the

cathode When conditions are optimized ZnO is depositedat the cathode according to the following reaction (2)

Zn2+ + 2OHminus 997888rarr ZnO +H2O (2)

In a first step a solution of distilledwater containing 01MKCl and 5times10minus3MZnCl

2which was purchased fromAldrich

Inc A constant cathodic current (119869 = minus013mAcm2)is applied for 2500 s at room temperature and the resultis simply a ZnO thin film on a 2 cm2 geometric surfaceThe grown thin layers are annealed at 100∘C for 10minwhich gives a buffer layer on which are deposited nanowiresZnO ZnO nanowire arrays were electrodeposited under aconstant potential (minus1 V) and the galvanostat potentiostat issettled in chronoamperometric mode The potentiostat wasmonitored by the Auto Lab software The compact thin layerwas deposited at 25∘C while the nanowires were obtainedat 80∘C Note that the deposition conditions used to obtainZnO nanowires namely 119881 = minus1V versus SCE 119879 = 80∘C[ZnCl

2] = 5 times 10minus4M and [KCl] = 01M are named ldquostandard

conditionsrdquo in this paperThe variation of the current measured between working

and against electrodes evolves as shown in Figure 3 We notethat this curve is essentially composed of two parts the firstpart gives a rapid decrease of the current intensity stagegiving the formation of the first ZnO grains and the secondpart is a horizontal portion giving the step of ZnO forming

The four-point probe measurements demonstrated goodconductivity of the ZnO nanowires with surface resistivity ofasymp 5sdot10

minus3Ωsdotcmwhich permits us to conclude that the formed

nanowires can be classified as a good conductor

24 Synthesis of ZnOZnS CoreShell Nanoparticles To pre-pare ZnOZnS coreshell nanowires arrays we use ZnOnanowires that will be put into a glass bottle containing032molsdotLminus1 Na

2S aqueous solution this is the sulfidation

that will remain for 4 h at 60∘CThe final product was washed


(a)

(b)

(c)

Figure 4 SEM images of ZnO nanowires (a) top view (b) cross section view and (c) one ZnO nanowire

with deionized water repeatedly to remove the possibleimpurities and then dried at 80∘C for 2 h before being studiedThe exchange of a thin layer from ZnO nanowires to ZnS isdone in three steps

Na2S salt decomposes in aqueous solution with Na+ and

S2minus ions as follows

Na2S

H2O997888rarr 2Na+ + S2minus (3)

A thin layer of ZnO nanowires reacts with hydroxideions (HOminus) present in the aqueous solution according to thefollowing reaction equation

ZnO + 2HOminus 997888rarr ZnO2

2minus+H2O (4)

which allows the exchange of the stable ZnO molecules withthe unstable ZnO

2

2minus ionsThis ZnO

2

2minus ions react with S2minus ions giving the expectedZnS as follows

ZnO2

2minus+ S2 minus + 2H

2O 997888rarr ZnS + 4HOminus (5)

Thereby there are forming ZnS nanoparticles that willcover ZnO nanowires in which the final structure is calledZnOZnS coreshell

3 Results and Discussion

The morphology of ZnO and ZnOZnS coreshell nanos-tructures observed by SEM is shown in Figure 4 From thisfigures we observe that the highly ordered ZnO nanowiresare grown at the ITOZnO substrate and tend to be perpen-dicular theretoWe also note that the section of eachnanowireformed is of hexagonal shape (Figure 4(b)) which proves thatthe finest method was used to produce ZnO nanowires

Figure 5 shows the composition of ZnOZn coreshellnanowires determined by the XPS The peaks located at162 eV 532 eV 1022 eV and 1045 eV are respectively dueto the S(2p) O(1s) Zn(2p32) and Zn(2p12) bindingenergies for XPS spectrum concerning the as-producedZnOZnS coreshell nanostructures on substrate constituted

by (ITOZnO thin film) By measuring peaks areas we candeduce the atomic percentages of each element present in theformed structure This atomic percentage is summarized inTable 1 when we find elements corresponding to the peaksand comprised in established nanowires and we provide thesuccessful sulfidation of S elements into ZnO nanowiresAlso we notice the existence of carbon which may be acontaminant in the sample and indium traces arising fromthe substrate

In order to confirm the chemical composition of theobtained products we have employed the EDX and XRDspectroscopy to analyze the synthesized products XRDcharacterization can establish the crystal structure of theobtained products Its spectrum shown in Figure 6 givespeaks corresponding to the ITO glass substrate and peaks ofthese ZnO nanowires which can be readily related to hexag-onal structure with cell constant 119886 = 324A∘ and 119888 = 519A∘characterizing the wurtzite structure (Joint Committee forPowder Diffraction Standards (JCPDS) number 36-1451)

And for the ZnO nanowires spectrum the existence ofthe (002) peak at the smaller angle (345∘) shows that thisorientation is the most dominant that is these preparednanowires are quasialigned along 119888-axis

The morphology of ZnOZnS coreshell nanostructuresobserved by SEM is shown in Figure 7(a) We note theexistence of a layer having a form apparently less dense orarising from a product different than that of ZnO and alsoothers Figures 7(b) and 7(c) present respectively the TEM(b)HRTEM(c) and the corresponding selected area electrondiffraction (SAED) pattern (d) images of thin ZnS coatingdeposited onto ZnO nanowire obtained after 1 h duration ofinsertion within which the ZnO nanowires appear with adiameter of about 193 nm surrounded by a thin ZnS layerof 18 nm thick In SAED pattern we observe three diffractionrings corresponding to the (111) (220) and (311) planes of zincblende ZnS and also it should be noted that the diffractionrings in the SAED pattern are discontinuous and consist ofrather sharp spots which indicates that the nanowires arewellcrystallized

Figure 8 shows the UV-Vis absorption spectra of ZnOand ZnOZnS coreshell nanowires we can see that for both


0 200 400 600 800 10000

Zn2p12

Inte

nsity

(au

)

Binding energy (eV)

Unannealed sample

Zn2p32

S2p

O1s

In3dC1s

times104

25

20

15

10

5

(a)

156 158 160 162 164 166 168 170 172

Inte

nsity

(au

)

Binding energy (eV)

S2p

S2p

times103

11

10

9

8

7

6

5

4

3

2

(b)

524 526 528 530 532 534 536 538 540

Inte

nsity

(au

)

Binding energy (eV)

O1s

O1s

times103

19

18

17

16

15

14

13

12

(c)

1015 1020 1025 1030 1035 1040 1045 1050

Zn2p12

Inte

nsity

(au

)

Binding energy (eV)

Zn2p

Zn2p32times10

4

10

9

8

7

6

5

4

3

2

(d)

Figure 5 XPS spectra for the ZnOZnS coreshell nanostructures

Table 1 Experimental data for peaks of ZnOZnS nanowires

Name Peak BE FWHM eV Area (P) CPSsdoteV AtC1s 28504 155 1459449 4197In3d 44461 174 710011 094Na1s 107249 002 98724 047O1s 53187 213 1382391 1439S2p 16167 208 1415420 2384Zn2p 102217 164 13678995 1840


20 30 40 50 60 700

1000ZnOITO

ITO

I (au

)

ZnOITOITO

(002

) (101

)

(102

)

(110

)

(103

)

(112

)(2

01)

2120579 (∘)

Figure 6 XRD spectra of the ITO substrate and the ZnO nanowires

100nm

(a)

100nm

(b)

100nm

(c)

100nm

(d)

Figure 7 (a) SEM image (b) TEM image (c) HRTEM image and (d) selected area electron diffraction (SAED) pattern image from (c) ofZnOZnS coreshell nanowires


200 300 400 500 600 700 800

045

050

055

060

065

Wavelength (nm)

ZnOZnOZnS

Abso

rban

ce (a

u)

Figure 8 UV-visible spectra of ZnO and ZnOZns coreshellnanowires

materials the absorption is higher in the UV range mainly inthe vicinity of 280 nm when it passes through a maximumand we remark in the visible range an intensity improvementafter the sulfidation operation This feeble shift is mayberelated to the quantum size effects imposed by the ZnS thinlayer having a thickness in the order of 18 nm

From the results of electrical conductivity XRD SEMand UV-Vis analyses for ZnOZnS coreshell nanowires wenote that they have a very high quality which can be appliedon the electrode of solar cell to improve its efficiency

4 Conclusion

In summary ZnO nanowires of approximately 3 120583m lengthand 200 nm diameter are prepared and implanted verticallyon (ITOZnO thin layer) substrates via electrodepositionprocess and these nanowires have been covered by a ZnSthin film of about 20 nm thick using a sulfidation processXRD SEM TEM and HRTEM results confirm the existenceof the ZnOZnS coreshell nanocomposite The electricalconductivity structural properties and UV-visible studyreveal that the prepared nanowires have high quality whichcan be applied on the electrode of solar cell

