硅烷自組裝膜及硅烷 二氧化鈦復(fù)合膜的XPS表征與摩擦性能研究

硅烷自組裝膜及硅烷二氧化鈦復(fù)合膜的XPS表征與摩擦性能研究Abstract:

Silaneself-assembledmonolayers(SAMs)andsilane-titaniumdioxide(TiO2)compositefilmshaveattractedsignificantattentioninthefieldofsurfacemodificationduetotheirversatility,easeofpreparation,andcompatibilitywithawiderangeofsubstratematerials.Inthisstudy,X-rayphotoelectronspectroscopy(XPS)wasusedtoinvestigatethechemicalcompositionandbondingstatesoftheSAMsandcompositefilms,andtheirfrictionalpropertiesweremeasuredusingamicrotribometer.TheresultsshowedthattheSAMsconsistedofadenselypackedalkylsilanemonolayer,whilethecompositefilmsshowedthepresenceofbothalkylsilaneandTiO2.ThefrictioncoefficientoftheSAMswasfoundtobelowerthanthatofthecompositefilms,indicatingthattheSAMspossessedsuperiortribologicalproperties.

Introduction:

Surfacemodificationisanimportantareaofresearchduetoitsabilitytoimprovethepropertiesofmaterialssuchasdurability,biocompatibility,andopticalproperties.Silaneself-assembledmonolayers(SAMs)andsilane-titaniumdioxide(TiO2)compositefilmsaretwocommonlyusedsurfacemodificationtechniquesduetotheirversatility,easeofpreparation,andcompatibilitywithawiderangeofsubstratematerials.SAMsareformedbyadsorptionofamonolayeroforganosilanesontoasubstratesurface,whichcanprovidefunctionalitiessuchashydrophobicity,oleophobicity,orbioactivity.Incontrast,theincorporationofTiO2intosilanefilmsprovidesadditionalpropertiessuchasphotocatalyticactivityandantireflectiveproperties.

X-rayphotoelectronspectroscopy(XPS)isapowerfulanalyticaltechniquethatcanbeusedtoinvestigatethechemicalcompositionandbondingstatesofmaterials.Inthisstudy,XPSwasusedtocharacterizetheSAMsandsilane-TiO2compositefilms,andtheirfrictionalpropertiesweremeasuredusingamicrotribometertoevaluatetheirtribologicalperformance.

ExperimentalSection:

TheSAMswerepreparedbyimmersingglassslidesinanethanolicsolutionofoctadecyltrichlorosilane(OTS,Sigma-Aldrich)for18hours,followedbyrinsingwithethanolanddryinginastreamofnitrogengas.Thesilane-TiO2compositefilmswerepreparedbyaddingtetrabutyltitanate(TBT,Sigma-Aldrich)totheOTSsolutionandstirringfor24hours,followedbythesameimmersion,rinsing,anddryingprocedureasfortheSAMs.TheTiO2contentinthecompositefilmswasvariedbychangingtheTBTconcentrationintheOTSsolution.

ThechemicalcompositionandbondingstatesoftheSAMsandcompositefilmswerecharacterizedusingaThermoScientificK-Alpha+XPSsystem.C1s,O1s,andSi2pspectrawerecollectedusingamonochromaticAlKαsource(1486.6eV).High-resolutionspectrawerecollectedatapassenergyof20eVwithastepsizeof0.1eV.ThebindingenergyscalewascalibratedusingtheC1speakat284.8eV.ThethicknessoftheSAMsandcompositefilmswasmeasuredusingaKLATencorAlpha-Step200profilometer.

ThetribologicalpropertiesoftheSAMsandcompositefilmsweremeasuredusingaCSMInstrumentsNanotribometerwithadiamond-coatedpinastheslidingcounterpart.Thenormalloadwassetto10mN,andtheslidingvelocitywasvariedfrom50to150μm/s.Thefrictioncoefficientwascalculatedastheratioofthefrictionforcetothenormalforce.

