NGHIN CU TNG HP V IU CHNH KCH THC HT NANO NG TRONG H NC/PVP

L Thanh Tr1, Hong Th Ngc Mai1 1Chuyn Ngnh Cng Ngh Ha, Khoa CNH - TP, Trng i Hc Lc Hng.

Email: hoangngocmai2209@gmail.com

TM TT Dung dch keo nano ng c tng hp bng phng php kh ha hc trong h nc/PVP t ng (II) chloride dihydrate (CuCl2.2H2O) vi cht kh l Sodium borohydride (NaBH4) c s hin din ca cht hot ng b mt cetyl trimethylammonium bromide (CTAB), cht bo v polyvinyl pyrrolidone (PVP, Mw = 40.000 g/mol) v cht tr bo v axit ascorbic. Cc thng s nh hng ti kch thc ca cc ht nano ng c nghin cu. Hnh dng, cu trc v s phn b cc ht nano ng trong dung dch sau khi tng hp c phn tch bi ph UV Vis, knh hin vi in t truyn qua TEM v nhiu x XRD. Ht nano ng c tng hp vi thng s tt nht c kch thc trung bnh l 3 1 nm.

T kha: ht nano ng, phng php kh ha hc, axit ascobic, polyvinylpyrrolidone.

1. T VN Trong nhng nm gn y, vt liu kim loi nano nhn c s quan tm c bit ca cc nh khoa hc trong v ngoi nc bi nhng tnh cht u vit nh: tnh cht quang, tnh cht in, tnh cht t, tnh cht c, tnh cht xc tc [6]. Hin nay, nhiu ht nano c tng hp t cc kim loi qu nh vng, bc v platin mc d gi thnh ca chng cao. Tuy nhin, ng l mt kim loi y ha hn v c dn in cao, gi thnh r, c kh nng khng v dit c nhiu loi nm [2]. V vy, nano ng nhn c s ch ng k v tim nng ng dng ca chng [9]. Nano ng c tng hp bng nhiu phng php khc nhau nh: phn hy nhit [7], phng php polyol [3], kh ha hc [4], phng php bc x [5], nhit vi sng [8] Trong , phng php kh ha hc c s dng ph bin bi c nhiu u im c bit ti nh: thit b n gin, d thc hin, chi ph thp, c th iu chnh kch thc v hnh dng ca ht nano ng bng cc thng s thc nghim [1].

Trong phm vi bi bo ny, chng ti tin hnh nghin cu tng dung dch keo nano ng bng phng php kh ha hc. Qu trnh c thc hin bng phn ng kh CuCl2 trong dung mi nc, cht kh l sodium borohydride (NaBH4) c s hin din ca cht hot ng b mt cetyl trimethylammonium bromide (CTAB), cht bo v polyvinylpyrrolidone (PVP, Mw = 40.000g/mol) v cht tr bo v axit ascorbic. Phng php ny c u im l phn ng din ra nhanh, d thc hin, d dng iu chnh kch thc v hnh dng ca ht nano ng. Kch thc ht nano ng c iu chnh bi cc thng s nh nhit , nng cht kh, hm lng CTAB v axit ascorbic. 2. NGUYN LIU V PHNG PHP NGHIN CU 2.1. Nguyn liu Ha cht c dng cho qu trnh tng hp dung dch keo nano ng:

ng (II) chloride dihydrate (CuCl2.2H2O), sodium borohydride (NaBH4), axit ascorbic (C6H8O6), cetyl trimethylammonium bromide (C19H42BrN), nc ct v polyvinylpyrrolidone (PVP, Mw = 40.000g/mol).

2.2. Phng php nghin cu Ph UV-Vis xc nh nh hp thu cc i, dch chuyn ca cc nh hp thu cc i, t c th d on c kch thc ht nano ng trong dung dch sau qu trnh tng hp. Gin nhiu x XRD xc nh cu trc tinh th ca nano ng thu c. nh TEM xc nh hnh thi cu trc, kch thc v kt hp vi phn mm xc nh s phn b kch thc ht nano ng trong dung dch.

