Research Article Microwave Assisted Synthesis of ZnO ...downloads.hindawi.com/archive/2013/478681.pdftemperature, irradiation time, microwave radiation power, and the addition of additives)

Hindawi Publishing CorporationJournal of MaterialsVolume 2013 Article ID 478681 11 pageshttpdxdoiorg1011552013478681

Research ArticleMicrowave Assisted Synthesis of ZnO NanoparticlesEffect of Precursor Reagents Temperature Irradiation Timeand Additives on Nano-ZnO Morphology Development

Gastoacuten P Barreto Graciela Morales and Ma Luisa Loacutepez Quintanilla

Centro de Investigacion en Quımica Aplicada Boulevard Enrique Reyna 140 25253 Saltillo COAH Mexico

Correspondence should be addressed to Gaston P Barreto gbarretofiouniceneduar

Received 27 December 2012 Accepted 26 March 2013

Academic Editor Antoni Morawski

Copyright copy 2013 Gaston P Barreto 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

The effect of different variables (precursor reagents temperature irradiation time microwave radiation power and additivesaddition) on the final morphology of nano-ZnO obtained through the microwave assisted technique has been investigated Thecharacterization of the samples has been carried out by field emission scanning electron microscopy (FE-SEM) in transmissionmode infrared (FTIR) UV-Vis spectroscopy and powder X-ray diffraction (XRD)The results showed that all the above-mentionedvariables influencedto some extent the shape andor size of the synthetized nanoparticles In particular the addition of an anionicsurfactant (sodium di-2-ethylhexyl-sulfosuccinate (AOT)) to the reaction mixture allowed the synthesis of smaller hexagonalprismatic particles (100 nm) which show a significant increase in UV absorption

1 Introduction

ZnO powder has been widely used into numerous mate-rials and products including paints plastics ceramics andadhesives It is a semiconductor of the IIndashVI semiconductorgroup with several favorable properties such as high elec-tron mobility wideband gap and strong room temperatureluminescence These properties make ZnO an attractivecompound for different emerging applications

In the last two decades many methods ranging from gas-phase processes to solution routes have been investigatedfor the synthesis of ZnO nanoparticles including solutionprecipitation [1 2] spray pyrolysis [3 4] hydrothermalsynthesis [5ndash7] sol-gel processes [8ndash11] and microemulsionsynthesis [12]

In cases where the synthesis has been carried out througha conventional thermostatic system the walls of the reactorare heated by convection or conduction the core of thesample needs longer time to achieve the target temperatureand this may result in inhomogeneous temperature profilesOne possible solution to this problem is the use of microwave

heating which has become a very promising method of syn-thesis for both organic [13 14] and inorganic [15] chemistryThis technique enables the rapid and homogenous heating ofthe reaction mixture to the desire temperature which savestime and energy

Themicrowave heating is based on two conversionmech-anisms of the electromagnetic radiation into heat energynamely dipolar rotation and ionic conduction which aredirectly related to the chemistry composition of the reactionmixture So that different compounds have different micro-wave absorbing properties and this behavior allows a selec-tive heating of compounds in the reaction mixture

The general advantages of microwave mediated synthesisover conventional ones are (1) reaction rate acceleration as aconsequence of high heating rates (2) wide range of reactionconditions that is mild conditions or autoclave conditions(3) high reaction yields (4) reaction selectivity due to dif-ferent microwave absorbing properties (5) excellent controlover reaction conditions and (6) simple handling allowingsimple and fast optimization of experimental parameters

2 Journal of Materials

Since 2007 the number of publications dealing withthe microwave assisted synthesis of ZnO has increasedsignificantly In this sense there have been many publishedresults concerned with aqueous and nonaqueous solutionmicrowave assisted synthesis where the effect of differentexperimental variables over ZnO size shape and physic-ochemical behavior have been analyzed [16ndash18] This irra-diation technique has been used to obtain nanostructureswith various morphologies including spherical particlesrods hexagonal rings hexagonal columns Flowers wireshexagonal tubes and sheets

Some authors [16] demonstrated the possibility of ZnOsynthesis with a novel three-dimensional morphology wheremicrowave radiation as heating source plays an importantrole in the formation of complex nanostructures In additionthe absence of metal catalyst template or surfactant in thismethod avoids the subsequent effort for the removal ofresidual additives

Other studies [18] dealt with the effect of power of micro-wave radiation on the shape and size of the synthetized ZnOnanostructures where the average particle size decreaseswithdecreasing microwave power being the optical propertiessensitive to the variation of this parameter

On the other hand other authors [19] analyzed the effectof solvent (water ethanol and isopropanol) on the synthe-tized ZnO nanostructures and an important change in thesize and shape of nanoparticles was reported When distilledwater was used as a solvent nanoparticles presented ellipseshape and larger size (larger axis was about 100 nm and size ofthe other axis was about 40 nm) With ethanol the obtainednanostructures had rod form with smaller sizes than thoseobtained in water and when isopropanol was used as thereaction medium spherical particles with radius of 10ndash12 nmwere obtained

However most synthetic studies did not show a completestudy about different parameters involved during the micro-wave assisted technique In this sense this work deals with acomplete analysis of different variables (precursor reagentstemperature irradiation time microwave radiation powerand the addition of additives) and their effect on the finalmorphology of nano-ZnO obtained through the microwaveassisted technique

2 Experimental

21 Synthesis of ZnO In a typical synthesis process15mL (16mol Lminus1) of a precursor salt (Zn(NO

3

)2

sdot6H2

OZn(CH

3

COO)2

sdot2H2

O or ZnCl2

) were diluted in 32mL ofdeionized water (or a sodium di-2-ethylhexyl-sulfosuccinateaqueous solution) to obtain a Zn+2 solution Afterwards4mL of a base (32mol Lminus1) (NaOH KOH or NH

4

OH) wasadded dropwise (2min) into the above-described solutionwith magnetic stirring at room temperature to get a colloidsystem which was maintained under stirring for 10minThen the reaction mixture was transferred into a Teflonautoclave and treated at selected temperature (80 100120 or 140∘C) for specific time (5 10 or 20min) undertemperature-controlled mode in a microwave accelerated

reaction system (Mars-X) operating at different powers(300 600 or 1200W) It must be mentioned that the systemwas programmed with a first temperature ramp where thetarget temperature was reached after 10min in all cases(Table 1) When the reaction was finished and cooled toroom temperature the white precipitate was collected byfiltration and washed with deionized water and ethyl alcoholseveral times Finally the product was dried at 65∘C in avacuum oven for 3 h

22 Characterization To investigate the structural proper-ties of ZnO nanoparticles field emission scanning elec-tron microscopy (FE-SEM) infrared (FTIR) UV-Vis spec-troscopy and powder X-ray diffraction (XRD) studies werecarried out ZnO powders synthetized were characterizedby X-ray diffraction with a Siemens D500 diffractometerDiffraction patterns were recorded from 10 to 80∘ 2120579 with astep size of 006∘ at 35 kV and 25mA The average crystallitesizes 119863 (Table 1) of the ZnO nanostructures were calculatedusing Scherrerrsquos formula

119863 =09120582

120573 cos 120579 (1)

where 120582 is the X-ray wavelength of Cu-K120572 radiation source 120573is the full width at half maximum intensity of the diffractionpeak located at 2120579 and 120579 is the Bragg angle

On the other hand an aliquot of solid state material wasplaced in a carbon label for analysis by FE-SEM (JSM-7401F)Samples were analyzed using a secondary electron detectorThe infrared spectra of ZnO nanoparticles were taken in aNicolet spectrophotometer model Nexus 470 Nicolet brandin transmittance mode The sample preparation was made intablet way by mixing nano-ZnO and KBr in an agate mortarThe solid samples were dispersed in deionized water andultrasonicated for 10min Then UV-Vis spectra of colloidalsystems were obtained through a Shimadzu double beamspectrophotometer model UV-2401PC

