vat lieu xop tren co so graphene (1)

8/13/2019 Vat Lieu Xop Tren Co So Graphene (1)

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Kha lun tt nghip GVHD: PGS.TS H Thc Huy

Trang 1

LI CM N

Em xin chn thnh cm n thy H Thc Huy, ngi thy truyn t kinthc v tn tnh hng dn cho em trongsut nhng nm hc qua cng nh trong

qu trnh thc hin titt nghip.

Em xin cm n thy inh Tn Thnh tn tm gip em trong bui u

thc hin ti tt nghip.

Em xin cm n anh Mai Thanh Tm, anh Thanh Long, anh Hunh Lp

Trung, ch Khnh Vn, ch inh Th Nho, ch Thu Hin v cc anh ch cao hc

phng Ha L Polymer chia s nhng kinh nghim qu bu v gip em rt

nhiu trong qu trnh thc hin ti.

Xin cm n cc thy c trng i hc Khoa Hc T Nhin dy d em

trong sut 4 nm hc qua.

Cm n cc bn 09Polymer, 09T Y Sinh v cc bn khoa Ha chia s v

ng vin ti vt qua nhng thi im kh khn trong qu trnh thc hin ti.

V cui cng, con xin cm n b ni, ba m v mi ngi trong gia nh lun bn con v ng h con.

Tp. HCM thng 07/2013


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LI M U

Lch s cho thy s pht trin ca vt liu gn lin vi nn vn minh ca

nhn loi. Tri qua qu trnh lch s lu di vt liu c nhiu thay i t thi k

qua ngv hin nay l thi k ca nhiu loi vt liu tin tin. c pht

hin v c lp thnh cng nm 2004, graphene c v nh mt vt liu thn k

vi nhiu tnh cht u vit m trc nay cha vt liu no c. Song cc cng trnh

nghin cu gn mi nm qua ch tp trung vo cu trc dng tm (2D) ca

graphene m t ch n cu trc dng xp (3D). Trong nm nm tr li y, cu

trc xp (3D) bc u c nghin cu vi s k vng vo ng dng trong cc

lnh vc y sinh nh lm v ca cht mang thuc, to khung cho m.. hay trong lnh

vc hp ph v nng lng.

Trn th gii cc nghin cu v xp graphene cn kh t, trong ti ny

chng ti xin a ra phng php tng hp xp graphene v bc u kho st s

hp ph du. Hy vng ti nghin cu ny s gp mt phn nh, b sung thm

kin thc v vt liu graphene.


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MC LCPhn 1.TNG QUAN ............................................................................................. 11

1.1.Gii thiu chung v graphite .................................................................. 111.2. Vt liu Graphene ................................................................................. 12

1.2.1. Lch s tm ra graphene ................................................................. 121.2.2 Cu trc ca graphene .................................................................... 121.2.3. Cc phng php tng hp graphene ............................................ 14

1.3. Gii thiu v graphite oxide (GO) ........................................................ 161.3.1 Tng hp Graphite oxide (GO) ...................................................... 171.3.2. Cu trc v tnh cht ca GO ......................................................... 171.3.4. Cc phng php kh GO ............................................................. 19

1.4. Vt liu xp trn c s graphene .......................................................... 201.4.1 Xp graphene .................................................................................. 211.4.2 Phng php ch to xp graphene. ............................................... 221.4.3. Mt s nghin cu tng hp xp graphene. ................................ 24

1.4.3.1 Phng phpkh thy nhit to xp graphene khng s dng

cht kh. ........................................................................................................ 241.4.3.2 Phng php kh thy nhit to xp graphene s dng cht

kh ................................................................................................................ 251.4.3.3 Phng php kh thy nhit to xp graphene s dng

Ammoniac ..................................................................................................... 271.5.Mt s k thut v phng php nghin cu ......................................... 29

1.5.1 Phng php ng c (Freeze Drying or Lyophillisation) ............. 291.5.1.1 C s khoa hc ca phng php ng c ............................. 30

1.5.1.2. Quy trnh ng c .................................................................... 31


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3.2.1 Hnh nh cc mu gel GO c tng hp sau qu kh tnh ........... 473.2.2. Cc kt qu phn tch cc mu rGO sau qu trnh kh ................. 49

3.2.2.1 Gin XRD ca mu GO v cc mu GO sau qu trnh kh

(rGO) ............................................................................................................. 493.2.2.2. Ph FT-IR ca mu GO v rGO. ............................................. 503.2.2.3. Ph tn x Raman ca graphite, GO v rGO.......................... 513.2.2.4. Gin TGA ca mu GO v cc mu rGO sau qu trnh kh

....................................................................................................................... 523.2.2.5. Kt qu o dn in ca mu GO v rGO.......................... 533.2.2.6. Kt qu tng hp xp graphene t gel graphene sau qu trnh

ng c .......................................................................................................... 553.3. Cc kt qu kho st xpgraphene (rGO-HI) ...................................... 56

3.3.1 Kt qu chp SEM xp graphene rGO-HI ..................................... 583.3.2 Kt qu o din tch b mt ca xp graphene rGO-HI. ................ 59

Phn 4. Kt lun v kin ngh ................................................................................ 614.1. Kt lun ................................................................................................. 614.2. Kin ngh ............................................................................................... 61

TI LIU THAM KHO ...................................................................................... 62PH LC


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DANH MC HNH NH

Hnh 1.1 Cu trc ca graphite ................................................................................. 11Hnh 1.2 Cu trc ca graphene ................................................................................ 12Hnh 1.3 Cc hnh thi ca graphene ........................................................................ 13Hnh 1.4 K thut ch to graphene t graphite ....................................................... 15Hnh 1.5 K thut ch to graphene t CVD ............................................................ 16Hnh 1.6 M hnh kh graphene oxide to graphene. ............................................... 16Hnh 1.6 Cu trc ca graphite oxide (GO) theo m hnh ca Lerf Klinowski ..... 18Hnh 1.7 Lin kt hydro gia cc lp graphite oxide[2]. ........................................... 18Hnh 1.8 Cu trc graphite oxide (a) v graphene oxide (b) .................................... 19Hnh 1.9 Xp graphene. ............................................................................................ 21Hnh 1.10 M t qu trnh to mng khng gian trong qu trnh tng hp xp

graphene 3D s dng cation ...................................................................................... 22Hnh 1.11 Quy trnh tng hp graphene t GO ........................................................ 23Hnh 1.12 M hnh kh tnh ...................................................................................... 23Hnh 1.13 Gin XRD ........................................................................................... 24Hnh 1.14 Gel graphene trc v sau khi kh tnh ................................................... 25Hnh 1.15 Xp graphene (a), Hnh SEM ca xp graphene (b)............................... 26Hnh 1.16 Cu trc v qu trnh hp ph du ca xp .............................................. 28Hnh 1.17 Kh nng hp ph dung mi ca xp graphene ....................................... 28Hnh 1.18 Gin pha ca nc ............................................................................... 30Hnh 1.19 Biu din qu trnh ng c. .................................................................... 31Hnh 1.20 My ng c ............................................................................................. 32Hnh 1.21Nguyn l chiu x tia X .......................................................................... 32


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Hnh 1.22 Dng th ng thng BET ................................................................. 34Hnh 2.1 H tng hp GO ......................................................................................... 38Hnh 2.2 S oxi ha graphite ............................................................................... 39Hnh 2.3 H GO huyn ph sau khi tng hp ........................................................... 39Hnh 2.4 Gel GO.. ..................................................................................................... 39Hnh 2.8 Hn hp Graphene oxide v cht kh trc khi phn ng ........................ 40Hnh 2.9 H autoclave ............................................................................................... 40Hnh 2.10 S kh tnh s dng cht kh ammoniac ............................................ 41Hnh 2.11 S kh thy nhit s dng cht kh Vitamin C .................................. 42Hnh 2.12 S kh tnh s dng cht kh HI ........................................................ 43Hnh 3.1 Ph XRD ca mu GO v graphite ............................................................ 44Hnh 3.2 Ph FT-IR ca mu GO ............................................................................. 45Hnh 3.3 Gin TGA ca GO v graphite ............................................................. 46Hnh 3.4 Graphene oxide trc khi kh (a); ............................................................. 47gel graphene to thnh sau khi kh (b) ..................................................................... 47Hnh 3.5 Gel graphene sau qu trnh kh bng NH3................................................ 47Hnh 3.6 Gel graphene sau qu trnh kh bng Vitamin C (VitC) ........................... 47Hnh 3.7 Gel graphene sau qu trnh kh bng HI ................................................... 48Hnh 3.8 Gin XRD ca mu GO, rGO-HI, rGO-VitC, rGO-NH3 ...................... 49Hnh 3.9 Ph FT-IR ca mu GO, rGO-HI, rGO-VitC, rGO-NH3 ........................... 50Hnh 3.10 Ph raman ca Graphite, GO v ca cc mu rGO................................. 51Hnh 3.11 Biu t l cng ID/IG ..................................................................... 52Hnh 3.12 Gin TGA ca cc mu GO v rGO-HI, rGO-VitC, rGO-NH3. ........ 53

