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B GIO DC V O TO
I HC HU
L TH LNH
NGHIN CU CH TO VNG NANO
V MT S NG DNG
LUN N TIN S HA HC
HU - NM 2015
B GIO DC V O TO
I HC HU
L TH LNH
NGHIN CU CH TO VNG NANO
V MT S NG DNG
Chuyn ngnh: Ha l thuyt v Ha l
M s: 62.44.01.19
LUN N TIN S HA HC
NGI HNG DN KHOA HC
1. GS. TS. Trn Thi Ha
2. PGS. TS. Nguyn Quc Hin
HU - NM 2015
LI CAM OAN
Ti xin cam oan y l cng trnh nghin cu ca ring ti, cc s liu v kt qu
nghin cu nu trong lun n l trung thc, c cc ng tc gi cho php s
dng v cha tng c cng b trong bt k mt cng trnh no khc.
Tc gi
L Th Lnh
LI CM N
Trc ht, ti xin c t lng bit n su sc n GS.TS. Trn Thi Ha v
PGS.TS. Nguyn Quc Hin, cc thy tn tnh hng dn, h tr v nh hng
cho ti trong sut thi gian thc hin lun n.
Xin by t nhng li cm n c bit n TS. inh Quang Khiu, TS.
Nguyn Hi Phong, cc thy hng dn, gip ti trong sut qu trnh thc
hin ti.
Xin chn thnh cm n Ban ch nhim khoa Ha hc trng i hc Khoa
hc Hu, B mn Ha l, B mn Ha Phn tch to iu kin thun li v c s
vt cht cho ti trong sut qu trnh th nghim.
Xin cm n Ban gim hiu, khoa Khoa hc i cng, trng Cao ng
Kinh t - K thut Qung Nam, to nhiu iu kin thun li v gip ti trong
cng tc ti hon thnh tt lun n ny.
Ti cng xin cm n TS. Nguyn Thanh nh, khoa Ha, trng i hc
British Columbia, Canada; TS. V Thnh Thn, phn vin Th y min Trung h
tr v gip ti trong vic tm kim ti liu v phn tch cc c trng cc mu
thc nghim trong lun n ny.
Xin cm n cc bn hc vin cao hc Ha l kha 2011-2013 h tr ti
trong qu trnh thc hin lun n.
Cui cng, ti cm n gia nh, bn b, cc ng nghip ng vin gip
ti hon thnh lun n ny.
L Th Lnh
MC LC
Trang
Trang ph ba
Li cam oan
Li cm n
Mc lc
Danh mc cc t vit tt
Danh mc cc bng
Danh mc cc hnh
M U 1
CHNG 1. TNG QUAN TI LIU 4
1.1. VT LIU VNG NANO .........................................................................4
1.1.1. Tnh cht cng hng plasmon b mt ..................................................4
1.1.2. Tng hp vng nano dng cu ...............................................................8
1.1.3. Tng hp vng nano dng thanh ..........................................................11
1.1.4. Cu trc ca vng nano dng thanh .....................................................15
1.1.5. C ch pht trin ca vng nano dng thanh .......................................16
1.1.6. Mt s khi nim lin quan n vng nano dng thanh ......................19
1.2. GII THIU V CHITOSAN ................................................................20
1.2.1. Cu trc ca chitosan ............................................................................20
1.2.2. deacetyl ha ca chitosan ...............................................................20
1.2.3. Phn ng N-acetyl ha chitosan to chitosan tan .................................22
1.3. NG DNG VNG NANO XC NH MELAMIN
TRONG SA ...........................................................................................23
1.3.1. Gii thiu v melamin ........................................................................23
1.3.2. S dng vng nano xc nh hm lng melamin trong sa .........24
1.4. NG DNG IN CC BIN TNH VNG NANO XC
NH HM LNG AXIT URIC BNG PHNG PHP
VON-AMPE HA TAN ...........................................................................25
1.4.1. Gii thiu phng php von-ampe ha tan .........................................25
