Research Article Synthesis, Characterization, and Visible

Research ArticleSynthesis Characterization and Visible Light PhotocatalyticActivity of Nanosized Carbon Doped Zinc Oxide

A B Lavand and Y S Malghe

Department of Chemistry The Institute of Science 15 Madam Cama Road Mumbai 400032 India

Correspondence should be addressed to Y S Malghe ymalgheyahoocom

Received 10 September 2014 Revised 24 December 2014 Accepted 25 December 2014

Academic Editor Shinya Maenosono

Copyright copy 2015 A B Lavand and Y S Malghe This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

ZnO precursor was prepared using microemulsion method Precursor was calcined in a furnace in a temperature range of 300ndash500∘Cwith an interval of 100∘C Precursor and calcined nanopowders were characterized using TGDTA XRD FT-IR EDX TEMSEM and particle size analyzer Precursor calcined at 300∘C for 2 h contains 387 carbon (C) Increase in calcination temperatureof precursor shows decrease in C content Precursor calcined at 500∘C for 2 h yielded pure ZnO UV-visible spectrophotometerwas used to analyze the concentration of MG during the degradation process In presence of visible light C doped ZnO obtainedby calcining precursor at 300∘C shows better photocatalytic activity for MG degradation Parameters affecting the photocatalyticprocess such as calcination temperature of catalyst catalyst loading MG concentration and pH of solution have been investigated

1 Introduction

Environmental pollution has become a major threat tothe human lives Pollutants from polluted air and industryeffluents create severe ecological problems Photocatalyticoxidation of organic pollutants from industrial waste waterby using semiconducting oxides can be an alternative toconventional methods for environmental remediation Dueto its mild operating conditions and the fact that it canbe powered by sunlight it allows green mineralization oforganic pollutants [1ndash4] Among the semiconductors TiO

2

photocatalyst has been extensively investigated Anatase TiO2

shows better photocatalytic activity and is used as photocat-alyst It is difficult to prepare phase pure anatase TiO

2 and

also preparation of TiO2is costly Zinc oxide (ZnO) can be

considered as a suitable alternative to TiO2photocatalyst due

to its nontoxic nature good environmental stability strongoxidizing power and same band gap energy and is relativelycheaperThemajor advantage of ZnO is that it absorbs a largefraction of solar spectrum than TiO

2[5ndash7] ZnO has been

used for the photodegradation of various dye pollutants [8ndash10] ZnO has a wide band gap of about 32 eV and can absorbUV light with wavelength below 387 nm due to the fact thatits photocatalytic activity is limited to irradiation wavelength

in UV region only Unfortunately solar light consists of lessthan 5 UV radiations and indoor lighting consists of lessthan 01 UV radiations Therefore it is necessary to modifyZnO in order to utilize major portion of sunlightindoorlights

For the development of visible light sensitive ZnO severalmethods are used It includes dye sensitization [11 12] semi-conductor coupling [13 14] metal or nonmetal doping [15ndash19] surface organic coating [20] and surface hybridization ofZnOwith carbon [21]Doping of ZnOwith nonmetals such ascarbon (C) nitrogen (N) and sulfur (S) leads to the formationof intermediate energy level between the band gap enabling itto absorb visible light [22 23] Among the nonmetal dopantsC has been found to be very efficient for visible light inducedphotocatalysis Its additional advantage is that it can promotethe separation of photoelectrons and holes by channelizingthe photoexcited electrons to nanosized C on the surfaceof catalyst thereby reducing the rate of recombination [24ndash26]

In this paper we report the synthesis of C doped ZnOnanorods by reverse microemulsion method Also its photo-catalytic activity is examined for the degradation of MG inpresence of visible light as a model photocatalytic reaction

Hindawi Publishing CorporationInternational Journal of PhotochemistryVolume 2015 Article ID 790153 9 pageshttpdxdoiorg1011552015790153

2 International Journal of Photochemistry

2 Experimental

21 Materials Malachite green (MG) (bis[p-dimethylamino-phenyl]phenyl-methylium oxalate) was obtained fromMerckChemicals Mumbai and used without any further purifi-cation Zinc nitrate hexahydrate (Zn(NO)

3sdot6H2O) cyclo-

hexane n-butanol NNN-cetyl trimethyl ammonium bro-mide (CTAB) acetone ferric nitrate nanohydrate (Fe(NO

3)3sdot

9H2O) sodium hydroxide (NaOH) and ethanol used for the

synthesis are of AR grade All these chemicals were procuredfrom SD Fine Chemicals Mumbai and used without furtherpurification

22 Synthesis of Precursor 1M solution of zinc nitrate wasprepared by dissolving 2974 g of Zn(NO

3)2sdot6H2O in 100mL

distilled water 2M sodium hydroxide solution was preparedby dissolving 8 g of NaOH in 100mL distilled water To288mL 1M zinc nitrate 355mL cyclohexane 8mL butanoland 590 g cetyltrimethylammonium bromide (CTAB) wereadded In another solution 288mL 2M NaOH 355mLcyclohexane 8mL butanol and 590 g CTAB were mixedBoth these solutions were stirred continuously with thehelp of magnetic stirrer to form clear solutions These clearsolutions were mixed with each other The mixture wastransferred to 250mL Teflon lined autoclave and heated inan oven at 150∘C for 1 h After 1 h autoclave was cooled toroom temperature The solid product formed was separatedby filtration washed with distilled water followed by ethanoland finally with acetone and dried in an oven at 60∘CThe hydrothermal product (precursor) thus obtained wascharacterized using various characterization techniques

