降解乙醛

MaterialsScienceinSemiconductorProcessing31(2015)397–404ContentslistsavailableatScienceDirectMaterialsScienceinSemiconductorProcessingjournalhomepage:www.elsevier.com/locate/msspSynthesisofmesoporoustitania–graphitecompositetemplatedbyhypocrellinsforvisible-lightphotocatalyticdegradationofacetaldehydeJiaqiangWangn,EncaiOu,JunjieLi,XiaoyunYang,WeiWang,ZhiyingYann,CongLiTheUniversities'CenterforPhotocatalyticTreatmentofPollutantsinYunnanProvince,SchoolofChemicalSciences&Technology,YunnanUniversity,Kunming650091,PRChinaarticleinfoAvailableonline31December2014Keywords:Visible-lightphotocatalysisPhotodegradationofacetaldehydeMesoporousanatasetitaniaHypocrellinstemplateGraphiticcarbonabstractAphotoactivecompoundextractedfromafungus(Hypocrellabambuase),namedhypo-crellins,wasusedastemplatetosynthesizethermallystablemesoporousmaterials.Thesynthesizedmesoporoustitaniasampleswerecharacterizedusingacombinationofvariousphysicochemicaltechniques,suchasN2adsorption/desorptionmeasurement,X-raydiffraction(XRD),scanningelectronmicroscopy(SEM),transmissionelectronmicroscopy(TEM),X-rayphotoelectronspectroscopy(XPS),UV–visdiffusereflectancespectroscopy(DRS)andFouriertransforminfraredspectroscopy(FT-IR).Theresultsofphysicochemicalcharacterizationsshowedthattheas-synthesizedsamplewasacompo-siteofhighlycrystallinemesoporousanatasetitaniaandgraphiticcarbon(gc–MTiO2),whichimpliesthedualfunctionofhypocrellinsastemplateand“dopant”.Theinsitudopedgraphiticcarbonsignificantlyincreasedthevisible-lightabsorbanceofTiO2.Thegc–MTiO2exhibitedefficientphotocatalyticactivityundervisible-lightforphotodegrada-tionofacetaldehyde,acommonindoorairpollutant.Thephotophysicsandelectrondynamicsinthisphotocatalyticprocesswerestudiedbytime-resolvedFT-IRspectra,inparticularonthenano-tomilli-secondtimescale.Itisobservedthatelectronswereinjectedintotheconductionbandofgc–MTiO2andtheyweredecayedtodeeptrapscausedbygraphiticcarbon.Thereportedstrategiescouldopenupnewusesformesoporoustitaniaself-dopedwithcarboninapplicationssuchassolarcells,photo-catalysts,photoelectricaldevices,andphoto-inducedsensors.&2014ElsevierLtd.Allrightsreserved.1.Introduction

Inviewofincreasinglyseriousenergyandenviron-mentalproblems,considerableeffortshavebeeninvestedindevelopingphotocatalystscapableofusingabundantCorrespondingauthors.Tel./fax:þ8687165031567.E-mailaddresses:jqwang@ynu.edu.cn(J.Wang),zhyyang@ynu.edu.cn(Z.Yan).http://dx.doi.org/10.1016/j.mssp.2014.12.0291369-8001/&2014ElsevierLtd.Allrightsreserved.nsolarlight.TiO2isthemostlyinvestigatedoneduetoitshighactivity,lowcost,lowtoxicityandgoodchemical/thermalstability[1].IthasalsobeenmodifiedbyusingmanymethodsbecausethebandgapofpureTiO2istoolarge(3.0–3.2eV)toutilizevisible-light[1–3].Recently,anumberofsystemsthatareabletooperateeffectivelyundervisible-lightirradiationhavebeenreportedsuchascarbondoping[4–8],nitrogendoping[9–13],elementsco-doping[14–17]andphotosensitization[18–23].Amongtheseapproaches,photosensitizationofTiO2nanoparticles398J.Wangetal./MaterialsScienceinSemiconductorProcessing31(2015)397–404ormesoporousTiO2byphotosensitizerswasfoundeffec-tiveinenhancingthephotocatalyticefficiencyandvisible-lightutilizationofTiO2[18,19].Thisisbecausephotosen-sitizersattachedtothesurfaceofTiO2areresponsibleforabsorbingtheincominglight[20,21].Andthisprocessisparticularlyemployedindye-sensitizedsolarcells[22,23].Generally,photosensitizerswereadsorbedbytitanianano-particles,filmsormesoporousmaterialsatroomtempera-turepriortophotoreaction.Thesephotosensitizersarethereforenotthermallyandphotochemicallystable[24].Inordertodevelopnewefficientphotosensitizationsystems,ZhouandHonmahaveattemptedtodopedyesintomesostructuredoxidematerialsthroughaco-organi-zingprocessofthesurfactantsanddyes,ratherthanexternaldopingafterthecalcinationforformationofthechannel[25,26].FaulandAntoniettihavedevelopedafacilemethodtosynthesizeafunctional,organiccompositemate-rialbysimpleprecipitationofchargeddyeswithoppositelychargedsurfactantsbecausesupramoleculardyemoleculesareeasilyavailable,haveanumberoffunctionalgroups,possessadefinedandregularshapeandmutualinterac-tions,andarealmosttheidealbuildingblocksforsupra-molecularchemistry[27].Morerecentlyinourgroup,14commercialsyntheticdyesweredirectlyusedasstructure-directingagentswhichwereconvertedtocarbonaceousmaterialsaftercalcinationinsynthesisofthermallystablemesostructuredtitania[28].Thisinsitudopedcarbonenhancedthevisible-lightphotocatalyticactivitiesofTiO2forthedegradationofaqueousdyes.However,thesephoto-catalystsexhibitedverylowactivitiesforphotodegradationofgaseousacetaldehyde.Andthecarbonspeciesincorpo-ratedinthetitaniadidnotexhibitanyobservablemorphol-ogy.Therefore,itwillbeinterestingtoinvestigatemorepotentialcoloredtemplatesanddevelopphotocatalystwithsignificantvisible-lightphotocatalyticactivityforthedegra-dationofgasphasepollutants.Inrecentyears,biologicaltemplateshaveattractedconsiderableattentioninthesynthesisofporousinorganicmaterialsbecausetheyaregenerallyinexpensive,abun-dantandenvironmentallybenign[29–31].However,thephotocatalyticpropertiesofthesematerialssynthesizedbyusingbiotemplatesareseldomexplored.Asoneofthefewexamples,mesoporoustitaniapreparedbyusingbacterialcellulosemembranesasbiologicaltemplateexhibitedgoodphotocatalyticactivityforphotodegradingRhoda-mineBunderUVlightirradiation[29].Recently,greenleaveswereappliedasbiotemplatestosynthesizemorph-TiO2whichexhibitedactivitiesforthedegradationofRhodaminedyeunderUVandvisible-lightirradiation[30].Wealsousedplantskins[31],algaeanddiatomsastemplatestofabricatemesoporoustitaniawithgoodphotocatalyticactivity.However,littleattentionhasbeenpaidtotheapplicationofphotoactivecompoundsextra-ctedfromplantsorfungusastemplateseventhoughchlo-rophyllhasbeenemployedasphotosentizersinthesynthesisofchlorophyll-basedphotocatalysts[32].Andsofarasweknow,thereisnoreportonusingbiotem-platedmesoporoustitaniawithgoodphotocatalyticactiv-ityforthedegradationofgasphasepollutants.Hypocrellins,includinghypocrellinA(HA)andhypocrellinB(HB),areperylenequinonoidderivativeswithphotosensitiveactivity.TheycanbeextractedfromaparasiticfungusHypocrellabambuase(B.etBr.)sacc.,whichisgrowingabun-dantlyinthenorthwesternregionofYunnanprovinceinChina[33–35].Theyareefficientphototherapeuticagentsowingtotheirhighquantumyieldsofreactiveoxygenspecies,i.e.,1O2,Od2À,andakindofphotosensitizerwithstrongandbroadabsorptioninvisible-lightregion[34].Moreover,hypo-crellinshaveseveraladvantages,includingeasypreparationandpurification,lowtoxicity,highstability,noaggregationandrapidmetabolism[35].Therefore,theyhaveattractedmuchattentioninrecentyears.Forexample,CdSphotoreduc-tionefficiencywasenhancedbyphotosensitizationofHAinvisible-lightregion[36].Recently,theintroductionofHBintoTiO2colloidsuccessfullyextendedthephoto-responseofTiO2tovisible-lightandmaintainedthehighgenerationofactiveoxygenundervisible-lightillumination[37].Butsofarthereisnoreportonusingthemastemplatesforpreparationofmesoporousmaterialsasweknow.Herein,inthecontinuationofourwork,wereportthesimultaneousachievementofhighlycrystallinemeso-scopicorderingandvisible-lightphotocatalyticactivitybyusinghypocrellinsasastructure-directingagent.Moreinterestingly,thesynthesizedmesoporoustitaniawithanatasecrystallinestructure(gc–MTiO2)wasdopedwithgraphiticcarbonandthishadnotbeenobservedwhenusing14commercialdyes[28].Thegc–MTiO2exhibitedefficientphotocatalyticactivityundervisible-lightforthephotodegradationofacetaldehyde,acommonindoorairpollutant.Ourworksuggeststhatthesephotoactivecom-poundscouldbepotentialtemplatesforthesynthesisofmesoporoustitaniaself-dopedwithcarbonforvisible-lightphotocatalysis.2.Experimental

2.1.ReagentsandsynthesisHypocrellinsisolatedfromthefungussacsofHypocrellabambuasewererecrystallizedtwiceusingacetoneassolventbeforeuse.Otherchemicalreagentssuchastita-niumisopropoxide(TTIP)andethanolwereuseddirectlywithoutfurtherpurification.Distilledwaterwasemployedthroughoutthestudy.Thegc–MTiO2wassynthesizedbyfollowingapreviousmethodwehaddevelopedbyusingcommercialdyesastemplates[28].Inthisprocess,ethanolwasstillusedasasolventtocontrolthehighreactivityoftitaniaprecursorstowardhydrolysisandcondensation.Inatypicalprepara-tionprocess,1ghypocrellinswasdissolvedin30mLethanolunderstirring,and3gTTIPwasaddedslowlyuntilthesolutionbecameacleargel.Then40mLwaterwasaddeddrop-wiseundercontinuousstirring,whichcausedtheimmediateprecipitationofawinesolid.Sub-sequently,themixturewasstirredfor24hinthedarkandthentransferredintoaTeflonbottleandtreatedunderautogenouspressureat363Kfor7days,filtered,washed,driedandcalcinedat673Kinairfor6h.Finallylight-yellowpowderwasobtained.PureMTiO2templatedbydodecylamine(DDA)wasalsopreparedbyusingamethodreportedelsewhere[38].J.Wangetal./MaterialsScienceinSemiconductorProcessing31(2015)397–4043992.2.CharacterizationsX-raypowderdiffraction(XRD)experimentswerecon-ductedusingaD/max-3BspectrometerwithCuKαradia-tion.Scansweremadeinthe2θrangeof7–901withascanrateof101/min(wideanglediffraction).Poresizedistribu-tions,BETsurfaceareasandporevolumesweremeasuredbyN2adsorption/desorptionusingaNOVA2000egassorptionanalyzer(QuantachromeCorp.).Priortotheanalysis,thesamplesweredegassedat1501Cfor1h.Scanningelectronmicroscopy(SEM)wascarriedonaJSM-6700Fmicroscopeatanacceleratingvoltageof30kV.Transmissionelectronmicroscopy(TEM),high-resolutiontransmissionelectronmicroscopy(HRTEM)imagesandselectedareaelectrondiffraction(SAED)pat-ternwereobtainedusingaJEOLJEM-2100microscope.ThelaserRamanspectraweremeasuredwithaspex1403spectrometerusingthe514.5nmlineofArþlaseremis-sionwitharesolutionof1cmÀ1.Fouriertransforminfra-redspectrum(FT-IR)measurementswereperformedusingaNicolet8700instrument.Potassiumbromidepelletscontaining0.5%ofthecatalystwereusedinFT-IRexperi-mentsand34scanswereaccumulatedforeachspectrumintransmission,ataspectralresolutionof4cmÀ1.ThespectrumofdryKBrwastakenforbackgroundsubtraction.UV–visdiffusereflectancespectra(DRS)weremeasuredatroomtemperatureinairusingaShimadzuUV-2401PCphotometerovertherangefrom200to800nm.X-rayphotoelectronspectroscopy(XPS)wasperformedusingaPHI5500ESCAanalyzer.Themainparameterswereasfollows:MgKα,200W,vacuum$10À7Pa.2.3.PhotodegradationproceduresAstaticreactorplacedinacirculatingwaterbathwasusedforthephotocatalyticdegradationofacetaldehyde.Thelightsourcewasa500Whalogenlamp.Acombina-tionoftwofilters,avisible-nearinfralongpassfilter(λ¼400nm)andacoloredglassfilter(λ4420nm)wasusedforvisible-lightirradiation.Alltheexperimentswereconsistentlycarriedoutatroomtemperature.Therequiredamountofthepowdersample(about5.0Â10À7kg)wasuniformlyspreadoverthewallofthereactor.200μLliquidacetaldehyde(40%)wasinjectedintoreactoranddepos-itedinthedarktoensuretheadsorption/desorptionequilibrium.Gaseoussamples(0.5mL)wereextractedwithasyringeandtheconcentrationsofacetaldehydeandCO2weredetectedbyusingagaschromatograph(ShimadzuGC-14C)equippedwithathermalconductivitydetector(TCD)andacapillarycolumn.3.Resultsanddiscussion

3.1.Synthesisandcharacterizationsofgc–MTiO2Thehypocrellintemplateisdeep-redincolor.Buttheas-synthesizedgc–MTiO2aftercalcinationwaslight-yellowpowderbecausethetemplatesweremostlydecom-posedandremoved.IntheX-raydiffractionspectrum(Fig.1),thediffractionpeaksat25.31,37.81,48.01,53.91,55.11,62.71,68.81,70.31and75.01,correspondingto(101),Fig.1.XRDpatternofgc–MTiO2.Fig.2.N2adsorption/desorptionisothermandBJHpore-sizedistribution(inset)ofgc–MTiO2.(004),(200),(105),(211),(204),(116),(220)and(215)facets,respectively(JCPDSNo.21-1272),confirmingthecrystallinephaseofanatasetitaniawereobserved.There-fore,itissuggestedthatgc–MTiO2hasanatasecrystal-linephase.TheBETsurfacearea,porevolumeandporediameterofgc–MTiO2were101m2/g,0.17cm3/gandof4.5nm,respec-tively.Fig.2showstheN2adsorption/desorptionisothermsofgc–MTiO2.ThesampleexhibitstypicalisothermoftypeIVhavinginflectionaroundP/P0¼0.4–0.7,acharacteristicofmesoporousmaterials.ThisisingoodagreementwithRefs.[39,40].Moreover,theBJHpore-sizedistributionofgc–MTiO2(Fig.2,inset)showsprimarypore-sizedistribu-tionsintheregionbetween2and12nm,indicatingthatthesamplehasmesoporouspores.Themorphologyandstructureofgc–MTiO2wereobservedbySEM.AsshowninFig.3a,theas-synthesizedgc–MTiO2possessesanirregularmorphologyandiscomposedofalargenumberofaggregatedTiO2nanocrystals.ThiscouldalsobeconfirmedbyTEM(Fig.3b).ThesizeoftheseTiO2nanopar-ticlesisabout10nmindiameter.TheHRTEMimage(Fig.3c)furtherrevealsthestructureofsingleTiO2nanoparticleswhichconstitutedthegc–MTiO2.ItcanbeseenthattheTiO2particlesarewellcrystallized.Thelatticespacingof0.35nmcorre-spondstotheinterplanardistancebetweenadjacent(101)400J.Wangetal./MaterialsScienceinSemiconductorProcessing31(2015)397–404Fig.3.(a)SEM,(b)TEM,(c)HR-TEMimagesand(d)SAEDpatternofgc–MTiO2.crystallographicplanesofanataseTiO2.Besides,SAEDalsoindicatestheanatasephaseofgc–MTiO2(Fig.3d),whichisingoodagreementwiththeresultfromXRD.Theringsareassignedtothe(101),(200),(004),(105)and(211)reflections.XPSmeasurementswerealsoperformedtoconfirmthesurfacechemicalcompositionandtheoxidationstateofgc–MTiO2.Theresultsshowthatthegc–MTiO2ismainlycomposedofTi,C,andO(Fig.4a).TheTi2p3/2andO1sbindingenergyshiftsof458.3eVand529.5eVmatchexactlywithvaluesforTiO2(Fig.4b)[41].Themostintensepeakat284.8eVintheC1sspectrumwasascribedtotheC1sofgraphiticcarbon(284.8eV,CÀCbonds)(Fig.4c)[42,43].Thepeaklocationatabindingenergyof286.2eVisattributedtoCÀObonds,whichindicatedatmosphericoxidation[42,43].ThepresenceofCÀObondsisalsodemonstratedinO1sspectra(Fig.4d).Thepeakatabindingenergyof287.5eVwasassignedtoCQO[44,45].Further-more,theO1sspectraofthegc–MTiO2showthecontribu-tionsoftheothertwominorcomponents:hydroxylgroups(O–H)ordefectiveoxides(531.570.5eV)andadsorbedwater(53371eV),whichinevitablyarisefromtheprepara-tionandtransferprocessofgc–MTiO2.However,nopeakscorrespondingtoTiÀCbondswereobserved.FT-IRspectraofgc–MTiO2,DegussaP25andhypocrellins(PQD)templatebetweenwavenumberof400and4000cmÀ1areshowninFig.5a.ItrevealsthatonlyvibrationsofO–H(around3670and1720cmÀ1)andTi–O(around482cmÀ1)appearedinthespectrumofgc–MTiO2.Thetypicalpeaksofhypocrellinsbetween1750and1065cmÀ1aretooweaktobeexaminedingc–MTiO2.Therefore,itisconfirmedthathypo-crellinstemplatehasbeenremovedcompletelyaftercalcina-tion.Thebroadpeakintherangeof400–1080cmÀ1iscontributedtotheanatasephasewhichisconsistentwiththeobservationofXRDandRamanspectra[46].Itisbelievedthatthebroadpeaksat3670and1720cmÀ1correspondtothesurface-adsorbedwaterandhydroxylgroups[47,48].SimilarresultswerealsoobtainedforDegussaP25.Thissurfacehydroxylationisveryadvantageousforthephotoca-talyticactivityofanatasebecauseitprovideshighercapacityforoxygenadsorption[49,50].J.Wangetal./MaterialsScienceinSemiconductorProcessing31(2015)397–404401Fig.4.(a)TypicalXPSsurveyspectrumofgc–MTiO2;(b)Ti2pXPSspectra;(c)C1sXPSspectra;and(d)O1sXPSspectra.peaksat197,396,519and639cmÀ1intheTiO2pattern(Fig.6a)[51].ThewelldefinedRamanpatternforthegc–MTiO2samplesismostprobablyduetothehighlevelofcrystallinityinthesamplesasobservedbyXRD.Thetwostrongpeaksatabout1265and1669cmÀ1areassignedtotheill-organizedgraphite(Fig.6b)[52,53].TheUV–visDRSspectraofDegussaP25andgc–MTiO2areshowninFig.7.gc–MTiO2exhibitedbroadabsorptionfromUVtovisible-lightregion.Abroadabsorptionupto$680nmprobablyduetothepresenceofgraphiticcarbonisseen.Furthermore,theabsorptionintensityofgc–MTiO2wasalsosignificantlyhigherinUVrangewhencomparedwiththatofDegussaP25.TheseobservationsjustifywhythesematerialscanbepotentialcandidatesforperformingphotocatalyticactivityinbothUVandvisible-light.3.2.Photocatalyticactivitiesundervisible-lightFig.5.FT-IRspectraofgc–MTiO2,DegussaP25andhypocrellins(PQD).Fig.6showstheRamanspectraofgc–MTiO2.Achar-acteristicanataseTiO2scatteringpatternwasobserved,withasharpandintensepeakat143cmÀ1,andfurtherThephotoactivitiesofthecatalystswereevaluatedbymeasuringthelossofacetaldehydeinthegasphaseuponvisible-lightirradiation.ThephotocatalyticdegradationofacetaldehydeoverDegussaP25andgc–MTiO2isshownin402J.Wangetal./MaterialsScienceinSemiconductorProcessing31(2015)397–404Fig.6.Ramanspectraofgc–MTiO2.Fig.7.UV–visDRSspectraofgc–MTiO2andDegussaP25.Fig.8a.Aftertheadsorption/desorptionequilibriumwasachievedinthedark,theacetaldehydeconcentrationwasfoundincreasedwhenthelightwasonduetothereleaseofacetaldehydeadsorbedbythephotocatalysts.Thedegrada-tionoftheacetaldehydewasobservedafter30minvisible-lightirradiationforgc–MTiO2.Fig.8bshowstheplotsofln(C0/Ct)versustime(t),whereC0andCtdenotethegasphaseconcentrationsofacetaldehydebeforeandafterphotoreac-tion.Theln(C0/Ct)valueincreasedlinearlywithtime,indicatingthatthephotocatalyticreactionsfollowedapseudo-first-orderratelawwithanapparentfirst-orderrateconstantof0.013minÀ1.Thegc–MTiO2photocatalystpreparedinasinglestepshowedsignificantactivityforthephotodegradationofacetaldehydeundervisible-light.ItisFig.8.(a)Photocatalyticdegradationofacetaldehydeovergc–MTiO2andDegussaP25undervisible-light.