1.4.2. Cc in cc s dng trong phng php von-ampe ha tan ..............26
1.4.3. S dng in cc bin tnh vng nano xc nh axit uric bng phng
php von-ampe ha tan ..........................................................................27
1.5. NGHIN CU KH NNG KHNG KHUN CA VNG NANO 29
1.5.1. Gii thiu v vi khun ..........................................................................29
1.5.2. ng dng khng khun ca vng nano ................................................30
CHNG 2. NI DUNG, PHNG PHP NGHIN CU V THC
NGHIM
2.1. MC TIU ................................................................................................32
2.2. NI DUNG NGHIN CU .....................................................................32
2.3. CC PHNG PHP NGHIN CU .................................................32
2.3.1. Phng php ph t ngoi - kh kin (Uv-Vis) ..................................32
2.3.2. Phng php hin vi in t truyn qua (TEM) .................................34
2.3.3. Phng php quang ph hng ngoi (IR) ...........................................34
2.3.4. Phng php nhiu x tia X (XRD) ....................................................36
2.3.5. Phng php sc k thm thu gel (GPC) ...........................................37
2.3.6. Phng php ph tn x nng lng tia X (EDX) ..............................37
2.3.7. Phng php ph cng hng t ht nhn (NMR) .............................38
2.3.8. Ph phn x khuch tn t ngoi kh kin (UV-Vis/DR) .................39
2.3.9. Phng php phn tch sc k lng hiu nng cao (HPLC) ................40
2.3.10. Phng php o nht .....................................................................40
2.3.11. Phng php phn tch in ha .......................................................41
2.3.12. Phng php thng k ........................................................................42
2.4. THC NGHIM ......................................................................................43
2.4.1. Ha cht ...............................................................................................43
2.4.2. iu ch chitosan tan trong nc ........................................................44
2.4.3. Tng hp vng nano dng cu bng phng php kh s dng
chitosan tan trong nc lm cht kh va lm cht n nh ................45
2.4.4. Tng hp vng nano dng thanh bng phng php pht trin
mm s dng CTAB lm cht bo v ................................................49
2.4.5. Nghin cu s dng vng nano dng cu xc nh melamin trong
mu sa .................................................................................................53
2.4.6. Nghin cu ch to in cc vng nano xc nh axit uric bng
phng php von-ampe ha tan ..........................................................56
2.4.7. Nghin cu kh nng khng khun ca vng nano .............................58
CHNG 3. KT QU V THO LUN
3.1. TNG HP VNG NANO DNG CU BNG PHNG PHP
KH S DNG CHITOSAN TAN TRONG NC LM CHT KH V
CHT N NH .............................................................................................60
3.1.1. iu ch chitosan tan trong nc .......................................................60
3.1.2. Tng hp vng nano dng cu .............................................................67
3.2. TNG HP VNG NANO DNG THANH BNG PHNG PHP