23 Characterization TG and DTA curves of precursorwere recorded using simultaneous TGDTA recording sys-tem (Rigaku Model-Thermo Plus TG8120) For recordingTGDTA curves 1420mg precursor was heated in a nitrogenatmosphere with a heating rate 10∘Cminminus1 For recordingDTA curve alumina was used as a reference material FT-IRspectra of precursor and the precursor calcined at 300 400and 500∘C were recorded using FT-IR spectrophotometer(Bruker) Precursor was calcined at 300 400 and 500∘Cfor 2 h and the XRD patterns of the product obtained atdifferent temperatures were recorded using X-ray diffrac-tometer (Rigaku Model-Miniflex II) using monochroma-tized CuK120572 radiation (120582 = 015405 nm) with scanning rateof 2∘2120579minminus1 Qualitative elemental analysis was carried outusing energy dispersive X-ray spectroscopy (EDX) (JEOL-JSM6360A) technique TEM images of C dopedpure ZnOpowder prepared in the present work were recorded usingtransmission electron microscope (Philips CM200) ForTEM sample was prepared by dispersing C dopedpure ZnOpowder in isopropyl alcohol and solution was sonicated for15minThe drop of solution was placed over C coated coppergrid and solvent was evaporated off under IR lamp Particlesize distribution study of product obtained at 300∘C was car-ried out using particle size analyzer (NanosightModel-NTA-LM-20) Band gap energies of synthesized nanopowders wereevaluated fromUV-visible spectra recorded using UV-visiblespectrophotometer (Shimadzu Model-1800)

0

minus10

minus20

100 200 300 400 500 600

50

0

minus50

minus100

minus150

Mas

s los

s (

)

EndoΔT120583V

exo

Temperature (∘C)

Figure 1 TG andDTA curves of ZnOprecursor recorded in flowingnitrogen

24 Photocatalytic Activity Study Photocatalytic activity ofnanosized pureC doped ZnO photocatalyst was tested fordegradation of malachite green (MG) solution Reactionsuspension was prepared by adding 005 g ZnO (obtained at300∘C) photocatalyst in 100mL 10 ppm MG solution Thisaqueous suspension was stirred in the dark for 30min toattain adsorption-desorption equilibrium Later the solutionwas irradiated with visible light The visible light irradiationwas carried out in a photoreactor using a compact fluorescentlamp (65W 120582 gt 420 nm Philips) Temperature of testsolutionwasmaintained constant throughout the experimentby circulating water around the solution The amount of MGwas monitored by sampling out 5mL of aliquot solution atregular time intervalsThe catalyst was first separated by cen-trifugation and the concentration of MG in the supernatantsolution was estimated using UV-visible spectrum recordedin the wavelength range of 200ndash800 nm

To evaluate the effect of various parameters on photocat-alytic activity of ZnO the same experiment was repeated byusing the catalyst calcined at different temperatures varyingthe amount of catalyst used and changing the pH andconcentration of MG

3 Results and Discussion

31 TG and DTA Study Simultaneous TG and DTA curveswere recorded for thermal decomposition studies of precur-sor and are presented in Figure 1 TG curve shows that thereis gradual weight loss from 25 to 200∘C and this can beattributed to vaporization of absorbed water molecules andcyclohexane Also this change is observed in DTA curve asan endothermic peak in the same temperature range withminima located near 104∘C In temperature range 200ndash330∘CTG curve exhibits a suddenweight loss which corresponds toburning of residual surfactant and gives weak endothermicpeak in DTA curve near 300∘C

International Journal of Photochemistry 3

Table 1 Properties of C doped and pure ZnO photocatalyst

Sample Calcination temperature (∘C) C content () Band gap energy (eV) Photodegradation efficiency() (irradiation time 60min)

1 300 387 269 982 400 072 288 843 500 0 308 67

20 30 40 50 60 70 80

2120579 (deg)

Inte

nsity

(au

)

(100

)(002

)(101

)

(102

)

(110

)

(103

)(200

)(112

)(201

)(004

)

(202

)

lowast Zn(OH)2

500∘C

400∘C

300∘C

Precursorlowast lowast lowastlowastlowast lowast lowast lowast lowast lowast lowast

Figure 2 XRD patterns of precursor and precursor calcined atdifferent temperatures

Above 400∘C there is no weight loss and TG curvegives a stable line It indicates that precursor yields stableproduct above 400∘C This information was used to selectthe calcination temperature to get ZnO powder from itsprecursor Precursor was calcined at 300 400 and 500∘Cfor 2 h and the product obtained was analyzed using X-raydiffractometer

32 X-Ray Diffraction (XRD) Study Figure 2 shows XRDpatterns of precursor and product obtained after heating theprecursor at 300 400 and 500∘C XRD pattern of precursorshows that it is the mixture of Zn(OH)

2and as-grown ZnO

particles These patterns suggest that product obtained byheating the precursor at different temperatures is crystallinein nature and is in good agreement with the wurtzite ZnOphase (JCPDS 36ndash1451) The average crystallite sizes of theproduct obtained were calculated from their XRD patternsusingDebye-Scherrer equation andwere found to be between20 and 35 nm

33 FT-IR Study FT-IR spectra of the precursor and productobtained after calcinations of the precursor at differenttemperatures for 2 h are presented in Figure 3 It showsthat precursor gives absorption peaks at 3452 and 1625 cmminus1which corresponds to the OndashH stretching and bending

3500 2500 1500 500

Wavenumber (cmminus1)

Abso

rban

ce

3452

cmminus1

2900

cmminus1

1625

cmminus1

1376

cmminus1

398

cmminus1

500∘C

400∘C

300∘C

Precursor

Figure 3 FT-IR spectra of precursor and precursor calcined atdifferent temperatures

vibration of the ndashOH bond [27] It indicates that the precur-sorhydrothermal product is the mixture of Zn(OH)