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors are pleased to acknowledge the financial supportof this study by the Scientific ResearchDeanship ofDammamUniversity under Project no 2013196 The authors alsoacknowledge Pr Radhouan Chtourou Leader of Labora-tory of Photovoltaic Semiconductors and Nanostructures

in Technopole Borj-Cedria for his scientific advices Theauthors give their thanks to Mr Amine Brayek for his helpin making some measurements

References

[1] T Gao Q Li and T Wang ldquoSonochemical synthesis opticalproperties and electrical properties of coreshell-type ZnOnanorodCdS nanoparticle compositesrdquoChemistry ofMaterialsvol 17 pp 887ndash892 2005

[2] J J Wu and S C Liu ldquoLow-temperature growth of well-alignedZnO nanorods by chemical vapor depositionrdquo Advanced Mate-rials vol 14 no 3 pp 215ndash218 2002

[3] L Guo Y L Ji and H B Xu ldquoRegularly shaped single-crystalline ZnO nanorods with wurtzite structurerdquo Journal ofthe American Chemical Society vol 124 pp 14864ndash14865 2002

[4] N W Emanetoglu C Gorla Y Liu S Liang and Y LuldquoEpitaxial ZnO piezoelectric thin films for saw filtersrdquoMaterialsScience in Semiconductor Processing vol 2 no 3 pp 247ndash2521999

[5] N Saito H Haneda T Sekiguchi N Ohashi I Sakaguchi andK Koumoto ldquoZinc oxide micropatterns using self assembledmonolayersrdquo Advanced Materials vol 14 pp 418ndash421 2002

[6] S Liang H Sheng Y Liu Z Hio Y Lu and H Shen ldquoZnOSchottky ultraviolet photodetectorsrdquo Journal of Crystal Growthvol 225 pp 110ndash113 2001

[7] Y Lin Z Zhang Z Tang F Yuan and J Li ldquoCharacterisationof ZnO-based varistors prepared from nanometre Precursorpowdersrdquo Advanced Materials for Optics and Electronics vol 9pp 205ndash209 1999

[8] Y XiaodanWQingyin J Shicheng andG Yihang ldquoNanoscaleZnSTiO

2composites preparation characterization and

visible-light photocatalytic activityrdquoMaterials Characterizationvol 57 no 4-5 pp 333ndash341 2006

[9] Z LWang ldquoNanostructures of zinc oxiderdquoMaterials Today vol7 no 6 pp 26ndash33 2004

[10] Y Ding and Z L Wang ldquoStructure analysis of nanowiresand nanobelts by transmission electron microscopyrdquo Journal ofPhysical Chemistry B vol 108 no 33 pp 12280ndash12291 2004

[11] M Bredol and J Merikhi ldquoZnS precipitation morphologycontrolrdquo Journal of Materials Science vol 33 no 2 pp 471ndash4761998

[12] G Sharma S D Han J D Kim S P Khatkar and Y WooRhee ldquoElectroluminescent efficiency of alternating currentthick film devices using ZnSCuCl phosphorrdquoMaterials Scienceand Engineering B vol 131 no 1ndash3 pp 271ndash276 2006

[13] P T Snee R C Somers G Nair J P Zimmer M G Bawendiand D G Nocera ldquoA ratiometric CdSeZnS nanocrystal pHsensorrdquo Journal of the American Chemical Society vol 128 no41 pp 13320ndash13321 2006

[14] A Ohtomo M Kawasaki T Koida et al ldquoMgxZn1-xO as a II-VI widegap semiconductor alloyrdquo Applied Physics Letters vol72 no 19 pp 2466ndash2468 1998

[15] T Dietl H Ohno F Matsukura J Cibert and D FerrandldquoZener model description of ferromagnetism in zinc-blendemagnetic semiconductorsrdquo Science vol 287 no 5455 pp 1019ndash1022 2000

[16] J H Li Y C Liu C L Shao et al ldquoEffects of thermal anneal-ing on the structural and optical properties of MgxZn1-xOnanocrystalsrdquo Journal of Colloid and Interface Science vol 283no 2 pp 513ndash517 2005


