2024年5月14日发(作者：小米手环3参数)

.1999,11,771-778771

Layer-by-LayerAssemblyofUltrathinCompositeFilms

fromMicron-SizedGraphiteOxideSheetsand

Polycations

khova,*

,†

er,

‡

,

‡

k,*

,‡

k,

§

va,

|

and

nskiy

|

InstituteofSurfaceChemistry,NationalAcademyofSciencesofUkraine,31,,

252022Kyiv,Ukraine;DepartmentofChemistry,ThePennsylvaniaStateUniversity,

UniversityPark,Pennsylvania16802;Metal-PolymerResearchInstitute,32AKirovStreet,

Gomel,246652,Belarus;enkoUniversity,64,VladimirskayaStr.,

252033Kyiv,Ukraine

ReceivedNovember24,dManuscriptReceivedDecember28,1998

Unilamellarcolloidsofgraphiteoxide(GO)werepreparedfromnaturalgraphiteandwere

grownasmonolayerandmultilayerthinfilmsoncationicsurfacesbyelectrostaticself-

tilayerfilmsweregrownbyalternateadsorptionofanionicGOsheets

andcationicpoly(allylaminehydrochloride)(PAH).Themonolayerfilmsconsistedof11-14

ÅthickGOsheets,withlateraldimensionsbetween150nmand9µnsubstrates

primedwithaminemonolayersgavepartialGOmonolayers,butsurfacesprimedwithAl

13

O

4

-

(OH)

24

(H

2

O)

12

7+

ionsgavedenselytiledfilmsthatcoveredapproximately90%ofthesurface.

WhenalkalineGOcolloidswereused,themonolayerassemblyprocessselectedthelargest

sheets(from900nmto9µm)case,manyoftheflexiblesheets

ayer(GO/PAH)

n

filmswereinvariablythickerthan

expectedfromtheindividualthicknessesofthesheetsandthepolymermonolayers,and

ayer(GO/PAH)

n

and(GO/

polyaniline)

n

filmsgrownbetweenindium-tinoxideandPtelectrodesshowdiodelike

behavior,andhighercurrentsareobservedwiththeconductivepolyaniline-containingfilms.

Theresisitivityofthesefilmsisdecreased,asexpected,bypartialreductionofGOtocarbon.

Introduction

Theassemblyofcompositethinfilmsfromlamellar

inorganicparticlesandorganicmacromoleculesisan

inexpensiveandversatileroutetofunctionalnanometer-

scalestructures.

1

Thesefilmsaregrownbyawet

chemical,layer-by-layeradsorptionmethod,whichis

similartothatdevelopedearlierbyDecherandco-

workersfororganicpolyelectrolytes.

2

Theadditionof

inorganiccomponentsoffersthepossibilityofadded

optical,electronic,magnetic,mechanical,andthermal

propertiesthatmaybedifficulttoachievebyusing

onally,thecontinuous

inorganicsheetsprovideabarriertointerpenetration

ofsequentiallydepositedpolymerornanoparticlelayers,

afeaturethatcanbeimportantinthinfilmsintended

toactascurrentrectifiers,photodiodes,orCoulomb

lelectronicandphotonicap-

NationalAcademyofSciencesofUkraine.

ThePennsylvaniaStateUniversity.

§

Metal-PolymerResearchInstitute.

|

enkoUniversity.

(1)(a)Iler,dInterfaceSci.1966,21,569.(b)Kleinfeld,

E.R.;Ferguson,e1994,265,370.(c)Fendler,J.H.;

Meldrum,.1995,7,607.(d)Mallouk,T.E.;Kim,H.-N.;

Ollivier,P.J.;Keller,rehensiveSupramolecular

Chemistry;Alberti,G.,Bein,T.,Eds.;ElsevierScience;Oxford,UK,

1996;Vol.7,pp189-218.

(2)Decher,e1997,277,1232.

‡

†

plicationsalongtheselineshaveestablishedtheutility

ofthismethod.

3

Thelayer-by-layerassemblymethodreliesonthe

exfoliationofsolidstoproducecolloidsofsheets,which

typicallyhavenanometerthicknessesandlateraldi-

ation

proceduresbasedonionexchangeandredoxreactions

havebeendevelopedforavarietyoflamellarsolids.

4

Thus,multilayerinorganic/organicfilmshavebeen

grownfromlamellarmetalphosphates,titanates,nio-

bates,

5

silicates,

1b

andmetalchalcogenides,

6

compounds

whichinbulkformpossesstransportpropertiesranging

ly,Fendlerand

co-workershaveshownthatsuchfilmscanalsobe

(3)(a)Kaschak,D.M.;Mallouk,.1996,118,

4222.(b)Feldheim,D.L.;Grabar,K.C.;Natan,M.J.;Mallouk,T.E.