Characterization data of all ZnO synthesis carried out isdescribed in Electronic Supplementary Material (ESM) thataccompanies this paper (see Supplemetary Material availableonline at httpdxdoiorg1011552013478681)

3 Results and Discussion

31 Temperature Effect The microwave system employed tosynthetize the ZnO particles allows to set a constant reactiontemperature In order to analyze the temperature effect onthe final morphology of the product obtained the syntheticreactions were carried out in the temperature interval 80ndash140∘C using Zn(NO

3

)2

as the precursor salt (from MW-1 toMW-4 Table 1) XRD studies (Figure 1) show that when thereaction is carried out for 20 minutes at 80 or 100∘C (MW-1and MW-2 resp) the signals are not clear and some peaksattributable to precursor reagents and unknown impuritiesare observed On the contrary at 120 and 140∘C (MW-3and MW-4 resp) all the diffraction peaks match those ofthe wurtzite ZnO with lattice constants of 119886 = 3250 Aand 119888 = 5207 A The strong diffraction peaks appear at

Journal of Materials 3

Table 1 Experimental conditions employed during microwave assisted synthesis of ZnO

Synthesiscode

Experimentalconditions

(irradiation timeatemperature andmicrowave power)

Zn precursor 15mL16mol Lminus1

Base 4mL32mol Lminus1 Yield Average crystallite

size nmAverage particle sizeh

120583m

MW-1 20min 80∘C 600W Zn(NO3)2 6H2O NaOH NA NA NA

MW-2 20min 100∘C 600W Zn(NO3)2 6H2O NaOH NA NA 0413 (Wi)0088 (Lj)

MW-3 20min 120∘C 600W Zn(NO3)2 6H2O NaOH 9351 805 1116 (W)3099 (L)


MW-5b 20min 140∘C 600W Zn(NO3)2 6H2O NaOH 9931 641 1534 (W)3577 (L)

MW-6c 20min 140∘C 600W Zn(NO3)2 6H2O NaOH 8702 641 0128 (W)0192 (L)

MW-7d 20min 140∘C 600W Zn(NO3)2 6H2O NaOH 9230 631 0123 (W)0059 (L)

MW-8e 20min 140∘C 600W Zn(NO3)2 6H2O NaOH 8272 753 0394 (W)0311 (L)

MW-9f 20min 140∘C 600W Zn(NO3)2 6H2O NaOH 8973 822 1308 (W)4092 (L)

MW-10 0min 140∘C 600W Zn(NO3)2 6H2O NaOH NA 825 NA





MW-15 20min 140∘C 600W Zn(NO3)2 6H2O KOH 8700 777 0870 (W)2375 (L)

MW-16 20min 140∘C 600W Zn(NO3)2 6H2O KOHg NA 781 0220 (W)1063 (L)

MW-17 20min 140∘C 600W Zn(NO3)2 6H2O NH4OH NA 754 1689 (W)4673 (L)

MW-18 20min 100∘C 600W Zn(CH3COO)2 2H2O NaOH NA 805 3716 (W)3662 (L)



MW-21 20min 140∘C 600W ZnCl2 NaOH NA NA NAaAn initial 10min period required to reach the target temperature must be considered in all casesbSolid product was isolated by centrifugation The product was not washedcChange in the addition orderd024 g of sodium di-2-ethylhexyl-sulfosuccinate dissolved in water were added before base additione050 g of sodium di-2-ethylhexyl-sulfosuccinate dissolved in water were added before base additionf1 g of ethylene glycol dissolved in water was added before base additiong13mL of base were added instead of 4mLhCalculated from SEM images employing ImageJ SoftwareiAverage width of the rod-like particlesjAverage length of the rod-like particlesNA not available


2120579 = 318 343 and 365∘ which correspond to the (100)(002) and (101) planes of wurtzite ZnO respectively FE-SEM images show an almost homogeneous morphologicaldistribution at a set reaction temperature of 140∘C In this casemost ZnO particles were formed as bihexagonal rods whichwere probably stacked from sheets with a starting growthfrom both sides Additionally a low population of ZnOparticles with a more complex three-dimensional structurecan be observed (MW-4 Figure 1)where a radial growth froma center seems to be favored yielding nanodandelions-likemorphologies [16] On the other hand when the precursorsare irradiated at 120∘C (MW-3 Figure 1) the FE-SEM imagesshow that while some particles are formed there is stilla heterogeneous background A possible explanation forthis behavior can be linked to the existence of a greaterirradiation to achieve a higher temperature which increasesthe polarization of the system by producing a more orderlysystem that favors the nucleation and growth of the ZnOnanoparticles as was also described by other authors [18]

On the other hand FTIR studies (Figure 1) show thecharacteristic vibrations of ZnO in the product obtained at140∘C In all the cases the FTIR spectrums show absorptionbands centered at about 3430 and 2344 cmminus1 which canbe assigned to the OndashH stretching vibrations and bandscentered at 1630 and 1384 cmminus1 that correspond to the asym-metric and symmetric C=O stretching modes (CO

2

modes)At lowwavenumbers there can be observed two peaks locatedat approximately 420 and 512 cmminus1 corresponding to theZnO rod like-nanostructures [20 21]

32 Precursors Effect Three different precursors were em-ployed to synthetize ZnO (temperature 140∘C power 600W)Zn(NO

3

)2

sdot6H2

O (MW-4) Zn(CH3

COO)2

sdot2H2

O (MW-20)and ZnCl

2

(MW-21) Figure 2 shows the correspondingmorphologies as well as XRD analysis for these samples

As it can be observed from Figure 2 XRD analysisshows that when Zn(NO

3

)2

and Zn(CH3

COO)2

are theprecursor salts all the diffraction peaks match those of thewurtzite ZnO as it was described above The morphologicaldistribution is homogeneous in both cases being in the firstcase particles with a bihexagonal rod-like structure of about6 120583m long and 2 120583m wide meanwhile in the second casethe morphology is of the hexagonal prismatic type and theaverage particle size is of about 3-4 120583m long and 1120583 wideIn these both systems the larger particles observed couldbe grown from small primary particles through an orientedattachment process in which the adjacent nanoparticles areself-assembled by sharing a common crystallographic orien-tation and docking of these particles at a planar interface

On the contrary when ZnCl2

is used as the precursorsalt the corresponding diffractogram shows many signalsattributed to precursor reagents and unknown impuritiesand a heterogeneous and non-well-defined morphology anda broad particle size distribution can be observed

Taking into account that the growth of large crystalsdepends on the counteranion as it was previously described[22] the difference in the morphology of the three analyzedsystems can be attributed to the fact that in the case of

the halide anion it adsorbs more strongly on surfaces thanacetate ions and nitrate ions which exhibits very weak surfaceinteraction As the adsorption on surfaces increases thegrowth process decreases conducting particles with lowersizes as it can be observed in Figure 2 where the size of thesynthesized ZnO particles decreases in the following orderNO3

minus

gt CH3

COOminus gt ClminusThis behavior can also be confirmed by the fact that

nitrate anion is a noncoordinative ligand so that the hexag-onal wurtzite prefers growing in the c axis (0001 plane)meanwhile in the case of acetate ion it is a chelating ligandthat allows a better control on the ZnO particle developmentyielding particles with lower particle size

On the other hand and for the case of Zn(NO3

)2

theorder of reagents addition during the synthesis of nano-ZnO was analyzed when a solution of Zn(NO

3

)2

precursorwas added dropwise over NaOH solution (basic route)differentmorphologies (short rows etc) were obtained in thefinal product (MW-6) with a wide particle size distributionand arranged in the form of agglomerates (Figure 3) Thisbehavior can be explained attending to the following reactionmechanism The first step in the synthetic reaction irrespec-tive of the route employed (acidic or basic) corresponds tothe formation of a colloidal system

