TAP CHI HOA HOC T. 51(6)744-779 THANG 12 NAM 2013
NGHIEN CU'U TONG HOP HAT NANO ZnO BANG PHU'aNG PHAP SOL-GEL VA PHUN TINH OIEN
Le Van Huynh*, Fham Thi Lien Truong Dgi hoc Kinh te - Ky thudt Cdng nghiep
Dan Tda soan 31-7-2013
Abstract
ZnO nano-sized particles as the matenal charactenstics such as direct band gap, large band gap Eg = 3.37 eV, large excilon binding energy of 60 meV, high chemical durability, compaUbility biology, nonhnear optical effects. Especially when moving forms of block to form ZnO nanostmcUires, the emergence of new charactenstics superior to bulk ZnO, nano ZnO are so many applications in different fields such as laser diodes, light emitting diodes optica! sensor fabrication. This paper is the research results of ZnO nanoparticles fabrication Sol-Gel and elecUostatic spray methods.
Effect of conditions on structural prototyping, surface morphology and optical properties of the matenal, was studied by X-ray diffraction measurements, SEM imaging and absorpUon spectroscopy. The obtained results showed that the samples ZnO nanoparticles was 38 nm m size by Sol-Gel method and 12 nm by electrostatic spray method, with good quality and no more interest in the optical form. The research results are the basis for the application of science to production m the manufacture of high quality products
Keywords: Synthesis of nanoparticles.
1, MO DAU
ZnO cd can triic nano thudc loai vat lieu ban dan A B , cd vimg cam rdng Eg = 3,37 cV d dieu kien thudng, chuyen rdi dien tir thang, exiton tu do cd nang lugng lien ket ldn cd 60 meV, nhiet do thang hoa va nhiet ndng chay cao, ben viing vdi mdi trudng hidro, tuong thich vdi cac ung dung trong m^di trudng chan khdng, ngoai ra ZnO con la chat dan dien, dan nhiet tdt, tinh chat nhiet dn djnh ZnO dugc irng dung trong thiet bi phat xa UV, pin mat trdi, thiel bi sdng am, cac linh kien dien tir, linh kien quang dien tir va cac Iinh kien dan sdng. Dac biet khi chuyen ZnO lii' dang khdi sang dang cau true nano, thi .xuat hien nhirng tinh mdi vugt trdi so vdi ZnO dang khoi nhu: do ben co hgc cao hon, tinh dan dien, cudng dp huynh quang Idn hon va budc sdng phat xa cd the dugc dieu khien de dang hon, chinh vi va\ ZnO nano dugc ung dung trong nhieu Imh vuc khac nhau [1, 3, 4, 6].
Do cd nhieu tinh chat uu viet nhu vay, nen vat lieu ZnO cd nhieu iing dung trong khoa hpc cdng nghe va ddi sdng. Cd nhieu phuang phap ch8 tao vat lieu ZnO nano khac nhau nhu: bdc bay xung laser, lang dpng pha hoi hoa hgc, phuang phap quay phii.., cac phuong phap nay ddi hdi thi6t bi tuong ddi dat tien, nen nhin chung la khd thuc hien trong
dieu kien Viet Nam. Chinh vi vay, phuong phap Sol - Gel va phuong phap Phun tmh dien dugc lira chgn dimg de che tao vat lieu nano ZnO vdi chi phi thap hon. Day la hai phuang phap cd the tao ra lugng san pham Idn trong thdi gian ngan, chat lugng dn djnh, than thien vdi mdi trudng [2, 4, 5].
Bai bao nay la ket qua nghien ciiu che tao hat nano ZnO bang phuong phap Sol-Gel va phuang phap phun tinh dien, da thu dugc nhtrng hat tinh the nano ZnO d dang bdt va dang mang, xac djnh chat lupng mau, thdng qua viec nghien ciru cau tnic, hinh thai be mat mau va tinh chat quang ciia mau, bang phep do nhieu xa tia X, chup anh SEM va phep do phd hap thu cho thay cac mau hat tinh the ZnO thu dugc deu cd kich thudc nanomet.
2. THUC NGHIEM
2.1. Che tao hat nano ZnO dang bot bang phuong phap Sol - Gel
Hda chat dugc sii dung nghien ciru la:
Zn(CH3COO)3.2H20.
Chat xiic tac la dung djch NH4OH.
