TAP CHi HOA HQC T. 51(1)46-50 THANG 2 NAM 2013
NGHIEN CLFU BIJ^N TJNH HAT NANOSILICA B A N G 3-AIVIINOPROPYLTRIETOXY SILAN
Thai Hoang'', Nguyen Thiiy Chinh', Lc Van Khu^ Nguyen Thj Thu Trang' 'Vi?n Ky thugt nhiet ddi. Vi?n Hdn lam Khoa hgc vd Cdng ngh? Vi?l Nam
^Khoa Hda hgc. Trudng Dgi hgc Suphgm Hd Ngi Den Tda sogn 10-8-2012
Abstract
In this study, silica nanopailiclcs or nanosilicas were prepared through a sol-gel process. Then, 3-amino- propyltrietoxy sitan (APTES) compounds were hydrolyzed in ethanol solvent and added the above silica nanoparlicles into the hydrolyzed APTES solution. The organic chains in APT1-;S grafted to surface of nanosilica were detected by Fourier Transform Infrared (FTIR) Surface characteristics (including specific surface area, pore volume and pore size) of nanosilica and modified nanosilica were measured by nitrogen adsorption and desorption. The grafting yield of APTES for monolayer formation on the nanoparlicles surface was determined by Thermogravimelric Analysis (TGA) technique. Finally, the morphology of unmodifed and modified nanosilica was characterized by Field Emission Scanning Electron Microscopy (FESCM) and Transmission Electron Microscopy (TEM). It can be seen thai agglomerated particle size in modified nanosilica decrease in comparison with unmodified nanosilica. The above results showed that surface treatment of nanosilica with APTES is successfull.
Keywords: Silica nanoparlicles, 3-aminopropyltriethoxysilan, modification, grafting yield, specific surface area.
1. MO DAU
Nanosilica la mgt trong cac phy gia dugc su dung ngay cang phd bien trong cac ITnh vyc khac nhau.
Tuy nhien viec ung dung nd van cdn gap nhieu khd khan do nang lugng ty do ldn, dc dang hap thy nudc d nhiet dg phong tao thanh cac nhdm bydroxyl, cac nhdm siloxan va nhdm silanol tren be mat nanosilica [I, 2], Sy hinh thanh cac nhdm siloxan tren be mat nanosilica lam cho cac hgt nanosilica cd xu hudng ket tu tao Ihanh cac hgt cd kich thudc Idn ban. Vi vay, bien linh be mat ciia nanosilica cd the tang tinh ki nudc, giam do phan eye be mat, giam kich thudc hgt ket tu ciia nanosilica. Cac hgt nanosilica cd the dugc bien tinh hda hgc be mat hoac bien tinh vat ly bang each nghien hay xu ly sieu am be mat cac hgt nanosilica. Viec nghien hay xir ly sieu am be mat cac hgt nanosilica can nang lugng ldn, khd cd the ung dung vdi qui md cdng nghiep. Trong khi dd, bien tinh hda hgc be mat nanosilica bang cac chit lien ket hoac tac nhan ghep polyme don gian va dl thuc hien hon, cd the ap dyng vdi qui md cdng nghiep. Trong thyc le, ngudi ta thudng biln tinh hda hgc be mat nanosilica bing cac chat lien kit hg silan, axit stearic, axit maleic, [3-11],
Dan Donescua va cac cgng sy da nghien cuu
bien tinh hgt nanosilica bang anhydrit maleic (MA) vdi ham lugng ghep len tdi 5% [3]. Bang phuang phap trgn tdc dg cao vdi xiic tac oxit kem, S. Sun va cac cgng sy da chung minh dugc phan ling ghep eiia dimetyl dlclorosilan (DMCS) hoac metyl aery I oxy propyl trimetoxy silan (KH570) vao nanosilica [4].
LA. Rahman ciing cac cgng sy da nghien cihi tdng hgp nanosilica gan nhdm hCru ca bang phuong phap ddng ngung ty y-aminopropyltrietoxysilan (APTES) [7]. Phd hdng ngogi (IR), anh hiln vi di?n tir iruyin qua (TEM), phan tich nhiet khdi lugng (TGA), pho cgng hudng tir ''C, ^'Si va phd tan xa nang lugng tia X (EDX) dIu chi ra cac h^t nanosilica vdi kich thudc hgt trung binh 60 nm da dugc gan mgt lugng ldn cac nhdm chuc hifu co hoat dgng tren be mat. Tuy nhien, cac tac gia chua khao sal dien tich be mat rieng, hieu suat gliep cung nhu anh hudng ciia ham lugng tac nhan ghep den hinh thai cua hat nanosilica bien tinh. Vi vay, bai bao nay trinh bay ket qua nghien cuu bien ti'nh cac hat nanosilica bang APTES trong dung mdi etanol vcfi cac ham lugng bien tinh khac nhau. Cac hat nanosilica trudc va sau khi bien tinh dugc dgc trung bang cac phuang phap phd IR, SEM, TEM, TGA va hap phu nita (BET).
