Research Article Highly Responsive UV Light Sensors Using Mg...

Research ArticleHighly Responsive UV Light Sensors UsingMg-Doped ZnO Nanoparticles

Mirza Shirjeel Alam1 Umair Manzoor12 Mohammad Mujahid3 and Arshad S Bhatti1

1Center for Micro and Nano Devices (CMND) Department of Physics COMSATS Institute of Information TechnologyIslamabad 44000 Pakistan2Alamoudi Water Research Chair King Saud University PO Box 2460 Riyadh 11451 Saudi Arabia3School of Chemical amp Materials Engineering (SCME) National University of Sciences amp Technology (NUST) Sector H-12Islamabad 44000 Pakistan

Correspondence should be addressed to Umair Manzoor umanzoorksuedusa

Received 30 December 2015 Revised 4 February 2016 Accepted 28 February 2016

Academic Editor Christos Riziotis

Copyright copy 2016 Mirza Shirjeel Alam et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Different concentrations of Mg-doped ZnO nanoparticles (NPs) were synthesized by coprecipitation technique at 60∘C XRDdata are used to study phase purity and crystal structure in different doping concentrations The results indicated that increasingthe doping from 0sim75 wt caused a subsequent increase in FWHM in XRD and an associated systematic shift towards higherwavelength in the optical properties Finally the sensing ofUV light is tested by observing the response of nanoparticles by exposingthem to UV light and measuring the resistance in presence and absence of UV light

1 Introduction

Oxides are now a smart choice and basis of advanced andmultifunctional devices [1] Device fabrication and synthesisusing oxides semiconductor have become more importantrecently because the physical properties are size dependentand can be tuned Among oxide semiconductor family ZnOis a wide bandgap material (337 eV at room temperature)with large exciton binding energy (60meV) and strongphotocatalytic optical and piezoelectric propertiesThey areused in solar cells photocatalysis and antibacterial activematerial [2] gas sensors [3] and UV (Ultraviolet) lightemittingdetecting devices [4] ZnO is also an integral partof green luminescence phosphor in fluorescent devices [5]

UV sensors are widely used in different applicationssuch as pollution monitoring flame sensing early missileplume detection and other advanced military applications[6] Different types of Si-based photodetectors are alreadyavailable in the market and are very sensitive with low noiseand quick response [5] However applications are limited assome need ultrahigh vacuum or high voltage supply (iein photomultipliers) or time dependent degradation and

lower efficiency [7] To overcome these disadvantages newmaterials such as diamond SiC oxide semiconductors andnitrides are a focus of research because of their intrinsicvisible-blindness Also chemical and thermal stability atoperating conditions are far better than the conventionalmaterials Moreover their optical properties are slightlytemperature dependent [8 9] One of the possible materialswhich fulfills most of these requirements is ZnO Thereforeit has been studied extensively recently to further explore itspotential applications in electronics and optoelectronics [10]Furthermore different doping in ZnO (ie Mg) can adjustbandgap to make UV photodetectors in different UV regime[11 12] Despite a great deal of research on ZnO UV detectormost of the research concentrated on the improvements of themicromask electrodes in order to enhance the performanceof the ZnO photoconductive detectors [11] ZnO sensingmechanism can be linked with surface reactions Hencegrain size defects and oxygen adsorption are importantparameters for controlling sensing response [3]

In the present study systematic Mg doping (0sim75 wt)in ZnONPs was achieved and is analysed by XRD FTIR and

Hindawi Publishing CorporationJournal of SensorsVolume 2016 Article ID 8296936 5 pageshttpdxdoiorg10115520168296936

2 Journal of Sensors

Table 1 Experimental details and chemical quantities used for the synthesis

age doping Zn(CH3

COO)2

(g) Mg(CH3

COO)2

(g) KOH (g) Ethanol (mL) Other constants (same for all experiments)1 0 1004 mdash 0990 80 Temperature 60∘C

Constant stirring 25 hoursCentrifuged to separate ZnO NPsRepeatedly washed with distilled water andethanol at 60∘C

2 25 1009 0020 1008 803 50 1007 0041 0960 804 75 1003 0078 0962 80

UV-Vis spectroscopy Optical properties were tuned by Mgdoping UV sensing properties are also demonstrated Themain focus of the study was the fast response time of Mg-doped ZnO NPs as active sensor material