Zn2+ (aq) + 2OHminus (aq) 997888rarr Zn(OH)2 (s) darr (2)

The zinc cations are known to reactwith hydroxide anionsto form stable Zn(OH)

4

2minus complexes which could act as thegrowing unit of ZnO nanostructures [23 24] Therefore thegrowth mechanism can be considered as follows when thesynthesis is carried out through the acidic route

Zn (OH)2

(s) + 2H2

O Microwave997888997888997888997888997888997888997888997888rarr Zn(OH)

4

2minus

+ 2H+

Microwave997888997888997888997888997888997888997888997888rarr ZnO + 3H

2

O(3)

When the addition is made in such a way that OHminus isaggregated over the Zn+2 solution reaction symbolized by (2)takes place and the formation of growing units during theirradiation stage is favored as it is symbolized in (3) In thissense Zn(OH)

4

2minus species are generated under microwaveeffect and it is well known that growing species can bepolarized [18] allowing a controlled and directed growth ofthe particles

On the other hand if Zn+2 is added slowly over the OHminussolution as in the case of MW-6 the growing units can beformed rapidly and the following reaction can occur beforeirradiation

Zn(OH)2

(s) + 2OHminus larrrarr Zn(OH)4

2minus (4)

The Zn(OH)4

2minus species formed have no polarization bymicrowave radiation and the growth of the particles is in arandom way

33 Washing Solvent Effect There has been described in theliterature the effect of different solvents (ethanol water or


10 20 30 40 50

500

060 70 80

2120579 (deg)

Inte

nsity

(au

)

4000 3000 2000 1000Wavenumbers (cmminus1)

MW-1 MW-180 ∘C100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(a)


MW-2MW-2

10 20 30 40 50 60 70 802120579 (deg)

600

400

200

0

Inte

nsity

(au

)

100 ∘C100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(b)

10 20 30 40 50 60 70 802120579 (deg)

100

101

102

11210

320

0 201

110

002

3000

2500

2000

1500

1000

500

0

Inte

nsity

(au

)


MW-3 MW-3120 ∘C100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(c)

10 20 30 40 50 60 70 802120579 (deg)


350030002500200015001000

5000

Inte

nsity

(au

)

MW-4 MW-4

100

101

102

11210

320

020

1

110

002

140 ∘C

O-HCO2 in air Asymmetric

Symmetric

Zn-O

100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

C=OC=O

(d)

Figure 1 Temperature effect during microwave synthesis of ZnO on its morphological development


10 20 30 40 50 60 70 802120579 (deg)

350030002500200015001000

5000

Inte

nsity

(au

)Zn(NO3)2

100

101

102

11210

320

020

1

110

002

MW-4

(a)

Zn(CH3COO)2

14001600

12001000

800600400200

0

Inte

nsity

(au

)

MW-20

10 20 30 40 50 60 70 802120579 (deg)

(b)

10 20 30 40 50 60 70 802120579 (deg)

ZnCI2MW-211200

1000

800

600

400

200

0

Inte

nsity

(au

)

(c)

Figure 2 Effect of precursor salt during microwave synthesis of ZnO on its morphological development at 140∘C and 600W

350030002500200015001000

5000

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

100

101

102 10

320

0 201

110

112

002

MW-5

(a)

10 20 30 40 50 60 70 802120579 (deg)

MW-5140012001000

800600400200

0

Inte

nsity

(au

)

(b)

2500

2000

1500

1000

500

010 20 30 40 50 60 70 80

2120579 (deg)

MW-6In

tens

ity (a

u)

(c)

Figure 3 Isolation and precursors order addition effects on ZnO final morphology

both) used during the washing step on the morphologicalparameters of the nano-ZnO [25] and it was evidenced thatthey can affect the morphological characteristics of the finalproduct damaging the surface of ZnO depending on thesolvent used and on its polarity and vapor pressure Attendingto these results it was decided to carry out a synthesis

where the isolation of nano-ZnOwas made by centrifugation(10min at 10000 rpm MW-5) without previous washesinstead water is a preferable solvent to be used for ZnO [25]XRD analysis for the former case it means centrifugationwithout further purification shows the wurtzite hexagonalZnO characteristics (Figure 3) From the images obtained by


Inte

nsity

(au

)

3000

2500

2000

1500

1000

500

0

MW-15

10 20 30 40 50 60 70 802120579 (deg)

(a)

10 20 30 40 50 60 70 802120579 (deg)

2500

2000

1500

1000

500

0

Inte

nsity

(au

)

MW-16

(b)

MW-17

2500

2000

3000

1500

1000

500

0

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

(c)

Figure 4 Base effect in microwave assisted ZnO synthesis (a) KOH (b) KOH 13mL and (c) NH4

OH

FE-SEM a more dispersed system from both morphologicaland size distribution aspects (Figure 3) can be observed witha less resolution on the lattices of the bihexagonal rod-likestructure

34 Precursor Base Effect The results presented up to thispoint have been obtained using NaOH as the precursor baseHowever KOH (MW-15) and NH

4

OH (MW-17) have alsobeen used under the same experimental conditions in orderto analyze their effect on the morphological characteristics ofthe nanoparticles produced In the case of using KOH twopopulations of well-defined morphologies can be observed(Figure 4(a)) one of them is similar to that obtained whenNaOH is used as the precursor base (Figure 1 MW-4) in theform of bihexagonal rods and there is another population ofparticles in the form of agglomerates which are constitutedby small particles When NH

4

OH is used as the base twomorphologies can be clearly observed the characteristichexagonal rods previously described in the case of NaOHand KOH and other one where two- or three-dimensionalgrowths are favored (Figure 4(c)) In this last case the growthis favored radially and in different directions yielding three-dimensional complex particles similar to the dandelionsparticles obtained by Huang et al [16] The changes in mor-phology are attributed to the different degrees of electrostaticeffects of the hydrated ion (Na+ K+ or NH

4

+) which canact on the surface of the growing crystals causing differentgrowth on their surfaces Therefore the size of hydrated ions(K+ cong NH

4

+ lt Na+) and their charge are important factorsin this approach

In this sense when the more bulky Na+ is present theZn+2 is preferably adsorbed on the 0001+minus planes so that the

crystals show oriented growth along these directions On thecontrary when K+ is the counterion there is a competitionbetween K+ and Zn+2 and K+ inhibited the adsorption ofZn+2 on the 0001+minus planes so Zn+2 must be adsorbed notonly on the 0001+minus planes but also onto the other six planesyielding particles with shorter length and higher diameter ina similar way as the behavior described by Nejati et al [26]

35 Stoichiometry Effect The stoichiometry relation betweenZn+2 and OHminus was also studied and instead of adding theamount of base described in the synthesis (Zn+2OHminus =1871) (Section 21) that allows carrying out the reaction atpH of 58 13mL of KOH (Zn+2OHminus = 1173) (MW-16) wereadded and a pH of 108 was reached This modification inOHminus concentration has been directly reflected in a morpho-logical change of the particles obtained (Figure 4(b)) Thiseffect is attributed to a different reaction mechanism in thegeneration of ZnO particles

If an excess of OHminus is added (like in MW-16 synthesis)to the aqueous solution the precipitated Zn(OH)

2

(s) speciesformed in (2) would dissolve back into the alkali solutionto form the initial ions [27] and after certain reaction timeduring the stirring period the reaction symbolized by (4) canoccur before irradiation with the formation of Zn(OH)

4

2minus

complexes As KOH concentration increases the Zn(OH)4

2minus

complexes are surrounded by a large amount of OHminus sothat the differences in the observed morphologies (Figures4(a) and 4(b)) can be attributed to the different stages wheregrowth unit can be formed and to the initial zinc species andtheir environment in the reactor as it was demonstrated byXuet al in the case of ZnO synthesis via a hydrothermal method[28]


