TAP CHI HOA HOC TAP 49(1), 108-111 T H A N G 2 N A M 2 0 1 ]
T 6 N G Hap HAT NANO PHAT QUANG CeP04:Tb TRONG DUNG MOI
NHIET DO SOI CAO B A N G PHU'ONG PHAP THUY NHIET
• • •
Dinh Xuan Lgc, Nguyen VO
I'ien Khoa hpc Vdt lien, Viin Khoa hpc vd Cdng nghi Viet Nam Din Tda soan 11-9-2010
Abstract
CeP04:Tb luminescent nanoparticles were successfully synthesized by hydrothermal method in high-boiling solvents such diethylene glycol (DEG) and tris(2-elhylhecxyl)-phosphate (TEHP) at 200"C for 4 hours. FESEM images show that synthesized nanoparticles are uniform in size and spherical in shape with a diameter about 20-50 nanometers.
Results from X-ray diffraction patterns exhibit the phase structure of materials are monazite CeP04:Tb with monoclinic stmcture. CeP04:Tb nanoparticles emit strongly in green region under 325 nm excitation wavelength from the He - Cd laser. The photoluminescent spectra are described by using the well-known 'D4 ^Fj transitions (J = 6, 5, 4, 3) of Tb^*
ions. The influence of synthesis time maintaining response to morphology, crystal stmcture, and fluorescence of nanomaterials will be discussed.
I.GI6I THIEU
Vdt lieu phdt quang ddt hilm cd cdu tnic nano dang thu hiit sy quan tam ciia nhilu nhdm nghiln ciiu. Tinh chdt quang manh cua vdt lieu nano so vdi vat lieu khdi da dugc phdt hiln vdi hieu iing phat xa ddi, hieu xuat lugng tii huynh quang cao vd mirc do dap tdt huynh quang theo nhilt do thdp. Cdc photphat ddt hilm phdt quang dugc iing dung nhiiu trong chilu sdng hieu ndng cao, trong hiln thj hinh anh, trong ddnh ddu bdo mat, ddnh ddu y sinh, lam cam biin sinh hod, [1 3]. Hg vdt lieu LnP04 pha tap Eu, Tb phat huynh quang cdc mdu dd vd xanh Id cay dugc sur dyng trong din huynh quang ba mau, trong mdn hinh tivi thi he mdi. Cdc vdt lieu Ceri photphat d dang cdu tnic dom td (monoclinic) vd lye gidc (hecxagonal) cdn dugc irng dyng nhiiu trong gdm chju nhilt, trong chi tao vdt lieu chju nhilt va chiu sy ma sdt [2, 3].
Phuang phap keo tii trong dung mdi nhict do sdi cao va phuang phdp thiiy nhilt la nhQ-ng phuang phdp khd mdi dl tao thdnh cdc hat vdt lieu nano.
U'ng dyng phuang phdp keo tu trong dung mdi nhilt do sdi cao, mgt sd nhdm nghiln ciiu da tao dugc vdt lieu nhdm A2B6 va Ti02 trong trioctylphotphin oxit (TOPO); InP vd InAs trong trioctylphotphin (TOP) [1,4]; LaP04:Eu trong tris(2-etylhecxyl)-photphat (TEHP) [5]. Vdi phuomg phdp thuy nhilt, cac nhdm:
Hua Gong da tdng hgp dugc nano ZnSe trong axit mecapto axetic [6], Yajuan Sun da tdng hgp dugc nano phdt quang YV04:Er trong mdi trudng kiim
[7], LixinYu da tdng hgp dugc GdP04:Tb trong moi trudng kilm [8], Ming Guo Ma da tdng hgp dugc nano core/shell (Idi/vd) CeP04/LaP04 vd nano core/shell CeP04/C trong mdi trudng H2O [9, 10]...
Tuy vdy, trong phuomg phdp thiiy nhiet, cdc hat vat lieu thu dugc thudng cd cd hat khd to vd khd dat dugc sy ddng diu. Dimg phuang phdp keo ty trong dung mdi nhilt do sdi cao, cdc hat vdt lieu thu dugc cd kich thudc nhd nhung phdi tdng hgp trong moi trudng khi tro vd vice khdng chl nhilt do dn djnh d 200''C Id rdt khd cung nhu thudng phdi klo ddi thdi gian tdng hgp trong nhilu gid.