Hnh 3.13 Mu p vin i o d dn in ................................................................. 54


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Hnh 3.14 Cc mu rGO-NH3, rGO-HI, rGO-VitaminC (vitC) sau khi ng c..... 55Hnh 3.15. M hnh in t trn benzen v 3 cu hnh sp xp ca vng thm

theo tng tc ................................................................................................... 56Hnh 3.16 Xp graphene rGO-HI sau ng c. ........................................................ 57Hnh 3.17 Hnh chp SEM mu xp rGO-HI cc kch thc khc nhau.............. 58Hnh 3.18 M hnh in t ca vng thm theo tng tc .............................. 58


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DANH MC BNGBng 1.1 Cc thng s ca graphite....11

Bng 1.2So snh kh nng kh GO ca cc cht kh....27Bng 3.1 dn in v in tr mt ca cc mu54

Bng 3.2 Kho st khi lng hp ph du diezen ca xp rGO-HI..59


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DANH MC CC T VIT TTGO: Graphite oxide.rGO-HI: Graphite oxide kh bng HI.

rGO-VitC: Graphite oxide kh bng Vitamin C.rGO-NH3: Graphite oxide kh bng NH3.XRD (X Ray Diffraction): nhiu x tia X.FT-IR (Fourier transformIfrared spectroscopy): Ph hng ngoi Fourier

TGA (Thermo gravimetric analysis): Phn tch nhit trng lng


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Phn1.TNGQUAN1.1.Gii thiu chung vgraphite [1]

Graphite l mt dng th hnh ca carbon. Carbon trong cu trc graphite cdng lai ha sp,trong 1 nguyn t carbon lin kt cng ha tr vi ba nguyn t

carbon khc to thnh mt phng gm cc vng lc gic dung hp.

Hnh 1.1 Cu trc ca graphite

Graphite c th tm thy trong t nhin hoc c tng hp. Graphite t

nhin gm ba loi chnh: dng flake (phin mng) hay thng c gi l than ch

(plumbago), dng kt tinh (crytalline) v dng v nh hnh (amrophous).

Cc tnh cht vt l ca graphite nh nhit si, nhit nng chy

c xc nh nhit cao trn 3000 K nn cc s liu mc kh nhiu sai s

v cha thng nht.

Bng 1.1 Cc thng stnh cht ca graphite

Ttrng, 300 K, 1atm 2.26g/cmThtch nguyn t 5.315 cm/mol

Nhit thng hoa, 1 atm 4000 K

im ba (c lng) 4200K

Nhit si (c lng) 4560 K

Nhit ha hi 716.9 kJ/mol

m in Pauling 2.5


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Tnh cht ha hc: graphite tr vi phn ln cc cht nh axit, kim, cc cht

n mn tuy nhin hot tnh phn ng ca graphite c th tng ng k khi c mt

tp cht ( ng vai tr xc tc ca graphite vi ha cht), nhng khuyt tt trong

tinh th (tng nng lng hot ha), xp ( xp cng cao, din tch b mt cng

ln lm tng hot tnh phn ng ca graphite).

1.2. Vt liu Graphene [2]

1.2.1. Lch stm ra graphene

Nhng bi bo co v graphene ln u xut hin vo nm 1970 nhng phi

n nm 2004 th graphene mi c c lp bng cch tch bc c hc t khi

graphite bi nhm ca gio s Andre Geim- Khoa Vt l i Hc Manchester,

Anh Quc. T lc c bc tch v c lp thnh cng, graphene xut hin trong

rt nhiu cc cng trnh nghin cu trong hu khp cc lnh vc ca khoa hc nh

dn in, cc b cm ng, lm u d kh, gia cng cho cc polymervv. Rt

nhiu tnh nng ang dn c khm ph v trong vt liu hp ph, lu tr

graphene cng l vt liu y tim nng.1.2.2 Cu trc ca graphene

Hnh 1.2 Cu trc ca graphene

Graphene c cu trc n lp nguyn t, c dng tm bao gm cc nguyn

t carbon trng thi lai ha sp trong cu trc t ong. Khong cch gia hai

nguyn tcarbon kcn l 0.142 nm, khong cch gia hai lp graphenel 3-4 ,


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chiu dy mi tm graphene l 0.35 1,0 nm. Graphene c xem nh l vt liu

mng nht trong v tr. Graphene cngl cu trc c bn hnh thnh cc vt liu

khc nh graphite, cacbon nanotube, fullerences.

Hnh 1.3 Cc hnh thi ca graphene

Thn duknc

Graphene c cu trc n lp nguyn t, c dng tm bao gm cc nguyn

tcacbon sp lin kt vi nhau to thnh mng li tong 2D. iu ny quyt nh

nn tnh cht ca graphene l vt liu kncthn du.

Ttrng thp

n vlc gic ca graphene gm mi cnh l 2 nguyn tsc din tch

l 0.052nm. Suy ra ttrng ca graphene l 0.77mg/m. Vi ttrng thp, graphene

nu c cu trc xp 3D sl mt trong nhng vt liu nhnht gip chng ddng

ni trn bmt cht lng (c ttrng cao hn graphene nh nc).

Din tch bmt.


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Din tch bmt ca graphene khong 2600m/g, cao hn din tch bmt

ca than hot tnh v ca ng nano cacbon. Do khnng hp phca graphene

l rt ln.

dn in

Graphene n lp c tnh cht dn in c bit, nng lng vng cm hu

nh khng c. iu ny c gii thch da trn cu trc ca graphene, trong

mi carbon trng thi sp sdng 3 AOsp(mi AO c 1 electron c thn) lin

kt vi 3 AO spca 3 carbon kcn, cn 1 AO p(c cha 1 electron c thn) s

xen phvi cc AOpcn li ca cc carbon kcn to mng li lin kt -rng

khp. Do cc electron c thddng di chuyn gia cc AOpm khng gp bt

ctrngi no hay ni cch khc: graphene n lp l vt liu siu dn in.

dn nhit

Sdn nhit ca graphene bchi phi bi cc phonon v c o xp x

l 5000 . ng thi nhit phng graphene c dn nhit l 401

. Nh th, graphene dn nhit tt hn ng gp 10 ln.

1.2.3. Cc phng php tng hp grapheneTrong cu trc ca graphite, cc lp graphene lien kt vi nhau bng lc

Vander Wall. Do khong cch gia cc lp rt nh(0,34nm) nn lc ny tng tc

ng kkhin cho vic tch cc lp rt kh khn. Hai phng php chyu ch

to graphene l:

Phng php i t trn xung(top down) [1]

y l phng php to ht kch thc nano tcc ht c kch thc ln

hn. Bng kthut nghin v bin dng bin vt liu thkhi vi tchc ht th

thnh cht kch thc nano. y l ccphng php n gin, rtin nhng rt

hiu qu, c thtin hnh cho nhiu loi vt liu vi kch thc kh ln (ng dng

lm vt liu kt cu)


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Hnh 1.4 Kthut chto graphene tgraphite, phn tn graphite oxide (a),

dung dch graphene oxide (b), tm graphene oxide (c).

i t than ch Graphite: Tch c hc: dng lc c hc tch lp Grapite.

Dng sng siu m tch cc lp graphite trong dung dch.

Phng php in ha.

S thy ha graphite.

i t dn xut graphite oxide (GO):

Phng php phn tn dung dch keo (GO colloid).

Phng php kh ha hc graphene oxide trn c s ha tan (CRG).

Phng php khnhit.

Phng php t di ln(bottom up)

y l phng php hnh thnh ht nano tcc nguyn t. Nguyn l ca

phng php ny l hnh thnh vt liu nano tcc nguyn thoc ion. Bao gm:

Phng php lng ng hi ha hc CVD.

Phng php phng in h quang.


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Phng php epitaxial pht trin trn SiC.