36 Power and Irradiation Time Effect In order to ana-lyze the microwave irradiation system controllable variablessuch as power and irradiation time on the produced ZnOmorphology some experiments were carried out under thesame experimental conditions but with different irradiationtimes only initial ramp (10min) (MW-10) to reach the targettemperature (140∘C) and 5 10 and 20min after reaching thedesirable temperature (Table 1 MW-11 MW-12 and MW-4resp) By XRD and IR techniques it could be observed thatonly in the case of using the initial ramp (MW-10) thereis evidence of signals indicating the presence of impuritiesin the final product In the other three cases (MW-11MW-12 and MW-4) only wurtzite hexagonal signals andZnO characteristics vibrations are present In Figure 5 themorphology evolution of ZnO nanoparticles with irradiationtime can be observed where an increase in this parametergenerates more defined structures and a final system with amore homogeneous particle size and morphology distribu-tion as a consequence of more time for the 0001 plane togrowth

On the other hand when the effect of power microwaveirradiation was analyzed (samples MW-13 MW-4 and MW-14 for 300 600 and 1200W resp Table 1) (Figure 6) itwas observed that the formation of aggregates is favoredas the microwave power increases As microwave powerincreases there is an increase in themixture aqueous solutiontemperature enhancing the tendency of the ZnO nucleito aggregate in a similar way to that described by Al-Gaashani et al [18] Moreover when the power is set to1200W (Figure 6(c)) the generation of agglomerates makesthe system not homogeneous and not well dispersed like theone obtained at 600W (Figure 6(b))

37 Additives Effect It is well known that the use of additivesleads to changes in ZnO crystal growth [29] In this work theeffect of the addition of an anionic surfactant (sodium di-2-ethylhexyl-sulfosuccinate (AOT)) and a dispersant (ethyleneglycol) on ZnO particles obtained by microwave syntheticmethod was evaluated In these experiments the syntheseswere carried out in the same way as it was previouslydescribed by dissolving Zn+2 in an additive (AOT or ethyleneglycol) aqueous solution

As it can be inferred fromFigure 7(a) when 1 g (16mmol)of ethylene glycol was added (MW-9) to the reaction mediathere were no significant changes neither in the morphologynor in the size of the obtained ZnO particles in comparisonwith the product obtained in the absence of any additive(MW-4)

On the contrary when AOT surfactant was addedimportant changes could be observed With 024 g of AOT(05mmol) (MW-7) the particles show a different morphol-ogy (Figure 7(b)) in the sense that there is a lower growthin c axis ([001] direction) so smaller hexagonal prismaticparticles are formed with sizes in the interval of 60ndash80 nm indiameter and length between 90 and 110 nm when comparedwithMW-4 Similar results were obtained when 05 g of AOT(11mmol) were added (MW-8) In this case characteristicvibrations of surfactant could be observed by FTIR due to

surfactant traces are still present after washes made withethanol and deionized water

The previous results can be attributed to the fact thatAOT can be acting as an external factor that can controlthe growth rate of various faces of the crystals due to theadsorption of the counterions on the negatively chargedsurfaces (precursor Zn(OH)

4

2minus) reducing the surface energyof the specific crystal faces This behavior can lead to thecontrol of the crystal growth while retaining in some way themorphology

38 Optical Properties Having inmind that the absorption ofcolloidal system depends on the particle size and shape [30]absorption spectra of some synthetized ZnO nanoparticleswere obtained As it can be observed from Figure 8 parti-cles with size higher than 500 nm do not show importantabsorption band and no maximum can be detected in theabsorbance curves (MW-4 MW-15 MW-17 and MW-20)However when surfactant AOT is added to the reactionmedia and smaller particles are produced (particles sizelt 100 nm) a significant increase in UV absorption and awell-defined maximum at 374 nm can be observed Thisabsorption is caused by two factors the first one is due tothe excitation of the electrons from the valence band to theconduction band when they are irradiated with UV lightwhich causes the absorption of UV radiation The second islight scatter the particle size of a colloidal solution within thewavelength of UV light results in light scattering which alsocauses the absorption

4 Conclusions

A simple and effective microwave assisted aqueous solutionmethod has been used to synthetize ZnO with high crys-tallinity and purity when Zn(NO

3

)2

is used as precursorreagent In addition several parameters have been evaluatedin order to analyze their effects on the ZnO nanoparticlesobtained An increase from 80∘C to 140∘C in set reactiontemperature allowed to obtain a system with high purity andhomogeneous in size and shape On the other hand threedifferent Zn+2 precursors were employed to synthetize thenanoparticles Zn(NO

3

)2

sdot6H2

O Zn(CH3

COO)2

sdot2H2

O andZnCl2

It was observed that as the adsorption of counteran-ions on surfaces increases the synthesizedZnOparticles sizesdecrease in the following order NO

3

minus gt CH3

COOminus gt ClminusWhen different OHminus precursors were employed (NaOH

KOH and NH4OH) some changes were observed in themorphological characteristics of the synthesized ZnO IfNH4

OH is used as the base two morphologies were foundthe hexagonal rods described in the case of NaOH and KOHand other ones where two- or three-dimensional growths arefavored The final reaction pH can be mentioned as anotherimportant variable that causes significant changes on themorphology of the final product

An increase in irradiation time generates more definedstructures and a final system with a more homogeneousparticle size and morphology distribution as a consequenceof more time for the 119888 direction to growth Furthermore it


(a) (b) (c)

Figure 5 FE-SEM images of ZnO obtained at different irradiation times (a) only initial temperature ramp (b) 5min at 140∘C and (c) 10minat 140∘C

(a) (b) (c)

Figure 6 FE-SEM images of ZnO obtained at different irradiation powers at 140∘C (a) 300W (b) 600W and (c) 1200W

was observed that the formation of aggregates is favored asthe microwave power increases

The addition of an anionic surfactant (AOT) to thereaction media allowed the synthesis of smaller particles anda significant increase in UV absorption and a well-definedmaximum at 374 nm was observed

As final conclusions it can be enounced that to obtaina very pure phase of ZnO of high density employingmicrowave as energy source it is recommended to useZn(NO

3

)2

as precursor

Acknowledgments

The authors would like to thank Miriam Lozano and JesusAngel Cepeda Garza for their contribution on the characteri-zation of the ZnOnanoparticles by FE-SEMAlso the authorswish to thank the Mexican National Council for Science andTechnology (CONACYT) for its financial support for therealization of this study through a postdoctoral fellowship forGaston P Barreto PhD (CB-2008-01 Project no 101934)

References

[1] LWang andMMuhammed ldquoSynthesis of zinc oxide nanopar-ticles with controlled morphologyrdquo Journal of Materials Chem-istry vol 9 no 11 pp 2871ndash2878 1999

[2] R Hong T Pan J Qian andH Li ldquoSynthesis and surfacemod-ification of ZnO nanoparticlesrdquo Chemical Engineering Journalvol 119 no 2-3 pp 71ndash81 2006

[3] F Paraguay W Estrada D R Acosta E Andrade and MMiki-Yoshida ldquoGrowth structure and optical characterizationof high quality ZnO thin films obtained by spray pyrolysisrdquoThinSolid Films vol 350 no 1 pp 192ndash202 1999

[4] T Tani L Madler and S E Pratsinis ldquoHomogeneous ZnOnanoparticles by flame spray pyrolysisrdquo Journal of NanoparticleResearch vol 4 no 4 pp 337ndash343 2002

[5] J Wang and L Gao ldquoWet chemical synthesis of ultralong andstraight single-crystalline ZnO nanowires and their excellentUV emission propertiesrdquo Journal of Materials Chemistry vol13 no 10 pp 2551ndash2554 2003