.1996,118,7640.(c)Keller,S.W.;Johnson,S.A.;

Yonemoto,E.H.;Brigham,E.S.;Mallouk,.

1995,117,12879.(d)Cassagneau,T.;Mallouk,T.E.;Fendler,J.H.J.

.1998,120,7848.

(4)(a)Jacobson,1994,152-153,1.(b)

Jacobson,rehensiveSupramolecularChemistry;Alberti,

G.,Bein,T.,Eds.;ElsevierScience;Oxford,UK,1996;Vol.7,pp315-

335.

(5)(a)Keller,S.W.;Kim,H.-N.;Mallouk,.

1994,116,8817.(b)Fang,M.,Kim,C.-H.;Saupe,G.B.;Kim,H.-N.;

Waraksa,C.C.;Miwa,T.;Fujishima,A.;Mallouk,tedto

.

(6)Ollivier,P.J.;Kovtyukhova,N.I.;Keller,S.W.;Mallouk,T.E.

.,.1998,1563.

10.1021/cm981085uCCC:$18.00©1999AmericanChemicalSociety

PublishedonWeb01/28/1999

.,Vol.11,No.3,1999

grownfromgraphiteoxide(GO),

7

whichcansubse-

quentlybereducedelectrochemicallytomakeelectroni-

rwork,GO

nanoparticleswerepreparedfromsyntheticgraphite.

Theynotedthatthemultilayerfilmsconsistedof

incompletelyexfoliatedplateletsthatweretensof

paper,

werevisittheassemblyofGO/polycationthinfilms,

that

exfoliatedGOderivedfromthesecrystalsisamechani-

callyrobustmaterialthatdepositsconformallyon

cationicsurfacesasmicron-sized,nanometer-thicksheets.

Graphiteoxideisapseudo-two-dimensionalsolidin

bulkform,withstrongcovalentbondingwithinthe

terlayercontactsaremadebyhydrogen

bondsbetweenintercalatedwatermolecules.

8-11

The

carbonsheetsinGOcontainembeddedhydroxyland

carbonylgroups,aswellascarboxylgroupssituated

mainlyattheedgesofthesheets.

8,9,12

Whilethereisno

consensusastotheprecisestructureofGOlayers,

differentstructuralmodels,

9a,b,10

whichcorrespondtoan

idealformulaofC

8

O

2

(OH)

2

,havebeenadvanced.A

recentstudyofthestructureofGOarguesfrom

13

Cand

1

HNMRevidenceforthepresenceofepoxygroups.

13

Nakajimaandco-workershaveproposedthatthecarbon

layersinGOarelinkedtogetherinpairsbysp

3

C-C

bondsperpendiculartothesheets.

10

AccordingtoKli-

nowskietal.,

13

thecarbonlayersinGOcontaintwo

kindsofdomains,aromaticregionswithunoxidized

benzeneringsandaliphaticregionswithsix-membered

ativesizeofthedomains,which

arerandomlydistributed,dependsonthedegreeof

models,thehydroxylgroupsproject

nolichydroxyl

groupsareacidicand,togetherwiththecarboxylgroups,

areresponsibleforthenegativechargeontheGOsheets

inaqueoussuspensions.

9,13

Thesurfacechargedensity

ofcolloidalGOparticles(degreeofoxidation85%)was

measuredbyFendlerandco-workersas0.4per100Å

2

.

7

TheGOinterlayerdistanceisnotconstantand

dependsstronglyontheGO:H

2

Oratio.

8-10,15

Invery

diluteaqueoussuspensions,theinterlayerdistanceis

large,sointeractionbetweenthelayersissufficiently

weakthatexfoliationoccurs.

8

Ourpreviousresearch

showedthatthenumberoflayersintheGOcolloidal

particlescanbecontrolledbythedilutionofthesuspen-

sions.

16,17

TheadsorptioncapacityforCu(II)ions,which

wasforbothaqueoussuspensions

16

andthinfilms

(7)(a)Kotov,N.A.;Dekany,I.;Fendler,.1996,8,

637.(b)Cassagneau,T.;Fendler,.1998,10,877.

(8)(a)Thiele,d-Z1948,111,15.(b)Croft,.

Rev.1960,14,1.

(9)(a)Scholz,W.;Boehm,.1969,369,

327.(b)Clauss,A.;Boehm,H.P.;Hofmann,.

1957,291,205.

(10)Nakajima,T.;Mabuchi,A.;Hagiwara,1988,26,357.

