FULLPAPERDOI:10.1002/ejic.201400098PreparationbySolvothermalSynthesis,GrowthMechanism,andPhotocatalyticPerformanceofCuSNanopowdersYu-QiaoZhang,[a]Bo-PingZhang,*[a]Zhen-HuaGe,[a]Li-FengZhu,[a]andYanLi[a]Keywords:Coppersulfide/Solvothermalsynthesis/Photocatalysis/Semiconductors/NanostructuresVariousCuSnanostructures,includingnanoflowers,dough-nut-shapednanospheres,densenanospheres,andmixturesofnanoneedles,nanoparticles,andnanoplates,weresynthe-sizedfromdifferentcopperandsulfursourcesbyasolvother-malmethod.Theformationmechanismsalongwithphoto-catalyticpropertiesforthedegradationofrhodamineB(RhB)undervisible-lightirradiationwereinvestigatedinthisstudy.TheexperimentalresultsindicatethatwhenthesulfursourceisfixedatCS(NH2)2inthesolvothermalreaction,sphericalnanoflowers,doughnut-shapednanospheres,anddensenanospherescouldbesynthesizedbyusingCuCl2,Cu-(NO3)2,andCuSO4asthecoppersource,respectively.Furthermore,atypicalnanoflowersandamixtureofnanoneedles,nanoparticles,andnanoplatescouldbeob-tainedwhenthesulfursourcewasswitchedtoNa2S2O3andNa2SwithafixedcoppersourceofCuCl2.Theenergygapscalculatedfromthelightabsorptionspectrumwere1.61,1.93,2.01,1.70,and1.82eVforthesphericalnanoflowers,doughnut-shapednanospheres,densenanospheres,atypicalnanoflowers,andthemixtureofnanoneedles,nanoparticles,andnanoplatesrespectively.Amongthesefivesamples,threepowderscomposedofsphericalnanoflowers,atypicalnanoflowersaswellasamixtureofnanoneedles,nanopar-ticles,andnanoplatesexhibitedexcellentphotocatalyticpropertiesandcandegraderhodamineBcompletelyinanhour.IntroductionInrecentyeas,semiconductorphotocatalysistechnology,whichprovidesarelativelysimplemethodforthechemicalconversionofsolarenergy,hasreceivedconsiderableatten-tionbecauseofitsapplicationforwatersplittingandtheeliminationofchemicalcontaminants.[1–3]SinceFujishimaandHondareportedwatersplittingbyTiO2underUVillu-minationin1972,[4]avarietyofphotocatalystshavebeensynthesizedandusedtoconvertsolarenergyintochemicalenergytodecomposematerialsintousefulmaterialssuchashydrogen[5–7]andhydrocarbons,[8]aswellastoremovepollutantsandbacteria[9–14]inairandwater.[15,16]Now-adays,TiO2isundoubtedlythemostwidelyusedphotocatalystbecauseofitsbiologicalandchemicalsta-bility,nontoxicity,costeffectiveness,andhighactivity.[17–20]However,TiO2canonlyutilizeultravioletlightowingtoitsbroadenergygap(3.2eV),whichseriouslyrestrictsitsapplications;therefore,thesearchforphotocatalyststhatcanutilizevisiblelighthasbecomeahotissue.Todate,anumberofsulfides,nitrides,andoxynitrideshavebeen[a]DepartmentofMaterialsScienceandEngineering,UniversityofScienceandTechnologyBeijing,Beijing100083,P.R.ChinaE-mail:bpzhang@ustb.edu.cnhttp://mse.ustb.edu.cn/yjsh.asp?id=d4SupportinginformationforthisarticleisavailableontheWWWunderhttp://dx.doi.org/10.1002/ejic.201400098.Eur.J.Inorg.Chem.2014,2368–2375investigatedasalternativematerialsforvisible-lightorsolarphotocatalysis.