[17] Y W Chen Y C Liu and S X Lu ldquoOptical properties of ZnOand ZnO in nanorods assembled by sol-gel methodrdquo Journal ofChemical Physics vol 123 Article ID 134701 2005

[18] J J Liu M H Yu and W L Zhou ldquo Well-aligned Mn-dopedZnO nanowires synthesized by a chemical vapor depositionmethodrdquoApplied Physics Letters vol 87 Article ID 172505 2005

[19] G Shen J H Cho J K Yoo G-C Yi and C J Lee ldquoSynthesisand optical properties of S-doped ZnO nanostructures nanon-ails and nanowiresrdquo Journal of Physical Chemistry B vol 109 no12 pp 5491ndash5496 2005

[20] TV Prevenslik ldquoAcoustoluminescence and sonoluminescencerdquoJournal of Luminescence vol 87 pp 1210ndash1212 2000

[21] Y-Z Yoo Z-W Jin TChikyowT FukumuraMKawasaki andH Koinuma ldquoS doping in ZnO film by supplying ZnS specieswith pulsed-laser-deposition methodrdquo Applied Physics Lettersvol 81 no 20 pp 3798ndash3800 2002

[22] B Y Geng G Z Wang Z Jiang et al ldquoSynthesis and opticalproperties of S-doped ZnO nanowiresrdquo Applied Physics Lettersvol 82 no 26 pp 4791ndash4793 2003

[23] C Ye X Fang G Li and L Zhang ldquoOrigin of the green pho-toluminescence from zinc sulfide nanobeltsrdquo Applied PhysicsLetters vol 85 no 15 pp 3035ndash3037 2004

[24] S Strbac and R R Adzic ldquoThe influence of pH on reactionpathways for O

2reduction on the Au(100) facerdquo Electrochimica

Acta vol 41 no 18 pp 2903ndash2908 1996[25] A Goux T Pauporte J Chivot and D Lincot ldquoTemperature

effects on ZnO electrodepositionrdquo Electrochimica Acta vol 50no 11 pp 2239ndash2248 2005

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


12 3

4

5

Figure 1 Experimental setup 1mdashworking electrode 2mdashagainst electrode 3mdashreference electrode 4mdashPotentiostat and 5mdashchemical solution

applied in several areas such as optical [10ndash12] photocatalyst[20] and photovoltaic devices [23]

Furthermore coreshell structured ZnOZnS nanowireshave been demonstrated to possess improved physical andchemical properties for electronics magnetism optics catal-ysis and other applications Therefore considerable efforthas been devoted to the design and controlled fabrication ofcoreshell structured ZnOZnS nanowires Up to now differ-ent preparationmethods have been explored for the synthesisof ZnO and ZnS nanowires and different morphologies wereobtained

In this study we report the growth of vertically well-aligned ZnO nanowires by cathodic electrodeposition inaqueous zinc chloride electrolyte moreover and after weproduce nanocomposites of ZnOZnS by partial conversionvia a sulfidation operation in surfaces ZnO nanowires whichreacts with Na

2S that is used as sulphur source By this simple

chemical method ZnO nanowires can be partially con-verted to ZnOZnS nanocomposites The structural electri-cal morphological and optical properties of ZnO nanowiresand ZnOZnS nanocomposites are studied in detail whichshowed the production of a material that is more efficientthan that produced in other works

2 Experimental Study

21 Materials The experimental setup used to synthe-size ZnO nanowires consists of the following elements(Figure 1) Auto Lab PGSTAT-30 (potentiostatgalvanostat)which involves three electrodes such as a platinum rodserved as against electrode a saturated silversilver chloride(AgAgCl in saturated KCl) was used as a reference electrodeand a polycrystalline glass coated with Sn-doped In

2O3

(ITO) was used as a substrate named working electrodeTheelectrolyte was an aqueous solution of ZnCl

2(5 times 10minus4M)

and KCl (01M) saturated with oxygen bubbled for 45minbefore and remains there during the experience Ultrapure

water (18MΩsdotcm) was provided by a Millipore setup Anhy-drous ZnCl

2salt (Aldrich purity gt 980) was used as the

Zn2+ precursor KCl (Aldrich purity gt 995) served as asupporting electrolyte Sodium sulfide (Na

2Ssdot119909H2O) used

for sulfidation conversion of ZnO Nanowires to ZnOZnScoreshell nanocomposites The chemicals were purchasedfrom Aldrich Chemical Corporation and used without fur-ther purification