Hnh 1.5 Kthut chto graphene tCVD

Phng php i t di ln cho graphene tinh khit hn nhng hm lng

graphene thu c theo phng php ny l rt thp. Hn na gi thnh sn xut r t

cao nn phng php i t trn xung thng c s dng trong cc lnh vc

khng i hi qu cao v tinh khit ca graphene. y l phng php mang li

nhiu hiu qu quy m phng th nghim. thu c graphene, tithc hin

theo phng phpphp t trn xung vi nguyn liu ban u l GO (graphite

oxide). C th qu trnh thc hin nh sau: bin tnh graphite to hp cht thn

nc l GO v sau khli thu c n lp graphite vi nhng tnh cht u

vit nh ban u.

Hnh 1.6 M hnh khgraphene oxide to graphene.

1.3. Gii thiu vgraphite oxide (GO)

Graphite oxide (GO) hay cn gi l acid graphite, c Brodie tng hp ln

u vo nm 1859, bng cch xl graphite vi hn hp kali chlorate v acid nitric

m c. Vsau cc phng php tng hp GO u da trn hn hp oxi ho mnh


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m Brodie a ra hn hp cha mt hoc nhiu acid mnh v cht oxide ho

m c.

1.3.1 Tng hp Graphite oxide (GO)

oxi ha graphite, s dng cc tc cht oxi ha mnh vi iu kin, thi

gian tin hnh phn ng thch hp, graphite c th b oxi ha cc mc khc

nhau. Khi graphiteb oxi ha, cc ni i C=C dn b thay th bi cc nhm chc

phn cc nh OH, -COOH, -CHO, nhm epoxy H lin hp ca graphiteb ph

hy nn graphite c mu nht hn graphiteban u. Ty theo phng php v loi

graphite s dng m mu sc graphite oxide khc nhau (t l C/O ln dung dch c

mu en nu, t l C/O nh dung dch c mu vng). Sau khi oxi ha, cc tnh cht

ca graphite gim ng k nh tnh dn in, dn nhit Cc tc cht oxi ha

thng dng l H2SO4 c, HNO3, KMnO4, KNO3, C ba phng php ch

yu iu ch graphite: phng php Brodie, phng php Staudenmeier, phng

php Hummers. Trong phng php Hummers c dng kh ph bin.

Phng php Brodie(y l phng php cin ra i sm nht) [3]

u im: n gin d thc hin.Nhc im: hao tn nhiu ha cht ra sn phm.

Phng php Staudenmeier: [3]

u im: n gin.

Nhc im: thi gian phn ng lu, h khng an ton vi ngi lm th

nghim.

Phng php Hummers: [4]

u im: thao tc an ton, to c graphite oxide vi hiu sut cao.

Nhc im: phc tp qua nhiu giai on.

1.3.2. Cu trc v tnh cht ca GO

C nhiu m hnh a ram t cu trc ca graphite oxide nhng m hnh

ca Lerf Klinowski ph bin hn c. Theo , graphite sau khi oxi ha, trn mt

phng nm ngang ca cc lp c cc nhm hydroxyl, epoxy.. v trn cc gc ca

mt phng nm ngang c th hnh thnh cc nhm chc carbonyl hoc carboxylic[5]


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Hnh 1.6 Cu trc ca graphite oxide (GO) theo m hnh ca LerfKlinowski

Cc vng thm, cc ni i, cc nhm epoxide c cho l nm trn mng

li Carbongn nh phng, trong khi carbon ni vi nhm OH hilch so vi cu

trc t dindn n cu trc lp hicong. Cc nhm chc c cho l nm c trn

ln di cc lp GO. V mi lp u cha cc nhm chc c oxygen mang in

tnh m, do c lc yxut hin gia cc lp, ng thi lm cho GO th hin

tnh a nc v trng c trong nc. Hn na, vic to lin kt hydrogen gia

cc mt phng thng qua cc nhm hydroxyl, epoxide v nc khin cc khoang

GO c nong rng ng k hn so vi graphite (0.65-0.75nm so vi 0.34nm, c

xc nh thng qua gin XRD).

Hnh 1.7 Lin kt hydro gia cc lp graphite oxide[2].

Tnhng tnh cht trn , cc nh khoa hc hy vng rng tgraphite oxide c

thbc tch cc lp ra vi nhau mt cch hon ton (trng thi exfoliated), sau

khcc lp graphene oxide ny vcc lp graphene hi phc cc tnh cht vn

c ca graphene.


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a

b

Hnh 1.8 Cu trc graphite oxide (a) v graphene oxide (b)

1.3.4. Cc phng php khGO

Tuy khi nim graphene c t lu, nhng vic tng hp chng vi s

lng ln lun gp kh khn. Nhng nghin cu gn y u tp trung vo nguyn

liu u l GO. Sau GO c khbng nhit (thermal), in ha hay ha hc

khi phc li tnh cht ca graphene.Khbng in ha: y l k thut s dng ngun in ngoi kh cc

mng graphite oxide thnh graphene. Trong phng php graphite oxide ny c

phn tn trong dung mi (thng l nc) ri sau c tch bc thnh graphene

oxide , tip theo graphene oxide c ph ln (thy tinh, vng .) cui cng

ghp mt in cc (dn in nu khng dn in) vo lp graphene oxide va

ph. Trong trng hp graphene oxide c ph trc tip ln in cc dn in th

khng cn . Sau thit lp h in ha choqu trnh kh din ra.Vi qu trnh

kh graphene oxide, phn ng bt u xy ra ti th (-0,6 V v cao nht l -0.87 V).

Thi gian phn ng rt nhanh khong 300 giy v c th ko di n 5000 giy.

Kh bng nhit: y l phng php s dng nhit thiu hy cc nhm

chc trn bmt GO ng thi tng p sut khin cc lp GO tch ri nhau.

Quy trnh: khi gia nhit, cc nhm chc trn GO bkhthnh CO2(vic kh

cc nhm chc thnh CO2 tng ng vi vic gim khong 30% khi lng ca sn

7,5 8,0


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phm), CO2 bay i to p sut bn trong cc lp. nhit cao vic nc bn

trong cc lp bay hi cng to nn mt p sut ln. Cc tnh ton c lng lc

lin kt van der Waals gia cc lp graphite l khong 26 Mpa, p sut to ra c

tkh CO2v nc cn st li trong GO ln lt l 100 v 60 Mpa, c2 p sut to

c ny u d thng c lc lin kt gia cc lp graphite. Do , cc lp

graphite oxide di tc dng ca p sut ln b tch ra to thnh cc tm n lp

graphene[7].

Khbng phng php ha hc: y lphng php dng cc cht kh

ha hc (nh hydrazine, NaB, Iodo, Hidro, NaHSv.vv.) phn ng vi cht

oxi ha l graphene oxide nhm khcc nhm chc ha hc v chuyn Csp3thnh

Csp2. Do khi phc li tm n lp graphene vi nhng tnh cht c bit vn c.

Quy trnh: graphite oxide c phn tn hon ton trong mi trng acid,

base hay nc (ty iu kin phn ng) thnh dung dch graphene oxide. Sau ,

mt lng cht kh ha hc c thm vo dung dch to thnh hoxi ha kh.

Hin c 2 phng php kh graphene oxide l thc hin trong iu kin kh

ng (c khuy) hay khtnh (khng khuy).Theo cc nghin cu gn y, phng php x l bng nhit, in ha hay

phng php khha hc (trong iu kin khng) khng to c cu trc xp

graphene 3D, chcphng phpkhbng ha cht mi cho cu trc xp graphene

3D.

1.4. Vt liu xp trn c sgraphene

Xut hin t nm 2004 n nay, graphene l ti c nghin cu v pht

trin rt nhiu, c mnh danhl vt liu thn k. V trong nm nm tr li y,

mt vt liu mi da trn c s graphene: xp graphene vi cu trc 3D c tng

hp thnh cng, nhanh chng thu ht s ch ca gii khoa hc vi nhiu ng

dng, gp phn m rng thm tim nng ca vt liu graphene.


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1.4.1 Xp graphene

Xp graphene 3D l vt liu da trn c s tm graphene 2D. Theo , cc

tm graphene khi xp chng mt cch mt trtt s to nn cu xp graphene 3D

v nh hnh.

Hnh 1.9 Xp graphene.

V dng cu trc xp 3D nn cc tnh cht ca graphene (dng tm 2D) b

gim bt nh din tch b mt, tnh cht dn in, dn nhit Nhng vi xp

cao, khi lng ring thp, l xp c kch thc micromet cho php cc ion c th

hp ph v gii hp nn xp graphene li l vt liu tim nng mang li mt s ng

dng trong nhiu lnh vc nh:

Y hc: to nn trong k thut nui cy t bo(substrate for cell growth) , to

khung cho m (tissue scaffolds), l v ca vt liu mang thuc (drug-delivery) [8]

Vt liu hp ph, cm bin: xp graphene s dng lm vt liu trong cc

thit b cm ng, lnh vc xc tc [9] [10] [11]v vtliu hp ph du y tim nng[12].

in t- nng lng: xp graphene rt c k vng trong vic ch to siu

t in, lu tr v chuyn i nng lng[13] [14].