2 Experimental Section

Zinc acetate dihydrate (Zn(CH3COO)

2 Sigma-Aldrich) and

1mL of water (distilled) were put into a flask containing80mL methanol They were mixed at 60∘C In a secondbeaker potassium hydroxide (KOH Sigma-Aldrich) wasdissolved in 23mL of methanolThe solution was then slowlyadded into the flasks containing zinc acetate This mixturewas then stirred for 25 hours The transparent solutionbecame opaque because of slow addition of KOH whichagain slowly transformed into a clear solution ZnO powderwas separated from the solvent by centrifuge and repeatedlywashed in distilled water and ethanol The powder was driedin convection oven at 60∘C For doping magnesium acetatedihydrate (Mg(CH

3COO)

2Sigma-Aldrich) was added in

appropriate quantities The experimental details and quanti-ties are shown in Table 1

The morphology was determined using transmissionelectron microscope (TEM JEOL) The phase analysis wasdone using X-ray diffraction technique (JDX-11 Japan) Dif-fuse reflectance spectroscopy (DRS) ofNPswas done by usinga Lamda-950 Perkin-Elmer Thick film sensors were madeby doctor blading (same area and thickness for all sensors)and resistance was measured using multimeter (Keithly 2000multimeter)

3 Results and Discussion

Figure 1 illustrates XRD spectrum of different NPs preparedby the coprecipitation method All major diffraction peakscan be assigned to diffraction from different ZnO planesrespectively (JCPDS card 780-0075) There is a weak peakat about 27∘ in 5 Mg-doped sample which can be due toZn(CH

3COO)

2as a result of unwanted residue left in the

sample [14] This revealed that the resultant NPs were phase-pure ZnO (no MgO peaks) with a hexagonal structure MgOhas rock-salt structure and ZnO has hexagonal structureTherefore phase separation can occur at higher concentra-tions The XRD spectra clearly suggest that there is no phaseseparation Zn andMg ions have similar ionic radii (060 and057 A) and it is expected that Mg ions are substituted for ZnThe systematic peak shift andbroader FWHMwith consistentincrease in Mg doping is are indication of doping suggestinga higher defect concentration and decreased quality of crystal

Pure ZnO

25 Mg

50 Mg

75 Mg

Arb

itrar

y in

tens

ity

(100

)(0

02) (1

01)

(102

)

(110

)

(103

)(2

00)

(112

)(2

01)

40 50 60 70302120579

Figure 1 XRD spectra of different levels of Mg doping in ZnONPs The results clearly show that all the major peaks correspond toZnO There is a systematic broadening of FWHM with an increasein doping concentration

with increase in Mg doping concentration Also there is aclear systematic (101) peak (highest intensity) shift towardshigher 2 theta value This again is another indication ofchange in ldquodrdquo spacing with increase in the doping concentra-tion Figure S1 (at Supplementary Material available online athttpdxdoiorg10115520168296936) shows a TEM imageof pure ZnO NPs and clearly suggests that the averageparticle size is less than 10 nm Also there are 2 minor peaks((200) and (201)) which disappear after doping One of thepossible reasons can be that these peaks shift because ofthe Mg-induced strain and merge into the broader (112)peak This peak broadening can be clearly observed if XRDspectra of pure ZnO and 25 Mg samples are comparedAlso the morphology is dependent on doping and previousresearchers suggested that grain size increases with increasein doping concentration

Figure 2 represents the FTIR results in the range of4000 cmminus1 to 500 cmminus1 3550 cmminus1 to 3250 cmminus1 band istypically the stretching vibration mode of OHminus group Also1650 cmminus1 band is the OHminus fundamental stretching modeThese bands are very typical signals of H

2O present on the

sample surface Zn-O stretching mode is located at 560 cmminus1

Journal of Sensors 3

Arb

itrar

y in

tens

ity

Pure ZnO

25 Mg

50 Mg

75 Mg

1000

1500

2000

2500

3000

3500

400050

0

Wave number (cmminus1)

