dat hiem huynh quang

8/4/2019 DAt Hiem Huynh Quang

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1

B GIO DC

V O TO

VIN KHOA HC

V CNG NGH VIT NAM

VIN KHOA HC VT LIU

LM TH KIU GIANG

NGHIN CU CH TO

VT LIU NANO THP CHIU

TRN NN YTRI, ZIRICONI

V TNH CHT QUANG CA CHNG

Chuyn ngnh: Vt liu quang hc, quang in tv quang tM s: 62. 44. 50. 05

TM TT LUN N TIN S KHOA HC VT LIU

H NI - 2011


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Cng trnh c hon thnh ti: Phng Quang hain t,Vin Khoa hc Vt liu, Vin Khoa hc v Cng ngh Vit

Nam.

Ngi hng dn khoa hc:

1. PGS.TS. L Quc Minh

2. PGS. TS. Trn Kim Anh

Lun n sc bo v trc Hi ng chm lun n cpVin hp ti: Vin Khoa hc Vt liu, Vin Khoa hc vCng ngh Vit Nam

vo hi gi ngy thng nm 2011.

C th tm hiu lun n ti thvin:- Th vin Vin Khoa hc v Cng ngh Vit Nam

- Th vin Vin Khoa hc Vt liu


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MU

Hin nay c rt nhiu loi vt liu nano cu trc khc nhau c quantm nghin cu. Trong , cc cu trc nano thp chiu da trn cc hpcht ca oxi vi kim loi ang l mi quan tm c bit ca nhiu nhmnghin cu trn th gii. Vit Nam, cc loi vt liu nano cng cnhiu nhm quan tm nghin cu t cui nhng nm 1990 v t cnhng thnh tu ng k. in hnh nh cc nghin cu v cc xit nano(ZnO, ZnS, TiO2)/chm lng t bn dn (AIIIBV, AIIBVI) ng dng trongquang in t, y sinh v chiu sng rn; cc ht cu nano SiO2ng dngthng tin quang hc; cc ht xit st nano ng dng trong x l mi

trng, iu tr v chun on bnh; cc ht nano Y2O3 pha tp t himng dng trong quang in t, nh du hunh quang y sinh v bo mt

Trong Y2O3 v ZrO2c bit n nh l hai nn cbn to racc vt liu/linh kin pht quang cht lng cao, c tn s dao ng

phonon thp, c bn nhit, bn chc cao, n nh v rt thn thinvi mi trng. Ngoi ra chng u c th kt hp tt vi LED to racc phosphor mu pht quang ng dng trong chiu sng; vt liu chuyn

ha nng lng s dng cho pin mt tri; vt liu pht quang chuyn ingc ng dng trong y sinh

Trn csk tha cc kt qu nghin cu ca tp th khoa hc v vtliu nano quang in t. Kt hp vi cc phn tch nh gi kt qutc ca nhiu nhm nghin cu trn th gii v trong nc v vt liunano cu trc thp chiu ng dng trong quang in t, quang t v y sinh.Chng ti chn ti Nghin cu ch to vt liu nano thp chiu trnnn ytri, ziriconi v tnh cht quang ca chng tp trung nghin cuv gii quyt mt s vn lin quan n cng ngh ch to, cu trc vtnh cht ha l cng nh mi quan h gia tnh cht quang v cu to cavt liu, c bit di gc ca vt liu nano.

ti tp trung gii quyt mt s vn sau:

- Xy dng quy trnh ch to c iu khin v kch thc v hnh dng

ca cc cu trc nano thp chiu (ht, l, dy, thanh, ng nano) nhmong mun trn cc h vt liu tinh khit v pha tp cc ion t himnn ytri v ziriconi vi lp li cao, hiu sut hnh thnh tng loi


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sn phm ring bit ln. T nghin cu mi lin h gia cu trc vtnh cht ha l ca h vt liu ny.

- Nghin cu tnh cht hunh quang, hunh quang truyn nng lng vhunh quang chuyn i ngc i vi cc hp cht pht quang chat him cu trc thp chiu.

ngha khoa hc v thc tin ca lun n: Kim sot c cc iukin cng ngh, ch to thnh cng tng dng cu trc nano thp chiukhc nhau (ht, dy, thanh, ng nano tit din trn/lc gic) nh mongmun trn cc hp cht Y(OH)3, Y2O3; Y(OH)3/Y2O3:(Eu

3+, Tb3+). Ch to

thnh cng cc ht nano ZrO2/ZrO2:RE

3+

(Eu,/Tb; Er,/Yb) kch thc 5-15nm vi hiu sut hnh thnh ln, phn b kch thc hp v lp li cao.Nghin cu nh hng ca iu kin cng ngh (khun mm, nhit phn ng/x l, p sut, vi sng, nng pha tp) n qu trnh hnhthnh, thnh phn pha v kch thc ca cc ht nano trn nn ZrO2. Xcnh c bc sng kch thch ph hp; nng /t l nng pha tp ccion t him trn mng nn Y2O3/ZrO2 ti u cc cu trc nano thpchiu pht quang mnh nht. Quan st thy du hiu truyn nng lng

ca ion Tb3+ sang cho ion Eu3+ trn ph hunh quang c hai nn Y2O3 vZrO2. Nghin cu v gii thch cch pht quang chuyn i ngc ivi cc mu ht nano ZrO2:Er

3+/,Yb3+. Cc kt qut c ca lun nm ra kh nng ch to cc vt liu nano c th iu khin c kchthc v hnh thi hc c ng nht cao ng dng trong cng nghchiu sng, vt liu quang t v lnh vc y sinh.

Lun n c h trv tin hnh trong khun kh ca mt s tinghin cu cbn trng im v ti nghin cu hp tc quc t viVin Vt l p sut cao, Vin Hn lm khoa hc Ba Lan. Lun n gm150 trang (phn mu, 5 chng ni dung vi 76 hnh v, 27 bng

biu, phn kt lun, danh mc cc cng trnh cng b, ph lc v tiliu tham kho). Cc kt qu chnh ca lun n c cng b trong12 cng trnh (06 bi trn tp ch quc t, 03 bi bo co ti Hi nghquc t, 03 bi trong tuyn tp bo co ti Hi ngh Hi ngh Vt l

cht rn v Khoa hc Vt liu ton quc) v 12 cng trnh khc c linquan.