46
TCHH, T. 51(1), 2013 2. THl/C NGHIEM 2.1. Nguyen lieu
Nanosilica dugc tdng hgp tir tetraetoxysilan (TEOS, Merck, Due) theo phuang phap sol-gel [12].
3-aminopropyltrietoxysilan (APTES, Aldrich, My) cd do tinh khilt 99%. Etanol (Trung Quoc).
2.2. Bien tinh nanosilica bing APTES Qua cac khao sat da trinh bay d [12], cac tac gia da rut ra dugc dieu ki§n thich hgp de tong hgp cac hgt nanosilica tir TEOS bang phuang ph^p sol-gel la ti le Ihl tich TEOS/C2H5OH/H2O/NH4OH 1/6/0,2/0,2 va khuay dung djch trong 20 phiit ke tir khi dua NH4OH vao. Cac hgt nanosilica thu dugc cd dgng hinh cau dac, kich thudc hgt trong khoang 50- 100 nm. De bien tinh nanosilica, dIu tien APTES dugc thuy phan trong dung mdi C2H5OH d 7 0 ^ trong 60 phut de thu dugc cac silanol. Sau dd, dua nanosilica vdi ham lugng da dugc tinh toan trudc vao dung dich tren. Tiep tuc khuay dung djch trong 2 gid, sau do Igc, rua bang etanol va say trong tii say chan khdng d 80''C trong 4 gid de thu duac hat nanosilica bien tinh (viet tat la m-silica). Cac mau silica bien tinh 5, 10, 15, 20, 25, 50 va 70% kl tuong irng ian lugt dugc ky hieu la m-silica 5, m-silica 10, m-silica 15, m-silica 20, m-silica 25, m-silica 50 va m-silica 70.
2.3. Phirang phap va thiet bi nghien ciru Phd FTIR dugc ghi bdi may phd hdng ngoai Fourier Nexus (My) vdi sd sdng bien doi tir 4000 den 400 cm' d nhiet dg phdng, sd ian quel 16 ian.
Anh SEM dugc chyp tren may S-4800 SEM (Hitachi, Nhat Ban) va anh TEM dugc chup tren kinh hien vi dien tir truyen qua JEMIOIO (JEOL, Nhat Ban) de xac dinh kich thudc va sy phan tan ciia cac hat nanosilica trudc va sau bien tinh. Dac trung nhiet khdi lugng eiia cac mlu dugc xac djnh tren may DTG-60H (Shimadzu, Nhat Ban) trong mdi trudng argon tir nhiet dg phdng den 600°C, tdc do gia nhiet 10°C/phiit. Di?n lich be mat rieng ciia cac mau dugc xac djnh theo phuang phap BET tren thiet bj TriStar 3000 V6.07A.
3. KET QUA v A T H A O LUAN
3.1.Phd hdng ngoai (IR) cua cac hat nanosilca va m-silica
Hinh I la pho IR cua nanosilica, APTES va m-
Thdi Hodng vd cgng sir silica biln tinh vdi 5% kl. APTES (m-silica 5). Tren phd IR cua mau nanosilica xuat hi^n cac pic manh dgc trung cho dao ddng hda trj va dao dgng bien dang cua nhdm OH tren be mgt hgt nanosilica tai 3450 cm"' va 1637 cm"'. Cac pic tgi 1052 cm ', 800 cm"' va 461 cm"' dgc trung cho dao dgng hda trj bat ddi xirng, dao dgng hda trj ddi xirng va dao dgng bien dgng ciia nhdm Si-O-Si. Ngoai ra, cdn xuat hien pic yeu tgi so sdng 955 cm"' dgc trung cho dao dgng hda trj ddi xirng ciia nhdm Si-OH [I].
Khi so sanh pho IR ciia m-silica vdi pho IR ciia nanosilica, ngoai su djch chuyen so sdng ciia cac pic dac trung cho nhdm OH va Si-O trong silica, tren pho IR ciia m-silica 5 cdn xuat hi?n cac pic mdi dac trung cho cac nhdm chirc hifu ca tuang ly nhu tren phd IR cua APTES (hinh 1). Vai phd d 3744 cm"' dgc trung cho dao dgng hda tn ciia nhdm amin bac 1. Pic yeu tgi 2921 va 2847 cm' tuang irng vdi dao dgng hda tri ciia nhdm CspsH, luy nhien cd cudng do nhd ban so vdi pic tuang irng tren phd IR ciia APTES [t 1]. Nhu vay, ket qua phan tich phd IR cho thay APTES da dugc gan len be mat hat nanosilica.