Figure 2 FTIR results of different levels of Mg doping in ZnONPsA clear change of ZnO stretchingmodes with increase inMg doping(around 500 cmminus1) suggests that Zn ions are replaced by Mg ions

to 600 cmminus1 [15]There is a slight systematic peak shift of Zn-O band which can be an indirect evidence of increasing Mgcontent in the lattice Mg-O stretching vibrations can alsobe clearly observed in the region of 1400 cmminus1 to 1450 cmminus1FTIR results give a clear indication that Mg was successfullydoped in ZnO lattice [15 16]

Bandgap of ZnO NPs can be effectively tuned by dopingMg2+ The bandgap of ZnO and MgO is 337 eV and 77 eVrespectively and it can be increased by Mg doping [12] TheUV-visible spectroscopy results are shown in Figure 3 Thebandgap of all the samples can be estimated by convertingwave length into the energy using the following equation

119864 = ℎ119888 120582 (1)

where ldquo119864rdquo is energy ldquoℎrdquo is Plankrsquos constant ldquo119888rdquo is velocity oflight and ldquo120582rdquo is the wave length A systematic blue shift inthe main UV peak can be clearly observed with the increasein the Mg doping and the bandgap ranges from 324 eV forpure ZnO to 333 eV for 75 Mg samples Our results are inaccordance with the previous studies and clearly show thatbandgap can be tuned by carefully controllingMg doping [1718] One of the possible explanations of this blue shift is theBurstein-Moss effect Fermi level of n type ZnO is inside theconduction bandWithMg doping the conduction bands arefilled This in turn shifts the absorption edge to the higherenergy [19]

Photoconductive response time is important for a UVsensor Electron-hole pairs are generated on UV exposureThese holes are then combined with trapped oxygen ionscommonly known as surface electron-hole recombinationThis effect is shown in [20]

h+ +O2

minus

(ad) 997888rarr O2(gas) (2)

Tran

smitt

ance

()

25 Mg

50 Mg

75 Mg

Pure ZnO

400 450 500350Wavelength (nm)

Figure 3 UV-Vis spectroscopy of samples with pure and differentconcentrations ofMg-doped ZnOThe results give a clear indicationof direct band emission in UV region for all the samples There isalso a systematic shift towards higher wavelength for UV emissionMinor peaks around 475 nm can be the defect related deep-levelemission peaks [13]

Unpaired electrons are freely available and enhance thephotocurrent Figure 4 is the sensing results of Mg-dopedZnONPs done at room temperatureTheOn-Off switch timewas very small (in seconds) and one of the main focusesof this experiment was to investigate the response timeand change in resistance with Mg doping The sensitivity(ratio of resistance in the dark and in the presence of UVlight) is 1060 1062 1088 and 1054 for 0 25 50and 75 respectively The enhanced response of Mg-dopedZnO NPs can be attributed to unpaired electrons added tothe photocurrent [21 22] In ZnO oxygen vacancies act aselectron donors Surface defects and charged species increaseafter the Mg doping thus more reaction and surface recom-bination results in faster response time Also NPs are a goodchoice for obtaining fast response of the devices due to anenhanced surface to volume ratio [23] However the decreasein sensitivity after 75 Mg can be attributed to severedamage in the crystal lattice Previous researchers have alsosuggested that the Mg-doped ZnO (and Zn

1minusxMgxO) havingpotential photodetectors with different detective wavelengthshave strong potential for being the sensor active materialHowever there is a wide miscibility gap and large latticemismatch in the ZnO-MgO binary system This is mainlybecause of the difference in crystal structure Thereforedefect density increases and crystal quality is low Also phasesegregation can occur This has become the major issue forsynthesis Also finding new materials with faster adsorptionand disadsorption characteristics is the main issue which isattracting the attention of researchers in this field [24ndash28]It was also suggested that usually with doping the bandgapis shifted to the lower energy region which enhances theabsorption spectrum of doped ZnO NPs [29] These are themain issues which are attracting the attention of researchersin this field


75

Mg

10 15 20 255Time (s)

385

390

395

400

405

410

Resis

tanc

e (M

Ohm

s)

(a)

50

Mg

370

380

390

400

Resis

tanc

e (M

Ohm

s)

10 15 20 255Time (s)

(b)

25

Mg

10 15 20 255Time (s)