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CHNG 1TNG QUAN V VT LIU NANO CU TRC THP CHIU

1.1.Mu1.2.Khi nim v vt liu v cng ngh nano

Vt liu nano l vt liu m cu trc cbn cu thnh nn n ckch thc nm thang nano. Hu ht cc tnh cht ca vt liu nanou ph thuc vo tnh cht v kch thc ca cc vin gch cbnto nn chng, tc l ph thuc vo tnh cht ca cc qu trnh vt lxy ra thang kch thc in hnh ca nguyn t v phn t.

1.3. Cc tnh cht c trng ca vt liu nano

Cc tnh cht c trng cho bn cht ca vt liu nh: hng sinmi, im nng chy, chit sut cng c th b thay i khi gim kchthc xung thang nano. Ngoi ra cn c nhiu tnh cht c trngkhc ca vt liu nh: hot tnh b mt, din tch b mt; cc tnh chtnhit, in, t, quang hc, chc, ha hc thm ch c sinh hc ca

vt liu cng b thay i khi gim kch thc.

1.4. Phn loi vt liu nano

Qu trnh tng hp cc cu trc nano khc nhau nh ht, thanh,dy, ng hay cc cu trc nano k d vi sng u v kch thc,hnh dng v pha tinh thang c t p trung nghin cu. Theo ,nhiu h vt liu nano mi vi nhng mc ch ng dng khc nhau

c to ra.1.5. Xu hng ch to vt liu nano

Hin nay c hai cch ch to vt liu nano l ch to theo kiu top-down v bottom-up. So vi cch th nht (top-down) ch yu s dngcc phng php vt l c thng mi ha trong cc ng dngcng nghip vi cc thit b hin i, t tin th cch bottom-up ch

yu s dng cc phng php ha hc lp ghp cc n v nguynt/phn t thu c cc dng cu trc nano c hnh thi hc tt, tnhng nht cao v khng i hi cc thit b hin i.


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1.6. Hunh quang ca cc hp cht t him cu trc nano

1.6.1.c im chung ca cc nguyn tt him

Tt c cc nguyn tt him thuc nhm lantanoit u c lp int 4f cha lp y. Tnh cht quang ca cc ion t him ch yu linquan n chuyn di ca in t 4f. Ngoi ra, cc nguyn tt himc kh nng hp th v pht x nh sng trong di bc sng hp, thigian sng trng thi gi bn ln, hiu sut lng t cao. Do vychng c vai tr quan trng trong lnh vc linh kin in t, thng tinquang hc v y sinh.

1.6.2. Cc qu trnh pht quang ca hp chtt him

i vi mt h pht quang cha cc hp cht t him, c hai qutrnh hunh quang chnh xy ra bao gm: bc x kch thch c hpth trc tip bi tm kch hot v bc x kch thch b hp th bi ccion hoc nhm cc ion khc (hnh 1.3).

Hnh 1.3: S mc nng lng ca qu trnh bc x kch thch: (a)hp th trc tip v (b) hp th bi cc ion hoc nhm cc ion khc.

1.6.3. Trin vngng dng v tnh hnh nghin cu ca mt svt liupht quang cha t him

Qu trnh ch to v nghin cu tnh cht quang hc ca cc vtliu nano thp chiu cha cc ion t him trn nn hp cht cha Y3+,Zr3+, Zn3+ ang l mt trong nhng hng nghin cu c nhiunh khoa hc trong v ngoi nc quan tm. Chng ha hn nhiu lnhvc ng dng mi trong khoa hc v i sng nh: xc tc, quang in

t, quang t, ch to cc vt liu composit, cht mu thn thin vi mitrng, ch to cc linh kin nano, cc sensor nano hay hunh quang ysinh v nh du sinh hc.


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CHNG 2

LA CHN PHNG PHP THC NGHIM CH TO V

KHO ST VT LIU NANO CU TRC THP CHIU2.1. La chn phng php ch to vt liu nano cu trc thp

chiu

Hin nay c hai phng php ch to vt liu nano cu trc thpchiu vi cc dng th hnh khc nhau (ht, dy, thanh, ng) l

phng php khun cng (khun c ch to sn) v phng php

khun mm (khun tan trong nc/dung mi phn cc v c nhhnh trong qu trnh phn ng).

Trong lun n ny, chng ti s dng phng php khun mmvi hai loi khun l DEG v PEG ch to c iu khin cc dngcu trc nano thp chiu khc nhau (ht, dy, thanh, ng) nh mongmun trn cc hp cht t him nn ytri v ziriconi.

2.2.Cc thit b sdng nghin cu cu trc v tnh cht cacc vt liu nanocu trc thp chiu

Cu trc v tnh cht ca cc cu trc nano thp chiu c tinhnh nghin cu trn cc h thit b sau:

- Knh hin vi in t: FESEM S-4800, Hitachi/SEM - LEO 1530.

- Knh hin vi in t truyn qua (TEM - JEM 2010, JEOL) v

(TEM - JEM 1010, JEOL).- H nhiu x k tia X: D5000 (SIEMENS) v PW3710 (Philips).

- H phn tch nhit vi sai DTA v phn tch nhit trng lng TGA.

- Ho ph hng ngoi (FTIR IMPAC 410).

- H o hunh quang: 2300i (Action), u thu CCD pixis 256

(Action); iHR550 (Jobin-Yvon), u thu CCD Synapse; THR 1000,u thu R928, R406; Ocean Optics SD2000, u thu CCD.


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CHNG 3

CH TO, CU TRC V TNH CHT CA

VT LIU NANO THP CHIU TRN NN YTRI

3.1. Mu

Chng ny ch yu trnh by cc kt qu t c ca lun ntrn c snghin cu cu trc v tnh cht ca cc vt liu nano thpchiu trn nn ytri bao gm: cc ht keo nano NaYF4:Er

3+/,Yb3+ ccphin, dy, thanh, ng nano Y(OH)3; Y2O3 v Y(OH)3/Y2O3 pha tp,ng pha t p cc ion t him (Eu3+, Tb3+); cc ht nanoY2O3:Eu

3+,Tb3+T, a ra cc gii php v quy trnh ch to tiu cho tng dng cu trc nano thp chiu c th nhm hng ti ccng dng trong lnh vc quang t, quang in t v y sinh.

3.2. Qu trnh hnh thnh cc ht keo nano NaYF4:Er3+, Yb3+

Cc ht keo nano NaYF4:Er3+/,Yb3+ ng knh t 10-30 nm, c

dng a din v c kh nng phn tn tt trong nc/dung mi hu cc ch to theo phng php khun mm p sut kh quyn (quytrnh 1, mc 2.1.4.1) (hnh 3.2b, 3.3b).