[21–24]Inparticular,nanocrystallinetransi-tionmetalchalcogenideshaveattractedmuchattentionoverthepastfewyearsbecauseoftheirinterestingpropertiesandmanypotentialapplications;[25–27]coppersulfide(CuS)isoneofthemostpromisingones.Asanimportantnanocrystallinetransitionmetalchalco-genideandp-typesemiconductor,CuSisoneofthemostintensivelystudiedmaterialsowingtoitsunusualelectronic,optical,andotherphysicalandchemicalproperties[28–32]andhasgreatpotentialinawiderangeofapplicationssuchasopticalfiltersandsuperionicmaterials,[33]solarcontrol-lersandsolarradiationabsorbers,[34]high-capacitycathodematerialsinlithiumsecondarybatteries,[35]low-temperaturesuperconductors,[36]waveabsorptionmaterials,[37–39]andthermoelectricmaterials.[40]Furthermore,CuSnanopar-ticleswithvariousmorphologies,suchasnanoflowers,[41]hierarchicalnanostructures,[42]urchinlikestructures,[43]nanoribbons,[44]nanowires,[45]microtubes,[46]andhollowspheres,[47,48]havebeensynthesizedbyvariousapproachessuchassolventlessandsolutionthermolysis,sacrificialtem-plating,solution-phasereactions,ultrasonicandmicrowaveirradiation,template-assistedmethods,microemulsion,elec-trodeposition,andchemicalvapordeposition,[49]manyofwhichhaveshownapplicationprospectsinphotocatalysis.Inspiteofthesevaluableinvestigations,itsdetailedforma-tionmechanismandphotocatalyticpropertiesarestillun-©2014Wiley-VCHVerlagGmbH&Co.KGaA,Weinheim2368www.eurjic.orgclear.Comparedwiththesyntheticmethodsabove,solvo-thermalmethodshavebeenincreasinglyusedasalow-cost,low-risk,andeasy-to-operatesynthetictechnique.WeadoptedafacilesolvothermalmethodandsynthesizedCuSpowderswithcontrollablemicrostructuresbyusingdif-ferentcoppersourcesandsulfursourcesunderrelativelymildconditionsof140°Cfor90min.TheformationmechanismsalongwiththephotocatalyticpropertiesforthedegradationofrhodamineB(RhB)undervisible-lightirra-diationwereinvestigatedwithspecialemphasisontheeffectofCuSnanopowderswithcontrollablemicrostructures.FULLPAPERResultsandDiscussionFigure1showstheXRDpatternsofsamplesa–esynthe-sizedbythesolvothermalmethodat140°Cfor90minfromvarioussulfurandcoppersources.Allofthesamplesexhi-bitapurehexagonalCuSstructure(PDF#06-04)with-outanytraceofimpurityphasesregardlessofthecopperandsulfursources.ThemeandiameteroftheCuScrystal-linegrainswasestimatedbyusingtheScherrerequation,D=0.9λ/βcosθ(λistheX-raywavelength,βisthefullwidthathalfmaximum(FWHM),andθisthediffractionangle),andtheresultsfollowtheordersampleb(20.2nm)Ͼsam-pled(18.4nm)Ͼsamplee(16.4nm)Ͼsamplea(15.5nm)Ͼsamplec(15.1nm).Na2StoNa2S2O3andthecoppersourcewaskeptasCuCl2.WithCS(NH2)2asthesulfursource,asimilarflowerlikestructurewasobtained,butitismorecompleteanduni-formwithoutnanoparticles,andtheaverageparticledia-meterincreasesfrom1–2to2–5μm(Figure2,cande).Theself-assemblednanoplatesintheflowerlikeCuSnano-sphereswithasmoothsurfacealsobecomethickerandsparser,asshowninFigure2,dandf,andtheiraveragethicknessincreasesfrom10–15to10–20nm(Figure2,dandf,insets)ThisphenomenonmaybeattributedtotheincreasedS/Curatios,whichwerefixedat1and4forNa2S2O3andCS(NH2)2,respectively.Thereby,thesolutionpreparedwithCS(NH2)2couldreleasemoreS2–ionstore-actwithCu2+ionsundersolvothermalconditionstoformmoreCuSnucleiatthesametime.Inthefollowingstep,theas-formedCuSnucleicouldaggregateintothelargerFigure1.XRDpatternsofsamplessynthesizedbythesolvother-malmethodat140°Cfor90minwithvarioussulfurandcoppersources.ApartfromthemuchalikeXRDprofilesinFigure1,clearlydifferentmorphologiesarenoticedinthesyntheticproductsdependingonthecopperandsulfursourcesasshowninthefield-emissionSEM(FE-SEM)imagesinFig-ure2.WithCuCl2andNa2Sasthecopperandsulfursources,amixedmicrostructurewithsomenanoneedles,nanoparticles,andnanoplateswithanaverageparticlesizeofca.100nmwasobserved(Figure2,aandb).Anaggre-gatedflowerlikemicrostructureself-assembledbymanynanoplateswithsomedispersednanoparticles(Figure2,candd)formedwhenthesulfursourcewaschangedfromEur.J.Inorg.Chem.2014,2368–2375Figure2.FE-SEMimagesofproductspreparedbythesolvother-malmethodat140°Cfor90minwithvarioussulfurandcoppersources:(aandb)Na2S+CuCl2,(candd)Na2S2O3+CuCl2,(eandf)CS(NH2)2+CuCl2,(gandh)CS(NH2)2+Cu(NO3)2,and(iandj)CS(NH2)2+CuSO4.©2014Wiley-VCHVerlagGmbH&Co.KGaA,Weinheim2369www.eurjic.orgnanoparticles.Asaresult,thesamplesshowedanincreasedparticlesizeasthesulfursourcewaschangefromNa2S2O3toCS(NH2)2.[50]Ontheotherhand,withthesulfursourcefixedasCS(NH2)2,thesyntheticproductsinFigure2(e–j)showclearlydifferentmorphologieswithCuCl2,Cu-(NO3)2,andCuSO4asthecoppersource.Differingfromthenanoflowers(Figure2,eandf)manydoughnut-shapednanospheresareobtainedwithCu(NO3)2(Figure2,gandh),andtheirsurfacesarecomposedofmanyhierarchicalnanoplates.WhenthecoppersourcewaschangedtoCuSO4,manydensesolidnanosphereswithfeatherlikesur-faceswereobtained(Figure2,iandj).ItisclearthatthesulfurandcoppersourcesexertagreatinfluenceonthemicrostructuresoftheCuSpowders.Onthebasisofpre-viousreports[51–58]andtheCuSstructureevolutionob-servedintheSEMimages,speculativeevolutionmecha-nismsofthemorphologiesareproposedindetailintheequationsbelowalongwithaschematicillustrationinFig-ure3.WithNa2Sasthesulfursource,Na2SisionizeddirectlyinashorttimetoreleaselotsofS2–ions,whichreactrapidlywithCu2+ionstoformCuScrystalnuclei.Eventually,copi-ouscrystalnucleiarecreatedandgrowintoamixedmicro-structurewithnanoneedles,nanoparticles,andnanoplates(seeFigures2,aandband3,a).[51]Incontrasttothereac-tionwithNa2S,withNa2S2O3orCS(NH2)2asthesulfursource,arelativelystablecomplexsuchas[Cu(S2O3)-(H2O)2]/[Cu(S2O3)2]2–or[Cu{CS(NH2)2}n]ClinitiallyformsbyreactionwithCuCl2inethanediolatroomtemperatureandthendecomposesintoCuSnucleiwhenthereactiontemperatureincreasestoamoderatesolvothermaltempera-tureofca.140°C.Inthefollowingstep,thesenucleiprefer-entiallygrowwithanorientationandfurtherformCuSnanoplates.Thesenanoplatesmeetandintersectwitheachothertoassembleintoflowerlikenanospheres(seeFig-ures2,c–fand3,a).Thepossibletwo-stepfor-FULLPAPERmationmechanismofCuSbythesolvothermaltreatmentofCuCl2·2H2OwithNa2S2O3·5H2OorCS(NH2)2isde-scribedin(seeEquations1,2,3,4,5,6and7).[52–55]CuCl2+Na2S2O3+2H2OǞ[Cu(S2O3)(H2O)2]+2NaClCuCl2+2Na2S2O3ǞNa2[Cu(S2O3)2]+2NaCl[Cu(S2O3)(H2O)2]ǞCuSȇ+H2SO4+H2O(1)(2)(3)Na2[Cu(S2O3)2]+2H2OǞCuSȇ+Na2SO4+H2SO4+H2SȆ(4)CuCl2+2CS(NH2)2Ǟ2CuClȇ+C2S2N4H6+2HClCuCl+nCS(NH2)2+1/2H2OǞ[Cu{CS(NH)2}n]Cl·1/2H2O[Cu{CS(NH2)2}n]ClǞCuSȇ(5)(6)(7)Ontheotherhand,withCS(NH2)2asthesulfursource,thereactionsbetweenCS(NH2)2andCu(NO3)2orCuSO4aredescribedasfollows(seeEquations8,9,10,11,12)].