380

385

390

395

400

405

Resis

tanc

e (M

Ohm

s)

(c)

Pure

ZnO

UV on

10 15 20 255Time (s)

380

385

390

395

400Re

sista

nce (

M O

hms)

UV off

(d)

Figure 4 Room temperature UV sensor results of different samples with Mg doping (a) 75 (b) 50 (c) 25 and (d) pure ZnO Theresults clearly suggest good sensitivity for all the doped and undoped samples

XRD UV-Vis spectroscopy and optical sensor results arein perfect agreement with each other There is a systematicpeak shift in XRD and UV-Vis results with increase in Mgdoping XRD peak shift also indicates changes in ldquod spacingrdquoThe UV sensing properties of Mg-doped ZnO NPs show fastswitching behavior due to adsorbed oxygen

4 Conclusions

Pure and Mg-doped ZnO NPs were prepared by coprecipita-tion method at 60∘C XRD spectra show a regular peak shifttowards higher angle with a wider FWHM FTIR results givea clear indication of the presence of Mg atoms in the latticeby showing Zn-O band shift towards the high energy and alsothe appearance of Mg-O vibration peak One of the motivesof Mg doping is to tune the optical properties of ZnO NPsThe bandgap of NPs was directly related to the concentration

ofMg atoms in particlesThe sensing results showed very fastresponse towards UV light for all the samples

Competing Interests

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

Authorsrsquo Contributions

Mirza Shirjeel Alam Umair Manzoor Mohammad Mujahidand Arshad S Bhatti contributed equally to this work

Acknowledgments

This project was funded by the National Plan for ScienceTechnology and Innovation (MAARIFAH) King Abdulaziz


City for Science and Technology Kingdom of Saudi ArabiaAward no 2623

References

[1] Z R Dai Z W Pan and Z L Wang ldquoNovel nanostruc-tures of functional oxides synthesized by thermal evaporationrdquoAdvanced Functional Materials vol 13 no 1 pp 9ndash24 2003

[2] K Rekha M Nirmala M G Nair and A Anukaliani ldquoStruc-tural optical photocatalytic and antibacterial activity of zincoxide and manganese doped zinc oxide nanoparticlesrdquo PhysicaB Condensed Matter vol 405 no 15 pp 3180ndash3185 2010

[3] M Amin U Manzoor M Islam A S Bhatti and N A ShahldquoSynthesis of ZnO nanostructures for low temperature CO andUV sensingrdquo Sensors vol 12 no 10 pp 13842ndash13851 2012

[4] L Peng L Hu and X Fang ldquoLow-dimensional nanostructureultraviolet photodetectorsrdquo Advanced Materials vol 25 no 37pp 5321ndash5328 2013

[5] H-M Xiong D G Shchukin H Mohwald Y Xu and Y-Y Xia ldquoSonochemical synthesis of highly luminescent zincoxide nanoparticles doped with magnesium(II)rdquo AngewandteChemiemdashInternational Edition vol 48 no 15 pp 2727ndash27312009

[6] W Bunjongpru P Panprom S Porntheeraphat et al ldquoUV-enhanced photodetector with nanocrystalline-TiO

2

thin filmvia CMOS compatible processrdquo in Proceedings of the IEEENanotechnology Materials and Devices Conference (NMDC rsquo11)pp 364ndash367 IEEE Jeju South Korea October 2011

[7] J Cao J Wang B Fang X Chang M Zheng and H WangldquoMicrowave-assisted synthesis of flower-like ZnO nanosheetaggregates in a room-temperature ionic liquidrdquo ChemistryLetters vol 33 no 10 pp 1332ndash1333 2004

[8] UManzoor andDK Kim ldquoSize control of ZnOnanostructuresformed in different temperature zones by varying Ar flow ratewith tunable optical propertiesrdquo Physica E Low-DimensionalSystems and Nanostructures vol 41 no 3 pp 500ndash505 2009

[9] W Q Peng S C Qu G W Cong and Z G Wang ldquoSynthesisand temperature-dependent near-band-edge emission of chain-like Mg-doped ZnO nanoparticlesrdquo Applied Physics Letters vol88 no 10 Article ID 101902 2006