PHT TRIN MM S DNG CTAB LM CHT BO V ................90
3.2.1. Cc yu t nh hng n qu trnh tng hp vng nano dng thanh 91
3.2.2. C ch hnh thnh vng nano dng thanh......................................... 108
3.2.3. Tnh cht, hnh thi v cu trc ca vt liu vng nano dng thanh 109
3.3. NG DNG VNG NANO XC NH HM LNG
MELAMIN TRONG SA ........................................................................... 111
3.3.1. Kt qu thit lp ng chun .......................................................... 112
3.3.2. C ch phn ng gia vng nano v melamin ................................. 115
3.3.3. Kho st cc yu t nh hng ......................................................... 116
3.3.4. nh gi tin cy ca phng php .............................................. 117
3.3.5. Xc nh melamin trong mu sa ..................................................... 119
3.3.6. nh hng ca mt s ion, aminoacetic axit v vitamin C n
qu trnh xc nh melamin trong sa ............................................... 121
3.4. NGHIN CU CH TO IN CC BIN TNH VNG NANO
XC NH AXIT URIC BNG PHNG PHP VON-AMPE
HA TAN ................................................................................................. 123
3.4.1. Kho st c tnh in ha ca cc loi in cc ............................. 125
3.4.2. Nghin cu qu trnh bin tnh in cc .......................................... 127
3.4.3. Nghin cu cc yu t nh hng n tn hiu ha tan ................... 130
3.4.4. nh gi tin cy ca phng php .............................................. 135
3.4.5. p dng thc t ................................................................................ 138
3.5. NGHIN CU KH NNG KHNG KHUN CA VNG NANO146
Kt lun chnh ca lun n .......................................................................... 151
Danh mc cc cng trnh ca tc gi
Ti liu tham kho
Ph lc
DANH MC CC CH VIT TT TRONG LUN N
AA Axit ascorbic
AR T l cnh (Aspect Ratio)
CV Phng php von-ampe vng (Circle Voltammetry)
CTAB Cetyl trimethyl ammonium bromide
CTS Chitosan
A deacetyl (Degree of Deacetylation)
EDX Ph tn x nng lng tia X (Energy Dispersive X-ray
spectrum)
DP-ASV Phng php von-ampe ha tan anot xung vi phn (Differential
Pulse Anodic Stripping Voltammetry)
ELISA Xt nghim hp th min dch lin kt vi enzyme
(Enzyme-Linked Immunosorbent Assay)
L-cys L-cystein
GNR Nano vng dng que (gold nanorods)
GNP Nano vng dng cu (gold nanoparticles)
GCE in cc than thy tinh (Glassy Cacbon Electrode)
GC-MS Sc k kh ghp khi ph (Gas Chromatography-Mass
Spectrometry)
GPC Sc k thm thu gel (Gel Permeation Chromatography)
HPLC Sc k lng hiu nng cao (High Performance Liquid
Chromatography)
IR Ph hng ngoi (Infrared Spectroscopy)
LC-MS Sc k lng ghp ni khi ph (Liquid Chromatography-Mass
Spectrometry)
LOD Gii hn pht hin (Limit of Detection)
LOQ Gii hn nh lng (Limit of Quantitative)
LSPR Cng hng plasmon b mt theo trc dc (Longitudinal
Surface Plasmon Resonance)
Mel Melamin
NMR Ph cng hng t ht nhn (Nuclear Magnetic Resonace)
PBS: m phosphate (Photphate Buffer Solution)
R H s hp th quang
SEM Hin vi in t qut (Scanning Electron Microscopy)
SPR Cng hng plasmon b mt (Surface Plasmon
Resonance)
TEM Hin vi in t truyn qua (Transmission Electron
Microscopy)
TSPR Cng hng plasmon b mt theo trc ngang (Transverse
Surface Plasmon Resonance)