2and as-

grown ZnO particles Peak at 1376 cmminus1 can be assigned toCndashO stretching in carbonyl This information indicates thatndashOH and ndashC=O functional groups are present in precursorThis spectrum also shows absorption peaks below 560 cmminus1which corresponds to the stretching frequency of ZnndashObond in zinc oxide FT-IR spectra of product obtained afterheating the precursor at 300 400 and 500∘C for 2 h showno absorption peak in higher frequency region but give thesharp peak below 600 cmminus1 which may be due to stretchingfrequency of ZnndashO bond in zinc oxide It indicates thatprecursor heated above 300∘C for 2 h gives ZnO as a product

34 Energy Dispersive X-Ray Spectroscopy (EDX) Study EDXspectra of the precursor heated at various temperatures wererecorded From EDX spectra amount of C present in thesample was estimated and data obtained is presented inTable 1 It shows that C is present in the product obtained aftercalcining the precursor at 300 and 400∘C and the amount ofC is 387 and 072 respectively (by weight) However theprecursor heated at 500∘C for 2 h yielded pure ZnO

35 Transmission Electron Microscopy (TEM) Study TEMimages of precursor calcined at different temperatures wererecorded and are presented in Figure 4 It shows that Cdoped ZnO prepared at 300∘C is having a rod-like structurewith diameter and length varying between 20ndash40 and 100ndash400 nm respectively Product obtained at 400∘C is heteroge-neous and consists of a mixture of rods and spheres HoweverZnO particles obtained at 500∘C are spherical in shape andsize of particles ranges from 15 to 35 nm


(a) (b)

(c)

Figure 4 TEM images of ZnO obtained at (a) 300 (b) 400 and (c) 500∘C

This is may be due to the addition of NaOH intoaqueous solution of Zn(NO

3)2leads to the formation of

white precipitate of Zn(OH)2 which during hydrothermal

treatment decomposes to ZnOThus the hydrothermal prod-uct obtained is a mixture of Zn(OH)

2and as-grown ZnO

particles This mixture was heated in air and gives ZnOnanoparticles with different morphologies [26]The probablereaction that occurred during thermal treatment could begiven as

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

Heating997888997888997888997888997888rarr ZnO (s) +H

2O(1)

Selected area electron diffraction patterns (SAED) of all thesamples (inset) show distinct rings that correspond to thediffraction pattern of ZnO indicating crystalline nature

36 Scanning Electron Microscopy (SEM) Study SEM imagesof precursor calcined at different temperatures were recordedand are presented in Figure 5 It shows that C doped ZnOprepared at 300∘C is having irregular shape At 400∘C thisirregular shape initiated to transform into spherical shapeand therefore it shows mixture of rods and spheres ZnOparticles obtained at 500∘C are spherical in shape and at thistemperature it shows aggregation

37 Particle Size Analysis Particle size distribution of ZnOsynthesized in present work was studied using particle sizeanalyzerThe particle size distribution curve for the precursorcalcined at 300∘C for 2 h is presented in Figure 6 This figure

shows that particle size of C doped ZnO prepared in thepresent work varies over range from 20 to 70 nmwith averageparticle size 43 nm which is in agreement with the sizeobtained from TEM studies

38 UV-Visible Spectrophotometery Study UV-visible spectraof ZnO nanopowders synthesized in present work are pre-sented in Figure 7 Figure 7(c) shows that pureZnO (obtainedat 500∘C) gave band gap absorption edge at 403 nm whereasC doped ZnO that is ZnO obtained by calcining precursorat 400 and 300∘C for 2 h gave absorption peaks at higherwavelength whose absorption edges are at 430 and 461 nmrespectively This distinct difference in absorption charac-teristics indicates that C is successfully doped on ZnO Theband gap energy of ZnO obtained at various temperatureswas estimated using Tauc plot (Figure 8) and is presented inTable 1Theband gap energy of ZnOobtained at 300 400 and500∘C is 269 288 and 308 eV respectively Band gap of ZnOobtained at 300∘C is less as compared to ZnO obtained at 400and 500∘C due to this reason it absorbs higher wavelength(visible) light

39 Visible Light Photocatalytic Activity Study Visible lightphotocatalytic degradation of MG dye was studied in pres-ence of nanosized pure and C doped ZnO UV-visible spectraof aqueous solution of MG irradiated with visible light atdifferent time intervals in presence ofCdopedZnO (obtainedat 300∘C) were recorded and are presented in Figure 9These spectra show characteristic peak maxima at 616 nmAs irradiation time increases the height of peak maxima at616 nm decreases indicating photocatalytic degradation of


(a) (b)

(c)

Figure 5 SEM images of ZnO obtained at (a) 300 (b) 400 and (c) 500∘C

Num

ber o

f par

ticle

s

Particle size (nm)0 100 200

9

30

43

Figure 6 Particle size distribution of C doped ZnO prepared at300∘C

MG Mechanism of this degradation can be explained asfollows

CndashZnO + ℎ] 997888rarr eminusCB + h+

VB (2)

eminusCB + h+

VB 997888rarr CndashZnO + heat (3)

eminusCB +O2(adsorbed) 997888rarr O2

minus∙ (4)

h+VB +H2O(adsorbed) 997888rarr H+ +HO∙ (5)

h+VB +HOminus(adsorbed) 997888rarr HO∙ (6)

OH∙ or h+VB +MG 997888rarr MG+∙ 997888rarr Oxidized (7)

Figure 9 shows that in presence of photocatalyst sim98MG isdegraded in 60min

Abso

rban

ce (a

u)