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1.4.2 Phng php chto xp graphene.

D ch mi c nghin cu gn y nhng xp graphene c nhiu quytrnh

tng hp khc nhaunh: quy trnh tng hp xp graphene khng s dng cht kh

ha hc [13] hay s dng cc cht kh ha hc l HI, Vitamin C.. [15]hay s dng

cht to mng khng gian nh cc cation 2+ (Mg2+, Ca2+) [16]v cc amine nh

EDA (ethylene diamine) [17]

Hnh 1.10 M tqu trnh to mng khng gian trong qu trnh tng hp xp

graphene 3D sdng cation[16].

Tuy xp graphene c nhiu quy trnh tng hp nhng u c mt im

chung l c tng hp da trn phng php kh tnh. Phng php kh tnh lphng php kh in-situ trong qu trnh kh v qu trnh t sp xp cc tm

graphene din ra cng mt lc. Phng php kh ny thc hin trn quy trnh sau:


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Hnh 1.11 Quy trnh tng hp graphene tGO

Hnh 1.12 M hnh khtnh

Nguyn l ca phng php ny l[13] [15]:

GO cha cc nhm chc COO-, -OH, C=O nn mang tnh a nc do

c th phn tn hon ton (di tc dng ca sng siu m) to thnh graphene

oxide (h huyn ph). Khi qu trnh kh tnh (khng c khuy) xy ra (di tc

dng ca nhit , p sut, cht kh), cc nhm chc trn b mt graphene oxideb

mt i, tnh k nc ca tm graphene oxide tng ln v c xu hng t li, xp

chng ln nhau. Cc tm ny c th xp song song vi nhau, hoc an cho m

khng tun theo mt quy lut sp xp c trt t. Kt qu l xp graphene 3D l xp


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c cu trc v nh hnh (hnh 1.13c,d,e) v c kch thc l xp khng u (kch

c micromet). Lc lin kt gia cc tm graphene trong khi xp l lc vt l nh:

tng tc , lin kt Vander Wall vlin kt hydrogen. Bn cnh , qu trnh

cc tm graphene kt t li s y nc ra khi cu trc khin cho gel graphene c

hnh dng nht nh (hnh dng ca bnh phn ng) (hnh 1.13b). Graphene c

tng hp theo hng bottom- up bng phng php ha hc kh t c trng thi

kh hon ton m vn cn mt s nhm chc phn cc trn b mt, chnh cc nhm

chc ny to lin kt hydrogen vi nc iu ny l gii cho gel graphene thu c

c cha nc bn trong cu trc v lin kt ny cng gp phn to khung nng

cho gel graphene trong qu trnh tng hp.

Hnh 1.13 Gin XRD ca GO (mu xanh), graphite (mu en), xp graphene

(mu ) v hnh cc mu graphene oxide (a), gel graphene (b), xp graphene

(c), hnh chp SEM ca xp graphene (d,e)

1.4.3. Mt snghin cu tng hp xp graphene.1.4.3.1 Phng php kh thy nhit to xp graphene khng s dng cht

kh[13].

Vo thng 3 nm 2011, cc nh khoa hc Yuxi Xu, Kaixuan Sheng v cc

cng s thuc i hc Thanh Hoa cng b trn tp ch ACS Nano phng php

kh thy nhit to xp graphene khng s dng cht kh. Theo bi bo ny, xp

graphene c tng hp dng nguyn liu l GO theo quy trnh sau:


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GO c phn tn vo trong nc to dung dch huyn ph. Sau , dung

dch huyn ph c cho vo bnh Teflon (h autoclave) v gia nhit ln 180 C

trong 24 gi. Kt thc qu trnh kh thy nhit thu c gel graphene. Gel graphene

c lm kh to xp graphene 3D.

Hnh 1.14 Gel graphene trc v sau khi khtnh(a), xp graphene (b), nh SEM

xp graphene (c,d,e), bng o in trca xp graphene (f).

Bi bo tng hp thnh cng xp graphene vi dn in khong

5.S/cm, modul tr (storage modulus) t 450kPa- 490kPa. Xp graphene 3D

c kvng ng dng lm siu tin vi in dung 175F/g. bn nhit ca

xp tnhit phng n100 C.

1.4.3.2 Phng php khthy nhit to xp graphene sdng cht kh[15]

Thng 4 nm 2011, trn trang RSC ng ti cng trnh nghin cu ca hai

nh khoa hc Wufeng Chen v Lifeng Yan v tng hp xp graphene 3D bng

phng php kh thy nhit s dng cc cht kh ha hc. Theo , xp graphene

3D c tng hp theo quy trnh nh sau:


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GO c phn tn vo trong nc to dung dch huyn ph. Sau cc tc

cht kh ha hc (Vitamin C, HI, , , hydorquinon) c thm vo

dung dch huyn ph v ton b dung dch cho vo bnh Teflon (h autoclave) v

gia nhit ln 95 C trong 3 gi. Kt thc qu trnh kh thy nhit thu c gel

graphene. Gel graphene c ra sch v lm kh bng phng php ng c.

Ring vi xp , sau khi ng c thu c khi xp, khi xp ny tip tc

c gia nhit ti 400 C trong 5 gitrong mi trng chn khng (khht cc

nhm chc vn cn trn bmt tm graphene).

Hnh 1.15 Xp graphene (a), Hnh SEM ca xp graphene (b)

Kt qu bi bo thu c nhiu xp graphene ng vi mi cht kh khc

nhau. Trong xp graphene c tng hp bng s dng cht kh HI cho dn

in cao nht.


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Bng 1.2 So snh khnng khGO ca cc cht kh[15]

Cht kh Vitamin C Na2S HI NaHSO3 NaHSO3

(chiu x) dnin (S/m) 23 6.8 110 17 87Khi lng ring

(mg/cm3)21 15 37 18 15

T s C/O 6.8 5.8 8.5 7.0 10.1

Bi bo tng hp xp graphene c in dung khong 156 F/g 166 F/g,

modul n hi khong 28KPa - 0.13MPa. Xp graphene rt nh, xp vi khi lng

ring 18mg/ cm, kch thc l trng khong t 3m- 6m.

1.4.3.3 Phng php khthy nhit to xp graphene sdng Ammoniac [12]

Xp graphene c cng btrn tp ch Materials View (Wileyonlinelibraly

6/2012) bi cc nh khoa hc Hengchang Bi , Xiao Xie, Rodney S. Ruoff * v cc

cng sti Trung Quc v M. Theo nghin cu ny, xp graphene c sdng

lm vt liu hp phcc dung mi hu c v du m.

Phng php iu chxp graphene:

Xp graphene c iu ch tnguyn liu u l GO. GO c phn tn

trong hn hp 35ml nc ct v NH3, sau hn hp c khuy siu m trong

15pht. Hn hp c mu en sm sc a vo bnh kn v gia nhit n 180C

trong 24gi. Sau ngui vnhit thng. Gel graphene sau khi c thu li

stip tc sdng phng php ng c trong 48githu xp graphene.

Tnh cht ca xp:

Xp graphene l xp nano, c chto trn c skhtnhGO. Kho st

cu trc xp cho thy xp l xp microporous, khong cch gia cc tm l 570-

620 micromet.


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Hnh 1.16 Cu trc v qu trnh hp phdu ca xp, qu trnh hp phdu

trong thi gian 80 giy ca xp (a-f),

gc thm t (g), nh SEM(h,i), nh TEM (j).

Xp graphene c khnng hp pht20 n 80 ln khi lng du so vi

khi lng ban u ca xp (hnh 1.17). Xp c thhp phcc dung mi l du,

cht bo v cdung mi phn cc nh dimethyl sulfoxide.

Hnh 1.17 Khnng hp phdung mi ca xp graphene


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Tnh cht ny c c l do: xp c ngun gc hu c v c cu trc l cc

tm graphene c gin cch nhau. Gc thm t ca xp t 1142, do xp l

vt liu knc nn ddng hp phdu v cc dung mi hu c khng phn cc

nh cht bo, dung mi hu c. Mt khc, qua qu trnh khgraphene oxide to

xp graphene, mt lng nhcc nhm chc nh hydroxyl, carbonyl ..cn trn b

mt xp lm cho xp c khnng hp ph mt sdung mi phn cc. Tnh cht

trn ca xp graphene c ng dng nhiu trong vic hp phcc dung mi c

hi. Theo cc gi tro c, xp c khi lng ring thp (density = 12 mg 5/

cm) v din tch bmt ring ln t 423m/g (BET) lm tng din tch tip xc t

tng hiu sut hp ph.