[6] B Liu and H C Zeng ldquoHydrothermal synthesis of ZnOnanorods in the diameter regime of 50 nmrdquo Journal of theAmericanChemical Society vol 125 no 15 pp 4430ndash4431 2003

[7] U Pal and P Santiago ldquoControlling the morphology of ZnOnanostructures in a low-temperature hydrothermal processrdquoJournal of Physical Chemistry B vol 109 no 32 pp 15317ndash153212005

[8] L Spanhel and M A Anderson ldquoSemiconductor clusters inthe sol-gel process quantized aggregation gelation and crystalgrowth in concentrated ZnO colloidsrdquo Journal of the AmericanChemical Society vol 113 no 8 pp 2826ndash2833 1991

[9] M Ristic SMusicM Ivanda and S Popovic ldquoSol-gel synthesisand characterization of nanocrystalline ZnO powdersrdquo Journalof Alloys and Compounds vol 397 no 1-2 pp L1ndashL4 2005



3000

2500

2000

1500

1000

500

0

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

MW-9 MW-9100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(a)

100110

8090

6070

4050

2030

10

Tran

smitt

ance

()


MW-7MW-7

10 20 30 40 50 60 70 802120579 (deg)

10001200140016001800

800600400200

0

Inte

nsity

(au

)

(b)

Figure 7 XRD FE-SEM and FTIR characterization of ZnO synthetized with different additives (a) 1 g ethylene glycol (b) 024 g AOT and(c) 05 g AOT (experimental conditions 140∘C 20min and 600W)

35

3

25

2

15

1

05

0200 250 300 350 400 450 500 550 600 650 700 750 800

(d)(c)

(e)

(b)

(a)

120582 (nm)

Abso

rban

ce

Figure 8 UV-Vis spectra of ZnO nanoparticles dispersed in water(a) MW-17 (b) MW-15 (c) MW-20 (d) MW-4 and (e) MW-7

[10] H M Cheng H C Hsu S L Chen et al ldquoEfficient UVphotoluminescence from monodispersed secondary ZnO col-loidal spheres synthesized by sol-gel methodrdquo Journal of CrystalGrowth vol 277 no 1ndash4 pp 192ndash199 2005

[11] Y Y Tay S Li F Boey Y H Cheng and M H Liang ldquoGrowthmechanism of spherical ZnO nanostructures synthesized viacolloid chemistryrdquo Physica B vol 394 no 2 pp 372ndash376 2007

[12] O A Yıldırım and C Durucan ldquoSynthesis of zinc oxidenanoparticles elaborated bymicroemulsionmethodrdquo Journal ofAlloys and Compounds vol 506 no 2 pp 944ndash949 2010

[13] V Polshettiwar and R S Varma ldquoMicrowave-assisted organicsynthesis and transformations using benign reaction mediardquoAccounts of Chemical Research vol 41 no 5 pp 629ndash639 2008

[14] C O Kappe ldquoControlledmicrowave heating inmodern organicsynthesisrdquo Angewandte ChemiemdashInternational Edition vol 43no 46 pp 6250ndash6284 2004

[15] I Bilecka and M Niederberger ldquoMicrowave chemistry forinorganic nanomaterials synthesisrdquo Nanoscale vol 2 no 8 pp1358ndash1374 2010

[16] J Huang C Xia L Cao and X Zeng ldquoFacile microwavehydrothermal synthesis of zinc oxide one-dimensional nanos-tructure with three-dimensional morphologyrdquo Materials Sci-ence and Engineering B vol 150 no 3 pp 187ndash193 2008

[17] D Sharma S Sharma B S Kaith J Rajput and M KaurldquoSynthesis of ZnOnanoparticles using surfactant free in-air andmicrowavemethodrdquoApplied Surface Science vol 257 no 22 pp9661ndash9672 2011

[18] R Al-Gaashani S Radiman N Tabet and A R Daud ldquoEffectof microwave power on themorphology and optical property ofzinc oxide nano-structures prepared via a microwave-assistedaqueous solutionmethodrdquoMaterials Chemistry and Physics vol125 no 3 pp 846ndash852 2011

[19] T D Canh N V Tuyen and N N Long ldquoInfluence ofsolvents on the growth of zinc oxide nanoparticles fabricated bymicrowave irradiationrdquo VNU Journal of Science Mathematics-Physics vol 25 pp 71ndash76 2009


[20] L Wu Y Wu Y Shi and H Wei ldquoSynthesis of ZnO nanorodsand their optical absorption in visible-light regionrdquoRareMetalsvol 25 no 1 pp 68ndash73 2006

[21] H Kleinwechter C Janzen J Knipping H Wiggers and PRoth ldquoFormation and properties of ZnO nano-particles fromgas phase synthesis processesrdquo Journal of Materials Science vol37 no 20 pp 4349ndash4360 2002

[22] Z Hu G Oskam R L Penn N Pesika and P C SearsonldquoThe influence of anion on the coarsening kinetics of ZnOnanoparticlesrdquo Journal of Physical Chemistry B vol 107 no 14pp 3124ndash3130 2003

[23] W Li E Shi W Zhong and Z-W Yin ldquoGrowth mechanismand growth habit of oxide crystalsrdquo Journal of Crystal Growthvol 203 no 1-2 pp 186ndash196 1999

[24] S Yamabi and H Imai ldquoGrowth conditions for wurtzite zincoxide films in aqueous solutionsrdquo Journal of Materials Chem-istry vol 12 no 12 pp 3773ndash3778 2002

[25] Y C Chen and S L Lo ldquoEffects of operational conditionsof microwave-assisted synthesis on morphology and photocat-alytic capability of zinc oxiderdquo Chemical Engineering Journalvol 170 no 2-3 pp 411ndash418 2011

[26] K Nejati Z Rezvani and R Pakizevand ldquoSynthesis of ZnOnanoparticles and investigation of the ionic template effect ontheir size and shaperdquo International Nano Letters vol 1 no 2pp 75ndash81 2011

[27] S Erten-Ela S Cogal and S Icli ldquoConventional andmicrowave-assisted synthesis of ZnO nanorods and effectsof PEG400 as a surfactant on the morphologyrdquo InorganicaChimica Acta vol 362 no 6 pp 1855ndash1858 2009

[28] H Xu H Wang Y Zhang et al ldquoHydrothermal synthesis ofzinc oxide powders with controllable morphologyrdquo CeramicsInternational vol 30 no 1 pp 93ndash97 2004

[29] J H Park and S G Oh ldquoPreparation of CaO as OLED gettermaterial through control of crystal growth of CaCO

3

by blockcopolymers in aqueous solutionrdquo Materials Research Bulletinvol 44 no 1 pp 110ndash118 2009

[30] E Koushki M H Majles Ara S H Mousavi and H Hara-tizadeh ldquoTemperature effect on optical properties of colloidalZnO nanoparticlesrdquo Current Applied Physics vol 11 no 5 pp1164ndash1167 2011

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


Since 2007 the number of publications dealing withthe microwave assisted synthesis of ZnO has increasedsignificantly In this sense there have been many publishedresults concerned with aqueous and nonaqueous solutionmicrowave assisted synthesis where the effect of differentexperimental variables over ZnO size shape and physic-ochemical behavior have been analyzed [16ndash18] This irra-diation technique has been used to obtain nanostructureswith various morphologies including spherical particlesrods hexagonal rings hexagonal columns Flowers wireshexagonal tubes and sheets

Some authors [16] demonstrated the possibility of ZnOsynthesis with a novel three-dimensional morphology wheremicrowave radiation as heating source plays an importantrole in the formation of complex nanostructures In additionthe absence of metal catalyst template or surfactant in thismethod avoids the subsequent effort for the removal ofresidual additives

Other studies [18] dealt with the effect of power of micro-wave radiation on the shape and size of the synthetized ZnOnanostructures where the average particle size decreaseswithdecreasing microwave power being the optical propertiessensitive to the variation of this parameter