[56]Cu2++2CS(NH2)2Ǟ2Cu++C2S2N4H6+2H+9CS(NH2)2+4Cu+Ǟ[Cu4{CS(NH2)2}9](NO3)4[Cu4{CS(NH2)2}9](NO3)4ǞCuSȇ6CS(NH2)2+2Cu+Ǟ[Cu2{CS(NH2)2}6]SO4[Cu2{CS(NH2)2}6]SO4ǞCuSȇ(8)(9)(10)(11)(12)Asimilarcomplexsuchas[Cu4{CS(NH2)2}9](NO3)4or[Cu{CS(NH2)2}6]SO4initiallyforms(Figure3,b).Asthetemperatureincreasestoamoderatesolvothermaltempera-tureofca.140°C,thesecomplexesdecomposeintoCuSnucleiandgrowintoirregularnanoparticlesalongwithad-sorbedNO3–orSO42–anionsinsolution.IncontrasttotheFigure3.SchematicillustrationofthegrowthmechanismoftheCuSmicrostructuressynthesizedfromthreedifferentsulfurandcoppersources:(a)CuCl2+Na2S/CS(NH2)2/Na2S2O3,(b)CS(NH2)2+Cu(NO3)2/CuSO4.Eur.J.Inorg.Chem.2014,2368–23752370©2014Wiley-VCHVerlagGmbH&Co.KGaA,Weinheimwww.eurjic.orgsimilarnucleationattheinitialstage,variedgrowthmecha-nismsareproposeddependingontheNO3–andSO42–anions.ForthenanoparticlesobtainedfromCu(NO3)2andCS(NH2)2,drivenbythecharacteristichexagonalstructureofCuS,theyaggregatetogetherandgrowintonanoplatesthatassemblewitheachotherandpackdensely.Then,thedensernanoplatesarebentandtransformedintolongnar-rowcurvedstripstominimizethetotalenergyofthesys-tem.Finally,densedoughnutlikeparticlesformwithcon-cavetops.[57]Inaddition,thefreeNO3–ionspreferentiallyabsorbontheprimarynanoplatesandleadtoaselectivesolubilizationandrecrystallizationofCuS.TheabsorbedNO3–ionscanfunctionaspotentialcrystal-faceinhibitorsinthesystemandformanioninterlayersonthenanoplatesthatbenefittheformationoforientednucleation.[58]Atlongerreactiontimes,thenanoplatesprotrudefurther,lead-ingtotheconstructionofhierarchicalstructuresbuiltofwell-orderedandorientednanoplates.TheevolutionofCuSnanostructureswithtimeduringthesolvothermalprocess(Figure4)alsoprovesthemechanismfortheformationofdoughnutlikeCuSstructuresdepictedabove.Duringtheinitial45min,theproductwascomposedofdoughnutlikeparticleswithadensesurface.Thesurfacedecomposedintomanylayerstructuresasthereactiontimeincreasedto90min.Atareactiontimeof10h,thelayerstructuresbe-comemoreobviousandthecavitiesinthespherebecomesmallerandaregraduallyfilledwithwell-orderedandori-entednanoplates.FULLPAPERenedandsomeprotruded.Thisphenomenonindicatesthatthenanoparticlesareformedfrommanynanoplates,whichshowagrowthtendencywiththetemperatureincrease.Figure5.FE-SEMimagesofCuSmicrostructuresobtainedfromCuSO4andCS(NH2)2atdifferenttemperaturesfor90min.Figure4.StructureevolutionofCuSnanospherespreparedfromCu(NO3)2.IncontrasttothesamplespreparedwithCu(NO3)2andCS(NH2)2,thefirstlyformedcomplex[Cu{CS(NH2)2}6]-SO4releasesCu2+andS2–ions,whichgrowintoCuSnucleiduringthesolvothermalprocessandaggregateintosolidsphereinthefollowingstep(Figure5).Noselectivesolubili-zationorfurtherclearchangeshappenedtothesolidspheresbecauseofthelowaggressivenessoftheSO42–ions.Theweakfeatherlikestructureonthesurfaceofthenanospheresshowsanincreasinglyroughtrendasthetem-peratureincreases.At180°C,thenanoplatesclearlythick-Eur.J.Inorg.Chem.2014,2368–2375Figure6showstheabsorptionspectraofRhBsolutionsphotocatalyzedbyCuSpowders(Figure6,A–E)alongwiththedegradationratecurvesofRhB(Figure6,F).CuSnanopowdersconsistingofmixtureofnanoneedles,nano-particles,andnanoplates(Figure6,A),atypicalnanoflow-ers(Figure6,B),andsphericalnanoflowers(Figure6,C)showgreatdegradationperformances;theabsorptioncurvebecomesastraightlineafter60min,whichindicatesthatover90%oftheRhBwasdegraded.Inparticular,CuSsphericalnanoflowerspreparedfromCuCl2andCS(NH2)2accomplishedthedegradationprocessinonly30min.Whendoughnut-shapednanospherespreparedfromCu(NO3)2andCS(NH2)2areusedasthephotocatalyst,theRhBdegradationrateonlyreachesca.70%in60min(Fig-ure6,D).Furthermore,Figure6(E)showstheabsorptionspectraofRhBsolutionsphotocatalyzedbydenseCuSnanospherespreparedfromCuSO4andCS(NH2)2.Amongallofthesamples,thissampleshowsthelowestdegradationrate,andonly20%oftheRhBisdegradedafterareactiontimeof60min.Thedegradationratecurves(a–f)inFigure6(F)werecalculatedfromtheabsorptionintensitiesfromFigure6(A–E),whichcorrespondtothemixtureofnanoneedles,nanoparticles,andnanoplates(a),atypicalnanoflowers(b),sphericalnanoflowers(c),doughnut-shapednanospheres(d),densenanospheres(e),andtheblankcontrolgroup(f),respectively.Clearly,theRhBsolutionoftheblankcontrolgroupwithoutCuSshowslittlechangesundervisible-lightirradiationafter60min,andsamplefshowsweakcatalyticactivityofonlyca.20%ofthedecompositionrate.Howeversamplesb,c,d,andeexhibitstrongphotocatalyticactivity,especiallysamplesb,c,andd,whichcandegrademorethan95%oftheinitialRhBdyeunderidenticalconditionsandshowsignificantlysuperiorperformancestootherreportedCuSsamples[41,59,60]andthecommercialP25photocata-lyst,[61–63]whichcouldonlyreachadegradationrateoflessthan80%in60min.Theseresultsrevealthatthemor-phologyhasagreatinfluenceonthephotocatalyticactivityoftheCuSpowders.Thespeculativemajorreactionstepsrelatedtothepho-tocatalyticmechanismofCuSsemiconductorsaresumma-rizedasfollows(seeEquations13,14,15,16,17,18)[,17]andareshownschematicallyinFigure7.©2014Wiley-VCHVerlagGmbH&Co.KGaA,Weinheim2371www.eurjic.orgFULLPAPERFigure6.AbsorptionspectraofRhBsolutions(A–E)andtherelationshipbetweenthemorphologyoftheCuSpowderandthedegrada-tionrateofRhB(F).Photocatalyst(CuS)+hνǞh+(CuS)+e–(CuS)H2OǞH++OH–e–(CuS)+O2Ǟ·O2–e–(CuS)+H2O2Ǟ·OH+OH–h+(CuS)+OH–Ǟ·OHRhB+·OH+·O2–Ǟdegradationproducts(13)(14)(15)(16)(17)(18)Figure7.Schematicillustrationofthemechanismforthephotoca-talysisbyCuSnanopowdersundervisible-lightirradiation.WhentheCuSsampleisirradiatedundervisiblelight,electrons(e–)areexcitedfromthevalenceband(VB)totheconductionband(CB)oftheCuSparticlesastheabsorp-tionofphotonenergyisgreaterthanorequaltoEgofCuS;thisleavesholes(h+)inthesamespotatwhichtheexci-tationofe–occurs.Thesephotogeneratede–andh+thentransfertothesurfaceoftheCuSparticlesandreactwithoxidantsandreductants,respectively.Generally,photo-Eur.J.Inorg.Chem.2014,2368–2375generatede–areexpectedtobetrappedbyO2insolutiontoformsuperoxideions(·O2–)and/orotherreactiveoxygenspecies.Thewater(H2O)intheRhBsolutionissplitintohydrogenions(H+)andhydroxyions(OH–),andh+areinducedtoreactwithOH–ionsaccordinglyintheRhBsolutiontoproduce·OHfreeradicalsandotherstronglyoxidizingfreeradicals.