Chiing tdi da kit hgp hai phuang phdp ndy lai de tdng hgp hat nano phdt quang CeP04:Tb bdng dung mdi dietylen glycol (DEG) vd fris(2-etylhecxyl)- photphat (TEHP) a nhilt do 200^0 trong 4 gid. Kit qua thu dugc \ at lieu cd dang cdu, cd cdu tnic tinh thi kieu monazite, kich thudc cd 20 - 50 nm vd kha ddng deu, cd hieu sudt phat quang cao. Mdt sd dieu kiln cdng nghe budc dau dugc khdo sdt di dat dugc mau cd cdu triic mong mudn, kich thudc nhd, phdt quang manh. Cdc nghiln cuu vi hinh thai, cdu tnic pha cua tinh thi vd huynh quang cua vat lieu da dugc tien hdnh d nhilt do phdng.
2. THUG NGHIEM 2.1. Hda chat
Axit octhor photphoric dang tinh thi, cdc dung 108
TCHH, T.49(l), 2011 Tong hgp vgt lieu phdt quang...
djch muoi ddt hiim nhu Ce(N03)3 vd TbCNOj), dietylen glycol (DEG), trioctyl amin (TOA), tiis(2-etylhecxyl)-photphat (TEHP)...
2.2. Tong hgp vat lieu
Dung djch hdn hgp gdm Ce(N03)3 vd Tb(N03)3 dugc lly theo ndng do pha tap 5%, dugc cd can d nhiet do 80°C. Sau dd, hdn hgp mudi dugc hda tan trong dung mdi DEG (hoac TEHP) blng vile khudy manh vd ndng nhilt dg hdn hgp lln trin lOOT. CJ mgt nhdnh khdc, TOA vd axit H3P04dugc hda tan trong DEG (hoac TEHP). Dung djch ndy dugc nhd gigt vdo dung djch mudi chira ddt hiim trong DEG (hodc TEHP) d tiln dk khdng bi kit tiia trong hon hgp phdn iing. Cudi ciing, hon hgp dugc cho vdo cdc teflon, rdi dugc dua vdo autoclave (ndi hap). Nhilt do ciia autoclave dugc ndng lln vdi tic do 5°C/phut vd giu d 200°C trong 4 gid, rii di ngudi ty nhiln vi nhilt do phdng. Dung djch keo thu dugc a dang tiong sudt khdng mdu. Cdc hat nano CeP04:Tb thu dugc bang ly tam d tdc do cao, rira bdng nudc khir ion vd etanol nhilu ldn. Kit tua sau dd dugc sdy khd trong chdn khdng d 75^0, thu dugc bdt mjn mdu frdng, xdp, khdng hiit am tiong dilu kiln bdo quan binh thudng. Mdu bdt mjn dugc kilm tra cdu tnic bang phuomg phdp nhilu xa tia X (XRD) trin mdy SIEMEN D5000, kich thudc hat dugc xac djnh bang dnh hiln vi diln tii quit FESEM (Hitachi, S4800). Phd huynh quang ciia vat lieu dugc do trin he do huynh quang, kich thich bang laser He-Cd cd budc sdng 325 nm.
3. KET QUA v A T H A O LUAN
Trin cdc gidn do nhilu xa tia X cua mdu bdt CeP04:Tb da tdng hgp dugc (hinh la va lb), ta thdy vat lieu cd tinh thi dang pha monazite CeP04 cua cau. tnic monoclinic khi so sanh vdi thi chuan 32-0199, phu hgp vdi kit qud da cdng bd vl cdu tnic vat lieu CeP04.xH20 vdi x = 0 cua nhdm Karpowich [II]. Cdc vach nhiiu xa md rdng cho thdy vat lieu chl tao dugc bang cd hai loai dung mdi diu cd kich thudc cd nanomet.