On the other hand other authors [19] analyzed the effectof solvent (water ethanol and isopropanol) on the synthe-tized ZnO nanostructures and an important change in thesize and shape of nanoparticles was reported When distilledwater was used as a solvent nanoparticles presented ellipseshape and larger size (larger axis was about 100 nm and size ofthe other axis was about 40 nm) With ethanol the obtainednanostructures had rod form with smaller sizes than thoseobtained in water and when isopropanol was used as thereaction medium spherical particles with radius of 10ndash12 nmwere obtained

However most synthetic studies did not show a completestudy about different parameters involved during the micro-wave assisted technique In this sense this work deals with acomplete analysis of different variables (precursor reagentstemperature irradiation time microwave radiation powerand the addition of additives) and their effect on the finalmorphology of nano-ZnO obtained through the microwaveassisted technique

2 Experimental

21 Synthesis of ZnO In a typical synthesis process15mL (16mol Lminus1) of a precursor salt (Zn(NO

3

)2

sdot6H2

OZn(CH

3

COO)2

sdot2H2

O or ZnCl2

) were diluted in 32mL ofdeionized water (or a sodium di-2-ethylhexyl-sulfosuccinateaqueous solution) to obtain a Zn+2 solution Afterwards4mL of a base (32mol Lminus1) (NaOH KOH or NH

4

OH) wasadded dropwise (2min) into the above-described solutionwith magnetic stirring at room temperature to get a colloidsystem which was maintained under stirring for 10minThen the reaction mixture was transferred into a Teflonautoclave and treated at selected temperature (80 100120 or 140∘C) for specific time (5 10 or 20min) undertemperature-controlled mode in a microwave accelerated

reaction system (Mars-X) operating at different powers(300 600 or 1200W) It must be mentioned that the systemwas programmed with a first temperature ramp where thetarget temperature was reached after 10min in all cases(Table 1) When the reaction was finished and cooled toroom temperature the white precipitate was collected byfiltration and washed with deionized water and ethyl alcoholseveral times Finally the product was dried at 65∘C in avacuum oven for 3 h

22 Characterization To investigate the structural proper-ties of ZnO nanoparticles field emission scanning elec-tron microscopy (FE-SEM) infrared (FTIR) UV-Vis spec-troscopy and powder X-ray diffraction (XRD) studies werecarried out ZnO powders synthetized were characterizedby X-ray diffraction with a Siemens D500 diffractometerDiffraction patterns were recorded from 10 to 80∘ 2120579 with astep size of 006∘ at 35 kV and 25mA The average crystallitesizes 119863 (Table 1) of the ZnO nanostructures were calculatedusing Scherrerrsquos formula

119863 =09120582

120573 cos 120579 (1)

where 120582 is the X-ray wavelength of Cu-K120572 radiation source 120573is the full width at half maximum intensity of the diffractionpeak located at 2120579 and 120579 is the Bragg angle

On the other hand an aliquot of solid state material wasplaced in a carbon label for analysis by FE-SEM (JSM-7401F)Samples were analyzed using a secondary electron detectorThe infrared spectra of ZnO nanoparticles were taken in aNicolet spectrophotometer model Nexus 470 Nicolet brandin transmittance mode The sample preparation was made intablet way by mixing nano-ZnO and KBr in an agate mortarThe solid samples were dispersed in deionized water andultrasonicated for 10min Then UV-Vis spectra of colloidalsystems were obtained through a Shimadzu double beamspectrophotometer model UV-2401PC

Characterization data of all ZnO synthesis carried out isdescribed in Electronic Supplementary Material (ESM) thataccompanies this paper (see Supplemetary Material availableonline at httpdxdoiorg1011552013478681)

3 Results and Discussion

31 Temperature Effect The microwave system employed tosynthetize the ZnO particles allows to set a constant reactiontemperature In order to analyze the temperature effect onthe final morphology of the product obtained the syntheticreactions were carried out in the temperature interval 80ndash140∘C using Zn(NO

3

)2

as the precursor salt (from MW-1 toMW-4 Table 1) XRD studies (Figure 1) show that when thereaction is carried out for 20 minutes at 80 or 100∘C (MW-1and MW-2 resp) the signals are not clear and some peaksattributable to precursor reagents and unknown impuritiesare observed On the contrary at 120 and 140∘C (MW-3and MW-4 resp) all the diffraction peaks match those ofthe wurtzite ZnO with lattice constants of 119886 = 3250 Aand 119888 = 5207 A The strong diffraction peaks appear at



Synthesiscode






120583m

























2



3

)2

sdot6H2

O (MW-4) Zn(CH3

COO)2

sdot2H2

O (MW-20)and ZnCl

2



3

)2

and Zn(CH3

COO)2






minus

gt CH3




)2


3

)2




4


Zn (OH)2

(s) + 2H2


4

2minus

+ 2H+


2

O(3)


4



Zn(OH)2


2minus (4)

The Zn(OH)4




10 20 30 40 50

500

060 70 80

2120579 (deg)

Inte

nsity

(au

)


MW-1 MW-180 ∘C100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(a)


MW-2MW-2

10 20 30 40 50 60 70 802120579 (deg)

600

400

200

0

Inte

nsity

(au

)

100 ∘C100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(b)

10 20 30 40 50 60 70 802120579 (deg)

100

101

102

11210

320

0 201

110

002

3000

2500

2000

1500

1000

500

0

Inte

nsity

(au

)


MW-3 MW-3120 ∘C100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(c)

10 20 30 40 50 60 70 802120579 (deg)


350030002500200015001000

5000

Inte

nsity

(au

)

MW-4 MW-4

100

101

102

11210

320

020

1

110

002

140 ∘C


Symmetric

Zn-O

100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

C=OC=O

(d)



10 20 30 40 50 60 70 802120579 (deg)

350030002500200015001000

5000

Inte

nsity

(au

)Zn(NO3)2

100

101

102

11210

320

020

1

110

002

MW-4

(a)

Zn(CH3COO)2

14001600

12001000

800600400200

0

Inte

nsity

(au

)

MW-20

10 20 30 40 50 60 70 802120579 (deg)

(b)

10 20 30 40 50 60 70 802120579 (deg)

ZnCI2MW-211200

1000

800

600

400

200

0

Inte

nsity

(au

)

(c)


350030002500200015001000

5000

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

100

101

102 10

320

0 201

110

112

002

MW-5

(a)

10 20 30 40 50 60 70 802120579 (deg)

MW-5140012001000

800600400200

0

Inte

nsity

(au

)

(b)

2500

2000

1500

1000

500

010 20 30 40 50 60 70 80

2120579 (deg)

MW-6In

tens

ity (a

u)

(c)





Inte

nsity

(au

)

3000

2500

2000

1500

1000

500

0

MW-15

10 20 30 40 50 60 70 802120579 (deg)

(a)

10 20 30 40 50 60 70 802120579 (deg)

2500

2000

1500

1000

500

0

Inte

nsity

(au

)

MW-16

(b)

MW-17

2500

2000

3000

1500

1000

500

0

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

(c)


OH



4


4


4


4






2


4

2minus


2minus










4



4 Conclusions


3

)2


3

)2

sdot6H2

O Zn(CH3

COO)2

sdot2H2

O andZnCl2


3

minus gt CH3






(a) (b) (c)


(a) (b) (c)





3

)2

as precursor

Acknowledgments


References












3000

2500

2000

1500

1000

500

0

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

MW-9 MW-9100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(a)

100110

8090

6070

4050

2030

10

Tran

smitt

ance

()


MW-7MW-7

10 20 30 40 50 60 70 802120579 (deg)

10001200140016001800

800600400200

0

Inte

nsity

(au

)

(b)


35

3

25

2

15

1

05

0200 250 300 350 400 450 500 550 600 650 700 750 800

(d)(c)