Khnng thu hi dung mi v ti sdng xp:

Thu hi dung mi v ti sdng xp l yu cu quan trng i vi vt liu

hp phdu khi vn nhim mi trng ngy cng gia tng..Bng cch chng

ct, du sau khi hp phc thc thu hi. Xp graphene c khnng thu hi du

t 99,9% v gim 1% kh nng thm ht sau 10 ln ti s dng. Do xp

graphene c kvng rt ln trong lnh vc chto vt liu hp ph.

1.5.Mt skthut v phng php nghin cu

1.5.1 Phng php ng c (Freeze Drying or Lyophillisation)

Trong qu trnh ch to xp graphene, vic tch nc ra khi gel graphene

m khng lm thay i, ph vcu trc ca xp l mt vn kh khn. Do nc

chim cc l trng c kch thc rt nh ( cmicromet) v khi lng ca nc

trong gel graphene ln ti 90% . Nhm gii quyt vn kh khn ny, cc nhkhoa hc p dng phng php ng c vo trong qu trnh ch to xp

graphene.

Phng php ng c (hay cn gi l ng kh, sy thng hoa) do k s

G.I.Lappa Stajenhexki pht minh 1921 ti Nga v c sdng rt rng ri trong

cc ngnh cng nghip thc phm v dc phm. u im ca phng php ny l


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tch loi nc ra khi cc loi thc phm (dc liu) m khng lm ph vcu trc

cng nh bin i cc tnh cht , thnh phn ca thc phm (dc liu).

1.5.1.1 C skhoa hc ca phng php ng c[19]

Trong tnhin, nc tn ti 3 trng thi l rn ,lng , kh (gin pha ca

nc).

Hnh 1.18 Gin pha ca nc

Tch nc thlng ra khi vt liu l qu trnh chuyn nc sang thkh

v nc bay hi. Hai cch tch c p dng:

Sy thng thng: l qu trnh chuyn nc tthlng sang thkh (ng

a-b-c hnh 1.18). y l qa trnh sy s dng nhit cao vi nhc im l

khng gic cu trc, tnh cht ban u ca vt liu.ng c: l qu trnh chuyn nc tthlng sang thrn, sau nc

thng hoa. Qu trnh ny gip cho vt liu sau khi tch nc vn gili c cu

trc, tnh cht nh ban u.


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Hnh 1.19 Biu din qu trnh ng c.

1.5.1.2. Quy trnh ng c [19]

Quy trnh ng c gm 3 giai on: lm ng, thng hoa nc v bc hi

m.

Giai on 1: Lm ng vt liu, chuyn nc trong vt liu tthlng sang

thrn. Yu cu ca giai on ny l nc c ng bng tht nhanh to thnh cc

tinh thrt nh(nhit -50 0C n -800C), trnh lm ph hy cu trc ca vt

liu.

Giai on 2: Thng hoa nc, nc chuyn tthrn sang thkh trong mi

trng chn khng vi p sut < 4.58mmHg (di im bar ca nc) v nhit

-500C.

Giai on 3: l giai on bc hi m cn li trong vt liu (cn goi l sychn khng vt liu). Mc ch ca giai on ny l lm bay hi m lin kt trong

vt liu. Khi kt thc giai on ny, m ca vt liu t t2% ti 4% .


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Hnh 1.20 My ng c

1.5.2. Phn tch nhiu xtia X (X-Ray)

Mt phng php phn tch cu trc tinh th ca vt liu, y l phng

php chiu mt chm tia X ti mu, ti y xy ra qu trnh nhiu x, pht ra cc tia

thcp v cho mi vi iu kin theo nh lut Bragg :

Hnh 1.21 Nguyn l chiu xtia X

Nh vy ch nhng cu trc kt tinh th mi cho mi trn gin XRD

(khong cch d theo 2).Mi kiu kt tinh khc nhau th c d khc nhau nn dn

n vtr cc mi trn gin cng khc nhau. T ta c thphn bit nh tnh

nh lut Braggn = 2dsin


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cc kiu tinh thkhc nhau, XRD cng c thphn tch nh lng thnh phn pha

da vo din tch mi trn gin .

1.5.3. Phhng ngoi (FT-IR)

Da trn dao dng ca cc nguyn t, ch yu l s thay i v moment

lng cc. Cc nguyn ttrong phn tdao ng khng ngng v tng tch ln

nhau, mi nguyn tli c sdao ng khc nhau. Nhvy, cung cp thng tin v

cu trc phn t, nh danh cc nhm chc phn cc trong vt liu, nhn din hp

cht.

1.5.4. Phng php o ng nhit hp ph- khhp phnit (BET)[19]

Vt liu hp ph du c xc nh din tch b mt ring bng cch p dng

phng trnh hp ph ng nhit theo Braunauner- Emmett- Teller (BET).

p dng phng trnh BET o b mt ring:

Phng trnh BET:

.

Trong :

P- p sut cn bng.

Pp sut hi bo ha ca cht b hp ph nhit thc nghim.

Vth tch ca kh b hp ph p sut P.

Vm - th tch ca lp hp ph n phn t tnh cho 1 gam cht hp ph trong

iu kin tiu chun.

C- hng s BET.


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Hnh 1.22 Dng thng thng BET

th :

theo P/ Pl mt ng thng, t c th xc nh Vm

v C. Bit Vm, ta c th tnh c din tch b mt cht hp ph:

S

Trong :

N: s Avogadro.

Wm: b mt chim bi mt phn t cht b hp ph lp n phn t.

Vo: th tch ca mt mol kh iu kin chun (22400 cm/ mol).

1.5.5. Knh hin vi in tqut (SEM)

Knh hin vi in t qut (SEM) s dng 1 chm in t hp (chm cc

electron) qut trn bmt mu, vic to nh mu dc thc hin thng qua vic ghi

nhn v phn tch cc bc xpht ra tbmt vt liu khi tng tc vi bmt

mu. Do cung cp thng tin bmt cng nh hnh thi ca vt liu.

1.5.6. Phn tch gim cp nhitThermo Gravimetric Analysis (TGA)

TGA kthut phn tch n gin tnh khi lng mu vt liu mt i (hay

tng ln) theo nhit . Vt liu c gia nhit v bgim khi lng do sbay hi


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nc hoc tcc phn ng ha hc chuyn ha vt liu thnh kh. Tuy nhin cng

c mt vi vt liu tng khi lng sau khi gia nhit do phn ng vi kh quyn

trong cc mi trng. Khi tin hnh phn tch gim cp nhit, cu trc ca mu b

ph hy ng thi cho bit ln, gii hn nhit dn n cc phn ng xy ra v

bn nhit ca vt liu.


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Mc tiu ca ti :

Vi cu trc xp, nh, dn in cao, din tch b mt ln, xp graphene 3D

ang l vt liu xp cho nhng ng dng y tim nng trong cc lnh vc y sinh,

vt liu hp ph, in t ,nng lng Da trn c s l thuyt v vt liu

graphene, chng ti xin a ra quy trnh tng hp xp graphene. Theo , xp

graphene c ch to t graphite thng qua trung gian GO. T GO chng ti s s

dng phng php kh tnh v qu trnh ng c kho st qu trnh to xp

graphene vi cc cht kh khc nhau nh:

- Cht kh Vitamin C: y l cht kh thn thin vi mi trng, gi thnh

r, mang li kt qu kh kh hiu qu.[15] [23]

- Cht kh NH3: y va l cht kh va gip to mi trng phn tn

graphite oxide thnh graphene oxide, h tr cho qu trnh kh thy nhit

nhit v p sut cao.[12]

- Cht kh HI: y l cht kh mang likt qu kh mang li hiu qu cao

cho vt liu graphene ng dng trong dn in.[15] [24]

Vi mc tiu ni trn, ti s c tin hnh vi cc ni dung sau : Tng hp graphit oxide bng phng php Hummers

Ch to gel graphenebng phng php kh tnh vi cc tc nhn

kh ln lt l : vitamin C, NH3, HI.

Ch to xp graphene t gel graphene thng qua quy trnh ng c.


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Phn 2. Thc nghim2.1. Thit bv dng c

Pipet 1.00ml, 5.00mL, 25.00mL. Phu nhgit.

My khuy c IKA, model RW16B, c.