TPP Sodium tripolyphosphate
WE in cc lm vic (Working Electrode)
WSC Chitosan tan trong nc (Water Soluble Chitosan)
XPS Ph quang in t tia X (X-ray Photoelectron Spectroscopy)
XRD Nhiu x tia X (X-Ray Diffraction)
UA Axit uric
UPD S kh di th (Under Potential Deposition)
DANH MC CC BIU BNG
Trang
Bng 2.1. Cc loi ho cht s dng chnh trong lun n 43
Bng 2.2. K hiu mu chitosan acetyl ha ti cc thi gian phn ng khc nhau 45
Bng 2.3. K hiu mu WSC ti cc thi gian phn ng vi H2O2 khc nhau 45
Bng 2.4. K hiu mu GNP ti cc thi gian kh khc nhau 47
Bng 2.5. K hiu mu GNP ti cc nhit kh khc nhau 47
Bng 2.6. K hiu mu GNP ti cc nng Au3+
khc nhau 48
Bng 2.7. K hiu mu GNP ti cc nng WSC khc nhau 48
Bng 2.8. K hiu mu GNP vi cc WSC c khi lng phn t khc nhau 49
Bng 2.9. K hiu mu GNP gia tng n nh 49
Bng 2.10. K hiu mu GNR ti cc t l mol [Ag+]/[Au
3+] khc nhau 51
Bng 2.11. K hiu cc mu GNR ti cc t l mol [AA]/[Au3+
] khc nhau 52
Bng 2.12. K hiu cc mu GNR vi cc nng CTAB khc nhau 52
Bng 2.13. K hiu cc mu GNR ti cc nng Au3+
khc nhau 53
Bng 2.14. K hiu cc mu GNR ti cc gi tr pH khc nhau 53
Bng 3.1. deacetyl ha (A) v kh nng ha tan trong nc ca mu 62
chitosan axetyl ha vi cc thi gian phn ng khc nhau
Bng 3.2. A v Mw ca cc mu WSC ti cc thi gian phn ng oxi ha 64
khc nhau
Bng 3.3. chuyn dch ha hc cc proton ca CTS v WSC trong ph 66
1H-NMR
Bng 3.4. Gi tr cc i hp th (Amax) ca cc mu sau cc thi gian lu tr 71
Bng 3.5. Bc sng hp th cc i (max), cc i hp th (Amax) v kch thc 73
ht (d) ca GNP ti cc nng Au3+
khc nhau
Bng 3.6. Bc sng hp th cc i (max), cc i hp th (Amax) v 75
kch thc ht (d) ca GNP ti cc nng WSC khc nhau
Bng 3.7. Gi tr cc i hp th (Amax) ca cc mu sau cc thi gian lu tr 77
Bng 3.8. Tc ban u c tnh 30 pht 84
Bng 3.9. Bc phn ng (a) ca Au3+
tnh t tc ban u 85
Bng 3.10. Gi tr hng s tc phn ng k v bc phn ng ca WSC 85
tnh theo tc ban u
Bng 3.11. Gi tr cc i hp th (Amax) ca cc mu sau cc thi gian lu tr 86
Bng 3.12. Bc sng hp th cc i (max), cc i hp th (Amax) v kch thc 89
ht ca cc mu vng nano ti cc t l [Au3+
]/[Au0] khc nhau
Bng 3.13. S thay i th kh tiu chun ca Au3+
v Au+
105
Bng 3.14. Gi tr t l A650/A520 v lch chun tng i ti cc nng 113
melamin khc nhau
Bng 3.15. Gi tr t l A650/A520 v thi gian chuyn mu ca dung dch 116
vng nano-melamin ti hai kch thc ht khc nhau
Bng 3.16. H s tng quan (R), nhy (b, h s gc), LOD v LOQ ca 118
phng php trc quang s dng vng nano xc nh melamin
Bng 3.17. Kt qu xc nh melamin trong 7 mu sa tht s dng vng nano 120
v phng php HPLC
Bng 3.18. So snh phng php trc quang s dng vng nano GNP xc nh 123
melamin trong sa vi mt s nghin cu khc
Bng 3.19. Cc thng s c c nh ban u trong phng php DP- ASV 124
Bng 3.20. Cc thng s c nh trong phng php CVS 124
Bng 3.21. Gi tr Ep, Ip, b, v RSD ca cc in cc lm vic trong DP-ASV 125
Bng 3.22. Gi tr Ep, Ip, b, v RSD ca cc in cc lm vic trong CVS 126
Bng 3.23. Gi tr Ep, Ip, b, v RSD ti cc nng L-cystein khc nhau 128
Bng 3.24. Gi tr Ep, Ip, b, v RSD vi cc vng qut khc nhau 129
Bng 3.25. iu kin thch hp bin tnh in cc 130
Bng 3.26. Gi tr Ep, Ip, v RSD vi cc gi tr pH khc nhau 131
Bng 3.27. Gi tr Ep, Ip, b, v RSD vi cc tc qut khc nhau 134
Bng 3.28. Cc iu kin th nghim xc nh UA bng phng php DP-ASV 135
s dng in cc GCE/L-cys/GNP
Bng 3.29. Kt qu xc nh khong tuyn tnh ca phng php DP-ASV 136