Che tao mau bdt dugc thuc hien nhu sau: Cho Zn(CH3COO)2.2H26 vao nudc cdt khuay deu dung dich bang may khuay tir trong khoang 30 phut de cac
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TCHH, T. 51(6), 2013
chat tan het. Sau khi cac chat da tan het, nhd tii tir dung djch xiic tac amoniac vdi tdc do khoang 1-2 gigt/phiit, giu nhiet dp on djnh d 60 "C va khudy trdn Hen tuc.
Trong qua trinh khuay trdn xay ra phan iing tao phirc [Zn(NH3)4]CH3COOH, phirc nay bi nudc thiiy phan thanh cac hidroxit Zn(0H)2 ket tua dudi dang huyen phii mau uang. Qua frinh nay dugc thuc hien frong khoang 5 gid, cho tdi khi con tir khdng quay dugc niia, cudi ciing thu dugc Gel am mau trang due, rdi mang Gel nay dem say d nhiet do 50 "C frong thdi gian 1 gid cho bay hoi het cac chat hiru co de chuyen thanh dang keo khd.
Cac mau Gel Bl; B2 va B3 dugc dem nung d nhung khoang nhiet do 450 °C, 500 °C va 550 °C, bang Id nung LENTON vdi thdi gian nung khoang 4 gid, rdi de ngudi den nhiet do thudng.
Qua trinh nung miu cd tac dung phan buy nhiet cac gdc axetat, bay hoi cac tap khdng can thiet, la khau rat quan trpng de hoan thien sir ket tinh ciia tinh the.
2.2. Che tao hat nano ZnO dang mang bang phuo'ng phap phun tinh dien
Dung dich tao mang dugc tao ra tir phuang phap Sol - Gel, Hda chat dugc sii dung la bdt Zn(CH3C00)2,2H2O dugc hda tan vao nudc va dung moi i,-,o propanol ancol (IPA) theo ty le 1PA:H;0 = 3:2. Khudy frdn lien tuc khdng gia nhiet d nhiet dp thudng trong 90 phiit, nhd vai gigt HCl cho tdi khi cac chdt tan hk thanh dung dich trong sudt dugc dung dich cd ndng dp 0,2 M.
Tao Sol: Hdn hgp dung djch dugc khudy trdn lien tuc bang may khudy tir khoang 90 phiit de hoa tan hk cac cbdt, rdi nhd tir tir dung djch CH3COOH d6ng thai khudy tiep trong 30 phut, cuoi cimg ta thu dugc Sol trong sudt khdng mau.
Tao mang: Dimg sol thu dugc d tren, tao mang ZnO bang phuang phap phun tinh dien tren de thuy tmh da dugc lam sach.
Phun bui dung djch: Duy fri nhiet do cac mau de M350; M400 va M45 la 350 °C, 400 °C va 450 X tign hanh phun tao mang. Hieu dien the giua kim phun va de la 20 KV, khoang each tir kim phun tdi di la 6,5 cm Chiim dung djch bi xe nhd dang hinh ndn bao triim toan bg de. De dugc sii dung la lam kinh cd dp truyen qua khoang 90 % va coi nhu trong sudt vdi anh sang kha kien. Do nhiet dp ciia de cao, nen tren be mat de xay ra qua trinh bay hoi dung mdi va hoi nudc, mang tren da ket tinh theo phuong trinh:
Zn(CH3COO)2,2H20 -1- O; ^
Le Vdn Huynh va cgng su ZnO + 4CO2 + 5H2
Mau mang sau khi phun xong, dugc dem li nhiet true tiep tren de trong khoang thdi gian 90 phiit. sau dd lay mau ra de ngudi den nhiet do thudng.
Cdng thiic Men he giiia hang sd mang a. b \'a c vdi chi sd mat phang mang (hkl) \a khoang each giira cac mat phang mang cd chi sd Miller (hkl) trong he luc giac Wurtzite la:
' (1) -{h'-\-k^-\-h.k) + f-.
Dua vao vi tri cac dinh ciia phd nhieu xa tia X, xac djnh duac hang sd mang a, b va c.
Kich thudc trung binh ciia mau hat tmh the ZnO duoc xac dinh theo cong thuc Debye - Scherrer:
fl=^^ (2, p.cosO
Trong dd: (5 la ban kinh rdng ciia dinh (rad);
X la budc sdng ciia nhieu xa tia X (A);
9 la gdc nhieu xa (do);
D la dudng kinh hat tmh the (A)
Pho nhieu xa tia X ciia cac mau nghien cuu, dugc do tren he may D5005-SIEMENS sir dung biic xa KJ cua Cu tai budc song hiu = 1,54056 A. Anh SEM ciia cac mau nghien ciru dugc chup tren may JMS 5410-Jeol, Phd hap thu ciia cac mau nghien ciru dugc thuc hien tren pho ke Jasco V-670.