200 400 600 800

Wavelength (nm)

ab

c

ab

c

Figure 7 UV-visible absorption spectra of ZnO prepared at (a) 300(b) 400 and (c) 500∘C

Several parameters affect the rate of photocatalytic degra-dation To optimize the photocatalysis process it is neces-sary to study these parameters Various parameters suchas calcination temperature amount of catalyst pH andconcentration of MG which affect the rate of photocatalyticdegradation were studied and are explained in the followingsection

391 Effect of Calcination Temperature of Catalyst MGsolution was exposed to visible light in presence of pureand C doped ZnO The UV-visible spectra of the MG


20 25 30 35 40

a b c

(120572)2

h (eV)

h

a b c

Figure 8 Tauc plots (120572ℎ])2 versus photon energy (ℎ]) for ZnOprepared at (a) 300 (b) 400 and (c) 500∘C

15

10

05

00

400 500 600 700 800

Abso

rban

ce (a

u)

Wavelength (nm)

0min

15min

30min

45min

60min

75min

Figure 9 UV-visible spectra of MG solution irradiated with visiblelight at different time intervals in presence of C doped ZnOphotocatalyst prepared at 300∘C

solution exposed for different time intervals were recordedand amount of MG degraded was calculated The plot ofconcentration of MG as a function of irradiation time inpresence of different catalyst is presented in Figure 10 Thisfigure shows that solution kept in dark for 30min in presenceof catalyst calcined at different temperatures exhibits totallydifferent behavior Adsorption efficiencies of photocatalystcalcined at 300 400 and 500∘C are 408 232 and 81respectively It was observed that as compared to pure ZnOC doped ZnO showed higher adsorption efficiency for MGdye in dark and this may be due to the enhancement inthe adsorption of organic pollutant assisted by doped C Theadsorption of the dye increases with increasing the C contentIn absence of catalyst no appreciable degradation of MG wasobserved even up to 180min whichmeansMG is fairly stableto visible light irradiation Photodegradation efficiency ofZnOdecreases with increasing the calcination temperature ofcatalyst As the calcination temperature increases C contentin ZnO decreases The catalyst calcined at 300∘C gives betterphotocatalytic activity reaching sim98 within 60min Thecatalyst calcined at 400 and 500∘Cdegradessim84 and 67MG

10

08

06

04

02

00

0 30 60 90 120 150 180

Time (min)

CC

o

Dark Visible light

Photolysisa

bc

Figure 10 Effect of calcination temperature of catalyst on pho-todegradation rate of MG catalyst calcined at (a) 300 (b) 400 and(c) 500∘C

within 60minThis can be due to difference in size and shapeas well as C content doped on ZnO at different temperaturesThe photodegradation efficiency of MG using photocatalystcalcined at different temperatures is estimated and presentedin Table 1

392 Effect of Catalyst Loading Effect of photocatalyst doseon photodegradation of MG dye was investigated usingdifferent amount of C doped ZnO photocatalyst obtainedat 300∘C For this study the amount of C doped ZnO wasvaried from 01 to 10 gLminus1 The concentration of MG used tostudy the dose of catalyst was kept constant at 10 ppm andpH was adjusted to 7 Photocatalytic degradation of MG as afunction of irradiation time in presence of varying amount ofcatalyst was investigated and the data obtained is presentedgraphically in Figure 11 The graph clearly indicates that asthe amount of photocatalyst in the MG solution increasesrate of photodegradation increases At 05 gLminus1 concentrationbetter photocatalytic activity was observed degrading sim98MG within 60min Further increase in the amount ofphotocatalyst showed decrease in the photodegradation ratePhotodegradation rate depends on presence of surface activesites If the catalyst loading increased rate of generation ofelectronhole pairs and degradation of pollutants increasesHowever further increase in the concentration of the catalystleads to aggregation affecting the number of active sitesavailable for generation of electronhole pairs Also whenconcentration of catalyst is more photonic flux within irra-diated solution decreases which reduces the degradation rate[28]

393 Effect of pH Photodegradation process is also stronglyaffected by pH of the solution Effect of pH ofMG solution onphotocatalytic degradation rate was studied and rate constantof photodegradation process as a function of pH of solution


Dark Visible light10

08

06

04

02

00

0 30 60 90

Time (min)

CC

o

01 gL05 gL10 gL

Figure 11 Effect of amount of catalyst on photodegradation rate ofMG

006

004

002

000

0 2 4 6 8 10 12

pH

Rate

cons

tant

(minminus1)

Figure 12 Photodegradation rate of MG as function of pH

is plotted and presented in Figure 12The figure indicates thatphotodegradation efficiency of MG is less at lower pH valuesand increases with increase in pH At pH = 9 almost 100dye degrades within 45min In acidic conditions it is difficultfor cationic dye to get adsorbed on catalyst surface Also atlow pH concentration of active ∙OH radicals is usually lowtherefore photodegradation rate ofMG remains slow At highpH formation of active ∙OH radicals favors due to improvedtransfer of holes and increases the photodegradation rate

394 Effect of Dye Concentration Effect of dye concentrationon MG photodegradation rate was studied by varying theconcentrations ofMG and keeping the amount of catalyst andpH constant (ie 05 gLminus1 and 7 resp) Photocatalytic dataobtained by varying the concentration of MG is presentedin Figure 13 As seen in the figure degradation efficiency isinversely affected by dye concentrationThis is because as the

10

08

06

04

02

00

0 30 60 90 120 150 180

Time (min)

CC

o

Dark Visible light

10ppm15ppm20ppm

Figure 13 Effect of initial concentration of MG on the photodegra-dation rate

Dark Visible light Dark Visible light Dark Visible light

10

08

06

04

02

00

CC

o

0 30 60 90 120 150 180 210 240 270

1st run 2nd run 3rd run

Time (min)