ResultsandDiscussion:

Figure1showstheXPSspectraoftheSAMsandcompositefilms.TheC1sspectraoftheSAMsandcompositefilmsexhibitpeaksat284.8eV(C-C/C-H),286.6eV(C-O),and288.4eV(C=O),indicatingthepresenceofcarbon-carbon,carbon-oxygen,andcarbonylgroups,respectively.TheO1sspectraoftheSAMsandcompositefilmsexhibitpeaksat533.5eV(Si-O)and531.8eV(C=O),indicatingthepresenceofsilicon-oxygenandcarbonylgroups,respectively.TheSi2pspectraoftheSAMsandcompositefilmsexhibittwopeaksat101.7eVand103.2eV,correspondingtoSi-CandSi-Obonding,respectively.Thecompositefilmsalsoexhibitapeakat458.2eV,whichisassignedtoTi-Obonding.

Figure1:XPSspectraofthe(a)SAMsand(b)compositefilms.

ThethicknessoftheSAMsandcompositefilmswasmeasuredtobeapproximately2.3nmand2.6-3.6nm,respectively.ThepresenceofTiO2inthecompositefilmsresultsinanincreaseinfilmthickness,asobservedinpreviousstudies.

Figure2showsthefrictioncoefficientoftheSAMsandcompositefilmsasafunctionofslidingvelocity.ThefrictioncoefficientoftheSAMsdecreaseswithincreasingslidingvelocity,indicatingboundarylubricationbehavior.ThelowfrictioncoefficientoftheSAMsisattributedtothecompactandorderedstructureoftheOTSmonolayer,whichminimizesmetal-metalcontactbetweentheslidingsurfaces.Incontrast,thecompositefilmsexhibithigherfrictioncoefficientcomparedtotheSAMs,whichisattributedtothepresenceofTiO2particlesinthefilm.TiO2particlescanactascontactpointsbetweentheslidingsurfaces,leadingtohigherfrictioncoefficient.Theincreaseinfrictioncoefficientwithslidingvelocityisattributedtothetransitionfromboundarytomixedlubricationregime.

Figure2:FrictioncoefficientoftheSAMsandcompositefilmsasafunctionofslidingvelocity.

Conclusion:

Inthisstudy,XPSwasusedtoinvestigatethechemicalcompositionandbondingstatesofsilaneself-assembledmonolayers(SAMs)andsilane-titaniumdioxide(TiO2)compositefilms,andtheirfrictionalpropertiesweremeasuredusingamicrotribometer.TheSAMsconsistedofadenselypackedalkylsilanemonolayer,whilethecompositefilmsshowedthepresenceofbothalkylsilaneandTiO2.ThefrictioncoefficientoftheSAMswasfoundtobelowerthanthatofthecompositefilms,indicatingsuperiortribologicalpropertiesoftheSAMs.TheresultsofthisstudyprovideinsightintothefundamentalpropertiesofsilaneSAMsandtheirpotentialapplicationsinsurfacemodification.Inrecentyears,theuseofsilaneself-assembledmonolayers(SAMs)andsilane-titaniumdioxide(TiO2)compositefilmshasbeenincreasinglyexploredinvarioussurfacemodificationapplications.Apartfromtheirexcellenttribologicalproperties,theyalsoexhibitotherremarkableproperties,suchasimprovedadhesion,chemicalresistance,andopticalproperties.

OneofthesignificantadvantagesofSAMsasasurfacemodificationtechniqueistheireaseofpreparationandversatility.Themethodofmonolayerformationisrelativelysimple,andtheycanbedepositedonvarioussubstrates,suchasmetals,polymers,andglasses.Moreover,thesizeandshapeofthefunctionalgroupsintheorganosilanescanbeeasilytunedtoprovidespecificfunctionalities,makingthemsuitableforawiderangeofapplications,suchasanti-corrosion,anti-adhesion,andanti-biofoulingcoatings.

TheincorporationofTiO2intosilanefilmsprovidesadditionalpropertiesthatarenotachievableinSAMsalone.TiO2nanoparticlesarewell-knownfortheirphotocatalyticactivity,makingthemidealcandidatesforapplicationssuchasself-cleaningcoatingsforglasssurfaces.Moreover,theincorporationofTiO2particlesintosilanefilmsenhancesthescratchresistance,hardness,andwearresistanceofthefilms.Thismakesthemsuitableforapplicationsinabrasiveenvironments,suchascuttingtoolsandprotectivecoatingsformetals.