[,17]Theseseparatedreactiveoxygenspeciesandfreeradicalscanparticipateinthephotocata-lyticreactionstodecomposeorganiccompoundssuchasRhB.Inourexperiment,twomainfactorsaffectthephoto-catalyticperformanceofthesamples.Thefirstisthecata-lyticactivityofthesample.Thatis,whetherthesamplescanrespondtosunlight,absorbphotonenergy,andlaunchthephotocatalyticreactioninthecorrespondingwavelengthrange.Inthisexperiment,allsamplesarecomposedofthehexagonalCuSphase.Accordingtotheopticalabsorptionspectraandrelationalgraphsof(αhν)2versushν(FiguresS1andS2intheSupportingInformation),theyallhavethepotentialforphotocatalysisundervisible-lightirradiation.CuSnanoflowerssynthesizedfromCuCl2andCS(NH2)2havetheminimumEg;therefore,ofallthesamples,theyshouldhavethegreatestpotentialfortheabsorptionofvis-iblelightandshowthebestphotocatalyticperformance.[65]FromFigure6(F),itcanbeseenthatsamplea(themixtureofnanoneedles,nanoparticles,andnanoplates)exertscom-parablephotocatalyticperformancetosamplec(sphericalnanoflowers)despiteitswiderEg.Thismayresultfromotherimportantfactorssuchasthespecificsurfacearea;whenthesamplehasahighspecificsurfacearea,thepar-ticlescanabsorbmoredyemoleculestotheirsurfacesandthephotocatalystcanmakegoodcontactwiththedye,whichimprovesthereactionprocessandincreasesthecata-lyticefficiency.Inaddition,thesmallgrainsizewillreducetherecombinationopportunitiesofthephotogenerated©2014Wiley-VCHVerlagGmbH&Co.KGaA,Weinheim2372www.eurjic.orge––h+pairsasaresultofthetraveldistanceinthevolume;therefore,theycaneffectivelymovetothesurfaceandde-gradetheabsorbedorganicpollutant.[16]Furthermore,as-cribedtothecavity-mirroreffectoftheflowerlikeCuSsu-perstructure(Figure8),thephotoabsorptioncanbeen-hancedbyreflectionmanytimesamongthenanoplates,whichserveas“mirrors”whenthewavelengthoflightisclosetothesizeofcavities.Inourcase,theflowerlikeCuSsuperstructures(samplesbandc)withcavitiesofca200nmto1μmcanserveasexcellentlight-cavitymirrorsofvisiblelight;thisleadstoagreatenhancementofthereflectionandabsorptionabilityforlight.[66,67]AccordingtotheopticalabsorptionspectraandEgshowninFiguresS1andS2,alloftheflowerlikeCuSstructureshavegreatspectralresponseinthevisible-lightregionand,therefore,havethepotentialtoutilizevisiblelightduringthephotocatalyticprocess.Therefore,inthephotocatalyticprocess,theflowerlikestructuresaremoreefficient.Ontheotherhand,thein-feriorphotocatalyticperformancewithalowadsorptionrateforthedyemoleculesforsamplesdandemaybeattrib-utedtotheirimpactedsphericalstructureswithreducedspecificsurfaceareas.FULLPAPERcatalytictestdemonstratesthatCuSnanopowderswiththesphericalnanoflowermicrostructure,atypicalnanoflowers,andthemixtureofnanoneedles,nanoparticles,andnano-plateshavegoodphotocatalyticperformance,andthede-gradationrateofRhBinthepresenceofpowderswithsphericalnanoflowersuperstructurescanreachover99%in30min.ExperimentalSectionMaterials:InthesynthesisofCuS,theanionsofdifferentcoppersourceshadadecisiveimpactonthetypeofproduct.Inthisexperi-ment,copperchloride(CuCl2),coppersulfate(CuSO4),andcuppernitrate[Cu(NO3)2]wereselectedasthecoppersources,andthio-urea[CS(NH2)2],sodiumsulfide(Na2S),andsodiumthiosulfate(Na2S2O3)wereselectedasthesulfursources.Ethanediolwasusedasthesolvent.Allchemicalreagentsusedinthisworkwereofanalyticalgrade.PreparationofthePhotocatalysts:Inatypicalexperiment,CuCl2·2H2O[CuSO4·5H2O/Cu(NO3)2·3H2O](0.06mol)wasfirstlyaddedintoethanediol(40mL),andthemixturewasstirredandheatedforafewminutestoformsolutionA.Meanwhile,CS-(NH2)2(0.24mol)wasintroducedtoethanediol(40mL)toformsolutionB.SolutionBwasdrippedslowlyintosolutionAwithstirringandheating.ThemixedsolutionwasthentransferredintoaTeflon-linedstainlesssteelautoclave(100mLcapacity),whichwassealedandmaintainedat140°Cfor90min.Theresultantblacksolidproductwascollectedbyfiltration,washedwithdeion-izedwaterandethanolthreetimes,anddriedinadryingoven(DHG-9053A,ShanghaiYihengInstrumentsCo.,Ltd.,China)at60°C.WhenCS(NH2)2wasusedtosynthesizeCuS,theCu/Sratioofthereagentswas1:4,andwhenNa2SandNa2S2O3wereusedasthesulfursource,theCu/Sratioofthereagentswas1.CharacterizationTechniques:ThephasestructureswereanalyzedbyX-raydiffraction(XRD:D/max-RB,RigakuInc.,Japan)withCu-Kαradiation(λ=0.15406nm)filteredthroughNifoil.Themorphologiesofthepowderswereobservedbyfield-emissionscan-ningelectronmicroscopy(FE-SEM:SUPRA55,CarlZeiss,Nak-ano,Japan).TheabsorptionspectraweremeasuredwithaUV/Visspectrophotometer(UV-2800,UNICOInstrumentsCo.,Ltd.,China).Thephotocatalyticactivitieswereevaluatedbythedegra-dationofRhodamineB(RhB)fromBeijingBeihuaFineChemicalCo.,Ltd.,undervisible-lightirradiationwitha20WXelamp(Beij-inginstituteofelectricallightsources,China)withacut-offfilter(λϾ400nm).ThephotocatalyticdecompositionofRhBbyCuSpowderswasexaminedwithaUV/Visiblespectrophotometer.Inthisexperiment,CuSpowdersasphotocatalysts(fixedweightof0.01g)wereaddedtoamixedsolutionofRhB(200mL,2.5mg/L)andH2O2(0.1mL,30%).Thereactionwaskeptatroomtem-peraturetopreventanythermalcatalyticeffect.Themixturewasstaticallyplacedinthedarktoreachtheadsorption–desorptionequilibriumbetweenphotocatalystandRhBbeforeillumination.TheLambert–BeerlawindicatesthattheconcentrationofRhBsolutionisindirectproportiontotheabsorptionintensityofitsUV/Visiblecharacteristicabsorptionpeak.Therefore,theab-sorbanceofthesolutionduringthephotocatalysisprocesscanbeusedasanindextocharacterizetheefficiencyofthephotocatalystforthedegradationofthedye.Inthisexperiment,thedegradationofRhBwasmonitoredfromtheintensityoftheabsorptionpeak©2014Wiley-VCHVerlagGmbH&Co.KGaA,WeinheimFigure8.Schematicillustrationofthecavity-mirroreffectoftheflowerlikeCuSsuperstructures.ConclusionsCuSsemiconductormaterialsofdifferentmicrostruc-turesweresynthesizedbythesolvothermalmethod,andtheirformationmechanismandphotocatalyticperformancewerestudied.SphericalnanoflowerCuSsuperstructurescanbesynthesizedfromCuCl2andCS(NH2)2bytheself-assemblyofnanoplatesat140°Cfor90min.Underthesamesolvothermalconditions,CuSmicrosphereswithacavityacrossthecentreanddenseCuSnanospherescanbesynthesizedwithCu(NO3)2andCuSO4asthecoppersources,respectively.OnthebasisofcalculationsfromtheirUV/Visabsorptionspectra,theenergygapsofthesampleswithdifferentmorphologiesare1.82eVforthemixtureofnanoneedles,nanoparticles,andnanoplates,1.70eVfortheatypicalnanoflowers,1.61eVforthesphericalnanoflowers,1.93eVfordoughnut-shapednanoflowers,and2.01eVforthenanospheres.TheexperimentaldataabovemanifeststhattheenergygapsofCuSnanopowderscanbeeffectivelycontrolledbyregulationoftheirmorphologies.Thephoto-Eur.J.Inorg.Chem.2014,2368