Hnh 3.3a:nh TEM ca cc htkeo nano NaYF4:1%Er

3+ chtotrong mi trng bnh phn ngh, lu lng kh Ar thi qua l

0,4 (lt/pht).

3.3.Qu trnh hnh thnh cc cu trc nano mt chiu trn nn ytri

3.3.1.nh hng ca nhit phn ngNhit phn ng l yu t quan trng nh hng n qu trnh

hnh thnh v pht trin ca cc cu trc nano mt chiu trn nn ytri.Cc dng cu trc nano mt chiu khc nhau ca Y(OH)3c ch totheo quy trnh 2 cc nhit t 120 n 200oC trong 24h, dng khun


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mm PEG 4000. iu kin ti u to c cc dy, thanh, ng nanotit din trn v ng nano tit din lc gic ln lt l 160-170, 190,195 v 200oC (hnh 3.6a; 3.8c; 3.9b; 3.9d, bng 3.1).

nh FESEM ca:Cc dy/thanh

nano Y(OH)3 chto 160oC, 24h

(hnh 3.6a) v

190oC, 24h (hnh

3.8c);

Cc ng nanoY(OH)3 tit dintrn/tit din lcgic chto

195oC, 24h (hnh

3.9b) v 200oC,

24h (hnh 3.9d)

(hnh 3.6a) (hnh 3.8c)

Hnh 3.9b Hnh 3.9dBng 3.1: Sph thuc gia cc dng cu trc khc nhau ca Y(OH)3vo nhit phn ng (thi gian phn ng 24h).

3.3.2.nh hng ca thi gian phn ng


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Cc kt qu thu c cho thy, thi gian phn ng nh hng nqu trnh hnh thnh v pht trin ca cc cu trc nano thp chiu trnnn ytri. Nu thi gian phn ng ngn (< 24h), hiu sut hnh thnh cc

cu trc mt chiu nh, ngc li thi gian phn ng qu di (> 24h)th cc cu trc nano mt chiu li b ph v.

iu kin ti u tng hp c cc ng nano Y(OH)3:5%Eu3+

(ng knh ngoi 100-250 nm, ng knh trong 50-100 nm v chiudi 4-5 m) vi hiu sut hnh thnh sn phm ln (trn 90%) l 200oCtrong 24h, dng khun mm PEG 4000 (hnh 3.15b).

Hnh 3.15b:nh FESEM ca muY(OH)3:5% Eu

3+ chto theo quytrnh 2 (mc 2.1.4.2) 200oC

trong 24h, khun mm PEG 4000.

3.3.3. nh hng ca cc loi khun mm khc nhauKhi dng khun mm l cc lin kt oliglome c trng lng phn

t nh (DEG, Mw=106), chng ti thu c cc ht nano ta cu ngu, ng knh khong 5 nm vi phn b kch thc h p (hnh3.17a). Tuy nhin, nu dng khun mm l cc lin kt polime vitrng lng phn t ln hn (PEG, Mw=4000-20000) cng iu kinth sn phm thu c li l cc cu trc nano mt chiu nh dy,

thanh, ng nano (hnh 3.17b).Hnh 3.17: (a)nh

TEM ca cc htnano ta cu Y2O3(khun mm DEGv (b) nh FESEM

ca thanh nano

Y(OH)3 (khun mmPEG 4000) chto190oC.


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3.4.Qu trnh hnh thnh cc ht nano Y2O3:Eu3+p sut cao

Mc d cc th nghim u c thc hin trong bnh kn vi thnh

phn mui tin cht, nng , th tch dung dch phn ng l nh nhau.Tuy nhin p sut th p (1-2at) v gia nhit bng t nng thngthng t ngoi vo, chng ti ch yu thu c cc cu trc nano mtchiu trn nn Y(OH)3. Trong khi cc th nghim p sut cao (55at)v gia nhit bng vi sng tn s 2450 Hz 315oC li to ra cc ht nanokch thc 5-15 nm trn nn cc hp cht dng xit (hnh 3.19).

Hnh 3.19 : (b)nh nhiu

xin tv (c)nhTEM ca ht nanoY2O3:5%Eu

3+ chto 315oC, 55at, 35 pht, gia

nhit bng vi sng, khunmm DEG.

Hnh 3.19b Hnh 3.19c

3.5.

Cc php o phn tch nhit TDA v TGACc s liu thu c trn ng phn tch nhit DTA cho thy, c

ba nh thu nhit (90, 305, 443oC) v mt nh pht nhit mnh(247oC), (hnh 3.20).

Hnh 3.20:ngcong phn tch nhit

DTA v TGA ca ng

nano Y(OH)3 tit dinlc gic ch to 200oC trong 24h.

Chng ti cho rng, nh thu nhit 90oC l do qu trnh bay hica nc v cc dung mi hu c, tip theo l phn ng phn hy cchp cht hyroxit chuyn thnh cc hp cht dng oxit ti cc nhit 305 v 443oC. Trong , 305oC l khong nhit xy ra qu trnh

phn hy Y(OH)3thnh Y2-xO3(OH)x v 443o

C l khong nhit xyra qu trnh phn hy phc gi bn gia Y(OH)3 v PEG thnh Y2O3;CO v hi nc.


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T cc kt qu thu c, chng ti tm ra quy trnh x l nhitti u (sao cho cc thanh, ng nano Y(OH)3/Y(OH)3:Eu

3+/,Tb3+ t b ntgy v co ngt v kch thc) nh sau: nhit 700-900oC vi tc

nng v h nhit l 5 oC/pht v n nh trong 2 gi.3.6.Pha tinh th ca cc cu trc nano mt trn nn Y(OH)3

Cc kt qu nghin cu v cu trc pha tinh th ca cc cu trcnano mt chiu trn nn Y(OH)3 ti cc nhit phn ng khc nhauthu c cho thy: 160oC, mi bt xut hin cc mm tinh th cutrc pha lc gic mc trn nn v nh hnh. Khi tng nhit phn

ng t 170 - 200

o

C, sn phm thu c c cu trc pha lc gic(P63/m), cc vch nhiu x sc nt hn, t l cng cc vch nhiux trn nhiu tng v khng thy xut hin cc vch l (hnh 3.21).