Figure 14 Reuse of photocatalyst up to third cycle

dye concentration increases adsorption of dye on the catalystsurface sites increases by decreasing OHminus concentration onthe same sites Also according to Beer-Lambertrsquos law asinitial dye concentration increases the intensity of photonsentering the solution decreases which results in lowering theabsorption of photons on catalyst surface hence the rate ofphotodegradation process decreases

310 Recycling of Photocatalyst For practical applicationsstability of photocatalyst during photodegradation is a crucialfactor C doped ZnO prepared at 300∘C exhibits betterphotocatalytic activity therefore its stability was studiedStability tests were performed by repeating the reaction threetimes using recovered photocatalyst The data obtained ispresented in Figure 14 The data reveals that there is no


noticeable decrease in photocatalytic activity up to thirdcycle which indicates that C doped ZnO prepared in thepresent work is highly stable and reusable photocatalyst

4 Conclusion

C doped ZnO nanorods were synthesized successfully bymicroemulsion method and have been confirmed to bevisible light active and exhibit better photocatalytic activitythan pure ZnO due to its decreased band gap (269 eV)Photocatalytic activity of ZnO increases with increase in Ccontent Enhanced photocatalytic activity under visible lightirradiation can be attributed to the effect of C doping onZnO and the major role of C as a channel in reducing therecombination of electron and hole pairs

Also it is observed that photocatalytic efficiency does notchange up to third cycle and catalyst is quiet stable

Conflict of Interests

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

Acknowledgment

The authors are thankful to SAIF IIT Bombay for recordingSEM and TEM images of sample

References

[1] G Liu H G Yang X Wang et al ldquoEnhanced photoactivity ofoxygen-deficient anatase TiO

2

sheets with dominant 001 facetsrdquoJournal of Physical Chemistry C vol 113 no 52 pp 21784ndash217882009

[2] M Liu L Piao W Lu et al ldquoFlower-like TiO2

nanostructureswith exposed 001 facets facile synthesis and enhanced photo-catalysisrdquo Nanoscale vol 2 no 7 pp 1115ndash1117 2010

[3] N Morales-Flores U Pal and E S Mora ldquoPhotocatalyticbehavior of ZnO and Pt-incorporated ZnO nanoparticles inphenol degradationrdquo Applied Catalysis A General vol 394 no1-2 pp 269ndash275 2011

[4] X F Chen X C Wang and X Z Fu ldquoHierarchicalmacromesoporous TiO

2

SiO2

and TiO2

ZrO2

nanocompos-ites for environmental photocatalysisrdquo Energy and Environmen-tal Science vol 2 no 8 pp 872ndash877 2009

[5] A Akyol H C Yatmaz and M Bayramoglu ldquoPhotocatalyticdecolorization of Remazol Red RR in aqueous ZnO suspen-sionsrdquo Applied Catalysis B Environmental vol 54 no 1 pp 19ndash24 2004

[6] C Lizama J Freer J Baeza and H D Mansilla ldquoOptimizedphotodegradation of reactive blue 19 on TiO

2

and ZnO suspen-sionsrdquo Catalysis Today vol 76 no 2ndash4 pp 235ndash246 2002

[7] B Dindar and S Icli ldquoUnusual photoreactivity of zinc oxideirradiated by concentrated sunlightrdquo Journal of Photochemistryand Photobiology A Chemistry vol 140 no 3 pp 263ndash2682001

[8] Y Hao M Yang W Li X Qiao L Zhang and S Cai ldquoPhoto-electrochemical solar cell based on ZnOdyepolypyrrole filmelectrode as photoanoderdquo Solar Energy Materials and SolarCells vol 60 no 4 pp 349ndash359 2000

[9] C Kormann D W Bahnemann and M R Hoffmann ldquoEnvi-ronmental photochemistry is iron oxide (hematite) an activephotocatalyst A comparative study 120572-Fe

2

O3

ZnO TiO2

rdquoJournal of Photochemistry and Photobiology A Chemistry vol48 no 1 pp 161ndash169 1989

[10] J G Yu and X X Yu ldquoHydrothermal synthesis and photo-catalytic activity of zinc oxide hollow spheresrdquo EnvironmentalScience and Technology vol 42 no 13 pp 4902ndash4907 2008

[11] Z Dong X Lai J E Halpert et al ldquoAccurate control ofmultishelled ZnO hollow microspheres for dye-sensitized solarcells with high efficiencyrdquoAdvancedMaterials vol 24 no 8 pp1046ndash1049 2012

[12] J Jiang X Zhang P Sun andL Zhang ldquoZnOBiOI heterostruc-tures photoinduced charge-transfer property and enhancedvisible-light photocatalytic activityrdquo Journal of Physical Chem-istry C vol 115 no 42 pp 20555ndash20564 2011

[13] V Jeena and R S Robinson ldquoConvenient photooxidation ofalcohols using dye sensitised zinc oxide in combination withsilver nitrate and TEMPOrdquo Chemical Communications vol 48no 2 pp 299ndash301 2012

[14] H Ma J Han Y Fu Y Song C Yu and X Dong ldquoSynthesisof visible light responsive ZnO-ZnSC photocatalyst by simplecarbothermal reductionrdquo Applied Catalysis B Environmentalvol 102 no 3-4 pp 417ndash423 2011

[15] S Anandan and M Miyauchi ldquoCe-doped ZnO (CexZn1minusxO)becomes an efficient visible-light-sensitive photocatalyst by co-catalyst (Cu2+) graftingrdquo Physical Chemistry Chemical Physicsvol 13 no 33 pp 14937ndash14945 2011