My khuy tiu nhit IKA, model RCT basic, c.

My c quay BIBBY model RE100B, M.

My li tm, phng th nghim Polymer, trng H KHTN

Bn siu m ELMA, model LC60H, HF- Frequ: 36kHz, c.

Thanh siu m model UP400S, HF- Frequ: 24kHz, c.

Tsy VENTICELL, M.

Cn phn tch Sartorius, chnh xc 0.0001g.

Cn in t, model EK-610i, chnh xc 0.01g.

My chp XRD gc rng, vin Du kh, Tp. HCh Minh.

My o TGA, Trung tm Manar, H Quc Gia Tp. HCh Minh.

My chp SEM, Vin khoa hc v cng ngh.

My phhng ngoi FT-FT-IR, Trung tm Manar, H Quc Gia Tp. HCh

Minh.

My chp BET, Trung tm Manar, H Quc Gia Tp. HCh Minh.

-My ng c, phng Hu C, H KHTN.

2.1. Ha cht

Graphite: sigma.

Acid sulfuric 98%, H2SO4, Trung Quc. Sodium nitrat, NaNO3, tinh khit 99%, Trung Quc.

Kali permanganat tinh khit, KMnO4,Vit Nam.

Hydrogen peroxide 30%, H2O2, Trung Quc.

Etanol 99% tinh khit, Vit Nam.

Aceton tinh khit, Chemsol, Vit Nam.

Acid Iodua, HI, Trung Quc.


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Vitamin C, borid acid, Trung Quc.

Amoniac, , hm lng 25%, Trung Quc.

Acid acetic, , Trung Quc.

Nc ct.

2.3. Thc nghim

2.3.1. Quy trnh thc nghim chto Graphite oxide (GO)

Hnh 2.1 Htng hp GO

Oxi ha graphite bng phngphp Hummers theo quy trnh nh sau:

Khuy 10.0 g graphite v 5,0 g trong 230 ml m c trongbnh cu 2 mnh 0 C. Cho t t 30g vo hn hp trn, tip tc khuy

mnh hn hp trong 30 pht. Nng nhit ca bnh phn ng ln 35 C v duy tr

nhit ny trong vng 1 gi 30 pht phn ng oxi ha xy ra, dung dch s dn

chuyn mu nu vng c kh mu nu thot ra v tng dn nht. Sau gim

nhit ca h xung 15 C v thm 460 ml nc ct vo bnh phn ng, c khi

trng thot ra mnh, dung dch c mu nu vng sng. Tip tc nng nhit hn

hp ln 98 C v gitrong vng 15 pht. Kt thc 15 pht thm 1000 ml nc ct


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vo hn hp. Sau khi thm nc ct, hnhit vri thm 500 ml vo

hn hp khv v, khuy trn u dung dch c mu vng

sng, sau ngui vnhit phng. GO c tch ra khi hn hp bng cch

ly tm v ra li nhiu ln vi nc ct (khong 7 ln) v PH = 5- 6 loi b ht

acid v ra li ln cui vi aceton. Sn phm cui cng thu c c dng gel mu

nu.

Hnh 2.2 S oxi ha graphite

Hnh 2.3 HGO huyn ph sau khi

tng hp

Hnh 2.4 Gel GO


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2.3.2. Qu trnh tng hp gel graphene tGO bng phng php kh

tnh.

Qu trnh kh GO c thc hin ln lt bng cc cht kh Ammoniac,

Vitamin C v HI thng qua phng php kh tnh. Mc ch ca qu trnh ny l

to cc h gel graphene , t chun b cho qu trnh to xp graphene. Cc mu

rGO sau khi tng hp c kho st cc tnh cht thng qua cc phng php TGA,

FT-IR, XRD thy c kh nng kh ca tng cht.

Hnh 2.8 Hn hp Graphene oxide v cht

khtrc khi phn ng

Hnh 2.9 Hautoclave

2.3.2.1. Quy trnh khtnh GO sdng cht khl ammoniac (rGO- NH3)[12]

Qu trnh c thchin nh sau:

Cn 0,057g GO cho vo bnh phn ng, sau thm 25,00 ml nc ri em

hn hp nh siu m (siu m thanh) cho n khi GO phn tn hon ton trongnc. Sau thm 12,00 ml Ammoniac (tng th tch dung dch nc +

ammoniac=37ml). Sau hn hp c nh siu m ( my nh siu m bn)

trong 25 pht. Sau khi nh siu m xong, hn hp c a vo bnh thp kn ( h

autoclave) v tng nhit ln 180 C trong 24 gi. Sau 24 gi, gel GO c ly ra v

ra schbng nc ct v pH= 7. Cui cng, gel rGO-NH3 em ing c thu sn

phm.


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Hnh 2.10 S khtnhsdng cht khammoniac

2.3.2.2. Quy trnh khtnhGO sdng cht khVitamin C (rGO- VitC) [15]

[23]

Quy trnh c thc hin nh sau:

Bt u cn 0.060g GO vo ly thy tinh sau thm 30,0ml nc. Dung

dch c nh siu m (siu m thanh) cho n khi phn tn hon ton GO trong

nc. Sau thm vo dung dch mt vi git ammoniac iu chnh pH dungdch 10. Tip tc thm0.30g vitamin C vo dung dch. Sau dung dch c a

vo bnh phn ng 30ml kn ri nng nhit ln T = 95 C trong 3 gi. Sau thi gian

kt thc phn ng, mu c ly ra v ra sch v pH= 6. Sau cng mu c em

i ng c (T= -44 C, p = 0.001bar) thu sn phm.


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Hnh 2.11 Skhthy nhit sdng cht khVitamin C

2.3.2.3. Quy trnh khtnhGO sdng cht khHI. (rGO- HI) [15] [24]

Quy trnh c thc hin nh sau:

Cn 0.057g GO vo ly thy tinh sau thm 20ml Acetic acid. Sau nh

siu m ( s dng siu m bn) hn hp cho n khi GO phn tn tng i trong

acid. Thm tip 2,00ml HI vo dung dch GO/Acetic acid. Tip dung dch a

vo bnh phn ng 30ml ri nng nhit ln T = 95 C trong 3 gi. Kt thc phn ngmu c ra bng NaHC, O v Aceton cho n khi ht acid v pH dung dch

bng 6. Sau khi ra sch, mu cem i ng c (T= -44 C, p = 0.001bar). Sau

cng, khi ktthc qu trnh ng c thu c sn phm.


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Hnh 2.12 S khtnhsdng cht khHI

2.3.4. Tng hp xp graphene tgel graphene bng phng php ng

c

Cc gel graphene sau khi tng hp t qu trnh trn s c ng c to xp

graphene. Xp graphene thu c sau qu trnh ng c s c kho st cc tnh

chtthng qua vic odin tch b mt (BET) v hnh chp SEM.


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Phn 3. Kt qu v bn lun3.1. Kt qutng hp graphite oxide theo phng php Hummers

3.1.1. Gin XRD ca mu graphite v GO

Hnh 3.1 PhXRD ca mu GO v graphite

Gin XRD ca graphite c mi gc 2 = 26,50 v d002 = 3,3721 .

Cng mirt cao cho thy graphite ban u c kt tinh cao, cu trc tinh th

gn nh hon ho. Trong khi , gin XRD ca GO cho thy c sdi miv

gc 2= 11,50v cng mikh thp so vi graphite cho thy GO khng cn

cu trc tinh thcao nh graphite. Khong cch d002 ca GO tng ln 7.7920 .

iu c don l do sau qu trnh oxy ha, trn bmt graphite c nh ln

cc nhm phn cc nh Hydroxyl, Carboxylic, Epoxide to thnh graphite oxide.

Chnh cc nhm chc ny nong rng khong cch gia cc lp ca GO.


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3.1.2. Kt quphFT-IR ca mu GO

Hnh 3.2 PhFT-IR ca mu GOPh FT-IR ca graphite oxide cho thy mi t rng 3382 cm-1c trng

cho nhm hydroxyl OH. Do tn hiu mi rng v hp thu su, chng t cc

nhm hydroxyl c lin kt hydrogen vi nhau, hoc lin kt vi nc vn cn trong

khoang ca GO. Tip theo mi v tr 1724 cm-1 l dao ng ca nhm carbonyl

C=O v c th l nhm chc carboxylic. Mi 1615 cm-1l dao ng ca ni i

C=C ca carbon trn lp GO. Bn cnh cn xut hin cc mi 1070 1230

cm-1c trng cho dao ng lin kt C-O, C-O-C ca nhm epoxide, C-OH.