3. KET QUA VA T H A O LUAN 3.1. Nghien ciru hat nano Zno dang hot
K^t qua do phd nhicn \ii na X ciia cac mau bpl ZnO va mSu mang ZnO duai, ihe hien fren hinh 1 cho thdy, tren pho cd 9 dinh nhieu xa, cac dinh pho d^u cd tinh ddi xiing cao, chirng td mau ket tinh tot.
So vdi the chuan ciia pha wurtzite, ta thay cac dinh nhilu xa thu dugc triing khit ve vj tri va phii hop vc cudng do tuong ddi vdi cac dinh pho chuan. Dieu nay cho thay mau thu dugc hoan loan don pha va cd cdu triic wurtzite. Cac dinh nhieu xa thu dugc lan lugt la (100), (002), (101), (102), (UO), (103).
(200), (112), (201). Cac k8t qua cho thdy, cac mau ZnO thu dugc d^u cd phd nhieu xa tia X gidng nhau ve so lugng va vj tri dinh pho.
Nhu vay cac mau d^u cd cau true lyc giac wurtzite va ket tinh tdt vdi khoang nhiet dg ii trong khoang nhiet do 450-550 T . Trong khoang nay Ihi nhiet dd khong lam anh hudng nhieu den qua trinh ket tinh ciia miu. Ket qua nghien ciru cac mau Bl.
B2, B3 thi hien tren bang I.
TCHH. T. 51 (6), 2013 Nghien ciru tdng hap hgt nano ZnO...
Bdng 1: Cac thdng sd thu dugc tir gian dd nhieu xa tia X cua miu bdt ZnO
Bl B2 B3
(IOO) I, cps 3140 3094 5619
(100) d,A 2.8197 2.8463 2.8165
(002) I, cps 32702 2632 4292
(002) d,A 2.6063 2.6064 2.6042
(101) I, cps J 4600 4644 8153
(101) d,A 2.4778 2.4767 2.4764
a = b A 3.249 3.251 3.252
c A 5.628 5.632 5.633 Ket qua tinh toan cac hang sd mang thdng qua
phd nhieu xa tia X cho thay. hang sd mang ciia cac mau thu duoc sai lech khdng nhieu so vdi the chuan. Sir dung ket qua do phd nhieu -xa tia X ciia mau bgt nano ZnO, tir vi tri cac dinh ta tinh dugc kich thudc hung binh ciia pha wurtzite theo cdng thuc (2) la:
a = b = 3.25 A ; c = 5,6 A Cac gia tri nay khdng khac nhieu so vdi mang chuan, do dd mau nghien ciru kha ddng deu va cd cau tnic tinh the tdt.
Bdng 2\ Kich thudc cac man hat Mail
Bl B2 B3
Kich tliirac hat, nm 38 40 50
Theo cdng thiic cdng thiic Debye - Scherrer (2), tinh dugc kich thudc hat nano ZnO, cac hat thu dugc kha ddng deu, c6 kich thudc nanomet the hien tren bang 2. Ket qua cho thay, qua trinh xu ly nhiet anh hudng rat ldn den kich thudc hat nano ZnO.
3.2. Nghien ciru hat nano ZnO dang mang Ket qua do phd nhieu xa tia X cua mau mang dugc the hien tren hinh 2 cho thay, mau mang ZnO phun tai cac nhiet dd de khac nhau, trong khoang nhiet dp khao sat deu the hien cau tnic Wurtzite, cac mau hoan toan don pha. Cac dinh triing khit the chuan, cac dinh ling vdi cac mat phang mang CO chi so miller la (100), (002), (101), (102), (UO). Cac dinh phd deu cd tinh ddi xiing cao, chirng td mau ket tmh tdt. So vdi the chuan ciia pha wurtzite, ta thay cac dinh nhieu xa thu dugc triing khit ve vj tri va phii hop ve cudng do tuong doi vdi cac dinh phd chuan bang 3.
Dac biet la do ban rdng cua cac dinh nhieu xa rdng han so vdi mau bdt chirng td cac hat trong mang cd kich thudc nhd han so vdi mau bgt. Day chinh la uu diem ciia phuong phap phun bui dung djch. Tir gian dd nhieu xa tia X ciia cac mau mang, xac dinh dugc hang sd mang a, b, c theo cdng thirc (1) la:
a = b = 3,24A;c = 5,6A.