[16] H Chen W Wen Q Wang et al ldquoPreparation of(Ga1minusxZn119909)(N1minusxO119909) photocatalysts from the Reaction of

NH3

with Ga2

O3

ZnO and ZnGa2

O4

in situ time-resolvedXRD and XAFS studiesrdquo Journal of Physical Chemistry C vol113 no 9 pp 3650ndash3659 2009

[17] A B Patil K R Patil and S K Pardeshi ldquoEcofriendly synthesisand solar photocatalytic activity of S-doped ZnOrdquo Journal ofHazardous Materials vol 183 no 1ndash3 pp 315ndash323 2010

[18] H Qin W Li Y Xia and T He ldquoPhotocatalytic activityof heterostructures based on ZnO and N-doped ZnOrdquo ACSApplied Materials and Interfaces vol 3 no 8 pp 3152ndash31562011


[20] RComparelli E FanizzaM L Curri PDCozzoli GMascoloand A Agostiano ldquoUV-induced photocatalytic degradation ofazo dyes by organic-capped ZnO nanocrystals immobilizedonto substratesrdquoApplied Catalysis B Environmental vol 60 no1-2 pp 1ndash11 2005

[21] L W Zhang H Y Cheng R L Zong and Y F Zhu ldquoPhoto-corrosion suppression of ZnO nanoparticles via hybridizationwith graphite-like carbon and enhanced photocatalytic activityrdquoJournal of Physical Chemistry C vol 113 no 6 pp 2368ndash23742009

[22] L-C Chen Y-J Tu Y-S Wang R-S Kan and C-M HuangldquoCharacterization and photoreactivity of N- S- and C-dopedZnO under UV and visible light illuminationrdquo Journal ofPhotochemistry and Photobiology A Chemistry vol 199 no 2-3pp 170ndash178 2008


[23] S Liu C Li J Yu and Q Xiang ldquoImproved visible-light photo-catalytic activity of porous carbon self-doped ZnO nanosheet-assembled flowersrdquoCrystEngComm vol 13 no 7 pp 2533ndash25412011

[24] P Zhang C Shao Z Zhang et al ldquoTiO2

carbon coreshellnanofibers controllable preparation and enhanced visible pho-tocatalytic propertiesrdquo Nanoscale vol 3 no 7 pp 2943ndash29492011

[25] P Zhang C Shao Z Zhang et al ldquoCoreshell nanofibers ofTiO2

carbon embedded by Ag nanoparticles with enhancedvisible photocatalytic activityrdquo Journal of Materials Chemistryvol 21 no 44 pp 17746ndash17753 2011

[26] N M Flores U Pal R Galeazzi and A Sandoval ldquoEffects ofmorphology surface area and defect content on the photocat-alytic dye degradation performance of ZnO nanostructuresrdquoRSC Advances vol 4 no 77 pp 41099ndash41110 2014

[27] A E Jimenez-Gonzalez J A S Urueta and R Suarez-ParraldquoOptical and electrical characteristics of aluminum-doped ZnOthin films prepared by solgel techniquerdquo Journal of CrystalGrowth vol 192 no 3-4 pp 430ndash438 1998

[28] M A Fox and M T Dulay ldquoHeterogeneous photocatalysisrdquoChemical Reviews vol 93 no 1 pp 341ndash357 1993

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2 Experimental

21 Materials Malachite green (MG) (bis[p-dimethylamino-phenyl]phenyl-methylium oxalate) was obtained fromMerckChemicals Mumbai and used without any further purifi-cation Zinc nitrate hexahydrate (Zn(NO)

3sdot6H2O) cyclo-

hexane n-butanol NNN-cetyl trimethyl ammonium bro-mide (CTAB) acetone ferric nitrate nanohydrate (Fe(NO

3)3sdot

9H2O) sodium hydroxide (NaOH) and ethanol used for the

synthesis are of AR grade All these chemicals were procuredfrom SD Fine Chemicals Mumbai and used without furtherpurification

22 Synthesis of Precursor 1M solution of zinc nitrate wasprepared by dissolving 2974 g of Zn(NO

3)2sdot6H2O in 100mL

distilled water 2M sodium hydroxide solution was preparedby dissolving 8 g of NaOH in 100mL distilled water To288mL 1M zinc nitrate 355mL cyclohexane 8mL butanoland 590 g cetyltrimethylammonium bromide (CTAB) wereadded In another solution 288mL 2M NaOH 355mLcyclohexane 8mL butanol and 590 g CTAB were mixedBoth these solutions were stirred continuously with thehelp of magnetic stirrer to form clear solutions These clearsolutions were mixed with each other The mixture wastransferred to 250mL Teflon lined autoclave and heated inan oven at 150∘C for 1 h After 1 h autoclave was cooled toroom temperature The solid product formed was separatedby filtration washed with distilled water followed by ethanoland finally with acetone and dried in an oven at 60∘CThe hydrothermal product (precursor) thus obtained wascharacterized using various characterization techniques