22 Used Devices for Characterizations The morphologyof the produced ZnO nanowires and ZnOZnS coreshellnanocomposites was studied by transmission electronmicroscopy (TEM) performed on a JEOL 2100F microscopeoperating at 200 kV

The structures of the produced ZnO nanowires wascharacterized by X-ray diffraction (XRD) using a PANalyticalEmpyrean equipped with a multichannel detector (Pixel 3D)using (CuK120572 45 kV-40mA) radiation in the 20ndash90∘ 2120579 rangewith a scan step of 0026∘ for 297 s A five-axe cradle withmotorized movements is used to obtain a perfectly plannedposition of the sample and amirror with a 116∘ slit is installedin the incident path to form a parallel beam necessary toanalyze the samples in grazing incident beam (GIXRD)

The microstructure was analyzed using a Supra40 ZEISSfield emission gun scanning electronmicroscope (FEG-SEM)operating at 5 kV We observed samples with an in-lensdetectorThe composition of the coating was analyzed using aJeol 6510 scanning electronmicroscope (SEM) equippedwithan SDD (Silicon Drift Diode) detector and operating at 10 kVThe software to obtain the EDX spectrum is IridiumUltra TMSpectra with constant time of 16 and a preset time of 50

The UV-visible diffuse reflectance spectra of ZnOnanowires and ZnOZnS coreshell nanocomposites wererecorded on a Perkin Elmer-Lambda 1050 spectrophotometerequipped with a PTFE coated integration sphere

Surface composition was further investigated by X-rayphotoelectron spectroscopy (XPS) measurements using


O

O ZnOOxygen

adsorptionOxygen

reductionO2

minusH2O

+Zn2+

OH

minusO

Hminus


Curr

ent (

mA

)


05

00

minus05

minus10

minus15

minus20

minus25

minus30

minus35

0 1 2 3 4 5 6 7 8 9
























(a)

(b)

(c)





Na2S




2minus+H2O (4)


2

2minus ionsThis ZnO

2


ZnO2













0 200 400 600 800 10000

Zn2p12

Inte

nsity

(au

)

Binding energy (eV)

Unannealed sample

Zn2p32

S2p

O1s

In3dC1s

times104

25

20

15

10

5

(a)

156 158 160 162 164 166 168 170 172

Inte

nsity

(au

)

Binding energy (eV)

S2p

S2p

times103

11

10

9

8

7

6

5

4

3

2

(b)

524 526 528 530 532 534 536 538 540

Inte

nsity

(au

)

Binding energy (eV)

O1s

O1s

times103

19

18

17

16

15

14

13

12

(c)

1015 1020 1025 1030 1035 1040 1045 1050

Zn2p12

Inte

nsity

(au

)

Binding energy (eV)

Zn2p

Zn2p32times10

4

10

9

8

7

6

5

4

3

2

(d)





20 30 40 50 60 700

1000ZnOITO

ITO

I (au

)

ZnOITOITO

(002

) (101

)

(102

)

(110

)

(103

)

(112

)(2

01)

2120579 (∘)


100nm

(a)

100nm

(b)

100nm

(c)

100nm

(d)



200 300 400 500 600 700 800

045

050

055

060

065

Wavelength (nm)

ZnOZnOZnS

Abso

rban

ce (a

u)




4 Conclusion




Acknowledgments



References






































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




O

O ZnOOxygen

adsorptionOxygen

reductionO2

minusH2O

+Zn2+

OH

minusO

Hminus


Curr

ent (

mA

)


05

00

minus05

minus10

minus15

minus20

minus25

minus30

minus35

0 1 2 3 4 5 6 7 8 9
























(a)

(b)

(c)





Na2S




2minus+H2O (4)


2

2minus ionsThis ZnO

2


ZnO2













0 200 400 600 800 10000

Zn2p12

Inte

nsity

(au

)

Binding energy (eV)

Unannealed sample

Zn2p32

S2p

O1s

In3dC1s

times104

25

20

15

10

5

(a)

156 158 160 162 164 166 168 170 172

Inte

nsity

(au

)

Binding energy (eV)

S2p

S2p

times103

11

10

9

8

7

6

5

4

3

2

(b)

524 526 528 530 532 534 536 538 540

Inte

nsity

(au

)

Binding energy (eV)

O1s

O1s

times103

19

18

17

16

15

14

13

12

(c)

1015 1020 1025 1030 1035 1040 1045 1050

Zn2p12

Inte

nsity

(au

)