Nhd cac nhdm amin trong APTES va nhdm silanol hinh thanh sau khi thuy phan APTES tao lien ket hidro va luang tac ludng cue - ludng eye vdi cac nhdm OH tren be mat hgt nanosilica.
Phd IR ciia cac mau m-silica bien tinh vdi 10, 15, 20 % kl APTES cung cho cac thdng tin luang ty nhu tren pho IR cua m-silica 5 nen chi thdng ke sd song dac trung ciia mgt sd nhdm nguyen tir trong bang 1.
S6s6ng(cin-1)
Hinh 1: Pho IR ciia nanosilica, APTES va m-silica 5
TCHH, T. 51(1), 2013 Nghien cvru bien tinh hgt nanosiUca.\
Bdng 1: So sdng dac trung cho cac nhdm chiic trong nanosilica, APTES va m-silica
Mau Nanosilica
APTES m-silica 5 m-silica 10 m-silica 15 m-silica 20
So song, cm"'
V N H
3745 3744 3750 3756 3754
2973 2928 2921 2847 2920 2847 2920 2852 2921 2852
SNH
1583
1550 (y) 1552 1553
5CSD3II
1453
1412 (y) 1414 1414
Voir
3448 3357 3445 3444 3447 3443
5oH 1639 1659 1634 1635 1634 1632
VSi-O
1052 800 1077 775 1095 797 1094 795 1093 796 1092 795
Vsi-OH
955 957 952 948 945 958
5 S I - 0 - S L
461 482 464 465 463 462 3.2. Dac tryng be mat cua cac hgt nanosilica va nhi?t nita ciia 2 mlu nanosilica va m-siliica 5. Dien m-silica tich be mat rieng (SDET). di?n tich vi mao quan (Svi IS), di?n tich ngoai (Sn^oai), di?n tich mao quan Be mat rieng va kich thudc mao quan ciia vat lieu trung binh (Sujn), the tich tdng (V,6„J, the tich vi nanosilica va cac mau m-silica dugc danh gia bang mao quan (Vv, \h), the tich mao quan trung binh phuang phap hap phu ding nhiet nita theo phuang (Vmu) va dudng kich Id xdp trung binh (d,n,ng tint)' trinh BET. Hinh 2 la dudng hap phu - giai hap dang dugc trinh bay d bang 2.
Bdng 2. Dien tich be mat, the tich Id xdp va dudng kinh Id xdp trung binh ciia nanosilica va m-silica 5
Mau
Nanosilica (a) m-silica 5 (b) (b-a)/a (%)
S B E T T
m'/g 253,97
78,72
•69,00
S . , IS,
mVg 148,63
11,50 -92,26
s.„..,
m / g 105,34 67,22 -36,19
SBJH , m'/g 108,41 68,49 -36,83
cmVg 0,44 0,46
V„is, cmVg 0,070 (15,40%)
0,004 (0,86 %)
VDJII, cmVg 0,37 (83,95%)
0,42 (90,71%)
'J irung binli
(A) 6,96 23,39
Hinh 2: Dudng hap phy - giai hap nita dang nhiet ciia nanosilica va m-silica 5 Theo
hap phu
phan loai ciia lUPAC, ducmg dang nhiet N2 ciia mau silica va m-silica 5 deu thudc
logi IV, vdi diem udn d khoang ap suat tuang doi cao P/Po = 0,7-0,8 tuang irng vdi sy ngung ty mao quan va deu cd kieu vdng tre, diiu nay cho thIy v|t lieu cd mao quan trung binh [9, 11]. Bang2 cho thay cac hat nanosilica cd be mat rieng Idn 253,97 (mVg).
Sy cd mat ciia APTES gan vao nanosilica lam giam di?n tich bl m§t rieng do sy giam mgnh di$n tich vi mao quan (92,26%), trong khi dd dien tich mao quan trung binh giam nh? (36,19%). Ket qua nay la do ai lye cua cac vi mao quan thudng ldn hem ai lye cua cac mao quan trung binh, nen APTES tap trung lap day cac vi mao quan trudc, sau dd mdi lap day cac mao quan trung binh [9]. Ket qua la dudng kinh lo xdp trung binh cua cac mau silica bien tinh tang do sy bien mat cua cac vi mao quan nhu dugc the hien trong bang 2.
So sanh the tich mao quan ciia cac mau trong bang 2 nhan thay thi tich giam d vi mao quan, trong
TCHH, T. 51(0,2013
khi do the tich ciia mao quan trung binh tang, d vung mao quan ldn, cac phan tir APTES bam tren bl mat nanosilica lam tang khoang each giifa cac thanh mao quan (do giam tuang tac tmh di^n giCra cac phan tir silica), gdp phin tang thi tich mao quan trung binh ciia nanosilica bien tinh [9].