20 30 40 50 60 70

200oC

190oC

180oC

170oC

131

2023

10

112

220

102

211

300

Cng(.v.t.)

2 ()

210

201

111

200

101

110

100

Hnh 3.21: Gin nhiu x tiaX ca mu Y(OH)3 chto theoquy trnh 2 (mc 2.1.4.2) 170-200oC trong 24h, khun mm

PEG 4000.

Chng ti cng pht hin thy hin tng mrng vch trn gin XRD cc mu pha tp t him, chng t cc ion t him ng vaitr km hm s pht trin ca cc tinh th nano (hnh 3.24).

Hnh 3.24 : Gin XRD ca cc ng nano: (a) Y2O3:3, 5 v7%Eu3+ (ng 1-3); (b) Y2O3 ng pha tp Eu3+& Tb3+ ti cc tl

nng Eu3+/Tb3+: 3/1, 3,5/1, 4/1, 5/1 v 5/1,25 (ng 1-5).


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3.7. Ph hp th hng ngoi khai trin Fourier ca cc thanh, ngnano Y(OH)3, Y2O3

Cc kt quo ph hp th hng ngoi thu c cc mu thanhv ng nano Y(OH)3 kh ging nhau. im khc bit duy nht l nhsc nt ng vi cc dao ng ko cng cbn ca nhm lin kt OH- s sng 3612 cm-1 ch yu xut hin trn cc mu ng nano ( hp thkhong 65%), trong khi cc mu thanh nano hp th ch khong15%. iu ny chng t cc thanh c s lng cc phn t nc hpth trn b mt thp hn so vi cc ng nano Y(OH)3.

3.8.

C ch hnh thnh cc dng cu trc nano mt chiu caRE(OH)3

Qua tt c cc kt qu nghin cu, c th gii thch cch hnh thnhcc cu trc nano mt chiu ca Y(OH)3 nh sau: Khi khun mm(PEG) c ha tan vo trong dung dch tin cht cha cc mui thim, khun s lin kt vi cc ion t him v to phc gi bn (PEG-RE(NO3)3) vi hng s tinh th ln. Khi cho thm NaOH vo hn hp

dung dch, phc gi bn dn dn b ho tan v phi t ban u cthay th bng phi t (OH-) mnh hn.

PEG - RE(NO3)3 n RE3+ + 3 NO3

-+ PEG

RE3++ 3 OH- RE(OH)3

Qu trnh to nhn ca cc hyroxit t him ph thuc mnh vonhit phn ng. Nhit phn ng tng ko theo p sut hi bo hatng l nguyn nhn dn n s tng v s lng cc thanh/ng nanoRE(OH)3 trong ton b sn phm ch to. Nu s to thnh cc ngnano c xt nh l mt phn ng ng hc c iu khin v qu trnh

pht trin ca cc ng nano cng c coi l phn ng khuch tn ciu khin th tc khuch tn theo chiu song song s quyt nhdin mo cui cng ca sn phm. Khi qu trnh khuch tn xy rachm, s to ra cc thanh nano, ngc li nu qu trnh khuch tn xyra nhanh, s to thnh cc ng nano. Khi nhit phn ng tng t 120

- 200o

C, cc cu trc nano mt chiu hnh thnh ln lt l: v nhhnh, to dy, l, thanh v cui cng l ng nano.


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CHNG 4CH TO, CU TRC V TNH CHT

CA VT LIU NANO THP CHIU TRN NN ZIRICONI

4.1. Mu

Cc vt liu nano pht quang trn nn ZrO2 l h vt liu ha hnnhiu ng dng mi trong cng ngh quang t. Vi nng lng phononthp, bn ha l cao, c kh nng to c cc vt liu/linh kin

pht quang trng thi rn (gm quang hc, cc lng knh quang hctrong sut), c th hot ng trong cc mi trng khc nghit cc

vt liu pht quang trn nn ZrO2ang thu ht s quan tm ca nhiunhm nghin cu trn th gii.

4.2. nh hng ca nhit phn ng v khun mm n qutrnh hnh thnh cc ht nano ZrO2 v ZrO2:RE

3+

Cc nghin cu v nh hng ca nhit phn ng v khunmm n cu trc v thnh phn pha tinh th thu c t gin nhiu

x tia X cho thy, nhit phn ng nh hng ln n cu trc, kttinh, thnh phn pha v qu trnh hnh thnh cc ht nano (hnh 4.1) cnkhun mm nh hng n thnh phn pha tinh th, gp phn tng tnhng u v gim kch thc, phn b kch thc ca cc ht nanoto thnh (hnh 4.3) .

Hnh 4.1

20 30 40 50 60 70 800

1000

2000

3000

4000

3

2

1

(220)

(202)

(211)

(112)

(110)

(101)

Cng(.v.t.)

2 ()

Hnh 4.3

20 30 40 50 60 70 800

1000

2000

3000

T

M

1

2 (220)

(202)

(211)

(112)

(110)

(101)

Cng(.v.t.

)

2 ()

Gin nhiu x tia X ca bt nano ZrO2:5%Eu3+ chto :

Hnh 4.1: 190, 200 v 315oC (ng 1-3) v Hnh 4.3: 315oC, 55at: (ng 1_ khng dng khun mm; ng 2_ dng DEG).


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4.3.nh hng ca nng pha tp

Cc kt qu nghin cu vnh hng ca nng pha tp cc ion

t him vo thnh phn pha, cu trc tinh th cng nh kch thc htv kch thc ht trung bnh thu c cho thy, khi tng nng phatp (t 0,1-15%), kch thc ht gim v c s chuyn t hn hp phat gic v sang n pha t gic. Trong , t l cng nh nhiu xcc i i din cho pha t gic (tng ng vi mt (101)) so vi phan t (tng ng vi mt (-111)) tng khi tng nng pha tp cc iont him. c bit l cc mu c nng pha tp t 5% mol trln,sn phm thu c c pha tinh th dng n pha t gic (hnh 4.5).

Hnh 4.5: Gin XRD ca mu: (a): ZrO2:Er3+

v (b): ZrO2:Yb

3+

ti cc nng 0-15% mol, 315oC trong 35 pht, 55at (DEG).

Cc tnh ton kch thc ht trung bnh theo cng thc Scherrer vcc php o din tch b mt (BET) trn t khi cho thy, cc ht nanothu c c kch thc trung bnh ca 5-15 nm (hnh 4.6). Kt qu nyhon ton ph hp vi kt qu chp nh TEM (hnh 4.7a).