(b)Pseudo-first-orderplotofphoto-catalyticacetaldehydedegradationovergc–MTiO2.stableandcouldbereusedforatleastthreecycleswithoutlossinphotocatalyticactivity.Moreover,eventhoughmesoporoustitaniaself-dopedgraphiticcarbontemplatedbycommercialsyntheticdyeshadUVandsolarlightactivitiesofdegradationdyes[28],thesephotocatalystsexhibitedverylowactivitiesforthephotodegradationofgasphaseacetaldehyde.3.3.Apossiblemechanismfortheformationofmesoporousgc–MTiO2Theformationoflarge-poremesoscopicallytitaniaviasuchasimpleproceduresuggeststhatthehypocrellinmole-culesareidealbuildingblocksforsupramolecularchemistry.Indeed,mechanismdetailfortheformationofthismesopor-ousmaterialisstillfarfromunderstanding.Weproposedthathydrogenbondingcouldbethedrivingforcefortheforma-tionofthemesophase.ExcessivewaterinducesamoreextendedcondensationofthemineralnetworkandleadstotheformationofhydrophilicTi-oxooligomers[54,55].ThesespeciescaninturnassociatewithhypocrellinsviaH-bondinginteractions.AcombinationofmoleculargeometryandintermolecularH-bondingandentropicinteractionsdrivesthesesolutionstoself-assembleintocolloidalsystems.ItissuggestedthatH-bondinginteractionsareresponsiblefortheJ.Wangetal./MaterialsScienceinSemiconductorProcessing31(2015)397–404403Fig.9.TemporalprofilesinatmosphereoftransientIRabsorptionat2084cmÀ1ofthegc–MTiO2,MTiO2,andDegussaP25.Thecatalystswerepumpedbya355nmlaserpulseof10Hz.titanium–hypocrellinslink,particularlyhydroxylgroupsinhypocrellinmoleculeswouldbebenificialforthehydrogen-bondformation.Porositybeginstoarisewhensolventisreleasedupondrying;thisprocessdoesnotdestroythemesostructure.Therefore,hypocrellinsactedbothastemplatefortheformationofmesoporoustitaniaandcarbonsourceforgraphiticcarbon.3.4.Thepossiblereasonsforthevisible-lightactivityofgc–MTiO2Duetothesignificantdifferencesbetweenhypocrellinstemplatesandthoseconventionalsurfactanttemplates,itisinterestingtoevokesomereasonswhygc–MTiO2exhibitedthevisible-lightphotocatalyticactivities.Thefirstexplana-tionisthatsturdygraphiticcarboningc–MTiO2transferredfromhypocrellinsshiftedtheabsorptionedgeofTiO2tothevisible-lightrangeandhasdefiniteabsorptionsinthevisibleregion.Thus,thisgraphiticcarbonactsasaphoto-sensitizer.Secondly,thegraphiticcarbonwithtransportingabilitywasgrownsturdilyonthesurfaceofmesoporousTiO2.Sothepresenceofbothgraphiticcarbonandmeso-porousstructureoftitaniahadthefacilesorptionofCH3CHO.Meanwhile,O2adsorbedonthesurfaceofgraphi-ticcarbonmayaccepteÀandformOd2À,whichleadtotheformationofmoredOHinthesystem.Thirdly,thecarbonspeciescouldserveasanelectronscavengertoprotecttheprocessofelectron–holerecombinationandthatcouldbeimportantbecauseoftheformationofmorefreecarriers[56,57]whichwasobservedbytime-resolvedFT-IRspectra.Fig.9showsthetransientabsorptionsofphotogener-atedelectronsingc–MTiO2,DegussaP25andMTiO2photocatalystsonμsscaledeterminedbytime-resolvedFT-IRspectra.Thedecaysofelectronsbyexposuretoatmosphereshowedthatthelong-livedelectrondecayofgc–MTiO2withgraphiticcarbonwasmuchfasterthanthoseofDegussaP25andMTiO2.Andtheamountofphotogener-atedchargecarrierspresentedinitiallyingc–MTiO2parti-cleswithgraphiticcarbonwasalsomuchgreaterthanthoseofDegussaP25andMTiO2.Weinterpretthisfactasfollows:electronsinjectedintosemiconductorsinitiallyexistintheconductionband,theDegussaP25andMTiO2haveonlyonedecaypath(backelectrontransfer),whiletheinjectedelectronsofgc–MTiO2havetwodecaypathsleadingtothedisappearanceofabsorption(backelectrontrans-ferþdecaytothedeeptrapscausedbygraphiticcarbon)[58].Electronsinjectedintosemiconductorsinitiallyexistintheconductionband.Thentheydecaytotrapsitesorgobacktovalanceband.Ifelectronsstayintheconductionbandorshallowtrapsites,theygiveabsorptionintheregionof2200–1000cmÀ1.However,onceelectronsdecayintotrapsitesthataredeepintermsofenergy,theygivesmallerornoabsorptionintheregionof2200–1000cmÀ1.Infact,particlesynthesismethodsandannealingtempera-tureareexpectedtochangethetrapsitedistributionanddensity;thatistosay,theinvestigationofelectronsfallingintodeeptrapscangiveindispensableinformationforthedevelopmentofthistypeofmaterial[58–61].Thismeansthathypocrellinssuccessfullyactedasbothatemplateanda“dopant”whichwastransferredtosturdygraphiticcarbon.Indeed,mechanismdetailsofthesevisible-lightdrivenprocessesandoftheformationofgraphiticcarbonarestillfarfromunderstanding.4.Conclusions

Insummary,thereportedstrategiescombinedsol–gelchemistryandself-assemblyroutestopreparehypocrel-linstemplatedmeso-structuredtitania,inwhichsturdygraphiticcarbonwasincorporatedaftercalcinationat4001C.Thisinsitugeneratedgraphiticcarbonenhancedthevisible-lightphotocatalyticactivitiesoftheTiO2forthedegradationofgasphaseacetaldehyde.Bycontrast,thecommercialDegussaP25TiO2didnotexhibitanymean-ingfulvisible-lightactivity.Moreover,dopingofgraphitecarbonwasnotobservedinmesoporousTiO2templatedbychemicaltemplate[38]orcommercialdyes[28].Sohypocrellinsshouldbeapromisingtemplatewhichhassignificantadvantagesforsynthesisofvisible-lightrespon-sivephotocatalyst.AcknowledgmentsTheauthorsthanktheNationalNaturalScienceFoun-dationofChina(ProjectNSFC-YNU1033603,21367024,21403190),theProgramforInnovativeResearchTeams(inScienceandTechnology)intheUniversitiesofYunnanProvince(IRTSTYN),KeyProjectofMinistryofPublicSecurity(2011ZDYJYLS7006)andProgramofKunmingScienceandTechnologyBureau(2014-04-A-S-01-3073)forfinancialsupport.References[1]M.Pelaez,N.T.Nolan,S.C.Pillai,M.K.Seery,P.Falaras,A.G.Kontos,P.S.M.Dunlop,J.W.J.Hamilton,J.A.Byrne,K.O’Shea,M.H.Entezari,D.D.Dionysiou,Appl.Catal.B125(2012)331–349.[2]R.Daghrir,P.Drogui,D.Robert,Ind.Eng.Chem.Res.52(2013)3581–3599.[3]S.G.Kumar,L.G.Devi,J.Phys.Chem.A115(2011)13211–13241.[4]F.Dong,S.Guo,H.Wang,X.Li,Z.Wu,J.Phys.Chem.C115(2011)13285–13292.[5]S.Sakthivel,H.Kisch,Angew.Chem.Int.Ed.42(2003)4908–4911.404J.Wangetal./MaterialsScienceinSemiconductorProcessing31(2015)397–404[6]K.Gutbrod,P.Greil,C.Zollfrank,Appl.Catal.B103(2011)240–245.[7]M.E.Rincón,M.E.Trujillo-Camacho,A.K.Cuentas-Gallegos,Catal.Today107(2005)606–611.[8]K.A.Saharudin,S.Sreekantan,C.W.Lai,Mater.Sci.Semicond.Process.20(2014)1–6.[9]Y.P.Peng,S.L.Lo,H.H.Ou,S.W.Lai,J.Hazard.Mater.183(2010)754–758.[10]Q.Xiang,J.Yu,W.Wang,M.Jaroniec,Chem.Commun.47(2011)6906–6908.[11]Y.K.Lai,J.Huang,H.Zhang,V.P.Subramaniam,Y.Tang,D.Gong,L.Sundar,L.Sun,Z.Chen,C.Lin,J.Hazard.Mater.184(2010)855–863.[12]Z.Xie,Y.Zhang,X.Liu,W.Wang,P.Zhan,Z.Li,Z.Zhang,J.Nanomater.2013(2013)930950.[13]M.Xie,Y.Feng,Y.Luan,X.Fu,L.Jing,ChemPlusChem79(2014)737–742.[14]Y.Ma,J.Zhang,B.Tian,F.Chen,L.Wang,J.Hazard.Mater.182(2010)386–393.[15]J.Yu,Q.Li,S.Liu,M.Jaroniec,Chem.Eur.J.19(2013)2433–2441.[16]S.Wang,X.J.Yang,Q.Jiang,J.S.Lian,Mater.Sci.Semicond.Process.24(2014)247–253.[17]X.Cheng,H.Liu,Q.Chen,J.Li,P.Wang,Electrochim.Acta103(2013)134–142.