Bng 3.30. H s tng quan (r), nhy (b, h s gc), LOD v LOQ ca 137
phng php DP-ASV dng in cc GCE/L-cys/GNP
Bng 3.31. Cc gi tr Ip,TB v lch chun ti cc gi tr nng UA khc nhau 138
Bng 3.32. K hiu v l lch mu 139
Bng 3.33. thu hi ca mt s mu nc tiu 140
Bng 3.34. Nng UA trong mt s mu nc tiu 141
Bng 3.35. Nng UA trong mu nc tiu xc nh bng 2 in cc 142
Bng 3.36. thu hi ca mt s mu huyt thanh 143
Bng 3.37. Nng ca UA trong nm mu huyt thanh 144
Bng 3.38. So snh phng php DP-ASV s dng in cc bin tnh vng nano 145
xc nh axit uric vi mt s nghin cu khc
Bng 3.39. Kt qu nghin cu kh nng khng khun ca vng nano 149
DANH MC CC HNH V
Trang
Hnh 1.1. Mu sc ca cc keo vng nano theo kch thc ht 4
Hnh 1.2. Cng hng plasmon b mt 5
Hnh 1.3. Hin tng SPR ca vng nano dng cu 6
Hnh 1.4. Hin tng SPR xy ra theo trc dc v trc ngang ca GNR (a); 7
ph UV-Vis tng ng ca GNR (b)
Hnh 1.5. S ph thuc ca hin tng SPR vo hnh dng v kch thc 8
ca ht vng nano
Hnh 1.6. Ph UV-Vis (a) v nh TEM (b) ca vng nano s dng chitosan 10
lm cht kh v cht n nh
Hnh 1.7. nh TEM (a) v phn b kch thc ht (b) ca vng nano s dng 11
chitosan lm cht kh v cht n nh
Hnh 1.8. nh TEM ca vng nano dng thanh vi AR 4 13
Hnh 1.9. S tng hp GNR bng phng php pht trin mm ca Jana v 13
cng s nm 2001(a) v c Nikoobakht ci tin nm 2003 (b)
Hnh. 1.10. M hnh cu trc vng nano ca Wang v cng s (a), Gain v 16
Harmer (b), Murphy v cng s (c) v Liz-Marzn v cng s (d)
Hnh 1.11. C ch hnh thnh ht vng nano dng thanh trong trng hp 17
khng c AgNO3
Hnh 1.12. C ch hnh thnh ht vng nano dng thanh t ht mm n tinh th (a) 19
v ht mm multiply twinned (b) di s nh hng ca Ag+
Hnh 1.13. Cu trc ca chitosan 20
Hnh 1.14. Cu to ca melamin 23
Hnh 1.15. S kt hp gia melamin v axit cyanuric 24
Hnh 1.16. Cng thc cu to ca L-cystein 27
Hnh 1.17. Cu trc phn t ca axit uric 28
Hnh 1.18. Tinh th axit uric kt ta trong khp xng 28
Hnh 1.19. Kh nng khng khun ca vng nano 31
Hnh 2.1. S nguyn l ca knh hin vi in t truyn qua 34
Hnh 2.2. Cc tia X nhiu x trn cc mt tinh th cht rn 36
Hnh 2.3. Nguyn tc tn x tia X dng trong ph EDX 38
Hnh 2.4. Phn x gng v phn x khuych tn t b mt nhm 39
Hnh 2.5. Quy trnh iu ch WSC 44
Hnh 2.6. S tng hp vng nano dng cu (GNP) s dng WSC 46
Hnh 2.7. S tng hp vng nano dng thanh (GNR) 50
Hnh 2.8. Quy trnh xc nh melamin trong mu sa tht 55
Hnh 2.9. S tin trnh th nghim theo phng php von-ampe vng 57
Hnh 2.10. S tin trnh th nghim theo phng php DP-ASV 57
Hnh 3.1. Ph IR ca cc mu chitosan acetyl ha vi cc thi gian khc nhau 60
Hnh 3.2. Gin XRD ca CTS v WSC 63
Hnh 3.3. Ph FTIR ca WSC3hOX, WSC6
hOX v WSC18
hOX 64
Hnh 3.4. Chitosan (a), chitosan tan dng rn (b) v dung dch chitosan tan (c) 65
Hnh 3.5. Ph 1H-NMR ca CTS (a); WSC (b) 66
Hnh 3.6. Hai loi mt xch monomer trong mch phn t chitosan 67
Hnh 3.7. Ph UV-Vis (a) v gin biu din cc i hp th (b) ca GNP ti 68
cc thi gian kh khc nhau
Hnh 3.8. Ph UV-Vis ca WSC, Au3+
, GNP-2h v GNP-8h 68
Hnh 3.9. nh TEM vi phn gii khc nhau v phn b kch thc ht ca 69
GNP ti cc thi gian kh 8 v 31 gi
Hnh 3.10. Ph UV-Vis ca GNP ti cc nhit kh khc nhau 70
Hnh 3.11. Ph UV-Vis ca GNP ti cc nng Au3+
khc nhau 72
Hnh 3.12. nh TEM ca GNP c phn gii khc nhau ti cc nng Au3+
: 73
0,25; 0,50; 1,00 v 1,50 mM
Hnh 3.13. Ph UV-Vis ca GNP ti cc nng WSC khc nhau 74
Hnh 3.14. nh TEM ca GNP c phn gii khc nhau ti cc nng WSC: 75
0,25; 0,50 v 1,00%
Hnh 3.15. Ph UV-Vis ca GNP vi cc WSC c khi lng phn t khc nhau 76
Hnh 3.16. Ph UV-Vis (a) v gin XRD ca WSC, GNP (b) 78
Hnh 3.17. nh TEM c phn gii khc nhau v phn b kch thc ht 78
ca GNP
Hnh 3.18. Ph FT-IR ca WSC trc v sau khi b oxi ha bi Au3+
(WSCOX) 79
Hnh 3.19. Ph UV-Vis/DR (a) v gin EDX (b) ca GNP 81
Hnh 3.20. C ch phn ng kh Au3+
bng WSC 82
Hnh 3.21. th biu din mi quan h gia: (a) logA v log[Au3+
]; 84
(b) logk v log[WSC]
Hnh 3.22. Ph UV-Vis ca GNP vi cc nng WSC thm khc nhau 86
Hnh 3.23. Ph UV-Vis ca GNP ti cc t l [Au3+
]/[Au0] khc nhau 88
Hnh 3.24. nh TEM ca cc ht vng nano GNP tng hp bng phng php 88
pht trin mm ti cc t l [Au3+]/[Au0] khc nhau
Hnh 3.25. M hnh minh ha s pht trin ht mm trong trng hp: khng c 90
d Au3+ trong dung dch (a) v c d Au3+ trong dung dch (b)
Hnh 3.26. Ph UV-Vis (a); v th biu din bc sng hp th cc i ca dao 92
ng LSPR v t s hp th quang (R) ca dao ng LSPR/dao
ng TSPR (b) ti cc t l mol [Ag+]/[Au
3+]: 0,0; 0,1; 0,2; 0,3; 0,4 v 0,5
Hnh 3.27. S minh ha tng tc ca nh sng phn cc trn vng nano 93
dng cu (A) v dng thanh (B)
Hnh 3.28. nh TEM ca cc mu GNR ti cc t l mol [Ag+]/[Au
3+] khc nhau 94
Hnh 3.29. V tr ca nguyn t Ag (dng cu mu ) trn mt tinh th (110) (a), 96
(100) (b) v (111) (c) ca cu trc lp phng
Hnh 3.30. C ch hnh thnh GNR di s nh hng ca ion Ag+
97
Hnh 3.31. Ph UV-Vis (a) v th biu din bc sng hp th cc i ca 98
dao ng LSPR, t s hp th quang R (b) ti cc t l mol [AA]/[Au3+
]:
1,0; 1,5; 2,0; 2,5
Hnh 3.32. nh TEM c phn gii khc nhau ca cc mu GNR ti cc t l mol 99
[AA]/[Au3+]: 1,0; 1,5; 2,0; v 2,5
Hnh 3.33. Ph UV-Vis (a) v th biu din cc i hp th ca dao ng LSPR 101
v t s hp th quang R (b) ti cc nng Au3+
: 5; 10; 15 v 20 mM
Hnh 3.34. nh TEM ca cc mu GNR ti cc nng Au3+
khc nhau 102
Hnh 3.35. Ph UV-Vis (a) v th biu din bc sng hp th cc i ca dao 103
ng LSPR v t s hp th quang R (b) ti cc nng CTAB
khc nhau
Hnh 3.36. nh TEM ca cc mu GNR ti cc nng CTAB khc nhau 104
Hnh 3.37. Ph UV-Vis (a); v th biu din bc sng hp th cc i ca dao 106
ng LSPR v t s hp th quang R (b) ti cc gi tr pH khc nhau
Hnh 3.38. S ph thuc kh nng kh ca AA vo pH 106
Hnh 3.39. nh TEM ca cc mu GNR ti cc gi tr pH khc nhau 108
Hnh 3.40. Giai on to mm trong qu trnh tng hp GNR 108
Hnh 3.41. C ch pht trin ca GNR di s nh hng ca Ag+ v CTAB 109
Hnh 3.42. Ph UV-Vis (a) v gin XRD (b) ca GNR 110
Hnh 3.43. nh TEM vi cc phn gii khc nhau ca GNR 110
Hnh 3.44. Gin EDX ca GNR 111
Hnh 3.45. S thay i mu (a) v ph UV-Vis (b) ca dung dch vng nano v 113
vng nano-melamin vi cc nng melamin khc nhau (mg/L)
Hnh 3.46. th biu din mi quan h gia t l A650/A520 v CMel 114
Hnh 3.47. Ph UV-Vis v nh TEM ca vng nano khi khng c melamin (a) v 114
khi c melamin (b)
Hnh 3.48. C ch phn ng gia GNPbt v melamin 115
Hnh 3.49. nh hng ca gi tr pH n t l A650/A520 117
Hnh 3.50. Ph UV-Vis ca GNP-Mel ti CMel=1,00 mg/L, lp li 7 ln 119
Hnh 3.51. Hnh nh xc nh melamin trong mu sa 119
Hnh 3.52. Ph UV-Vis ca cc dung dch vng nano-sa 120
Hnh 3.53. nh hng ca cc ion, aminoacetic axit (AA) v vitamin C (VC) n 121
t l A650/A520 ti cc nng khc nhau ca tc nhn nh hng (a)
v ti nng cht nh hng bng 0,10 g/L (b)
Hnh 3.54. Dung dch vng nano GNP trc v sau khi thm dung dch sa 122
( x l) c cha melamin hoc cc yu t nh hng khc