(e)

(b)

(a)

120582 (nm)

Abso

rban

ce























3










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





Synthesiscode






120583m

























2



3

)2

sdot6H2

O (MW-4) Zn(CH3

COO)2

sdot2H2

O (MW-20)and ZnCl

2



3

)2

and Zn(CH3

COO)2






minus

gt CH3




)2


3

)2




4


Zn (OH)2

(s) + 2H2


4

2minus

+ 2H+


2

O(3)


4



Zn(OH)2


2minus (4)

The Zn(OH)4




10 20 30 40 50

500

060 70 80

2120579 (deg)

Inte

nsity

(au

)


MW-1 MW-180 ∘C100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(a)


MW-2MW-2

10 20 30 40 50 60 70 802120579 (deg)

600

400

200

0

Inte

nsity

(au

)

100 ∘C100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(b)

10 20 30 40 50 60 70 802120579 (deg)

100

101

102

11210

320

0 201

110

002

3000

2500

2000

1500

1000

500

0

Inte

nsity

(au

)


MW-3 MW-3120 ∘C100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(c)

10 20 30 40 50 60 70 802120579 (deg)


350030002500200015001000

5000

Inte

nsity

(au

)

MW-4 MW-4

100

101

102

11210

320

020

1

110

002

140 ∘C


Symmetric

Zn-O

100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

C=OC=O

(d)



10 20 30 40 50 60 70 802120579 (deg)

350030002500200015001000

5000

Inte

nsity

(au

)Zn(NO3)2

100

101

102

11210

320

020

1

110

002

MW-4

(a)

Zn(CH3COO)2

14001600

12001000

800600400200

0

Inte

nsity

(au

)

MW-20

10 20 30 40 50 60 70 802120579 (deg)

(b)

10 20 30 40 50 60 70 802120579 (deg)

ZnCI2MW-211200

1000

800

600

400

200

0

Inte

nsity

(au

)

(c)


350030002500200015001000

5000

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

100

101

102 10

320

0 201

110

112

002

MW-5

(a)

10 20 30 40 50 60 70 802120579 (deg)

MW-5140012001000

800600400200

0

Inte

nsity

(au

)

(b)

2500

2000

1500

1000

500

010 20 30 40 50 60 70 80

2120579 (deg)

MW-6In

tens

ity (a

u)

(c)





Inte

nsity

(au

)

3000

2500

2000

1500

1000

500

0

MW-15

10 20 30 40 50 60 70 802120579 (deg)

(a)

10 20 30 40 50 60 70 802120579 (deg)

2500

2000

1500

1000

500

0

Inte

nsity

(au

)

MW-16

(b)

MW-17

2500

2000

3000

1500

1000

500

0

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

(c)


OH



4


4


4


4






2


4

2minus


2minus










4



4 Conclusions


3

)2


3

)2

sdot6H2

O Zn(CH3

COO)2

sdot2H2

O andZnCl2


3

minus gt CH3






(a) (b) (c)


(a) (b) (c)





3

)2

as precursor

Acknowledgments


References












3000

2500

2000

1500

1000

500

0

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

MW-9 MW-9100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(a)

100110

8090

6070

4050

2030

10

Tran

smitt

ance

()


MW-7MW-7

10 20 30 40 50 60 70 802120579 (deg)

10001200140016001800

800600400200

0

Inte

nsity

(au

)

(b)


35

3

25

2

15

1

05

0200 250 300 350 400 450 500 550 600 650 700 750 800

(d)(c)

(e)

(b)

(a)

120582 (nm)

Abso

rban

ce























3










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






2



3

)2

sdot6H2

O (MW-4) Zn(CH3

COO)2

sdot2H2

O (MW-20)and ZnCl

2



3

)2

and Zn(CH3

COO)2






minus

gt CH3




)2


3

)2




4


Zn (OH)2

(s) + 2H2


4

2minus

+ 2H+


2

O(3)


4



Zn(OH)2


2minus (4)

The Zn(OH)4




10 20 30 40 50

500

060 70 80

2120579 (deg)

Inte

nsity

(au

)


MW-1 MW-180 ∘C100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(a)


MW-2MW-2

10 20 30 40 50 60 70 802120579 (deg)

600

400

200

0

Inte

nsity

(au

)

100 ∘C100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(b)

10 20 30 40 50 60 70 802120579 (deg)

100

101

102

11210

320

0 201

110

002

3000

2500

2000

1500

1000

500

0

Inte

nsity

(au

)


MW-3 MW-3120 ∘C100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(c)

10 20 30 40 50 60 70 802120579 (deg)


350030002500200015001000

5000

Inte

nsity

(au

)

MW-4 MW-4

100

101

102

11210

320

020

1

110

002

140 ∘C


Symmetric

Zn-O

100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

C=OC=O

(d)



10 20 30 40 50 60 70 802120579 (deg)

350030002500200015001000

5000

Inte

nsity

(au

)Zn(NO3)2

100

101

102

11210

320

020

1

110

002

MW-4

(a)

Zn(CH3COO)2

14001600

12001000

800600400200

0

Inte

nsity

(au

)

MW-20

10 20 30 40 50 60 70 802120579 (deg)

(b)

10 20 30 40 50 60 70 802120579 (deg)

ZnCI2MW-211200

1000

800

600

400

200

0

Inte

nsity

(au

)

(c)


350030002500200015001000

5000

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

100

101

102 10

320

0 201

110

112

002

MW-5

(a)

10 20 30 40 50 60 70 802120579 (deg)

MW-5140012001000

800600400200

0

Inte

nsity

(au

)

(b)

2500

2000

1500

1000

500

010 20 30 40 50 60 70 80

2120579 (deg)

MW-6In

tens

ity (a

u)

(c)





Inte

nsity

(au

)

3000

2500

2000

1500

1000

500

0

MW-15

10 20 30 40 50 60 70 802120579 (deg)

(a)

10 20 30 40 50 60 70 802120579 (deg)

2500

2000

1500

1000

500

0

Inte

nsity

(au

)

MW-16

(b)

MW-17

2500

2000

3000

1500

1000

500

0

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

(c)


OH



4


4


4


4






2


4

2minus


2minus










4



4 Conclusions


3

)2


3

)2

sdot6H2

O Zn(CH3

COO)2

sdot2H2

O andZnCl2


3

minus gt CH3






(a) (b) (c)


(a) (b) (c)





3

)2

as precursor

Acknowledgments


References












3000

2500

2000

1500

1000

500

0

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

MW-9 MW-9100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(a)

100110

8090

6070

4050

2030

10

Tran

smitt

ance

()


MW-7MW-7

10 20 30 40 50 60 70 802120579 (deg)

10001200140016001800

800600400200

0

Inte

nsity

(au

)

(b)


35

3

25

2

15

1

05

0200 250 300 350 400 450 500 550 600 650 700 750 800

(d)(c)

(e)

(b)

(a)

120582 (nm)

Abso

rban

ce























3










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




10 20 30 40 50

500

060 70 80

2120579 (deg)

Inte

nsity

(au

)


MW-1 MW-180 ∘C100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(a)


MW-2MW-2

10 20 30 40 50 60 70 802120579 (deg)

600

400

200

0

Inte

nsity

(au

)

100 ∘C100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(b)

10 20 30 40 50 60 70 802120579 (deg)

100

101

102

11210

320

0 201

110

002

3000

2500

2000

1500

1000

500

0

Inte

nsity

(au

)


MW-3 MW-3120 ∘C100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(c)

10 20 30 40 50 60 70 802120579 (deg)


350030002500200015001000

5000

Inte

nsity

(au

)

MW-4 MW-4

100

101

102

11210

320

020

1

110

002

140 ∘C


Symmetric

Zn-O

100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

C=OC=O

(d)



10 20 30 40 50 60 70 802120579 (deg)