Hnh 4.6:nh hng ca nng pha tp ccion t him n kch thc ht trung bnh ca

ZrO2:Er3+

/Yb3+

tnh theo: (a) cng thcScherrer; (b) din tch bmt

Hnh 4.7a:nhTEM ca mu

ZrO2:1%Er3+


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16

4.4. nh hng ca cch gia nhit n hnh dng v cu trc phatinh th ca cc ht nano ZrO2 v ZrO2:RE

3+

Cch gia nhit cng l mt trong nhng yu tnh hng n hnhdng v cu trc pha tinh th ca sn phm. Cc kt qu thu c chothy, khi gia nhit bng vi sng p sut cao (10-55at) sn phm thuc l cc ht nano ng u, tinh th dng hn h p pha t gic vn t, trong khi gia nhit bng t nng t ngoi vo trn h phn ngthy nhit (autoclave) di p sut thp (1-2at), sn phm thu c lcc cu trc nano dng con nhng (hnh 4.9) vi pha tinh th dng

baddeleyite (s th 37-1484) .

Hnh 4.9:nh FESEM ca mu ZrO2:1%Er3+ chto 200oC

trong: (a) 20h, gia nhit bng autoclave theo quy trnh 2 v (b)trong 1h, gia nhit bng vi sngtn s2450 Hz theo quy trnh 3.

4.5. nh hng ca cc qu trnh xl nhit

Kt qu nghin cu s bin i v cu trc pha tinh th v kchthc ht thu c cho thy, khi tng nhit x l mu t 70 n1200oC tinh th chuyn t dng hn hp pha t gic v n t thnh

n pha n t. c bit l mu x l nhit 1200o

C trong 2h, ton bsn phm chuyn sang cu trc pha n t (hnh 4.11).

20 30 40 50 600

5000

10000

15000(

020)

(110)

(111

)

(-111)

Cng(.v.t.)

2()

ZrO2: 1 %Er

3+

M+T

M

5

6

4

3

21

Hnh 4.11: Gin XRD ca muZrO2 :1% Er

3+ xl nhit: 70oC(ng 1); 600oC,1h (ng 2);800oC, 1h (ng 3); 1000oC, 1h(ng 4); 1200oC, 1h (ng 5)v 1200oC, 2h (ng 6).


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17

4.6.Cch hnh thnh cc ht nano ZrO2

Khc vi cc tin cht i hon ton t mui nh cc mui t him

(RE(NO3)3.nH2O), khi tan trong nc ZrOCl2.8H2O khng phn lithnh Zr4+ v Cl- m tn ti di dng phc cht sau:

ZrOCl2. nH2O + H2O ZrOOH+ + HCl

Cc phn t t lp rp ca khun mm sau khi ha tan vo hn hpdung dch phn ng s lin kt vi nhau v to phc gi bn gia phcca ZrOCl2.8H2O; cc ion kim loi tin cht (Er

3+, Yb3+, Eu3+, Tb3+) v

cc lin kt (C-O-C) lun phin.Khi phn ng thc hin p sut thp (1-2at) v gia nhit ng tnh

bng t nng t ngoi vo, p sut hi hu nh khng i trong sutqu trnh phn ng, cc tm pht trin cng chuyn ng rt t. Kt qul hnh thnh cc cu trc nano dng con nhng, ng knh 40-50 nm,chiu di 100-150 nm.

Di tc dng ca vi sng tn s 2450 Hz, cc phn t c phn cc cao (OH-, cc lin kt phc cht...) trong dung dch phn ngs h p th mnh nng lng ca sng in t trong khi cc lin ktng ha tr nh C-C, C-H li khng hp th nng lng . Kt qu ltrong ton b dung dch phn ng ch c mt s vng b kch thch trctip v nng ln do chu nh hng ca vi sng.

Cch gia nhit t trong lng mi tm hp th v pht x nhit ny

s gy nn hin tng nng cc b trong lng cc tm pht trin. Ccphn ng t gy hay kt hp ch xy ra i vi cc tm pht trin chacc ion Zr4+, RE3+, OH- m khng xy ra i vi cc lin kt C-O-Clun phin ca khun mm. Ni cch khc, khun mm hu nh khngnh hng n hnh dng ca sn phm thu c. Chnh v vy mdi tc dng ca vi sng p sut cao (55at), cc ht nano thu crt ng u, c kch thc nh (5-15 nm), hiu sut hnh thnh cao v

c kh nng pha tp vi nng ln.


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18

CHNG 5TNH CHT HUNH QUANG CA VT LIU NANO

CU TRC THP CHIU TRN NN YTRI V ZIRICONI

5.1. Mu

C hai nn Y2O3 v ZrO2 u c nng lng phonon th p (nnglng phonon ca Y2O3 l 600 cm

-1 v ca ZrO2 dao ng t 270-470cm-1), bn nhit v chc cao, thn thin vi mi trng V vyn rt ph hp pht trin cc ng dng trong cc lnh vc quang int, quang t v y sinh.

Chng ny ch yu trnh by cc nghin cu chi tit v mi quanh gia nng cc ion t him, nhit mu n tnh cht quangca cc cu trc nano thp chiu trn nn ytri, ziriconi pha tp/ng phatp cc ion t him (Eu3+/,Tb3+, Er3+/,Yb3+).

5.2.Tnh cht quang ca cc cu trc nano thp chiu trn nn ytri5.2.1. Phkch thch hunh quang ca cc ht keo nano Y2O3:5%Eu

3+

Cc kt quo ph kch thch hunh quang trn mu Y2O3:5% Eu

3+

thu c cho thy, mu cng hng mnh ti cc vch kch thch 327,363, 382, 394, 467 v 534 nm ln lt tng ng vi cc nhy mcin t t trng thi cbn 7F0 ln trng thi kch thch

5H3,5D4,

5Gj,5L6,

5D2 v5D1 (hnh 5.1).

300 350 400 450 500 550 600

0.0

2.0x107

4.0x107

6.0x107

8.0x107

5D1

5D2

5L6

5Gj

5D4

5H3

Cng@6

11nm(.v.t.