2.3. Tng hp dung dch keo nano ng Cn 0,2g PVP cho vo becher vi mt lng nc ct nh trc. Hn hp c khuy cho ti ng nht trn my khuy t gia nhit. Sau dung dch CuCl2 0,2M c nh lng thm vo dung dch polymer to hn hp. Tip theo thm vo hn hp mt lng dung dch axit ascorbic, CTAB nh trc v trn u trong 2 pht. Gia nhit hn hp n nhit phn ng, sau nh t t dung dch sodium borohydride thc hin phn ng. Khi phn ng kt thc, nhn bit s to thnh dung dch keo nano ng thu c c mu c trng c kim chng bng ph UV Vis, gin nhiu x XRD v nh TEM. 3. KT QU V BN LUN 3.1. Kt qu chp XRD

Kt qu t gin nhiu x XRD trn hnh 1 cho thy 3 nh c cng cao nht hon ton trng hp vi ph chun ca kim loi ng ti v tr cc gc 2 = 43,22o (d = 2,0902); 50,36o (d = 1,8090); 74,04o (d = 1,2794) tng ng vi cc mt (111), (200) v (220) thuc mng Bravais trong cu trc Fcc ca kim loi ng [7].

Hnh 1. Gin nhiu x XRD ca mu nano ng 3.2. Nghin cu cc yu t nh hng ti kch thc ht nano ng 3.2.1. nh hng ca nng cht kh kho st nh hng ca nng cht kh n qu trnh tng hp ht nano ng, qu trnh c thc hin vi t l khi lng c nh Cu2+/PVP = 3%, axit ascorbic/Cu2+ = 1,0,

nhit phn ng c nh 600C, nng NaBH4 khc nhau t 0,1 0,5M.

Kt qu UVVis trn hnh 2 cho thy rng, khi thay i nng cht kh th v tr cc

nh hp thu cc i cng c s thay i. Khi tng nng cht kh t 0,1 0,3M th v tr

cc nh hp thu cc i cng dch chuyn dn v pha bc sng nh hn t 582 570 nm. Khi nng cht kh tng qu cao (0,4 n 0,5M) th v tr cc nh hp thu cc i dch chuyn dn v pha bc sng ln hn t 574 578 nm. Kt qu ny cho php d on cc ht nano ng to ra c kch thc nh nht ti nng cht kh 0,3M. Nh vy, nng cht kh cng c s nh hng ln n kch thc ht nano ng thu c. nng cht kh thp, lng ht nhn sinh ra vi hm lng nh, qu trnh to mm din ra nhanh. Ngc li, qu trnh pht trin v hnh thnh ht nano ko di, cc ht c xu hng kt t trong qu trnh pht trin thnh ht ln hn. Khi nng cht kh tng (0,3M), qu trnh hnh thnh ht nhn v pht trin ht l tng thch dn n cc ht nano c n nh c kch thc nh hn. Khi nng cht kh tng cao (0,4M; 0,5M), tc phn ng din ra qu nhanh, lng ht nhn sinh ra nhiu trong thi gian ngn lm qu trnh pht trin ht d dng c s kt t hnh thnh cc ht c kch thc ln hn. Kt qu cho thy nng cht kh thch hp nht cho qu trnh to ht nano l 0,3M.

Hnh 2. Ph UV Vis ca dung dch keo nano ng c tng hp theo nng cht kh

NaBH4 0,1 0,5M

Hnh 3 l nh TEM biu hin s phn b kch thc ca ht nano ng c tng hp vi nng cc cht kh khc nhau. nng cht kh NaBH4 0,3M (hnh 3a), cc ht nano ng to ra c s phn b u, a s dng hnh cu trong phm vi kch thc trung bnh l

20 6 nm. Vi nng cht kh NaBH4 0,5M (hnh 3b), cc ht nano ng to ra c s

phn b u trong phm vi kch thc trung bnh 39 13 nm. Kt qu ny ph hp vi kt

qu phn tch UV-Vis trn hnh 2.