[10] U Manzoor M Islam L Tabassam and S U Rahman ldquoQuan-tum confinement effect in ZnO nanoparticles synthesized byco-precipitate methodrdquo Physica E Low-Dimensional Systemsand Nanostructures vol 41 no 9 pp 1669ndash1672 2009

[11] X L Zhang K S Hui and K N Hui ldquoHigh photo-responsivityZnO UV detectors fabricated by RF reactive sputteringrdquoMate-rials Research Bulletin vol 48 no 2 pp 305ndash309 2013

[12] Y Jin Y Ren M Cao and Z Ye ldquoDoped colloidal ZnOnanocrystalsrdquo Journal of Nanomaterials vol 2012 Article ID985326 8 pages 2012

[13] E Burstein ldquoAnomalous optical absorption limit in InSbrdquoPhysical Review vol 93 no 3 pp 632ndash633 1954

[14] F K Shan B I Kim G X Liu et al ldquoBlueshift of near bandedge emission in Mg doped ZnO thin films and agingrdquo Journalof Applied Physics vol 95 no 9 pp 4772ndash4776 2004

[15] D L Golic G Brankovic M P Nesic et al ldquoStructural charac-terization of self-assembled ZnO nanoparticles obtained by thesolndashgel method from Zn(CH

3

COO)2

2H2

Ordquo Nanotechnologyvol 22 no 39 Article ID 395603 2011

[16] G H Ning X-P Zhao and J Li ldquoStructure and opticalproperties of Mg

119909

Zn1minus119909

O nanoparticles prepared by sol-gelmethodrdquo Optical Materials vol 27 pp 1ndash5 2004

[17] R Wahab S G Ansari Y S Kim et al ldquoLow temperaturesolution synthesis and characterization of ZnO nano-flowersrdquoMaterials Research Bulletin vol 42 no 9 pp 1640ndash1648 2007

[18] A Ohtomo K TamuraM Kawasaki et al ldquoRoom-temperaturestimulated emission of excitons in ZnO(Mg Zn)O superlat-ticesrdquo Applied Physics Letters vol 77 no 14 pp 2204ndash22062000

[19] H-C Hsu C-YWu H-M Cheng andW-F Hsieh ldquoBand gapengineering and stimulated emission of ZnMgO nanowiresrdquoApplied Physics Letters vol 89 Article ID 013101 2006

[20] U Manzoor and D K Kim ldquoSynthesis and enhancement ofultraviolet emission by post-thermal treatment of unique zincoxide comb-shaped dendritic nanostructuresrdquo Scripta Materi-alia vol 54 no 5 pp 807ndash811 2006

[21] K ul Hasan N H Alvi J Lu O Nur and M WillanderldquoSingle nanowire-based UV photodetectors for fast switchingrdquoNanoscale Research Letters vol 6 article 348 2011

[22] H Kind H Yan B Messer M Law and P Yang ldquoNanowireultraviolet photodetectors and optical switchesrdquo AdvancedMaterials vol 14 no 2 pp 158ndash160 2002

[23] C Soci A Zhang B Xiang et al ldquoZnO nanowire UV photode-tectors with high internal gainrdquo Nano Letters vol 7 no 4 pp1003ndash1009 2007

[24] M-W Chen C-Y Chen D-H Lien Y Ding and J-HHe ldquoPhotoconductive enhancement of single ZnO nanowirethrough localized Schottky effectsrdquo Optics Express vol 18 no14 pp 14836ndash14841 2010

[25] R Afrin J Khaliq M Islam I H Gul A S Bhatti and UManzoor ldquoSynthesis of multiwalled carbon nanotube-basedinfrared radiation detectorrdquo Sensors and Actuators A Physicalvol 187 pp 73ndash78 2012

[26] H Liu Z Zhang L Hu et al ldquoNew UV-A photodetectorbased on individual potassium niobate nanowires with highperformancerdquoAdvanced Optical Materials vol 2 no 8 pp 771ndash778 2014

[27] N Naderi and M R Hashim ldquoVisible-blind ultraviolet pho-todetectors on porous silicon carbide substratesrdquo MaterialsResearch Bulletin vol 48 no 6 pp 2406ndash2408 2013

[28] X Fang L Hu K Huo et al ldquoNew ultraviolet photodetectorbased on individual Nb