Hnh 3.55. ng von-ampe ha tan ca UA theo cc ln thm chun (a); ng 126
von-ampe ha tan ca UA trong 4 ln lp li (b) in cc GCE/L-cys/GNP
Hnh 3.56. Cc ng CVS ca 3 loi in cc khc nhau 126
Hnh 3.57. Qu trnh bin tnh in cc GCE 127
Hnh 3.58. S ph thuc ca Ip. UA vo nng L-cystein 127
Hnh 3.59. ng von-ampe ha tan ca UA sau cc ln thm chun (a); ng 128
von-ampe ha tan ca UA trong 4 ln lp li vi nng L-cystein
1,0 mM (b)
Hnh 3.60. S ph thuc ca Ip. UA vo s vng qut L-cystein 129
Hnh 3.61. ng von-ampe ha tan ca UA sau cc ln thm chun (a); ng 130
von-ampe ha tan ca UA trong 4 ln lp li vi s vng qut 20 vng
Hnh 3.62. S ph thuc ca Ip vo pH (a) v cc ng von-ampe ha tan ca 131
UA ti gi tr pH khc nhau (b)
Hnh 3.63. ng hi quy tuyn tnh biu din mi tng quan gia Ep v pH 132
Hnh 3.64. Cc ng von-ampe ca UA cc tc qut t 20 n 120 mV/s 134
Hnh 3.65. ng von-ampe ha tan ca UA vi khong nng 2100 M 136
Hnh 3.66. th biu din mi quan h gia Ip v CUA (TN1) 136
Hnh 3.67. ng von-ampe ha tan ca UA, lp li 9 ln 138
a) CUA = 6 M; b) CUA =20 M; c) CUA = 40 M
Hnh 3.68. ng von-ampe ha tan ca UA: TN1 (a); TN2 (b) ca mu NT1 141
v TN1 (c); TN2 (d) ca mu NT5
Hnh 3.69. ng von-ampe ha tan ca UA ca mu NT4 sau 3 ln lp li 142
Hnh 3.70. ng von-ampe ha tan ca UA 2 ln ch to in cc (mu NT4) 142
Hnh 3.71. ng von-ampe ha tan ca UA: TN1 (a); TN2 (b) ca mu HT2 v 144
TN1 (c); TN2 (d) ca mu HT4
Hnh 3.72. ng von-ampe ha tan ca UA ca mu HT2 sau 3 ln lp li 144
Hnh 3.73. Kt qu khng khun ca mu GNP (a: quan st bng mt thng; 146
b: s dng thuc th Alamar Blue)
Hnh 3.74. Kt qu khng khun ca mu GNR (a,b: quan st bng mt thng; 148
c,d: s dng thuc th Alamar Blue)
Hnh 3.75. Biu biu th gi tr MIC ca vng nano v khng sinh i vi 150
4 loi vi khun
1
M U
Vng nano l mt trong nhng vt liu kch thc nano ang thu ht s quan
tm ca nhiu nh khoa hc trong v ngoi nc bi nhng tnh cht quang hc c
o ca chng, c bit l hin tng cng hng plasmon b mt (surface plasmon
resonance, SPR) [35], [39], [81], [93], [102], [126] v nhng ng dng to ln ca
chng trong nhiu lnh vc khc nhau nh xc tc [4], [19], [87], in ha [26],
[45], [104], [105], cm bin sinh hc [40], [93], [103], khuch i tn x Raman b
mt (surface enhanced Raman scattering, SERS) [32], c bit l trong y hc
chn on v iu tr ung th [18], [39], [40], [126].
Cho n nay, c nhiu phng php khc nhau c nghin cu tng
hp vng nano nh phng php chiu x [1], [23], [65], [66], phng php kh
ha hc [4], [12], [43], kh sinh hc [13], [43], [52], phng php in ha [63],
[122], phng php quang ha [70], phng php pht trin mm [10], [17], [40],
[115], [127], ... Mi phng php u to ra cc ht vng nano vi hnh dng, kch
thc khc nhau nh dng cu, dng thanh, dng si, hnh tam gic, hnh lng tr,
hnh t din, hnh lp phng, ... [28], [31], [70]. Chng hn, tng hp ra vng
nano dng cu th phng php ph bin nht l s dng tc nhn kh ha hc nh
NaBH4 hay natri citrate [4], [12]. Tuy nhin, nhc im ca phng php ny l
s dng cc tc nhn c hi, gy nh hng i vi mi trng. Gn y, cc nh
khoa hc s dng "phng php xanh (green method) [13], [37], [80], [92]
tng hp vng nano dng cu vi mc ch khc phc hn ch ni trn. Trong khi
, tng hp vng nano dng thanh th phng php c cho l ti u nht cho
n thi im hin ti l phng php pht trin mm [70], [93], [96]. Sn phm to
thnh t phng php ny c n phn tn, c th kim sot c t l
di/ngang (t l cnh) bng cch thay i cc yu t nh hng [70], [96].