23 Characterization TG and DTA curves of precursorwere recorded using simultaneous TGDTA recording sys-tem (Rigaku Model-Thermo Plus TG8120) For recordingTGDTA curves 1420mg precursor was heated in a nitrogenatmosphere with a heating rate 10∘Cminminus1 For recordingDTA curve alumina was used as a reference material FT-IRspectra of precursor and the precursor calcined at 300 400and 500∘C were recorded using FT-IR spectrophotometer(Bruker) Precursor was calcined at 300 400 and 500∘Cfor 2 h and the XRD patterns of the product obtained atdifferent temperatures were recorded using X-ray diffrac-tometer (Rigaku Model-Miniflex II) using monochroma-tized CuK120572 radiation (120582 = 015405 nm) with scanning rateof 2∘2120579minminus1 Qualitative elemental analysis was carried outusing energy dispersive X-ray spectroscopy (EDX) (JEOL-JSM6360A) technique TEM images of C dopedpure ZnOpowder prepared in the present work were recorded usingtransmission electron microscope (Philips CM200) ForTEM sample was prepared by dispersing C dopedpure ZnOpowder in isopropyl alcohol and solution was sonicated for15minThe drop of solution was placed over C coated coppergrid and solvent was evaporated off under IR lamp Particlesize distribution study of product obtained at 300∘C was car-ried out using particle size analyzer (NanosightModel-NTA-LM-20) Band gap energies of synthesized nanopowders wereevaluated fromUV-visible spectra recorded using UV-visiblespectrophotometer (Shimadzu Model-1800)

0

minus10

minus20

100 200 300 400 500 600

50

0

minus50

minus100

minus150

Mas

s los

s (

)

EndoΔT120583V

exo

Temperature (∘C)

Figure 1 TG andDTA curves of ZnOprecursor recorded in flowingnitrogen

24 Photocatalytic Activity Study Photocatalytic activity ofnanosized pureC doped ZnO photocatalyst was tested fordegradation of malachite green (MG) solution Reactionsuspension was prepared by adding 005 g ZnO (obtained at300∘C) photocatalyst in 100mL 10 ppm MG solution Thisaqueous suspension was stirred in the dark for 30min toattain adsorption-desorption equilibrium Later the solutionwas irradiated with visible light The visible light irradiationwas carried out in a photoreactor using a compact fluorescentlamp (65W 120582 gt 420 nm Philips) Temperature of testsolutionwasmaintained constant throughout the experimentby circulating water around the solution The amount of MGwas monitored by sampling out 5mL of aliquot solution atregular time intervalsThe catalyst was first separated by cen-trifugation and the concentration of MG in the supernatantsolution was estimated using UV-visible spectrum recordedin the wavelength range of 200ndash800 nm

To evaluate the effect of various parameters on photocat-alytic activity of ZnO the same experiment was repeated byusing the catalyst calcined at different temperatures varyingthe amount of catalyst used and changing the pH andconcentration of MG

3 Results and Discussion

31 TG and DTA Study Simultaneous TG and DTA curveswere recorded for thermal decomposition studies of precur-sor and are presented in Figure 1 TG curve shows that thereis gradual weight loss from 25 to 200∘C and this can beattributed to vaporization of absorbed water molecules andcyclohexane Also this change is observed in DTA curve asan endothermic peak in the same temperature range withminima located near 104∘C In temperature range 200ndash330∘CTG curve exhibits a suddenweight loss which corresponds toburning of residual surfactant and gives weak endothermicpeak in DTA curve near 300∘C




1 300 387 269 982 400 072 288 843 500 0 308 67

20 30 40 50 60 70 80

2120579 (deg)

Inte

nsity

(au

)

(100

)(002

)(101

)

(102

)

(110

)

(103

)(200

)(112

)(201

)(004

)

(202

)

lowast Zn(OH)2

500∘C

400∘C

300∘C





2and as-grown ZnO



3500 2500 1500 500


Abso

rban

ce

3452

cmminus1

2900

cmminus1

1625

cmminus1

1376

cmminus1

398

cmminus1

500∘C

400∘C

300∘C

Precursor



2and as-





(a) (b)

(c)






2and as-grown ZnO




2O(1)








(a) (b)

(c)


Num

ber o

f par

ticle

s


9

30

43




VB (2)

eminusCB + h+



minus∙ (4)





Abso

rban

ce (a

u)

200 400 600 800

Wavelength (nm)

ab

c

ab

c





20 25 30 35 40

a b c

(120572)2

h (eV)

h

a b c


15

10

05

00

400 500 600 700 800

Abso

rban

ce (a

u)

Wavelength (nm)

0min

15min

30min

45min

60min

75min



10

08

06

04

02

00

0 30 60 90 120 150 180

Time (min)

CC

o

Dark Visible light

Photolysisa

bc







08

06

04

02

00

0 30 60 90

Time (min)

CC

o

01 gL05 gL10 gL


006

004

002

000

0 2 4 6 8 10 12

pH

Rate

cons

tant

(minminus1)




10

08

06

04

02

00

0 30 60 90 120 150 180

Time (min)

CC

o

Dark Visible light

10ppm15ppm20ppm



10

08

06

04

02

00

CC

o

0 30 60 90 120 150 180 210 240 270


Time (min)






4 Conclusion





Acknowledgment


References


2






2

SiO2

and TiO2

ZrO2




2





2

O3

ZnO TiO2









NH3

with Ga2

O3

ZnO and ZnGa2

O4


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




1 300 387 269 982 400 072 288 843 500 0 308 67

20 30 40 50 60 70 80

2120579 (deg)

Inte

nsity

(au

)

(100

)(002

)(101

)

(102

)

(110

)

(103

)(200

)(112

)(201

)(004

)

(202

)

lowast Zn(OH)2

500∘C

400∘C

300∘C





2and as-grown ZnO



3500 2500 1500 500


Abso

rban

ce

3452

cmminus1

2900

cmminus1

1625

cmminus1

1376

cmminus1

398

cmminus1

500∘C

400∘C

300∘C

Precursor



2and as-





(a) (b)

(c)






2and as-grown ZnO




2O(1)








(a) (b)

(c)


Num

ber o

f par

ticle

s


9

30

43




VB (2)

eminusCB + h+



minus∙ (4)





Abso

rban

ce (a

u)