)

Bc sng kch thch (nm)

414

417

em

= 611 nm

534

467394

382

363327

Hnh 5.1: Phkch thch hunhquang ca mu Y2O3:5% Eu

3+

Trn csph kch thch hunh quang kt hp vi tnh hnh thit

bo thc t, chng ti la chn cc ngun kch thch bc sng325 v 337 nm.5.2.2. Phhunh quang ca cc ng nano Y(OH)3:Eu

3+


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19

Cc kt qu o ph hunh quang thu c cho thy, cng hunh quang ph thuc vo cu trc v hnh dng ca cc cu trc nanomt chiu. C th l cc mu phin nano hay cc mu gm nhiu dng

cu trc nano khc nhau c cng hunh quang nh hn so vi ccng nano Y(OH)3:5%Eu

3+ (hnh 5.2a).

Hnh 5.2a: Phhunh quangngnano Y(OH)3:5% Eu

3+ ch totheo quy trnh 2 200oC trong

thi gian 6-32h, (exc=325nm).

Cc ng nano Y(OH)3:5%Eu3+ ch yu pht quang vng bc

sng 690 nm tng ng vi dch chuyn lng cc in (5D0-7F4), c

bit l cc mu c t lng ln. Ngoi ra cc mu cn pht quang trongvng bc sng 590, 615, 644 v 660 nm tng ng vi cc chuyn di5D0 -

7F1,5D0 -

7F2 v5D0 -

7F3 ca ion Eu3+ vi cng nh hn.

5.2.3. Phhunh quang ca mu Y2O3:Eu3+ cu trc mt chiu

Cc cu trc nano mt chiu trn nn xit (Y2O3:5% Eu3+) ch yu

pht quang mnh trong vng bc sng 610 nm, tng ng vi chuyndi 5D0 -

7F2. Cc mu Y2O3:5% Eu3+ c s lng ng hnh thnh nhiu

s pht quang tt hn so vi cc mu Y2O3:5% Eu3+ cu trc thp chiu

khc cng loi. (hnh 5.3).

450 500 550 600 650 700 750

0

5000

10000

15000

Cng(.v.t.

)

24h18h

12h6h

5Do-7F

4

5Do-7F

2

5Do-7F

1

Bc sng (nm)

nh 5.3: Ph hunh quang camu Y2O3:5% Eu

3+ ch to theoquy trnh 2 200oC trong thi gian6-32h v nhit700oC trong 2h,tc nng v h nhit l5oC/pht (exc=325nm).

5.2.4. Phhunh quang ca cc ht nano Y2O3:Eu3+


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20

Khc vi cc cutrc mt chiu, cc ht

nano Y2O3:Eu

3+

ch yu pht quang mnh trongvng bc sng 619 nmtng ng vi chuyndi lng cc in 5D0 -7F2 ca ion Eu

3+ (hnh5.5).

Hnh 5.5a: Phhunh quangca cc ht nano

Y2O3:3; 5 v 7%Eu3+ ch totheo quy trnh 3

315oC-55 attrong 35 pht,

khun mmDEG.

5.2.5. Phhunh quang ca mu Y2O3:Eu3+&Tb3+ cu trc nano mtchiu

Kt quo ph hunh quang khi mu c kch thch bc sng325 nm thu c cho thy, c s tng vng pht x bc sng 610nm tng ng vi chuyn di 5D0 -

7F2 ca ion Eu3+ v gim vng pht

xbc sng 544 nm tng ng vi chuyn di 5D4-7F5 ca ion Tb

3+trn cc mu ng pha tp Eu3+& Tb3+ (hnh 5.6).

Hnh 5.6: Ph hunhquang ca mu Y2O3

pha: (a) 5Eu3+;

4Eu3+&1Tb3+;

5Eu3+&1,25Tb3+;

(b)1,25Tb3+ ,(c) phsau khi chun hatheo cng pht

x ca ion Eu3+.

5.3. Tnh cht quang ca cc ht keo nano NaYF4:Er3+

Cc ht keo nano NaYF4:1% Er3+ sau khi hp th nng lng ca

photon kch thch vng hng ngoi bc sng 940 nm s pht hunhquang chuyn i ngc trong vng kh kin bc sng 500-700 nm

tng ng vi cc chuyn di2

H11/2 ,4

S3/2 &4

F9/2 v4

I15/2 ca ion Er3+

.


21/28

21

450 500 550 600 650 700 7500

5000

10000

15000

NaYF4: 1% Er3+

exc

=940 nm

2H11/2

, 4S3/2

- 4I15/2

4F

9/2-

4I

15/2

Cng(a.u)

Bc sng (nm)

Hnh 5.8: Phhunh quangchuyn i ngc ca mu

NaYF4:1% Er3+.

5.4. Tnh cht quang ca cc ht nano ZrO2:RE3+ (Eu3+, Tb3+,

Er3+, Yb3+)

5.4.1. Phhunh quang ca ht nano ZrO2:Eu3+

Khc vi cc ht/ng nano nn ytri, cc ht nano ZrO2:Eu3+ ch yu

pht quang trong vng bc sng 591 v 606 nm tng ng vi di phrng hn (hai vai ph ng vi hai chuyn di 5Do-

7F1 v5Do-

7F2 ccng gn nh tng ng nhau), (hnh 5.9).

550 600 650 700 750

0

20000

40000

60000

80000

Bc sng (nm)

Cng(.v.t.)

5Do-

7F4

5Do-7F1

5Do-7F2

ZrO2: 7% Eu

3+

ZrO2: 5% Eu

3+

ZrO2: 3% Eu

3+

exc

= 370 nm

Hnh 5.9: Ph hunh quangca cc ht nano ZrO

2pha

tp 3; 5 v 7% mol Eu3+ chto theo quy trnh 3 315oC,55 at, 35 pht, (exc=370 nm).

5.4.2. Phhunh quang ca ht nano ZrO2:Eu3+/ Tb3+

Cc ht nano ZrO2:Eu3+&Tb3+ c cng hunh quang ln hn so

vi cc mu ZrO2pha tp n l. T l mol gia Eu

3+

v Tb

3+

ti u mu pht hunh quang mnh nht l 5/1 (hnh 5.11).

500 550 600 650 700 750

0

40000

80000

120000

160000

Cng(.v.t.)