2

O5

nanobeltsrdquo Advanced FunctionalMaterials vol 21 no 20 pp 3907ndash3915 2011

[29] S Y Bae C W Na J H Kang and J Park ldquoComparativestructure and optical properties of Ga- In- and Sn-doped ZnOnanowires synthesized via thermal evaporationrdquoThe Journal ofPhysical Chemistry B vol 109 no 7 pp 2526ndash2531 2005

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Active and Passive Electronic Components

Control Scienceand Engineering

Journal of



RotatingMachinery


Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design



Shock and Vibration


Civil EngineeringAdvances in

Acoustics and VibrationAdvances in



Electrical and Computer Engineering

Journal of

Advances inOptoElectronics


Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of


Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014


Chemical EngineeringInternational Journal of Antennas and

Propagation




Navigation and Observation



DistributedSensor Networks



Table 1 Experimental details and chemical quantities used for the synthesis

age doping Zn(CH3

COO)2

(g) Mg(CH3

COO)2

(g) KOH (g) Ethanol (mL) Other constants (same for all experiments)1 0 1004 mdash 0990 80 Temperature 60∘C

Constant stirring 25 hoursCentrifuged to separate ZnO NPsRepeatedly washed with distilled water andethanol at 60∘C

2 25 1009 0020 1008 803 50 1007 0041 0960 804 75 1003 0078 0962 80

UV-Vis spectroscopy Optical properties were tuned by Mgdoping UV sensing properties are also demonstrated Themain focus of the study was the fast response time of Mg-doped ZnO NPs as active sensor material

2 Experimental Section

Zinc acetate dihydrate (Zn(CH3COO)

2 Sigma-Aldrich) and

1mL of water (distilled) were put into a flask containing80mL methanol They were mixed at 60∘C In a secondbeaker potassium hydroxide (KOH Sigma-Aldrich) wasdissolved in 23mL of methanolThe solution was then slowlyadded into the flasks containing zinc acetate This mixturewas then stirred for 25 hours The transparent solutionbecame opaque because of slow addition of KOH whichagain slowly transformed into a clear solution ZnO powderwas separated from the solvent by centrifuge and repeatedlywashed in distilled water and ethanol The powder was driedin convection oven at 60∘C For doping magnesium acetatedihydrate (Mg(CH

3COO)

2Sigma-Aldrich) was added in

appropriate quantities The experimental details and quanti-ties are shown in Table 1

The morphology was determined using transmissionelectron microscope (TEM JEOL) The phase analysis wasdone using X-ray diffraction technique (JDX-11 Japan) Dif-fuse reflectance spectroscopy (DRS) ofNPswas done by usinga Lamda-950 Perkin-Elmer Thick film sensors were madeby doctor blading (same area and thickness for all sensors)and resistance was measured using multimeter (Keithly 2000multimeter)

3 Results and Discussion

Figure 1 illustrates XRD spectrum of different NPs preparedby the coprecipitation method All major diffraction peakscan be assigned to diffraction from different ZnO planesrespectively (JCPDS card 780-0075) There is a weak peakat about 27∘ in 5 Mg-doped sample which can be due toZn(CH

3COO)

2as a result of unwanted residue left in the

sample [14] This revealed that the resultant NPs were phase-pure ZnO (no MgO peaks) with a hexagonal structure MgOhas rock-salt structure and ZnO has hexagonal structureTherefore phase separation can occur at higher concentra-tions The XRD spectra clearly suggest that there is no phaseseparation Zn andMg ions have similar ionic radii (060 and057 A) and it is expected that Mg ions are substituted for ZnThe systematic peak shift andbroader FWHMwith consistentincrease in Mg doping is are indication of doping suggestinga higher defect concentration and decreased quality of crystal

Pure ZnO

25 Mg

50 Mg

75 Mg

Arb

itrar

y in

tens

ity

(100

)(0

02) (1

01)

(102

)

(110

)

(103

)(2

00)

(112

)(2

01)