Anh FESEM frIn hinh 2a vd 2b cho chiing ta thdy vat lieu CeP04:Tb tdng hgp dugc cd kich thudc khodng 20-50nm, hat cd dang hinh clu khi dugc tong hgp frong cd hai dung mdi DEG vd TEHP Tuy nhiln ta cd thi quan sat thdy sy kit tu cua cdc hat d mlu ting hgp bdng DEG. Hiln tugng nay cd thi dugc gidi thich nhu sau: do bl mat cdc hat keo tich diln ldn vd ndng lugng ty do cao nin khdng bin vl mat nhilt ddng, vi vay ludn cd xu hudng kit dam dl gidm bi mat rilng vi trang thdi bin hom [12]. Mdu dugc ting hgp blng dung mdi TEHP dugc chyp FESEM khi hay cdn d dang keo, do dd, ta thdy rd
tiing hat nano CeP04:Tb. Trong qua trinh ting hgp, do hdn hgp phdn iing d trong trang thai tmh, khdng dugc khudy trgn manh, nen sy keo ty ciia dung mdi keo tia tryc tiip chua bao quanh hit cdc hat nano CeP04:Tb trong qud trinh hinh thdnh tinh thi. Hoac cd thi lugng dung mdi keo ty tinh todn cdn it so vdi lugng mlu tinh thi CeP04:Tb, vi vdy cdc hat tinh thi dugc tao thdnh cdn tu lai thdnh ddm nhd hai, ba hat md chua tach rdi hdn ra thdnh timg hat clu rilng bilt.
Qua khao sdt, chiing tdi thdy niu klo ddi thdi gian ting hgp trong dung mdi TEHP, thi vdt lieu thu dugc lai cd dang hinh thanh.
Hinh 1: Gidn do nhilu xa tia X cua mdu CeP04:Tb tdng hgp trong cdc dung mdi DEG (a) vd TEHP (b)
Dudi kich thich bang laser He-Cd cd budc sdng 325 nm, vat lieu phdt xa mdu xanh Id cdy. Hinh 3a vd 3b trinh bdy pho huynh quang cua vdt lieu nano CeP04:Tb. Phd huynh quang thu dugc cua vat lieu tdng hgp tir cd hai dung mdi diu tuomg tu vd cd gdm bdn ddi phat xa hep ddc trung cho huynh quang ciia ion pha tap Tb^^ vdi vi tri ciia cdc dinh phd la: 489, 543, 583 vd 618 nm, trong do dinh phd d vj fri 543 nm Id manh nhdt. Cdc dinh phd ndy tuomg iing dugc quy cho cdc chuyin ddi diln tur 4f cua ion Tb^^ tir miic kich thich ^D4 vl trang thdi co ban ^Fj (vdi j = 6, 5, 4, 3). Cdc pho huynh quang ciia vdt lieu thu dugc nay hodn todn phii hgp vdi kit qud cua cdc nhdm khac thu dugc bang thyc nghiem vd tinh todn ly thuylt [13-16]. Phd huynh qudng khdng xuat hiln phdt xa img vdi sy chuyin diln tir tir miic ^Ds bdi qud trinh phuc bii ngang: ^D3 + ^Fg -^ ^D4+ ^FQ [15].
Cdc ddi phd thu dugc cd sy tdch dinh tuomg ddi tdt: vdi ddi phd iing vdi viing 543 nm ta cd thi quan sdt thay ba dinh. Chiing tdi da sir dung kit qud vi tri cdc miic nang lugng do sy tdch Stark ddi vdi cac miic ^D4, ^Fs trong cau tnic tinh thi cua Tb:Y3Ga50i2 [17] dl xac djnh vi tri cac vach phdt xa img vdi sy chuyin cua diln tir tir miic vl cdc miic Stark, s i miic Stark tdi da la 2J -i-l, nin ^D4 cd tdi 109'
TCHH, T.49(l), 2011 Dinh Xudn Ldc vd cdng sir
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Hinh 2: FESEM ciia mau CeP04:Tb ting hgp trong dung mdi DEG (a) vd TEHP (b) da 9 miic Stark vd ^Fs cd 11 mirc Stark. Do vdy, sd
vach phd do chuyin miic "''D4 -> ^Fs gdy bdi sy tdch Stark xudt hiln khd nhilu vd sy chdng chap cua chiing gdy ra sy md rgng cua cdc dinh phd nhdn dugc.