Thng qua ph FT-IR mt ln na khng nh chnh cc nhm phn cc

Hydroxyl, Carboxylic, Epoxide lm gia tng khong cch gia cc lp trn

graphite oxide, c chng minh trn gin XRD trn.


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3.1.3. Gin TGA ca mu GO v graphite

Hnh 3.3 Gin TGA ca GO v graphiteKt qu phn tch nhit trng lng ca graphite cho thy graphite b gim

cp, tuy nhin tng khi lng st gim khng ng k (2,7%). Mt d graphite

c bit n vi kh nng bn nhit cao, nhng trn graphite ban u vn c cc

nhm tp nh OH, metyl bin, . Cho nn kt qu TGA cho thy graphite vn

c s gim khi lng khi a ln hn 800 oC.

i vi graphite oxide gin TGA c s khc bit r rt, qu trnh gim

cp nhit bt u xy ra khi nhit ln n khong 500C v cho n 1100C khilng st gim l 8,57%. S st gim khi lng ny c cho l bay hi ca nc

trong cc khoang ca GO. c bit, s st gim khi lng cc i ti 222 oC vi

khi lng gim 34,2% . l s phn hy ca cc nhm carboxylic, hydroxyl,

peroxide trn b mt. Trong khong nhit tip theo c s gim lin tc khi

lng, iu ny do qu trnh gim cp ca cc lp graphite oxide (cu trc ca cc

lp graphite oxide khng c bn vng nh graphite).


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Kt qu phn tch TGA tng thch vikt qu ca qu trnh phn tch

FT-IR cng nh kt qu XRD.

3.2. Kt quphn tch tng hp cc cht khtrong qu trnh chto gel

Hnh 3.4 Graphene oxide trc khi kh(a);

gel graphene to thnh sau khi kh(b)

3.2.1 Hnh nh cc mu gel GO c tng hp sau qu khtnh

Hnh 3.5 Gel graphene sau qu trnh

khbng NH3

Hnh 3.6 Gel graphene sau qu trnh

khbng Vitamin C (VitC)


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Hnh 3.7 Gel graphene sau qu trnh khbng HI

Nhn xt: gel graphene c tng hp thnh cng bng phng php kh

tnhs dng cht kh. Gel graphene to thnh c cu trc dng xp hnh tr. Khung

ca xp l cc tm graphene xp chng, phn th tch trng cn li trong xp do

nc chim gi.


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3.2.2. Cc kt quphn tch cc mu rGO sau qu trnh kh

3.2.2.1 Gin XRD ca mu GO v cc mu GO sau qu trnh kh(rGO)

Hnh 3.8 Gin XRD ca mu GO, rGO-HI, rGO-VitC, rGO-NH3

T gin XRD cho thy, GO sau khi b kh bi cc cht ch HI,

Ammoniac, Vitamin C mt mi c c trng gc 2= 11,5 v khng cn xut

hin mi c cng cao. iu ny c gii thch nh sau: khi qu trnh khxy

ra, cc nhm chc trn bcc tm graphene oxide sgim dn, tnh knc cng

tng ln. Do cc tm graphene oxide sc xu hng ttp li v xp chng ln

nhau. Qu trnh xp chng cc tm graphene oxide khng tun theo trt t, cc tm

ny c thxp song song hoc xin cho dn n xp graphene c cu trc v nh

hnh v khng xut hin mi c trng trn phXRD.


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3.2.2.2. PhFT-IR ca mu GO v rGO.

Hnh 3.9 PhFT-IR ca mu GO, rGO-HI, rGO-VitC, rGO-NH3

TphFT-IR cho thy qua qu trnh kh, cc mi c trng ca GO vn

xut hin nh mi t khong 3400cm-1ca nhmOH, mi v tr 1724 cm-1l

dao ng canhm carbonyl C=O ca nhm chc carboxylic. Mi 1615 cm-1l dao

ng ca ni i C=C ca carbon trn lp GO. Mi t 1000 cm -11300 cm-1l dao

ng ca nhm C-O-C. Ngoi ra s xut hin mi CO2 cng cao trn mu rGO-VitC v rGO-NH3c th c l gii nh sau: trong qu trnh thc nghim, 2 mu

u c s dng NH3lm tc nhn kh (vi mu rGO-NH3) hay to mi trng phn

ng (vi mu rGO-VitC), NH3 trong dung dch s phn ng vi CO2(H2CO3) sinh

ra ngay trong qu trnh kh to mui (NH4)2CO3. Mui amonium cacbonate bm

trn sn phm kh v d b phn hy khin cho mi CO 2xut hin vi cng

cao trn ph FT-IR.


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Bn cnh , vic xut hin cc mi dao ng c trng trn ph FT-IR cho

thy qu trnh kh khng hon ton, mt snhm chc a nc vn cn trn b

mt ca tm graphene. V thgel graphene sau khi tng hp vn ginc trong cu

trc thng qua lin kt hydro gia cc nhm chc trn.

3.2.2.3. Phtn xRaman ca graphite, GO v rGO

(a) (b)

Hnh 3.10 Phraman ca Graphite, GO v ca cc mu rGO phn ny, s dng kt qu ph Raman nhm tmra s khc bit nhn

danh rGO, thng qua vic so snh ph raman ca cc mu RGO vi GO v graphit.

i vi graphit, cc mi G (~1570 cm-1), D (~1330 cm-1) v 2D (~2700 cm-1) c

tm thy trn ph . Cng mi D c mi tng quan vi s hin din ca cc

khuyt tt xut hin trn tm graphit. Cng mi D cng ln tng ng vi t l

ID/ IGcng ln, xut hin nhiu khuyt tt trn mng. Tnh cht ny cng p dng

tng t i vi GO v rGO. Da vo gin (a), ta thy rng mi tn hiu D ca

Graphit c cng yu hn so vi GO v cc mu RGO. y l mt c im

quan trng nhm phn bit graphitvi GO v rGO. GO v rGO c cng mi D

ln chng t trong qu trnh oxi ha v kh c nhng bin i tc ng vo mng

cu trc gy ra nhiu khuyt tt.Theo nh kt qu thuc cng mi D ca 4

mu rGO kh u ln hn GO, iu ny mt ln na chng minh rng cc qu

trnh kh GO bn cnh loi b cc nhm phn cc trn GO th ng thi li


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nhiu sai hng dn n cc khuyt tt trn tm RGO. y cng l mt nhc

im ln nht ca qu trnh tng hp rGO t graphite oxide. Cc mu kh rGO thu

c u c t l ID/ IGln, cho thy bt n trong cu trc ca mu cao, xut

hin nhiu khuyt tt trong cu trc.D dng nhn thy t l ID / IGca rGO-HI l

cao nht , xut hin nhiukhuyt tt hn so vihai mu kh cn li.

Bn cnh mi 2D(gin b)ca hu ht cc mu kh u c cng

cao hn so vi mu GO. iu ny chng t, qu trnh kh c hin tng ti cu

trc lin hp trn graphen nn xut hin mi 2D. Tuy nhin cc mi 2D khng cao,

y l nhc im kh ha hc cha hon ton, li nhiu khuyt tt.

Hnh 3.11 Biu tlcng ID/IG

3.2.2.4. Gin TGA ca mu GO v cc mu rGO sau qu trnh kh


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Hnh 3.12 Gin TGA ca cc mu GO v rGO-HI, rGO-VitC, rGO-NH3.Theo gin TGA c ththy mt khi lng trong khong tnhit 150

C ti 400C ca mu rGO-HI l thp nht so vi cc mu rGO-NH3, rGO-VitC v

GO. yl khong nhit din ra sphn hy mnh mca cc nhm chc trn

GO.Ngoi ra, lng tro ca mu rGO-HI (74.25%) ln nht so vi mu rGO-NH3

(73.78%), mu rGO- VitC (53.11%) v thp nht l mu GO (38.66%). Do lng

tro thp hn cng nh ht gim khi lng cho thy cc nhm chc cn li trn

rGO-HI t hn mu rGO cn li. T c thkt lun rng HI l cht khtt nht

trong scc tc nhn kh.

3.2.2.5. Kt quo dn in ca mu GO v rGO.

Mt trong nhng tnh cht quan trng nht, mang tnh quyt nh, l

dn in (hay thng qua in tr mt). dn in l bng chng thuyt phc

nht v kh nng kh ca mt tc nhn kh, ca mt phng php s dng.

dn in ca rGO khng ch ph thuc vo tnh hon ho ca b mt (cng hng


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lin tc, khng b khuyt tt) m cn ph thuc ln vo kch thc tm RGO v

phng php ch to mu trc khi o. Di tc dng ca qu trnh oxy ha kh

nhiu giai on, lm cho tm rGO b x vn, cho kch thc nh hn so vi

graphit ban u (1 lp graphit).