Cac gia frj nay khdng khac nhieu so vdi mang chuan, do do mau nghien cii'u kha ddng deu va c6 cau triic tinh the tdt.
VNU-HN-SIEMENS O5005 - Mau mang ZnO
Hinh !: Phd nhieu xa tia X cua mau
BI,B2, B3 Hinh 2: Phd nhilu xa tia X ciia
M350, M400, M450
TCHH, T. 51(6), 2013 Le Vdn Huynh vd cgngsu Bdng 3: Cac thdng sd thu dugc tir gian do nhieu xa tia X ciia mau mang ZnO
^ ^ ^ D i n h Mau ^ \ ^
M350 M400 M450
(100) I, cps 170 152 95,5
(100) d,A 2.8089 2.8053 2.8102
(002) 1, cps 103 76,6 87,0
(002) d,A 2 5951 2.5907 2.5925
(101) 1, cps 247 228 152
(101) d,A 2.4688 2.4703 2.4677
a = b A 3.243 3.239 3.244
c A 5.616 5.610 5.620 Ket qua nghien ciru cho thay hang sd mang a, b
va c cd thay doi, nhung khdng dang ke, chirng td yeu td nhiet trong khoang khao sat tir 350 °C tdi 450 °C khdng lam anh hudng nhieu den hang sd mang. Tir gian dd nhieu xa tia X, xac djnh dugc kich thudc hat trung binh theo cdng thirc Scherrer (2) the hien tren bang 4.
Tren bang 4 cho thay, khi nhiet do ciia de tang tir 350 °C din 450 °C, thi kich thudc hat thay ddi khdng dang ke, kich thudc hat trung binh co khoang 12 nm.
Nhu vay cac mau thu dugc deu cd cau tnic luc giac wurtzite va ket tinh tdt vdi nhiet dp de khoang 350- 450 "C. Trong khoang nay thi nhiet do khong lam anh hudng nhieu den qua frinh ket tinh ciia mau, nhu vay kich thudc hat nano ZnO thu dugc bang phuang phap phun tTnh dien, tuong ddi nhd han so vdi mau ddang bgt.
Bdng 4: Kich thudc cac mau hat Mau
M350 M400 M450
Kich thirac hat, nm 12 11 12
Thuc nghiem da chi ra rdng, neu nhict do de nho han 200 "C, mang sau khi pluin cd do bam
dinh khdng tdt, de bj chay thanh dang keo, be mat mang xuat hien cac hat li ti, chiing td hat chua cd dp bam dinh vao de.
Neu nhiet do de ldn bon 200 °C. dp bam dinh ciia mang tdt hon. Tuy nhsen, nhiet do de phai tren 350 °C mirng phun mdi cd su ddng deu va bam dinh tdt hon. Khoang each tir kim phun tdi de tdt nhat cho su ket tinh ciia mang la 6 tdi 7 cm. Thdi gian phun tot nhat khoang 20-30 phiit Sau khi xii ly nhiet, mang trd nen mjn han. Qua trinh ii nhiet tao su on djnh cho cau triic ciia mang.
3.3. Nghien cuu anh huong ciia nhiet do den hinh thai be mat eua mang
Ket qua nghien ciiu dugc the hien Iren hinh 3 anh SEM cua cac mau M350, M_400, M450 cho thdy, cau tnic cac hat tuong doi deu. the liicn cau tnic kic giac dac trung ciia nano ZnO, cd su lu dam hinh 3a,
Chup anh be mat ciia mang phun d nhiOl do de 400"C hinh 3b. Kit qua cho thdy kich thirdc hat ddng deu hon so vdi mau d nhiet dg 350 "C, bicn gidi cac hat kha ro rang. Hien tugng lu dam giam.
hat the hien cau triic luc giac ro rang ban K6t qua do anh SEM cua cac mau mang ZnO cho bicl hinh thai be mat ciiii mau.
Hinh 3: Anh SEM ciia (a) M350; (b) M400; (c) M450
Khi nhiet dp d6 d 4 5 0 T hinh 3c cho thiy, hat su tu dam nhung da giam dang ke, Kich thudc hat k^t tinh tuong ddi ddng diu, bl mat hat nhan, cd deu han. Chung td cac mang ZnO chua cac hat
TCHH, T. 51(6), 2013
tuang ddi ddng diu nhau, chung deu cd kich thudc nanomet. Trong ca ba mSu cd the quan sat thay su hinh thanh cac hat hinh luc giac, diiu nay chimg td da cd sir ket tinh tdt cua tinh the ZnO.