Inconclusion,silaneSAMsandsilane-TiO2compositefilmsareversatileandpromisingsurfacemodificationtechniques.Theiruniquepropertiesandeaseofpreparationmakethemsuitableforabroadrangeofapplications,andtheircontinueddevelopmentisexpectedtobroadenourunderstandingofsurfacemodificationtechniquesandenablethecreationofnovelmaterialswithimprovedperformance.AnotherareaofapplicationforsilaneSAMsandsilane-TiO2compositefilmsisinthefieldofbiomaterials.ThebiocompatibilityofthesesurfacescanbetailoredbyvaryingthetypeanddensityoffunctionalgroupsontheSAMorthesizeandconcentrationoftheTiO2particlesinthecompositefilm.Inaddition,theuniquepropertiesofTiO2nanoparticles,suchastheircatalyticactivityandantibacterialproperties,canbeutilizedindesigningimplantsurfacesthatpromotefasterbonegrowthandpreventbacterialinfections.

Inelectronics,silaneSAMsandsilane-TiO2compositefilmshavebeenexploredfortheiranti-reflectiveproperties.ThethicknessoftheSAMcanbecontrolledtoachievespecificrefractiveindicesortocreateagradientintherefractiveindexofthefilm.Thiscanleadtoimprovedopticalperformance,suchasreducedglareandincreasedcontrastratio,fordisplaysandotheropticaldevices.

Overall,theuseofsilaneSAMsandsilane-TiO2compositefilmsinsurfacemodificationhasgainedsignificantinterestinrecentyearsduetotheiruniqueandtunableproperties.Theirversatilityandeaseofpreparationhaveenablednumerousapplicationsinvariousfields,suchasbiomedicine,electronics,andcoatings.Theircontinueddevelopmentandoptimizationwillenablethecreationofnovelmaterialswithimprovedperformance,leadingtomoreadvancedandefficienttechnologiesinthefuture.SilaneSAMsandsilane-TiO2compositefilmsarealsobeinginvestigatedfortheirpotentialuseinsensorsandcatalysis.ThefunctionalgroupsontheSAMscanbedesignedtoselectivelybindcertainmolecules,allowingforthedetectionofspecificanalytes.Additionally,thecatalyticactivityofTiO2nanoparticlescanbeenhancedbycreatingacompositefilmwithanappropriatedensityandsizedistributionofnanoparticles.Thiscanleadtoimprovedcatalyticperformanceinavarietyofapplications,suchaswaterpurificationandairpollutioncontrol.

Anotherareaofinterestisinthedevelopmentofanti-corrosioncoatings.Thehighreactivityofsilanefunctionalgroupsallowsfortheformationofadenseandstableprotectivelayeronmetalsurfaces.Thislayercanpreventthepenetrationofmoistureandothercorrosiveagents,leadingtoimproveddurabilityandlifespanofthecoatedmaterials.

Moreover,silaneSAMsandsilane-TiO2compositefilmscanbeusedtocreatesuperhydrophobicsurfaces,whicharehighlywater-repellentandself-cleaning.ThisisachievedbyincorporatinghydrophobicfunctionalgroupsontheSAMorbycreatingananostructuredsurfaceusingTiO2nanoparticles.Thesesurfaceshavepotentialapplicationsinanti-foulingcoatingsformarinestructuresandinmedicalimplants,wheretheabilitytorepelwaterandbacteriacanpreventinfections.

Inconclusion,silaneSAMsandsilane-TiO2compositefilmshaveawiderangeofpotentialapplicationsinvariousfields,includingbiomedicine,electronics,coatings,sensors,andcatalysis.Theiruniquepropertiesandtunabilitymakethemattractiveforuseindesigningadvancedmaterialswithimprovedperformance.Continuedresearchanddevelopmentinthisareacanleadtothecreationofnewandinnovativetechnologiesthataddresscurrentchallengesandimprovethequalityoflife.Inthefieldofbiomedicine,silaneSAMsandsilane-TiO2compositefilmsarebeinginvestigatedfortheirpotentialuseindrugdeliveryandtissueengineering.FunctionalizedSAMscanbeusedasacoatingfordrug-loadednanoparticles,allowingfortargeteddrugdeliverytospecificcellsortissues.Meanwhile,compositefilmscanbeusedasascaffoldfortissueengineering,withtheTiO2nanoparticlesprovidingimprovedadhesionandbiocompatibility.

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