Trong ti ny, cc mu rGO c p vin v o dn bng my o 4 u d.

Hnh 3.13 Mu p vin i o ddn in

Bng 3.1: dn in v in tr mt ca cc mu.

Tn muvin

dy vin d (mm) in tr mt RS(/o)

dn in *(S/m)

GO 0.18 rt ln 0.00

rGO-NH3 0.19 17.7 296.57

rGO-VitC 0.21 14.2 335.10

rGO-HI 0.18 3.23 1718.94* dn in c xc nh bng cng thc: =1/(Rsx d), trong d c

n vl m, Rsn v l /th c n v l S/m. Nu d c n v l cm th c

n v l S/cm.

Rt d nhn bit c GO v rGO c kh t GO. GO hu nh khng dn

in do vi phm yu t cng dng in, cng dng qu b gn nh khng

c dng i quacc tm GO. T bng s liu trn c th nhn thy rng mu rGO-HI

c dn in cao gp 5 ln so vi 2 mu rGO-NH3v rGO-VitC. iu ny cho


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thy h thng in t pi ca tm graphene sau khi kh bng HI c phc hi v

lin hp tt. Qua ph Raman cho thy HI l tc nhn kh li nhiu khuyt tt.

Song ph Raman li khng cung cp thng tin nh lng v kh nng kh nhiu

hay t nn c th a ra gi thuyt rng: khi xt trn ton tm graphene, h thng

in t pi vn kt ni khng b t qung, nn cho dn cao. T c th khng

nh rng HI l tc cht kh tt hn NH3v Vitamin C. Kt qu ny ph hp vi

kt qu TGA trc .

3.2.2.6. Kt qutng hp xp graphene tgel graphene sau qu trnh ng c

Hnh 3.14 Cc mu rGO-NH3, rGO-HI, rGO-

VitaminC (vitC) sau khi ng c.

Nhn xt: Qua qu trnh ng c, chc mu gel graphene khbng HI l

to thnh xp graphene. Cc mu rGO khbng Vitamin C v NH3sau khi ng

c, gel graphene khng cn gi c cu trc dng khi, sn phm thu c c

dng bt.

Lp lun: Trong 3 mu gel graphene chc mu rGO-HI l tng hp xp

thnh cng, chng tlin kt gia cc tm graphene trong gel graphene ca rGO-HIbn hn rGO-NH3v rGO-VitC. Trong xp graphene, lc lin kt gia cc tm

graphene l lin kt vt l gm tng tc [20], lc Vander Walls (khuch tn)

v lin kt hydrogen (gia cc nhm chc cn tn ti trn tm graphene sau qu

trnh kh) [13].


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Hnh 3.15. M hnh in t trn benzen (d) v 3 cu hnh sp xp ca vng

thm theo tng tc , kiu song song (a),

kiu xp cho (lch) (b), kiu chT (c).

V cc tm graphene l mng nguyn tcacbon trng thi Csp2 vi hthng

rng khp nn tng tc c nh hng ln nht n bn ca gelgraphene. Do ,khi qu trnh khc hiu quxy ra, cc nhm chc trn bmt

tm graphene bmt i cng nhiu th hthng lin hp ca c khi phc

cng ln, tng tc gia cc tm cng stng ln khin xp graphene bn

hn. Bn cnh , phn ng khcng ng thi lm tng tnh knc cc tm

graphene khin lc khuch tn gia chng tng ln, gp phn lm tng bn ca

lc lin kt gia cc tm graphene.

Tnhng nhn nh trn c ththy rng, khnng khca cc tc nhn

khsquyt nh n bn ca xp graphene. Theo , tc nhn khhiu qus

cho sn phm xp graphene bn. HI l mt tc nhn khmnh hnNH3v Vitamin

C, (iu ny c chng minh bng phIR v gin TGA pha trn) vy nn

xp rGO-HI bn hn rGO-NH3 v rGO-VitC.

Xp rGO-HI sau khi tng hp thnh cng sc kho st cc tnh cht v

cu trc thng qua nh chp SEM v o din tch bmt BET.3.3. Cc kt qukho st xp graphene (rGO-HI)


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Hnh 3.16 Xp graphene rGO-HI sau ng c.


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3.3.1 Kt quchp SEM xp graphene rGO-HI

Hnh 3.17 Hnh chp SEM mu xp rGO-HI cc kch thc khc nhau.

Tkt quchp SEM cc kch thc khc nhau cho thy xp graphene c

cu trc xp v nh hnh vi kch thc lxp cmicromet (ph hp vi kt qu

XRD). iu ny c gii thch da trn tng tc gia cc tm graphene .

Hnh 3.18 M hnh in tca vng thm theo tng tc , kiu song


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song (a), kiu xp chp (lch) (b), kiu chT (c). [25]

Theo tng tc , cc tm graphene c thxp theo kiu song song, ch

T v kiu xp cho. Trong , nng lng lin kt ca kiu song song (sandwich)

khong -2.0 kcal/mol, kiu xp cho (parallel displaced) khong -2.8 kcal/mol, kiu

chT (T-shaped) khong -2.7 kcal/mol [20].Do khi qu trnh khxy ra, cc tm

graphene skt tli v c xu hng xp theo 2 kiu chT hay kiu xp cho hn

l xp song song v c u tin hn vnng lng. Chnh ssp xp ny to nn

cu trc khung 3D v nh hnh ca xp graphene thay v cu trc lp trt tnh

graphite ban u.

3.3.2 Kt quo din tch bmt ca xp graphene rGO-HI.

Din tch bmt ca xp graphene rGO-HI (dng bt) o c l 456,520

m2/g cn dng xp l 735.947 m/g [ph lc]. Din tch bmt ca xp rGO-HI

cao hn so vi xp c din tch bmt 426m2/g c chto bi cc nh khoa hc

Trung Quc (mc 1.4.2.3). Vi din tch bmt cao mra hng ng dng trong

lnh vc vt liu hp ph, xc tc cho xp rGO-HI. Theo kho st s bca ti,

xp rGO-HI hp phhn 70ln khi lng du so vi khi lng ban u ca xp(wt/wt = 70) . Kt quny cao hn rt nhiu so vi vt liu hp phdu hin nay

nh polymer (wt/wt =18) hay khong st (wt/wt = 1418)[21] [12].

Bng 3.2 kho st khi lng hp phdu diezen ca xp rGO-HI

Ln

kho

st

Khi lng xptrc khi

hp ph du diezen (g)

Khi lng xp sau khi

hp ph du diezen(g)

Kh nng hp

ph du W

(wt/wt)

1 0.0059 0.4613 77.19

2 0.0053 0.3471 64.49

3 0.0063 0.5131 80.44

4 0.0034 0.2663 77.32

5 0.0031 0.2191 69.68

Kh nnghp ph du trung bnh: 73 6

Kh nnghp ph du(W) = khi lng xp sau hp ph/ khi lng xp trc


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hpph (wt/wt)[22]


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Phn 4. Kt lun v kin ngh4.1. Kt lun

1/ tng hp Graphit Oxide t graphite bng phng php Hummers.2/ tng hp gel graphene bng phng php kh tnh thng qua cc tc

nhn kh Vitamine C, NH3, HI. Trong cc tc nhn kh kho st, tc nhn kh HI

cho kt qu kh tt nht.

3/ thc hin qu trnh ch to xp graphene t gel graphenebng phng

php ng c. Kt qu thc nghim cho thy vi cc phng php kh tnh thy

nhit bng cc tc nhn kh Vit C, NH3, HI; ch c phng php kh GO bng HI

l c kh nng to xp. Kh nng kh cng cao th tng tc trong cu trc

r-GO cng tt , t lm tng kh nng to xp.

4/ kho st s b kh nng hp ph du ca xp graphene, kh nng ny

cao hn cc vt liu hp ph du hin ang s dng trong cng nghip.

4.2. Kin ngh

Do thi gian thc hin ti c hn, chng ti xin a ra mt skin ngh

cho hng nghin cu ny. Tc thmrng tim nngng dng ca

ti trong thc tin.

Kho st, tng khnng nn dn ca xp graphene t ng dng trong

vt liu hp phdu m.

Kho st cc tnh cht sinh hc t ng dng lm vt liu m, cht nn

sdng trong kthut nui cy tbo.

Kho st tnh cht in, nhit ng dng trong vt liu cm ng, dn in

v chto tin.


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