(11)Karpenko,G.;Turov,V.;Kovtyukhova,N.;Bakai,E.;Chuiko,

.(Russ.)1990,1,102.

(12)Hadzi,D.;Novak,.1955,51,1614.

(13)Lerf,A.;He,H.;Forster,M.;Klinowski,.B

1998,102,4477.

(14)Hennig,.1959,1,125.

(15)Lagow,R.J.;Badachhape,R.B.;Wood,J.L.;Margrave,J.L.

1974,1268.

(16)Kovtjukhova,N.I.;Karpenko,1992,

91-93,219.

(17)(a)Kovtyukhova,N.I.;Chuiko,cts;FallMeeting

oftheMaterialsResearchSociety,1994,Boston,C9.6.(b)Kovtyukhova,

N.I.;Buzaneva,E.V.;Senkevich,1998,36,549.

Kovtyukhovaetal.

depositedfromthesesuspensionsonpowdersupports

(ZnO,Al

2

O

3

,fumedSiO

2

),

17

increasedwithdecreasing

-

ample,theadsorptioncapacityofGOfilmsonSiO

2

increasedbyafactorof2.4whentheGOconcentration

inthestartingsuspensionwasdecreasedfrom1.0to

0.3g/sultshowsthatmorecompleteexfoliation

providesincreasedaccesstotheGOfunctionalgroups.

ForsamplespreparedfromthecolloidswithGOcon-

centrationsof0.02-0.3g/L,themaximumadsorption

capacity,22-24mmol/g,lueis

closetothetotalquantityofoxygen-containinggroups

inGO(25mmol/g

9

)andgivesindirectevidencethat

diluteGOcolloidsareexfoliatedasmonolayers.

Wereporthereadetailedstudyofthepreparation

andcharacterizationofGO/polycationfilmsgrownon

planarSiandAl

2

O

3

/tomicforce

microscopy(AFM),ellipsometry,andelectricalmea-

surements,thefollowingquestionshavebeenaddressed:

Whatdoesthefirstlayerofthesheetsadsorbedona

substratelooklikemicroscopically?

Canweaffectthequalityofmono-andmultilayer

filmsbyvaryingtheconditionsoftheirdepositionand

thechemicalcompositionofthesubstratesurface?

WhataretheelectronicpropertiesofGO/polycation

films,andhowaretheyinfluencedbythenatureofthe

polycation?

ExperimentalSection

ynthesizedfromnaturalgraphite

powder(325mesh,GAK-2,Ukraine)bythemethodofHum-

mersandOffeman.

18

Itwasfoundthat,priortotheGO

preparationaccordingtoref18,anadditionalgraphiteoxida-

ise,incompletelyoxidized

graphite-core/GO-shellparticleswerealwaysobservedinthe

phitepowder(20g)wasputintoan80

°CsolutionofconcentratedH

2

SO

4

(30mL),K

2

S

2

O

8

(10g),and

P

2

O

5

(10g).Theresultantdarkbluemixturewasthermally

isolatedandallowedtocooltoroomtemperatureoveraperiod

turewasthencarefullydilutedwithdistilled

water,filtered,andwashedonthefilteruntiltherinsewater

ductwasdriedinairatambient

eoxidizedgraphitewasthen

subjectedtooxidationbyHummers’dized

graphitepowder(20g)wasputintocold(0°C)concentrated

H

2

SO

4

(460mL).KMnO

4

(60g)wasaddedgraduallywith

stirringandcooling,sothatthetemperatureofthemixture

wasnotallowedtoreach20°turewasthenstirred

at35°Cfor2h,anddistilledwater(920mL)

15min,thereactionwasterminatedbytheadditionofalarge

amountofdistilledwater(2.8L)and30%H

2

O

2

solution(50

mL),afterwhichthecolorofthemixturechangedtobright

turewasfilteredandwashedwith1:10HCl

solution(5L)roduct

wassuspendedindistilledwatertogiveaviscous,brown,2%

dispersion,whichwassubjectedtodialysistocompletely

ulting0.5%w/vGO

dispersion,whichisstableforaperiodofyears,wasusedto

prepareexfoliatedGO.

Exfoliationwasachievedbydilutionofthe0.5%GOdisper-

sion(1mL)withdeionizedwater(24mL),followedby15min

ultinghomogeneousyellow-brownsol,

whichcontained0.2g/LGO,wasstableforaperiodofmonths

andwasusedforfilmpreparation.

Anaqueoussolution(0.01M)ofpoly(allylaminehydrochlo-

ride),PAH,(Aldrich,MW)50000-65000)wasadjustedto

pH7withNH

3

andwasusedforgrowthofpolycationlayers.

(18)Hummers,W.;Offeman,.1958,80,1339.