200 400 600 800

Wavelength (nm)

ab

c

ab

c





20 25 30 35 40

a b c

(120572)2

h (eV)

h

a b c


15

10

05

00

400 500 600 700 800

Abso

rban

ce (a

u)

Wavelength (nm)

0min

15min

30min

45min

60min

75min



10

08

06

04

02

00

0 30 60 90 120 150 180

Time (min)

CC

o

Dark Visible light

Photolysisa

bc







08

06

04

02

00

0 30 60 90

Time (min)

CC

o

01 gL05 gL10 gL


006

004

002

000

0 2 4 6 8 10 12

pH

Rate

cons

tant

(minminus1)




10

08

06

04

02

00

0 30 60 90 120 150 180

Time (min)

CC

o

Dark Visible light

10ppm15ppm20ppm



10

08

06

04

02

00

CC

o

0 30 60 90 120 150 180 210 240 270


Time (min)






4 Conclusion





Acknowledgment


References


2






2

SiO2

and TiO2

ZrO2




2





2

O3

ZnO TiO2









NH3

with Ga2

O3

ZnO and ZnGa2

O4


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


(a) (b)

(c)






2and as-grown ZnO




2O(1)








(a) (b)

(c)


Num

ber o

f par

ticle

s


9

30

43




VB (2)

eminusCB + h+



minus∙ (4)





Abso

rban

ce (a

u)

200 400 600 800

Wavelength (nm)

ab

c

ab

c





20 25 30 35 40

a b c

(120572)2

h (eV)

h

a b c


15

10

05

00

400 500 600 700 800

Abso

rban

ce (a

u)

Wavelength (nm)

0min

15min

30min

45min

60min

75min



10

08

06

04

02

00

0 30 60 90 120 150 180

Time (min)

CC

o

Dark Visible light

Photolysisa

bc







08

06

04

02

00

0 30 60 90

Time (min)

CC

o

01 gL05 gL10 gL


006

004

002

000

0 2 4 6 8 10 12

pH

Rate

cons

tant

(minminus1)




10

08

06

04

02

00

0 30 60 90 120 150 180

Time (min)

CC

o

Dark Visible light

10ppm15ppm20ppm



10

08

06

04

02

00

CC

o

0 30 60 90 120 150 180 210 240 270


Time (min)






4 Conclusion





Acknowledgment


References


2






2

SiO2

and TiO2

ZrO2




2





2

O3

ZnO TiO2









NH3

with Ga2

O3

ZnO and ZnGa2

O4


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


(a) (b)

(c)


Num

ber o

f par

ticle

s


9

30

43




VB (2)

eminusCB + h+



minus∙ (4)





Abso

rban

ce (a

u)

200 400 600 800

Wavelength (nm)

ab

c

ab

c





20 25 30 35 40

a b c

(120572)2

h (eV)

h

a b c


15

10

05

00

400 500 600 700 800

Abso

rban

ce (a

u)

Wavelength (nm)

0min

15min

30min

45min

60min

75min



10

08

06

04

02

00

0 30 60 90 120 150 180

Time (min)

CC

o

Dark Visible light

Photolysisa

bc







08

06

04

02

00

0 30 60 90

Time (min)

CC

o

01 gL05 gL10 gL


006

004

002

000

0 2 4 6 8 10 12

pH

Rate

cons

tant

(minminus1)




10

08

06

04

02

00

0 30 60 90 120 150 180

Time (min)

CC

o

Dark Visible light

10ppm15ppm20ppm



10

08

06

04

02

00

CC

o

0 30 60 90 120 150 180 210 240 270


Time (min)






4 Conclusion





Acknowledgment


References


2






2

SiO2

and TiO2

ZrO2




2





2

O3

ZnO TiO2









NH3

with Ga2

O3

ZnO and ZnGa2

O4


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


20 25 30 35 40

a b c

(120572)2

h (eV)

h

a b c


15

10

05

00

400 500 600 700 800

Abso

rban

ce (a

u)

Wavelength (nm)

0min

15min

30min

45min

60min

75min



10

08

06

04

02

00

0 30 60 90 120 150 180

Time (min)

CC

o

Dark Visible light

Photolysisa

bc







08

06

04

02

00

0 30 60 90

Time (min)

CC

o

01 gL05 gL10 gL


006

004

002

000

0 2 4 6 8 10 12

pH

Rate

cons

tant

(minminus1)




10

08

06

04

02

00

0 30 60 90 120 150 180

Time (min)

CC

o

Dark Visible light

10ppm15ppm20ppm



10

08

06

04

02

00

CC

o

0 30 60 90 120 150 180 210 240 270


Time (min)






4 Conclusion





Acknowledgment


References


2






2

SiO2

and TiO2

ZrO2




2





2

O3

ZnO TiO2









NH3

with Ga2

O3

ZnO and ZnGa2

O4


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



08

06

04

02

00

0 30 60 90

Time (min)

CC

o

01 gL05 gL10 gL


006

004

002

000

0 2 4 6 8 10 12

pH

Rate

cons

tant

(minminus1)




10

08

06

04

02

00

0 30 60 90 120 150 180

Time (min)

CC

o

Dark Visible light

10ppm15ppm20ppm



10

08

06

04

02

00

CC

o

0 30 60 90 120 150 180 210 240 270


Time (min)






4 Conclusion





Acknowledgment


References


2






2

SiO2

and TiO2

ZrO2




2





2

O3

ZnO TiO2









NH3

with Ga2

O3

ZnO and ZnGa2

O4


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



4 Conclusion





Acknowledgment


References


2






2

SiO2

and TiO2

ZrO2




2





2

O3

ZnO TiO2









NH3

with Ga2

O3

ZnO and ZnGa2

O4


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

Documents

Research Article Synthesis, Characterization, and Visible