40 50 60 70302120579

Figure 1 XRD spectra of different levels of Mg doping in ZnONPs The results clearly show that all the major peaks correspond toZnO There is a systematic broadening of FWHM with an increasein doping concentration

with increase in Mg doping concentration Also there is aclear systematic (101) peak (highest intensity) shift towardshigher 2 theta value This again is another indication ofchange in ldquodrdquo spacing with increase in the doping concentra-tion Figure S1 (at Supplementary Material available online athttpdxdoiorg10115520168296936) shows a TEM imageof pure ZnO NPs and clearly suggests that the averageparticle size is less than 10 nm Also there are 2 minor peaks((200) and (201)) which disappear after doping One of thepossible reasons can be that these peaks shift because ofthe Mg-induced strain and merge into the broader (112)peak This peak broadening can be clearly observed if XRDspectra of pure ZnO and 25 Mg samples are comparedAlso the morphology is dependent on doping and previousresearchers suggested that grain size increases with increasein doping concentration

Figure 2 represents the FTIR results in the range of4000 cmminus1 to 500 cmminus1 3550 cmminus1 to 3250 cmminus1 band istypically the stretching vibration mode of OHminus group Also1650 cmminus1 band is the OHminus fundamental stretching modeThese bands are very typical signals of H

2O present on the

sample surface Zn-O stretching mode is located at 560 cmminus1


Arb

itrar

y in

tens

ity

Pure ZnO

25 Mg

50 Mg

75 Mg

1000

1500

2000

2500

3000

3500

400050

0





119864 = ℎ119888 120582 (1)



h+ +O2

minus

(ad) 997888rarr O2(gas) (2)

Tran

smitt

ance

()

25 Mg

50 Mg

75 Mg

Pure ZnO






75

Mg

10 15 20 255Time (s)

385

390

395

400

405

410

Resis

tanc

e (M

Ohm

s)

(a)

50

Mg

370

380

390

400

Resis

tanc

e (M

Ohm

s)

10 15 20 255Time (s)

(b)

25

Mg

10 15 20 255Time (s)

380

385

390

395

400

405

Resis

tanc

e (M

Ohm

s)

(c)

Pure

ZnO

UV on

10 15 20 255Time (s)

380

385

390

395

400Re

sista

nce (

M O

hms)

UV off

(d)



4 Conclusions



Competing Interests




Acknowledgments




References







2











3

COO)2

2H2



119909

Zn1minus119909














2

O5





RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Arb

itrar

y in

tens

ity

Pure ZnO

25 Mg

50 Mg

75 Mg

1000

1500

2000

2500

3000

3500

400050

0





119864 = ℎ119888 120582 (1)



h+ +O2

minus

(ad) 997888rarr O2(gas) (2)

Tran

smitt

ance

()

25 Mg

50 Mg

75 Mg

Pure ZnO






75

Mg

10 15 20 255Time (s)

385

390

395

400

405

410

Resis

tanc

e (M

Ohm

s)

(a)

50

Mg

370

380

390

400

Resis

tanc

e (M

Ohm

s)

10 15 20 255Time (s)

(b)

25

Mg

10 15 20 255Time (s)

380

385

390

395

400

405

Resis

tanc

e (M

Ohm

s)

(c)

Pure

ZnO

UV on

10 15 20 255Time (s)

380

385

390

395

400Re

sista

nce (

M O

hms)

UV off

(d)



4 Conclusions



Competing Interests




Acknowledgments




References







2











3

COO)2

2H2



119909

Zn1minus119909














2

O5





RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










75

Mg

10 15 20 255Time (s)

385

390

395

400

405

410

Resis

tanc

e (M

Ohm

s)

(a)

50

Mg

370

380

390

400

Resis

tanc

e (M

Ohm

s)

10 15 20 255Time (s)

(b)

25

Mg

10 15 20 255Time (s)

380

385

390

395

400

405

Resis

tanc

e (M

Ohm

s)

(c)

Pure

ZnO

UV on

10 15 20 255Time (s)

380

385

390

395

400Re

sista

nce (

M O

hms)

UV off

(d)



4 Conclusions



Competing Interests




Acknowledgments




References







2











3

COO)2

2H2



119909

Zn1minus119909














2

O5





RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











References







2











3

COO)2

2H2



119909

Zn1minus119909














2

O5





RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









Research Article Highly Responsive UV Light Sensors Using Mg...

Documents

Transcript of Research Article Highly Responsive UV Light Sensors Using Mg...