–23752373www.eurjic.orgofRhB(560nm)relativetoitsinitialintensitybyusingthespectro-photometerundervariousilluminationtimesonthebasisofthefollowingformula:η=(A0–At)/A0ϫ100%,ηisthedecolorizationratioofthereaction,A0istheabsorbanceoftheRhBsolutionbeforethereaction,andAtistheabsorbanceoftheRhBsolutionaftertmin.SupportingInformation(seefootnoteonthefirstpageofthisarti-cle):Opticalabsorptionspectraandrelationalgraphsof(αhν)2ver-sushνforCuSpowderswithdifferentmorphologies.FULLPAPERAcknowledgmentsThisworkwassupportedbytheNationalNaturalScienceFounda-tionofChina(NSFC)(grantnumber51272023)andtheNationalBasicResearchProgramofChina(grantnumber2013CB632503).[1]M.Anpo,S.Dohshi,M.Kitano,Y.Hu,M.Takeuchi,M.Mat-suoka,Ann.Rev.Mater.Res.2005,35,1–27.[2]G.Hitoki,T.Takata,J.N.Kondo,M.Hara,H.Kobayashi,K.Domen,Electrochemistry2002,70,463–465.[3]Y.Tian,T.Tatsuma,J.Am.Chem.Soc.2005,127,7632–7637.[4]A.Fujishima,K.Honda,Nature1972,238,37–38.[5]A.Kudo,Y.Miseki,Chem.Soc.Rev.2009,38,253–278.[6]K.Maeda,J.Photochem.Photobiol.C:Photochem.Rev.2011,12,237–268.[7]R.Abe,J.Photochem.Photobiol.C:Photochem.Rev.2010,11,179–209.[8]T.Inoue,A.Fujishima,S.Konishi,K.Honda,Nature1979,277,637–638.[9]L.Caballero,K.A.Whitehead,N.S.Allen,J.Verran,J.Pho-tochem.Photobiol.A:Chem.2009,202,92–98.[10]R.Cai,K.Hashimoto,K.Itoh,Y.Kubota,A.Fujishima,Bull.Chem.Soc.Jpn.1991,,1268–1273.[11]T.Matsunaga,R.Tomoda,T.Nakajima,H.Wake,FEMSMicrobiol.Lett.1985,29,211–214.[12]C.McCullagh,J.Robertson,D.Bahnemann,P.Robertson,Res.Chem.Intermed.2007,33,359–375.[13]J.R.Peller,R.L.Whitman,S.Griffith,P.Harris,C.Peller,J.Scalzitti,J.Photochem.Photobiol.A:Chem.2007,186,212–217.[14]E.J.Wolfrum,J.Huang,D.M.Blake,P.Maness,Z.Huang,J.Fiest,W.A.Jacoby,Environ.Sci.Technol.2002,36,3412–3419.[15]J.Zhao,B.Zhang,Y.Li,L.Yan,S.Wang,J.AlloysCompd.2012,535,21–26.[16]S.Li,Y.Lin,B.Zhang,J.Li,C.Nan,J.Appl.Phys.2009,105,054310.[17]M.R.Hoffmann,S.T.Martin,W.Y.Choi,D.W.Bahnemann,Chem.Rev.1995,95,69–96.[18]A.L.Linsebigler,G.Q.Lu,J.T.Yates,Chem.Rev.1995,95,735–758.[19]K.Su,Z.H.Ai,L.Z.Zhang,J.Phys.Chem.C2012,116,17118–17123.[20]C.Chen,X.Hu,P.Hu,Y.Qiao,L.Qie,Y.Huang,Eur.J.Inorg.Chem.2013,5320–5328.[21]F.E.Osterloh,Chem.Mater.2008,20,35–54.[22]H.Shao,X.Qian,Z.Zhu,J.SolidStateChem.2005,178,3522–3528.[23]P.S.Lunawat,S.Senapati,R.Kumar,N.M.Gupta,Int.J.Hy-drogenEnergy2007,32,2784–2790.[24]J.S.Jang,U.A.Joshi,J.S.Lee,J.Phys.Chem.C2007,111,13280–13287.[25]Y.Liu,P.D.Kanhere,C.L.Wong,Y.Tian,Y.Feng,F.Boey,T.Wu,H.Chen,T.J.White,Z.Chen,Q.Zhang,J.SolidStateChem.2010,183,24–29.Eur.J.Inorg.Chem.2014,2368–2375[26]B.B.Kale,J.O.Baeg,S.M.Lee,H.Chang,S.J.Moon,C.W.Lee,Adv.Funct.Mater.2006,16,1349–1354.[27]X.Fang,T.Zhai,U.K.Gautam,L.Li,L.Wu,Y.Bando,D.Golberg,Prog.Mater.Sci.2011,56,175–287.[28]R.Córdova,H.Gómez,R.Schrebler,P.Cury,M.Orellana,P.Grez,D.Leinen,J.R.Ramos-Barrado,R.D.Río,Langmuir2002,18,87–8654.[29]W.P.Lim,C.T.Wong,S.L.Ang,H.Y.Low,W.S.Chin,Chem.Mater.2006,18,6170–6177.[30]S.Erokhina,V.Erokhin,C.Nicolini,F.Sbrana,D.Ricci,E.D.Zitti,Langmuir2003,19,766–771.[31]S.Gorai,D.Ganguli,S.Chaudhuri,Cryst.GrowthDes.2005,5,875–877.[32]C.Wu,G.Zhou,D.Mao,Z.Zh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