350030002500200015001000

5000

Inte

nsity

(au

)Zn(NO3)2

100

101

102

11210

320

020

1

110

002

MW-4

(a)

Zn(CH3COO)2

14001600

12001000

800600400200

0

Inte

nsity

(au

)

MW-20

10 20 30 40 50 60 70 802120579 (deg)

(b)

10 20 30 40 50 60 70 802120579 (deg)

ZnCI2MW-211200

1000

800

600

400

200

0

Inte

nsity

(au

)

(c)


350030002500200015001000

5000

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

100

101

102 10

320

0 201

110

112

002

MW-5

(a)

10 20 30 40 50 60 70 802120579 (deg)

MW-5140012001000

800600400200

0

Inte

nsity

(au

)

(b)

2500

2000

1500

1000

500

010 20 30 40 50 60 70 80

2120579 (deg)

MW-6In

tens

ity (a

u)

(c)





Inte

nsity

(au

)

3000

2500

2000

1500

1000

500

0

MW-15

10 20 30 40 50 60 70 802120579 (deg)

(a)

10 20 30 40 50 60 70 802120579 (deg)

2500

2000

1500

1000

500

0

Inte

nsity

(au

)

MW-16

(b)

MW-17

2500

2000

3000

1500

1000

500

0

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

(c)


OH



4


4


4


4






2


4

2minus


2minus










4



4 Conclusions


3

)2


3

)2

sdot6H2

O Zn(CH3

COO)2

sdot2H2

O andZnCl2


3

minus gt CH3






(a) (b) (c)


(a) (b) (c)





3

)2

as precursor

Acknowledgments


References












3000

2500

2000

1500

1000

500

0

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

MW-9 MW-9100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(a)

100110

8090

6070

4050

2030

10

Tran

smitt

ance

()


MW-7MW-7

10 20 30 40 50 60 70 802120579 (deg)

10001200140016001800

800600400200

0

Inte

nsity

(au

)

(b)


35

3

25

2

15

1

05

0200 250 300 350 400 450 500 550 600 650 700 750 800

(d)(c)

(e)

(b)

(a)

120582 (nm)

Abso

rban

ce























3










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




10 20 30 40 50 60 70 802120579 (deg)

350030002500200015001000

5000

Inte

nsity

(au

)Zn(NO3)2

100

101

102

11210

320

020

1

110

002

MW-4

(a)

Zn(CH3COO)2

14001600

12001000

800600400200

0

Inte

nsity

(au

)

MW-20

10 20 30 40 50 60 70 802120579 (deg)

(b)

10 20 30 40 50 60 70 802120579 (deg)

ZnCI2MW-211200

1000

800

600

400

200

0

Inte

nsity

(au

)

(c)


350030002500200015001000

5000

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

100

101

102 10

320

0 201

110

112

002

MW-5

(a)

10 20 30 40 50 60 70 802120579 (deg)

MW-5140012001000

800600400200

0

Inte

nsity

(au

)

(b)

2500

2000

1500

1000

500

010 20 30 40 50 60 70 80

2120579 (deg)

MW-6In

tens

ity (a

u)

(c)





Inte

nsity

(au

)

3000

2500

2000

1500

1000

500

0

MW-15

10 20 30 40 50 60 70 802120579 (deg)

(a)

10 20 30 40 50 60 70 802120579 (deg)

2500

2000

1500

1000

500

0

Inte

nsity

(au

)

MW-16

(b)

MW-17

2500

2000

3000

1500

1000

500

0

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

(c)


OH



4


4


4


4






2


4

2minus


2minus










4



4 Conclusions


3

)2


3

)2

sdot6H2

O Zn(CH3

COO)2

sdot2H2

O andZnCl2


3

minus gt CH3






(a) (b) (c)


(a) (b) (c)





3

)2

as precursor

Acknowledgments


References












3000

2500

2000

1500

1000

500

0

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

MW-9 MW-9100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(a)

100110

8090

6070

4050

2030

10

Tran

smitt

ance

()


MW-7MW-7

10 20 30 40 50 60 70 802120579 (deg)

10001200140016001800

800600400200

0

Inte

nsity

(au

)

(b)


35

3

25

2

15

1

05

0200 250 300 350 400 450 500 550 600 650 700 750 800

(d)(c)

(e)

(b)

(a)

120582 (nm)

Abso

rban

ce























3










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Inte

nsity

(au

)

3000

2500

2000

1500

1000

500

0

MW-15

10 20 30 40 50 60 70 802120579 (deg)

(a)

10 20 30 40 50 60 70 802120579 (deg)

2500

2000

1500

1000

500

0

Inte

nsity

(au

)

MW-16

(b)

MW-17

2500

2000

3000

1500

1000

500

0

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

(c)


OH



4


4


4


4






2


4

2minus


2minus










4



4 Conclusions


3

)2


3

)2

sdot6H2

O Zn(CH3

COO)2

sdot2H2

O andZnCl2


3

minus gt CH3






(a) (b) (c)


(a) (b) (c)





3

)2

as precursor

Acknowledgments


References












3000

2500

2000

1500

1000

500

0

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

MW-9 MW-9100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(a)

100110

8090

6070

4050

2030

10

Tran

smitt

ance

()


MW-7MW-7

10 20 30 40 50 60 70 802120579 (deg)

10001200140016001800

800600400200

0

Inte

nsity

(au

)

(b)


35

3

25

2

15

1

05

0200 250 300 350 400 450 500 550 600 650 700 750 800

(d)(c)

(e)

(b)

(a)

120582 (nm)

Abso

rban

ce























3










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials











4



4 Conclusions


3

)2


3

)2

sdot6H2

O Zn(CH3

COO)2

sdot2H2

O andZnCl2


3

minus gt CH3






(a) (b) (c)


(a) (b) (c)





3

)2

as precursor

Acknowledgments


References












3000

2500

2000

1500

1000

500

0

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

MW-9 MW-9100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(a)

100110

8090

6070

4050

2030

10

Tran

smitt

ance

()


MW-7MW-7

10 20 30 40 50 60 70 802120579 (deg)

10001200140016001800

800600400200

0

Inte

nsity

(au

)

(b)


35

3

25

2

15

1

05

0200 250 300 350 400 450 500 550 600 650 700 750 800

(d)(c)

(e)

(b)

(a)

120582 (nm)

Abso

rban

ce























3










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b) (c)


(a) (b) (c)





3

)2

as precursor

Acknowledgments


References












3000

2500

2000

1500

1000

500

0

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

MW-9 MW-9100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(a)

100110

8090

6070

4050

2030

10

Tran

smitt

ance

()


MW-7MW-7

10 20 30 40 50 60 70 802120579 (deg)

10001200140016001800

800600400200

0

Inte

nsity

(au

)

(b)


35

3

25

2

15

1

05

0200 250 300 350 400 450 500 550 600 650 700 750 800

(d)(c)

(e)

(b)

(a)

120582 (nm)

Abso

rban

ce























3










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





3000

2500

2000

1500

1000

500

0

Inte

nsity

(au

)

10 20 30 40 50 60 70 802120579 (deg)

MW-9 MW-9100110

8090

6070

4050

2030

10

Tran

smitt

ance

()

(a)

100110

8090

6070

4050

2030

10

Tran

smitt

ance

()


MW-7MW-7

10 20 30 40 50 60 70 802120579 (deg)

10001200140016001800

800600400200

0

Inte

nsity

(au

)

(b)


35

3

25

2

15

1

05

0200 250 300 350 400 450 500 550 600 650 700 750 800

(d)(c)

(e)

(b)

(a)

120582 (nm)

Abso

rban

ce























3










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials














3










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 Microwave Assisted Synthesis of ZnO ...downloads.hindawi.com/archive/2013/478681.pdftemperature, irradiation time, microwave radiation power, and the addition of additives)