Bc sng (nm)

exc

= 370nm

(5)

(4)

(3)

(2)(1)

5Do-

7F2

(Eu3+)

5Do-

7F1

(Eu3+)

5D4 -

7F5

(Tb3+)

Hnh 5.11: Ph hunh quang camu ZrO2 pha t p: 1) 1Tb

3+; 2)

0.5Eu3+ &1Tb3+; 3) 3Eu3+&1Tb3+;

4) 5Eu3+; 5) 5Eu3+&1Tb3+chtotheo quy trnh 3 315oC, 55at

trong 35 pht, kch thch bcsng 370 nm


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22

Chng ti cho rng nguyn nhn dn n hin tng tng cng hunh quang vng bc sng 591 v 606 nm tng ng vi chuyndi 5Do-

7F1 v5Do-

7F2 l do s truyn nng lng gia c p ion

Eu3+/Tb3+.

5.4.3. Phhunh quang chuyn i ngc ca ZrO2:Er3+

Khi kch thch vng hng ngoi (830 nm), mu ch yu phtquang vng bc sng 545 v 561 nm tng ng vi chuyn di2H11/2 v

4S3/2 v4I15/2 ca ion Er

3+ (hnh 5.12). Trong khi nu kchthch 940 nm, mu li ch yu pht quang vng bc sng 660 nm

tng ng vi chuyn di 4F3/2 -4I15/2 ca ion Er3+ (hnh 5.13).Hnh 5.12

500 600 7000

50000

100000

Cng(.v.t.

)

Bc sng (nm)

*10

exc = 830 nm

(d)(c)

(b)(a)

Green

2H11/2

- 4I15/2

4S

3/2-

4I

15/2

Red

a- 1200oC, 1 h

b- 1000oC, 1 h

c- 600oC, 1 h

d- sy kh 70 oC

4F9/2

- 4I15/2

Hnh 5.13

Ph hunh quang chuyn i ngc ca mu: (hnh 5.12)ZrO2:1%Er

3+ x l nhit70; 600; 1000 v 1200oC trong 1h (exc=830 nm) v (hnh 5.13) ZrO2:1; 5 v 10%Er

3+ x l nhit1200oC,1h (exc= 940 nm).

Cch pht quang ca ion Er

3+

trn nn ZrO2c gii thch datrn gin cc mc nng lng ca Er3+ nh sau:

Cc ion Er3+ trng thi c bn sau khi h p th nng lng cangun kch bc sng 830 nm s nhy ln mc 1 (4I9/2). Ngay sau ,cc photon c cng bc sng bm s b kch tip v nhy ln mc 2(2H9/2). Ti y nguyn t c xu hng hi phc khng pht x v cctrng thi c nng lng thp hn (2H11/2 ,

4S3/2 &4F9/2) v cui cng l

hi phc pht xbc sng 545 nm, 561 nm & 660 nm ng vi ccchuyn di 2H11/2 -

4I15/2,4S3/2 -

4I15/2 v4F9/2 -

4I15/2.


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23

Ngc li, khi kch thch bc sng 940 nm, cc ion Er3+trngthi c bn nhn nng lng kch thch v nhy ln mc 4I11/2 (chkhng phi l mc 4I9/2 nhi vi trng hp kch 830 nm). Sau ,

cc photon c cng bc sng bm s b kch tip n mc 2 (4F7/2) vhi phc khng pht x v cc trng thi c nng lng thp hn (2H11/2, 4S3/2 &

4F9/2) v cui cng l hi phc pht x v mc4I15/2. y cc

in t ch yu hi phc khng pht x v mc 4F9/2 v sau pht xmu ng vi chuyn di 4F9/2

4I15/2.

5.4.4. Phhunh quang chuyn i ngc ca ZrO2:Er3+& Yb3+

Hnh 5.14 l ph hunh quang chuyn i ngc ca cc ht nanoZrO2:1% Er

3+ & 18% Yb3+ so snh vi ph pht quang chuyn ingc ca cc ht nano ZrO2:1% Er

3+ ( nhit 1200 oC- 1 h), kch bc sng 940 nm.

500 600 7000

100000

200000

300000

400000

(b)(a)

Bc sng (nm)

exc

= 940 nm

a- 1% Er3+& 18% Yb3+

b- 1% Er3+

4F9/2

- 4I15/2

(Red)

2H11/2

, 4S3/2

- 4I15/2

(Green)

Cng(.v.t.)

Hnh 5.14 : Ph hunh quang chuyn i ngc ca muZrO2:1%Er

3+ v mu ZrO2:1%Er3+&18%Yb3+ chto theo quy trnh

3 315oC, 55at, 35 pht, xl nhit1200oC, 1h, (exc= 940 nm).

Cc kt thu c chng t c sng gp ca ion tng nhy (Yb3+)vo qu trnh pht hunh quang chuyn i ngc ca cc muZrO2:Er

3+&Yb3+. C th l cng hunh quang ca muZrO2:1%Er

3+&18%Yb3+ ln gp 2,3 ln so vi mu ZrO2:1%Er3+.Khi

tng nng ca Yb3+

trong cc mu ZrO2 ng pha t p 1%Er3+

vYb3+, t l cng pht hunh quang chuyn i ngc gia vngGreen/Red gim.


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24

KT LUN

Lun n c nhng ng gp v khoa hc trong lnh vc nghin

cu v vt liu pht quang cha t him vi cc kt qu mi nh sau:

1. ch to thnh cng cc cu trc nano thp chiu khc nhau (ht,

dy, thanh, ng nano tit din trn v ng nano tit din lc gic) nn

ytri v ziriconi v tm c iu kin ch to ti u cho tng loi c

th. Cc cu trc nano thu c ng u, phn b kch thc hp, hiu

sut hnh thnh cc dng cu trc nano ln v qui trnh ch to c

lp li cao. c bit l bng cch kt hp gia khun mm v gia nhit

bng vi sng p sut cao, ch to thnh cng cc ht nano Y2O3,

ZrO2 kch thc nh (ng knh 5-15nm).

2. nghin cu chi tit nh hng ca qu trnh chuyn pha cu trc

n cng pht quang chuyn i ngc ca vt liu. C th s

chuyn pha t gic sang n t ng vai tr quyt nh trong vt liuZrO2 pha Er

3+. Cng pht x cc i ca mu ZrO2:1% Er3+ pha

n t tng gp khong 115 ln so vi pha t gic.

3. quan st thy s gia tng cng hunh quang chuyn i

ngc trn cc mu ng pha tp Yb3+ v Er3+. Cng hunh quang

ca cc mu ht nano ZrO2:1%Er3+&18%Yb3+ ln g p 2,3 ln so vi

mu ZrO2:1%Er3+. quan st thy tnh pht quang lc la trn ccmu ng pha tp. C th pht x ca mu mu xanh (545-561 nm) khi

kch thch bng bc sng 830 nm, v pht x mu (645-680 nm)

khi kch thch bc sng 940 nm.