3.3. Xac dinh hieu suat qua trinh bien tinh Xay dung dudng cong hieu suat la phuang phap cd hi^u qua de tdi uu hda qua trinh bien tinh nanosilica bang APTES. Nhd phuang phap TGA, ham lugng ghep APTES duge xac djnh bing each lay khdi lugng mil ciia mau bien tinh trir di khoi lugng mit ciia mlu ban dau d nhiet do 300°C (trudc nhiet dd bat dau phan hiiy cua silan hiru ca - 315''C) [7, 13].
Hinh 3 cho thay khdi lugng phan irng ciia APTES tang khi lang ham lugng APTES trong hdn hgp phan irng. Khi tang ham lugng APTES trong hdn hgp tir 0,25 den 2 g/10 g nanosilica, khdi lugng APTES ghep tren 10 g nanosilica tang tir 0,1 den 0,35 g. Tuy nhien, khi tang ham lugng APTES cao han, mac dii chiing van cd the ghep vao be mat ciia hgt nanosilica nhung ham lugng du APTES se de dang hda tan trong dung mdi trong qua trinh bien tinh nen lugng APTES ghep chi tang tir 0,35g den 0,4 g/10 g nanosilica (khi tang khoi lugng APTES trong hdn hgp phan ung lu 3 den 7 g). O ham lugng nho, khoi lugng APTES lien ket bien ddi luyen linh do sy hinh thanh don Idp silan tren be mgt hgt nanosilica, tuy nhien, khi tang ham lugng APTES >
10 % kl, khdi lugng APTES lien ket bien ddi theo dudng cong do su polyme hda cac phan tir silan tren be mat nanosilica va khi APTES khdng the ghep them len be mat hgt nanosilica nua thi khdi lugng APTES lien ket bien ddi gan nhu theo dudng thang nam ngang [13]. Tir hinh 8, cd the thay ham lugng 13,5 %kl APTES la thich hgp nhit dk biln tinh hgt nanosilica.
Thdi Hodng vd cong su Cac hinh 4, 5 va 6 bieu dien anh SEM va TEM ciia cac hat nanosilica va m-silica. Quan sat cac hinh 4 va 6 ta thay cac hgt nanosilica cd dgng hinh cau dgc, kich thudc hgt khdng deu, khoang 50-80 nm.
Do sy hinh thanh lien ket hidro lien phan tir nen cac hgt nanosilica ket ty vdi nhau thanh tirng cum hat vdi kich thudc Idn, cd 300-500 nm [7].
Hmh 3: Dudng cong hieu suit ham lugng APTlvS ghep len be mat hgt nanosilica 3.4. Hinh thai cau true cua nanosilica va m-silica
h—m—^M^MiiiMiir 1 TI n n i r 1111 —ni—iaMrtiiin Hinh 5: Anh FESEM ciia cac hgt nanosilica bien
tinh APTES, (A): m-silica 5, (B); m-silica 10, (C): m-silica 15, (D): m-silica20 Sau khi bien tinh vdl APTES, cac hat m-silica kha ddng deu vdi kich thudc nhd han, khoang 40-70 nm (hinh 5 va 6). Mac dii van cd sy ket ty nhung kich thudc cac hgt ket tu da giam dang ke. Dieu nay cd the giai thich la do be mat cac hgt m-silica dugc bao bgc bdi mdt ldp silan hiiu co lam tang linh kj nudc ciing nhu lam giam nang lugng be mat ciia hat nanosilica.
Khi lang ham lugng ciia APTES len den 20%kl, cac hgt m-silica phan tan kem ddng deu hon, kich thudc hgt kit ty tang len so vdi cac mau bien tinh vdi 5, 10 va 15%kl APTES. Nguyen nhan cd the do khi sir dung ham lugng tac nhan bien tinh ldn, do day ldp hiru ca phii tren be mat hat nanosilica tang len va cac ldp hifu ca nay lgi tuang tac vdi nhau (polyme hda cac phan tir APTES), vi vay kich thudc va sd lugng hgt ket tu tang len.
T C H H , T. 51(1), 2013
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^ ^
lliiili 6. Anh I l-Al t
4. K E T L U A N
So sanh cac pho IR ciia nanosilica va m-siliea cd the thay A P T E S da d u g c gan len be mat hat nanosilica. Ham lugng A P T E S thich h g p nhat de b i l n tinh hat nanosilica la 13,5%kl. Anh T E M , SEM va dac trung be mat cac mau khao sat cho thay sau khi bien tinh A P T E S , sy ket tu cua cac hat nanosilica giam dang ke, d u d n g kinh Id xdp trung binh ciia nanosilica tang va dien tich be mat rieng ciia chiing giam.
Loi c a m a n : Cdng trinh nay duac tdi trg bdi Quy Phdt tnen Khoa hgc vd Cdng nghe Quoc gia (NAFOSTED), mas6 104.04-2010.02
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