(a)

(b) Hnh 3. nh TEM v biu s phn b kch thc ca ht nano ng c tng hp vi

nng cht kh NaBH4 thay i: (a) 0,3M; (b) 0,5M 3.2.2. nh hng ca nhit Nhit cng l mt yu t nh hng ti qu trnh tng hp ht nano ng. nh gi s nh hng ca nhit , qu trnh th nghim c kho st ti cc gi tr nhit khc

nhau t 300C 800C, t l khi lng c nh Cu2+/PVP = 3%, axit ascorbic/Cu2+ = 1,0, nng

NaBH4 0,3M. Kt qu UV-Vis trn hnh 4 cho thy rng, khi thay i nhit th v tr cc nh hp

thu cc i c s dch chuyn vi gi tr bc sng theo quy lut ca s dch chuyn xanh

(blue shift) t 30 50oC v dch chuyn (red shift) t 50 80oC vi gi tr bc sng ln

lt, 300C l 580 nm, 400C l 575 nm, 500C l 566 nm, 600C l 570 nm, 700C l 577 nm v 800C l 580 nm. Kt qu ny cho php d on cc ht nano ng to thnh c s thay i

kch thc theo gi tr nhit khc nhau. C th, khi tng nhit t 30 50oC th kch

thc ht nano ng to ra gim dn. Tuy nhin, khi tng tip nhit t 50 80oC th kch

thc ht nano ng li tng ln. Theo kt qu ny, nhit thch hp nht cho qu trnh tng hp nano ng l 50oC.

Hnh 4. Ph UV Vis ca dung dch keo nano ng c tng hp theo nhit

(a)

(b)

Hnh 5. nh TEM v biu s phn b kch thc ca ht nano ng c tng hp nhit khc nhau

Hnh 5 l nh TEM biu hin s phn b kch thc ca ht nano ng c tng hp vi nhit khc nhau. Hnh 5a cho thy ti nhit 300C cc ht nano ng to ra vi

phn b rng, vi kch thc trung bnh l 36 16 nm, ngoi hnh cu cn thy dng khc v

c s hp thu cc ht nh trn b mt ht ln hn. Hnh 5b nhit 500C cc ht nano ng

to ra vn dng hnh cu nhng kch thc nh hn 21 6 nm, phn b u v khng c s

kt t. Nh vy, nhit cng l yu t nh hng mnh ti kch thc v s phn b ht nano ng to thnh. Khi tng nhit (30 50oC), qu trnh hnh thnh ht nhn v pht trin

mm din ra nhanh hn qu trnh pht trin v to ht, do cc ht nano ng to thnh c kch thc nh v ng u hn. Khi nhit tng cao (> 50oC), lm phn ng din ra nhanh v mnh lit. Trong thi gian ngn lng ht nhn sinh ra nhiu, cc cht bo v khng th bao ph b mt ht nano hnh thnh trong thi gian ngn, v th c s kt t gia cc ht nano ng hnh thnh cc ht c kch thc ln hn. 3.2.3. nh hng ca t l axit ascorbic/Cu2+ Axit ascorbic ng vai tr l cht bo v, ngn chn s kt t v qu trnh oxi ha b mt ht nano ng. nh gi nh hng ca axit ascorbic ti qu trnh tng hp nano ng, cc th nghim c tin hnh vi t l khi lng axit ascorbic/Cu2+ = 0,5; 1,0; 1,5; 2,0; 2,5 v 3,0, nhit c nh l 500C, t l khi lng c nh Cu2+/PVP = 3%, nng NaBH4 l 0,3M.