[18]J.He,J.Zhao,T.Shen,H.Hidaka,N.Serpone,J.Phys.Chem.B101(1997)9027–9034.[19]E.Bae,W.Choi,Environ.Sci.Technol.37(2003)147–152.[20]D.Chatterjee,S.Dasgupta,N.N.Rao,Sol.EnergyMater.Sol.Cells90(2006)1013–1020.[21]O.Ozcan,F.Yukruk,E.U.Akkaya,D.Uner,Appl.Catal.B1(2007)291–297.[22]U.Bach,D.Lupo,P.Comte,J.E.Moser,F.Weissortel,J.Salbeck,H.Spreitzer,M.Grätzel,Nature395(1998)583–585.[23]B.O’Regan,M.Grätzel,Nature353(1991)737–740.[24]M.Kitano,M.Matsuoka,M.Ueshima,M.Anpo,Appl.Catal.A325(2007)1–14.[25]H.S.Zhou,I.Honma,Adv.Mater.11(1999)683–685.[26]I.Honma,H.S.Zhou,Chem.Mater.10(1998)103–108.[27]C.F.J.Faul,M.Antonietti,Chem.Eur.J.8(2002)27–2768.[28]J.Wang,J.Wang,Q.Sun,W.Wang,Z.Yan,W.Gong,L.Min,J.Mater.Chem.19(2009)6597–6604.[29]D.Zhang,L.Qi,Chem.Commun.5(2005)2735–2737.[30]X.Li,T.Fan,H.Zhou,S.K.Chow,W.Zhang,D.Zhang,Q.Guo,H.Ogawa,Adv.Funct.Mater.19(2009)45–56.[31]Y.Miao,Z.Zhai,B.Li,J.Li,J.He,J.Wang,Mater.Sci.Eng.C30(2010)839–846.[32]M.Joshia,S.P.Kambleb,N.K.Labhsetwara,D.V.Parwatec,S.S.Rayalu,J.Photochem.Photobiol.A204(2009)83–.[33]T.Wu,M.Weng,S.Chen,L.Wang,Z.Bi,T.Li,M.Zhang,T.Shen,J.Photochem.Photobiol.A118(1998)1–195.[34]L.Wang,X.Wang,H.Zhang,DyesPigment.67(2005)161–166.[35]S.Xu,S.Chen,M.Zhang,T.Shen,X.Zhang,Z.Wang,J.Photochem.Photobiol.78(2003)411–415.[36]L.Li,Z.Zhang,D.Wang,Q.Wan,J.Photochem.Photobiol.A102(1997)279–284.[37]S.Xu,J.Shen,S.Chen,M.Zhang,T.Shen,J.Photochem.Photobiol.B67(2002)–70.[38]W.Yao,H.Fang,E.Ou,J.Wang,Z.Yan,Catal.Commun.7(2006)387–390.[39]D.M.Antonelli,Y.J.Ying,Angew.Chem.Int.Ed.34(1995)2014–2017.[40]C.Liu,L.Fu,J.Economy,J.Mater.Chem.14(2004)1187–11.[41]J.Yu,L.Zhang,Z.Zheng,J.Zhao,Chem.Mater.15(2003)2280–2286.[42]T.I.T.Okpalugo,P.Papakonstantinou,H.Murphy,J.McLaughlin,N.M.D.Brown,Carbon43(2005)153–161.[43]L.Licea-Jiménez,P.Y.Henrio,A.Lund,T.M.Laurie,S.A.Pérez-García,L.Nyborg,H.Hassander,H.Bertilsson,R.W.Rychwalski,Compos.Sci.Technol.67(2007)844–854.[44]H.Hiura,T.W.Ebbesen,K.Tanigaki,Adv.Mater.7(1995)275–276.[45]M.T.Martínez,M.A.Callejas,A.M.Benito,M.Cochet,T.seeger,A.Ansón,J.Schreiber,C.Gordon,C.Marhic,O.Chauvet,J.L.G.Fierro,Carbon41(2003)2247–2256.[46]R.Sanjinés,H.Tang,H.Berger,F.Gozzo,G.Margaritondo,F.Lévy,J.Appl.Phys.75(1994)2945–2951.[47]T.Peng,D.Zhao,H.Song,C.Yan,J.Mol.Catal.A238(2005)119–126.[48]G.Soler-Illia,A.Louis,C.Sanchez,Chem.Mater.14(2002)750–759.[49]C.Anderson,A.J.Bard,J.Phys.Chem.B101(1997)2611–2616.[50]B.Ohtani,Y.Ogawa,S.J.Nishimoto,J.Phys.Chem.B101(1997)3746–3752.[51]K.Page,R.G.Palgrave,I.P.Parkin,M.Wilson,S.L.P.Savin,A.V.Chadwick,J.Mater.Chem.17(2007)95–104.[52]H.Hiura,T.W.Ebbesen,K.Tanigaki,H.Takahashi,Chem.Phys.Lett.202(1993)509–512.[53]L.Grigorian,K.A.Williams,S.Fang,G.U.Sumanasekera,A.L.Loper,E.C.Dichey,S.J.Pennycook,P.C.Eklund,Phys.Rev.Lett.80(1998)5560–5563.[54]G.J.deA.A.Soler-Illia,C.Sanchez,B.Lebeau,J.Patarin,Chem.Rev.102(2002)4093–4138.[55]C.Liang,Z.Li,S.Dai,Angew.Chem.Int.Ed.47(2008)3696–3717.[56]M.Janus,M.Inagaki,B.Tryba,M.Toyoda,A.W.Morawski,Appl.Catal.B63(2006)272–276.[57]H.Sun,Y.Bai,Y.Cheng,W.Jin,N.Xu,Ind.Eng.Chem.Res.45(2006)4971–4976.[58]K.Takeshita,Y.Sasaki,J.Phys.Chem.B107(2003)4156–4161.[59]G.Rothenberger,J.Moser,M.Gratzel,N.Serpone,D.K.Sharma,ChargeCarrierTrapping,J.Am.Chem.Soc.107(1985)8054–8059.[60]D.E.Skinner,D.P.ColomboJr.,J.J.Cavaleri,R.M.Bowman,J.Phys.Chem.99(1995)7853–7856.[61]T.Chen,Z.Feng,G.Wu,J.Shi,G.Ma,P.Ying,C.Li,J.Phys.Chem.C111(2007)8005–8014.