Vi cdc mirc 'D4 vd ^F, diu cd sy tdch Stark, ddng thdi phIp do dugc thyc hiln d nhilt do phdng, nin ta thay cd sy md rdng cua cdc dinh phd. Sy tdch Stark tiln phd huynh quang nhdn dugc Id tuomg ddi tdt (do cd thi do dugc ngay cd d nhilt do phdng) cho thay hat vdt lieu CeP04:Tb thu dugc sau phdn iimg da kit tinh khd tdt. Huynh quang ciia vdt lieu ciing cho thdy rang, dii dung dung mdi ndo dl tdng hgp, cdc dinh huynh qiiang cdng khdng thay ddi.
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450 500 550 600 Bu6c s6ng (nm)
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450 500 550 - 600 Budc s6ng (nm)
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Hinh 3: Phi huynh quang cua mlu CeP04:Tb ting hgp frong dung mdi DEG (a) vd TEHP (b)
Thdi gian duy tri phdn img tdng hgp d ddy c6 dnh hudng khd manh den hinh thdi cua vdt lieu.
Trong phdn irng tdng hgp vdi dung mdi Id TEHP, khi klo ddi thdi gian lln 7 din 9 gid thi vdt lieu thu dugc se cd dang thanh nano. Tuy nhiln, thdi gian duy tri phdn iing lai khdng ldm dnh hudng vj tii cac dinh phd phdt quang cua vat lieu, khi klo ddi thai gian phdn iing len 10 hay 13 gid ta vdn thdy dang phd huynh quang khdng thay ddi. Thdi gian duy tri phdn img ciing dnh hudng din cau tnic pha cua tinh thi [18], nlu thdi gian phdn iing klo ddi thi cdu tiiic pha ciia tinh thi ciing thay ddi. Cdu tnic pha cua tinh thi vdt lieu CeP04:Tb sl chuyin thdnh dang monoclinic hodc dang hecxagonal tuy theo phdn ung duy fri d thdi gian ngan hay ddi hang chuc gid.
Nhu vdy, tuy theo y djnh sir dung loai cdu tiTtc tinh thi ndo, ta cd thi dilu chinh thdi gian phdn img ddi hay ngan dl dat dugc cdu tnic tinh thi ciing nhu hinh thdi cua vat lieu theo y mudn.
4. KET L U A N
Chimg tdi da tdng hgp thanh cdng vdt lieu CeP04:Tb cd kich thudc nano bdng phuomg phap thuy nhilt dung dung mdi keo ty d nhilt do soi cao vdi cdc dung mdi khdc nhau Id diethylenglycol va tris(2-etylhecxyl)3photphat.
Vdt lieu cd tinh thi dang pha monoclmic cua cdu tnic monazite la ddc trung, cd huynh quang manh d viing mdu xanh Id cay khi dugc kich thich bang laser He-Cd cd budc sdng 325 nm. Chiing toi da budc ddu khdo sdt dugc dnh hudng cua yeu to thdi gian den hinh thdi hat nano, cau tnic pha tinh the ciing nhu huynh quang cua vat lieu.
Vdi viec dimg dung mdi keo tu nhilt do soi cao vdo phuang phdp thuy nhilt, chiing tdi da giam dugc thdi gian, dom gian dugc qua frinh khing che nhilt do, khdng phdi sii dung mdi trudng khi tra trong tdng hgp vat lieu.
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TCHH, T.49(l), 2011
Ldi cam oti, Xin chdn thdnh cdm an cdc thgc si: Dd Hung Mgnh, Trdn Ddng Thdnh, Trinh Dice Thiin vd
Trdn Thi Kim Chi da tan tinh giup da chung tdi trong cdc phep do ddnh gid kit qud. Cdc thi nghiim tdng hap hgt nano CeP04:Tb dugc thuc hiin tgi Phdng Thi nghiim Trpng diim nhd nudc vi Vdt Hiu vd Linh kiin diin tic, Viin Khoa hpc Vdt lieu.
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Tong hgrp vdt lieu phdt quang...
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