Hnh 6. Ph UV Vis ca dung dch keo nano ng c tng hp theo t l axit

ascorbic/Cu2+

Dung dch keo nano ng thu c trn hnh c phn tch UV-vis cho kt qu nh trn hnh 6. Kt qu cho thy, khi tng t l axit ascorbic/Cu2+ th v tr cc nh hp thu cc

i cng dch chuyn dn v pha bc sng nh hn t 582 571 nm vi gi tr bc sng

ln lt l 0,5 (582 nm); 1,0 (579 nm); 1,5 (572 nm); 2,0 (571 nm); 2,5 (572 nm) v 3,0 (571 nm). Kt qu cng cho thy khng c s thay i bc sng cc nh hp thu cc i khi t l

axit ascorbic/Cu2+ thay i t 1,5 3,0. Nh vy, t l axit ascorbic/Cu2+ thch hp nht cho

qu trnh tng hp nano ng l 1,5. Hnh 7 l nh TEM biu hin s phn b kch thc ca ht nano ng c tng hp vi t l axit ascorbic/Cu2+ khc nhau. Hnh 7a cho thy vi t l axit ascorbic/Cu2+ = 0,5 cc

ht nano ng to ra dng hnh cu trong phm vi kch thc ln 25 4 nm, c s kt t.

Hnh 7b t l axit ascorbic/Cu2+ = 1,5 cc ht nano ng to ra vn dng hnh cu nhng

kch thc nh hn, trung bnh l 5 2 nm nhng cc ht phn b khng u.

(a)

(b) Hnh 7. nh TEM v biu s phn b kch thc ca ht nano ng c tng hp vi

hm lng axit ascorbic/Cu2+ khc nhau 3.2.4. nh hng ca t l Cetyl trimethylammonium bromide (CTAB)/Cu2+

nh gi nh hng ca t l CTAB/Cu2+ ti qu trnh tng hp ht nano ng, cc th nghim c tin hnh ti nhit c nh l 500C, t l khi lng Cu2+/PVP = 3%, axit

ascorbic/Cu2+ = 1,5; nng NaBH4 l 0,3M; t l CTAB/Cu2+ thay i t 0,0 2,5.

Hnh 8. Ph UV Vis ca dung dch keo nano ng c tng hp theo t l CTAB/Cu2+

Dung dch keo nano ng c phn tch UV-Vis cho kt qu nh trn hnh 8. Kt qu cho thy rng khi tng t l CTAB/Cu2+ th v tr cc nh hp thu cc i cng c s thay i. C th, cc gi tr bc sng ln lt l 574 nm, 572 nm, 570 nm vi t l CTAB/Cu2+ = 0,0; 0,5 v 1,0. V tr cc nh hp thu cc i gn nh khng c s thay i khi t l CTAB/Cu2+

tng t 1,5 2,5 vi gi tr bc sng n nh t 567 568 nm. Kt qu ny cho thy cc ht

nano ng to ra c kch thc n nh v nh nht khi dng vi t l CTAB/Cu2+ = 1,5. Hnh 9 l nh TEM biu hin s phn b kch thc ca ht nano ng c tng hp khi c mt ca CTAB.

Hnh 9. nh TEM v biu s phn b kch thc ca ht nano ng c tng hp khi

khng c v khi c mt ca CTAB Hnh 7b v 9 l nh TEM biu hin s phn b kch thc ca ht nano ng c tng hp khi khng c v c mt ca CTAB vi t l CTAB/Cu2+ = 1,5. Kt qu cho thy cc ht nano ng to ra ch yu vn dng hnh cu, c phn b u vi kch thc trung bnh

ln lt l 5 2 nm v 3 1 nm.