4. pht hin thy hin tng gim kch thc ht vt liu nano lin

quan ti s km hm qu trnh hnh thnh v pht trin ca mm vt

liu bi cc ion t him dn n hn ch s ln ln ca kch thc ht.


25/28

25

Ngoi ra chng ti ln u tin quan st v khng nh s chuyn

ha t dng ng nano trn sang ng nano lc gic i vi h vt liu

nn ytri. tin hnh pha tp v ng pha tp cc ion t him nhEu3+, Tb3+, Er3+, Yb3+ nng cao to ra cc nanophosphor pht

quang c hiu ng pht quang ln, c bit thu c hiu ng truyn

nng lng v pht quang chuyn i ngc. kho st v phn tch

nh gi c ch hnh thnh cc vt liu cu trc nano thp chiu nn

ytri, cc cu trc nano ln lt hnh thnh c th l t v nh hnh

chuyn sang l, dy, thanh, ng tit din trn v ng tit din lc gic.C ch ny hon ton ngc vi c ch hnh thnh ca cc ng v

thanh xit titan. Vic tm ra cch hnh thnh cc vt liu cu trc nano

gp phn ng k vo vic ti u ha cng ngh ch to vt liu nano

thp chiu ca cc hp cht hyroxit khc nhau.

Cc kt qu nghin cu ny m ra mt kh nng ch to cc vt

liu nan iu khin c kch thc v hnh thi hc c ng nhtcao ng dng trong cng ngh chiu sng, vt liu quang t v y

sinh.


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26

DANH MC CC CNG TRNH CNG B

1. Lam Thi Kieu Giang, Opalinska A., Chudoba T., Benkowski K.,

Lojkowski W., Tran Kim Anh, Nguyen Thanh Binh and Le Quoc

Minh (2010), Preparation and Characterization of

ZrO2:Er3+,Yb3+ Nanoparticles by using High Pressure Assisted

Soft Template, Adv. Nat. Sci.: Nanosci. Nanotechnol. 1, ID

025008.

2. Le Quoc Minh, Tamio Endo, Tran Thu Huong, Nguyen Thanh

Huong, Lam Thi Kieu Giang, Le Dac Tuyen, Dinh Xuan Loc and

Tran Kim Anh (2010), Synthesis, Structures and Properties of

Emission Nanomaterials Based on Lanthanide Oxides and Mix

oxides, Transactions of the Materials Research Society of

Japan, 35, pp. 417-422.

3. Tran Kim Anh, Dinh Xuan Loc, Lam Thi Kieu Giang, Wieslaw

Strek and Le Quoc Minh (2009), Preparation, optical properties

of ZnO, ZnO:Al nanorods and Y(OH)3:Eu nanotube,Journal of

Physics :Conference Series, 146, ID 012001.

4. Tran Thu Huong, Nguyen Thanh Huong, Lam Thi Kieu Giang,

Tran Kim Anh, ojkowski W., and Le Quoc Minh (2009),

Preparation, characterization and optical properties of ZrO2:Er3+,

Yb3+ nanomaterials,Journal of Physics: Conference Series, 187,

ID 012082.


27/28

27

5. Tran Kim Anh, Paul Benalloul, Charles Barthou, Nguyen Vu,

Lam Thi Kieu Giang, and Le Quoc Minh (2007), Luminescence,

Energy Transfer and Up - Conversion Mechanisms of Y2O3Nanomaterials Doped with Eu, Tb, Tm, Er and Yb ions, Journal

of Nanomaterials, ID 48247.

6. Lam Thi Kieu Giang, Nguyen Vu, Dinh Xuan Loc, Man Hoai

Nam, Gyu-Chul Yi, Tran Kim Anh and Le Quoc Minh (2009),

Preparation and optical properties of one dimensional nano

hydroxides and oxides, Springer Physics and Engineering of

New Materials, pp. 87-93.

7. Lm Th Kiu Giang, Trn Kim Anh, Trn Thu Hng, Nguyn

Thanh Bnh, Witold ojkowski v L Quc Minh (2009), Tng

hp bt nanoZrO2:Eu3+,Tb3+ bng phng php khun mm

p sut cao v tnh cht hunh quang ca chng, Hi ngh Vt l

cht rn v Khoa hc Vt liu ton quc ln th VI (SPMS-

2009), pp. 626-629.

8. Le Quoc Minh, Lam Thi Kieu Giang, Tran Thu Huong, Le MinhAnh Tu, David Hui and Tran Kim Anh (2008), Nanomaterials

with low dimension structures from some lanthanides hydroxides

and oxides of Y, Tb, Gd, and Eu, Proceedings of International

Conference on Composite and NanoEngineering, Kunming,

China, pp. 391-394.


28/28

28

9. Lm Th Kiu Giang, Trn Kim Anh, L Quc Minh (2007), Ch

to v nghin cu tnh cht pht quang trong vt liu thanh v

ng nano Y(OH)3, Y2O3 pha t p Eu3+; Tb3+, Tuyn t p cc boco Hi ngh Vt l Cht rn ton quc ln th V, Nh xut bn

Khoa hc v k thut, H Ni, pp. 858-861.

10. Trn Thu Hng, Lm Th Kiu Giang, Trn Kim Anh, L Quc

Minh (2007), Chto, nghin cu tnh cht ca thanh, ng nano

Tb(OH)3 & Tb3O4, Tuyn tp cc bo co Hi ngh Vt l Cht

rn ton quc ln th V, Nh xut bn Khoa hc v k thut, H

Ni, pp. 1036-1039.

11. Lam Thi Kieu Giang, Tran Kim Anh, David Hui, Le Quoc Minh

(2007), Synthesis and construction of one dimensional

nanostructures of yttrium hydroxide Y(OH)3 by polyol mediated

method, Proceeding of fifteenth annual international conference

on composites/nano engineering, Hainan, China, pp. 490-491.

12. Lam Thi Kieu Giang, Tran Kim Anh, Le Quoc Minh (2006),

Formation of Ytrium hydroxide nanorods and nanotubes in

polyethylenglycol, Proc. of the 1st IWOFM 3rd IWONN

Conference, Halong, Vietnam, December 6-9, pp. 433-435.

dat hiem huynh quang

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