Binding energy (eV)

Zn2p

Zn2p32times10

4

10

9

8

7

6

5

4

3

2

(d)





20 30 40 50 60 700

1000ZnOITO

ITO

I (au

)

ZnOITOITO

(002

) (101

)

(102

)

(110

)

(103

)

(112

)(2

01)

2120579 (∘)


100nm

(a)

100nm

(b)

100nm

(c)

100nm

(d)



200 300 400 500 600 700 800

045

050

055

060

065

Wavelength (nm)

ZnOZnOZnS

Abso

rban

ce (a

u)




4 Conclusion




Acknowledgments



References






































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a)

(b)

(c)





Na2S




2minus+H2O (4)


2

2minus ionsThis ZnO

2


ZnO2













0 200 400 600 800 10000

Zn2p12

Inte

nsity

(au

)

Binding energy (eV)

Unannealed sample

Zn2p32

S2p

O1s

In3dC1s

times104

25

20

15

10

5

(a)

156 158 160 162 164 166 168 170 172

Inte

nsity

(au

)

Binding energy (eV)

S2p

S2p

times103

11

10

9

8

7

6

5

4

3

2

(b)

524 526 528 530 532 534 536 538 540

Inte

nsity

(au

)

Binding energy (eV)

O1s

O1s

times103

19

18

17

16

15

14

13

12

(c)

1015 1020 1025 1030 1035 1040 1045 1050

Zn2p12

Inte

nsity

(au

)

Binding energy (eV)

Zn2p

Zn2p32times10

4

10

9

8

7

6

5

4

3

2

(d)





20 30 40 50 60 700

1000ZnOITO

ITO

I (au

)

ZnOITOITO

(002

) (101

)

(102

)

(110

)

(103

)

(112

)(2

01)

2120579 (∘)


100nm

(a)

100nm

(b)

100nm

(c)

100nm

(d)



200 300 400 500 600 700 800

045

050

055

060

065

Wavelength (nm)

ZnOZnOZnS

Abso

rban

ce (a

u)




4 Conclusion




Acknowledgments



References






































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 200 400 600 800 10000

Zn2p12

Inte

nsity

(au

)

Binding energy (eV)

Unannealed sample

Zn2p32

S2p

O1s

In3dC1s

times104

25

20

15

10

5

(a)

156 158 160 162 164 166 168 170 172

Inte

nsity

(au

)

Binding energy (eV)

S2p

S2p

times103

11

10

9

8

7

6

5

4

3

2

(b)

524 526 528 530 532 534 536 538 540

Inte

nsity

(au

)

Binding energy (eV)

O1s

O1s

times103

19

18

17

16

15

14

13

12

(c)

1015 1020 1025 1030 1035 1040 1045 1050

Zn2p12

Inte

nsity

(au

)

Binding energy (eV)

Zn2p

Zn2p32times10

4

10

9

8

7

6

5

4

3

2

(d)





20 30 40 50 60 700

1000ZnOITO

ITO

I (au

)

ZnOITOITO

(002

) (101

)

(102

)

(110

)

(103

)

(112

)(2

01)

2120579 (∘)


100nm

(a)

100nm

(b)

100nm

(c)

100nm

(d)



200 300 400 500 600 700 800

045

050

055

060

065

Wavelength (nm)

ZnOZnOZnS

Abso

rban

ce (a

u)




4 Conclusion




Acknowledgments



References






































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




20 30 40 50 60 700

1000ZnOITO

ITO

I (au

)

ZnOITOITO

(002

) (101

)

(102

)

(110

)

(103

)

(112

)(2

01)

2120579 (∘)


100nm

(a)

100nm

(b)

100nm

(c)

100nm

(d)



200 300 400 500 600 700 800

045

050

055

060

065

Wavelength (nm)

ZnOZnOZnS

Abso

rban

ce (a

u)




4 Conclusion




Acknowledgments



References






































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




200 300 400 500 600 700 800

045

050

055

060

065

Wavelength (nm)

ZnOZnOZnS

Abso

rban

ce (a

u)




4 Conclusion




Acknowledgments



References






































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Documents

Research Article Synthesis and Characterization of ZnO/ZnS ...downloads.hindawi.com/journals/jnm/2014/989632.pdf · Synthesis of ZnO/ZnS Core/Shell Nanoparticles. To pre-pare ZnO/ZnS