Nh vy, CTAB c vai tr quan trng trong qu trnh tng hp nano ng. N c vai tr bo v v n nh trong qu trnh tng hp ht nano ng thng qua c ch to ht mixen. Khi cng tng hm lng CTAB th cng nhiu cc phn t CTAB bao bc v lm gim hot tnh b mt ht nano ng, do cc ht nano ng to ra c kch thc nh v ng u hn. 4. KT LUN Chng ti tng hp c dung dch keo nano ng trong mi trng nc vi cht kh l sodium borohydride (NaBH4) c s hin din ca cht hot ng b mt cetyl trimethylammonium bromide (CTAB), cht bo v polyvinylpyrrolidone (PVP, Mw = 40.000g/mol) v cht tr bo v axit ascorbic. Kch thc v s phn b cc ht nano ng c th iu chnh c bng cc thng s nh: nng cht kh, nhit , t l tc cht/cht bo v. Cu trc Fcc ca dung dch keo nano ng c xc nh bng gin nhiu x XRD, ph UV Vis cho thy cc ht nano ng to ra c kch thc khc nhau cho cc nh hp

thu cc i khc nhau t 566 580 nm. Ht nano ng c tng hp vi cc thng s tt

nht c kch thc trung bnh l 3 1 nm.

ABSTRACT Copper nano colloid was synthesized by chemical reduction method in water/PVP systems of copper (II) chloride dihydrate (CuCl2.2H2O) with the reducing agent is sodium borohydride (NaBH4)

in the presence of surface-active substances cetyl trimethylammonium bromide (CTAB), protective

polyvinylpyrrolidone (PVP, Mw = 40.000 g/mol) and were supported protective by ascorbic acid. The

inuence of parameters on the size of copper nanoparticles was studied. The shape with structure and the distribution of the synthesized copper nanoparticles were characterized by ultravioletvisible Spectrophotometry (UVVis), transmission electron microscopy (TEM) and powder X-ray diffraction (XRD). The average size of nanoparticles was found to be 3 1 nm at optimum conditions.

Keywords: copper nanoparticle, chemical reduction method, ascobic acid, polyvinylpyrrolidone.

TI LIU THAM KHO [1]. Cao Vn D, Nguyn Th Phng Phong, Nguyn Th Kim Phng (2013), Nghin cu tng hp v iu chnh kch thc ht nano ng trong h glycerin/PVP, Tp ch Ha hc, 745-749.

[2]. Nguyen Thi Phuong Phong, Ngo Hoang Minh, Tran Duc Tho, Cao Van Du, Vo Quoc

Khuong, Bui Duy Du (2010), GreenSynthesisOf Mettalic Copper Nanoparticles And Used As Anti-Corticium Salmonocolor Agent For Rubber Tree, The 5th International Workshop on Advanced Materials Science and Nanotechnology (IWAMSN2010), Hanoi, Vietnam.

[3]. Bong Kyun Park, Sunho Jeong, Dongjo Kim, Jooho Moon, Soonkwon Lim, Jang Sub

Kim (2007), Synthesis and size control of monodisperse copper nanoparticlesby polyol method, Journal of Colloid and Interface Science 311, 417424. [4]. Han-Xuan Zhang, Uwe Siegert, Ran Liu, Wen-Bin Cai (2009), Facile Fabrication of Ultrane Copper Nanoparticles in Organic Solvent, Nanoscale Res Lett 4,705708. [5]. Jafar Moghimi-Rad (2010), Effect of ultrasound radiation size and size distribution of synthesis copper particles, J. Mater Sci. 45, 3804 3811. [6]. Jin Wen, Jie Li, Shijun Liu, Qi-yuan Chen (2011), Preparation of copper nanoparticles in a water/oleic acid mixed solvent via two-step reduction method, Colloids and Surfaces A: Physicochemical and Engineering Aspects 373, 2935. [7]. Masoud Salavati-Niasari, Fatemeh Davar, Noshin Mir (2008), Synthesis and characterization of metallic copper nanoparticles via thermal decomposition, Polyhedron 27, 3514-3518.

[8]. Mayur Valodkar et al (2011), Synthesis and anti-bacterial activity of Cu, Ag and Cu-Ag alloy nanoparticles: A green approach, Materials Research Bulletin 46, 384-389. [9]. P.K.Khanna, S. Gaikwad, P.V. Adhyapak, N. Singh,R. Marimuthu (2007), Synthesis and characterization of copper nanoparticles, Materials Letters 61, 47114714 .