Nhu vay, mang mdng che tao bang phuong phap phun tTnh dien cho hat cd kich_ thudc nanomet. Tuy nhien kich thudc hat nhu the la cdn kha ldn so vdi ban kinh exiton Borh la 1,8 —> 2,0 nm. Khi thay ddi nhiet dp de trong khoang khao sat, thi kich thudc hat thay ddi khdng dang ke. Nhiet dp cang cao thi kha nang ket tinh ciia hat cang tdt, tao ra cac hat cd kich thudc cang ddng deu han.
3.4. Nghien cuu anh hudng cua nhiet do cua de leu phd hap thu
Phuong phap do phd bap thu dua tren hien tugng hap thu anh sang trong qua trinh anh sang lan fruyen trong mdi trudng vat chat nghien cuu.
Trong qua trinh nay, neu tan sd ciia chiim tia sang phii hop vdi tan sd chuyen ddi cac electron ciia cac nguyen tir trong moi trudng vat chat dang nghien cu'u, thi chiim tia se bj tat dan, tiic la anh sang bi hap thu mdt phan, chi phan anh sang khong bj hap thu mdi truyen qua dugc, cho ta pho hap thu ciia vat chat dang nghien cuu.
Tien hanh do pho hap thu ciia cac mau mang M350, M400 va M450 cho thdy:
Nghien cuu long hap hgt nano ZnO...
C) tat ca cac mau mang deu xuat hien mgt bd vimg hap thu rd rang frong mien UV. Bd hap thii nay lien quan den su tai hgp exciton tu do. De chuyen muc, tir viing hda fri Ien vimg dan dien tii phai hap thu photon cd nang lugng cao hon nang lugng viing cam. Bd hap thu cd gia tri xung quanh vj tri vdi budc sdng 360 nm, djch chuyen ve phia cd budc sdng Idn hon khi nhiet do ciia de tang, ket qua the hien tren hinh 4 va bang 5.
Bdng 5: Budc sdng phd hap thu va do rdng viing cam ciia mau mang ZnO Mau
M350 M400 M450
Birac song, nm 360 362 365
Eg, eV 3,43 3,41 3,39
Ky hieu B D F Tir cdng thiic: Eg = h.dX -^ Eg= 1238/X (eV).
Ket qua nghien cuu, da xac djnh dugc dp rgng viing cam ciia mau nghien ciru la 3,41 eV.
Nhu vay, ket qua nghien ciiu ve phd nhieu xa tia X, hinh thai be mat cua mau, phd hap thu cua cac mau mang ZnO da chirng td rdng, cac mau mang thu dugc cd do ket tinh tdt, hat thu duac co kich thudc nanomet.
,B
-
B fv535D
— D M 4 0 0 F M 4 5 D
Budc sdng, nm
ITinh 4: Phd hap thu cua (B) M350; (D) M400; (F) M450 4, KET LUAN
Da tdng hgp dugc hat nano ZnO bang phuong phap Sol-Gel va phuong phap phun tTnh dien, mau thu dugc CO cau tnic wurtzite va kich thudc nanomet. Vdi mau bdt thi hat ket tinh tdt nhat o nhiet dp 550 °C, cdn mau mang thi hat ket tinh tdt nhat khi nhiet dp ciia de d 450 °C.
Che tao thanh cdng mang mdng ZnO bang
phuong phap phun tTnh dien, d cac nhiet dg dekhac nhau 350 °C, 400 "C, 450 °C. Phan tich phd nhilu xa tia X, kinh hien vi dien tu quet cho thay, cac mau deu cho ket qua tdt, tinh the cd cau true lyc giac Wurtzite, hoan toan sach pha, kich thudc hat tuong ddi ddng deu cd kich thudc khoang 12 nm.
Phd hap thu cho thdy, mau mang ZnO che tao dugc cd do tinh khiet cao va khdng cd tam tap quang hpc trong mau. Be rpng dai viing cam ciia mau la
TCHH, T. 51(6), 2013
3,41 eV thu dugc tir ket qua do phd hdp thu. Kit qua nghien ciru cho thay cac mau che tao bang hai phuang phap diu cho chat lugng tdt.
Ket qua nghien ciiu la co sd khoa hgc cho viec img dung ket qua nghien ciru vao cac qua trinh cdng nghe san xuat.
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Lien hi Le Van Huynh
Trudng Dai hpc Kinh te - Ky thuat Cdng nghiep 353 Tran Hung Dao, Thanh phd Nam Djnh va 456 Minh Khai, quan Hai Ba Trung Ha Npi Email: [email protected] Dien thoai 0912 208 709.
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