Nhim bn melamin trong sa gy nh hng nghim trng n sc khe
ca tr em v l mt vn thu ht s ch ca ng o cng ng x hi [12],
[20], [22], [44]. Do , vic xc nh melamin trong thc phm ni chung v trong
sa ni ring l iu ht sc cn thit. Cho n nay, cc phng php thng c
s dng, l sc k kh ghp ni khi ph (GC/MS) [41], sc k lng ghp ni
2
khi ph (LC/MS) [41], [95], sc k lng hiu nng cao (HPLC) [85], ELISA [49],
[95]. Nhn chung, nhng phng php ny c chnh xc cao nhng yu cu thit
b t tin, tn nhiu thi gian v phi c chuyn vin thc hin. Gn y, mt s
tc gi trn th gii tm ra phng php mi, s dng vng nano xc nh
melamin vi u im r, nhanh, n gin v nhy cao [32], [33], [36], [112].
Da vo s thay i mu ca dung dch vng nano khi c mt melamin, c th d
dng nh tnh melamin bng mt thng. ng thi, c th nh lng hm lng
melamin trong sa da vo php o trc quang. Cc ht vng nano c tng hp
t cc phng php khc nhau c s dng cho mc ch ny. Tuy nhin, vic
s dng vng nano xc nh melamin vn cha c nghin cu mt cch y .
Phng php von-ampe ha tan l mt phng php phn tch in ha hin
i vi nhiu u im nh chi ph thp, nhy cao, gii hn pht hin thp,
chn lc cao [34], [98], [106]. in cc lm vic thng c s dng l in cc
thy ngn vi u im l c kh nng to hn hng c vi nhiu kim loi, ng
thi khong th hot ng v pha m ln [106]. Tuy nhin, nhc im ca n l
d tc mao qun v c tnh cao [34], [98]. Do vy, xut hin ngy cng nhiu cc
cng trnh nghin cu bin tnh in cc khc phc hn ch ny, trong in
cc bin tnh vng nano ang thu ht s quan tm ng k ca nhiu nh khoa hc
bi nhng tnh cht c o ca n khi kch thc nano. Hin nay, cc nh khoa
hc trn th gii ch to thnh cng in cc bin tnh vng nano xc nh
mt s ion kim loi v hp cht hu c [45], [62], [98]. Trong , vic xc nh axit
uric trong cc i tng sinh hc ang nhn c s quan tm ln bi v nng
axit uric trong mu huyt thanh, nc tiu s gip chng ta bit du hiu ca mt s
bnh, c bit l bnh gout [26], [34], [45], [68], [98], [104], [109].
Hin nay, hin tng khng thuc ca vi khun ang tr nn ngy cng ph
bin. Do vy, cc nh khoa hc nghin cu s dng cc ht nano kim loi vi
mc ch c ch s pht trin ca vi khun. c mt s cng b tng hp vng
nano t cc dch chit qu nho, hoa hng dng, tr, ... v s dng vng nano tng
hp c c ch vi khun vi nhiu kh quan [11], [13], [24], [52], [55]. Tuy
nhin, nghin cu khng khun ca vng nano cng cha c pht trin y .
3
Mc d vng nano c nghin cu v ng dng trong nhiu lnh vc
khc nhau, tuy nhin vn cn nhiu vn mi m, ha hn nhiu khm ph mi t
chng. Trong xu th , ti Vit Nam hin nay cng c nhiu nh khoa hc quan
tm nghin cu tng hp vng nano cng nh kho st cc ng dng ca chng.
Tuy nhin, cha c mt cng trnh no nghin cu mt cch h thng qu trnh tng
hp vng nano cng nh cc yu t nh hng. Do vy, tip tc i su nghin cu
tng hp v kho st cc ng dng ca chng l rt cn thit.
Xut pht t thc t trn, chng ti chn ti: "Nghin cu ch to vng
nano v mt s ng dng.
Cu trc ca lun n:
Phn m u
Chng 1. Tng quan
Chng 2. Ni dung, phng php nghin cu v thc nghim
Chng 3. Kt qu tho lun gm cc vn chnh sau:
- Nghin cu tng hp vng nano dng cu (k hiu GNP) s dng chitosan
tan trong nc lm cht kh v cht n nh
- Nghin cu tng hp vng nano dng thanh (k hiu GNR) bng phng
php pht trin mm s dng CTAB lm cht bo v
- Nghin cu mt vi ng dng ca vng nano:
+ Nghin cu s dng vng nano pht hin melamin trong sa
+ Nghin cu s dng in cc bin tnh vng nano xc nh axit uric
+ Nghin cu kh nng khng khun ca vng nano
Phn nhn xt chung v kt lun
Danh mc cc bi bo lin quan n lun n
4
CHNG 1
TNG QUAN TI LIU
1.1. VT LIU VNG NANO
Vt liu nano kim loi ni chung v vng nano ni ring ang nhn c s
quan tm ca cc nh khoa hc bi nhng tnh cht quan trng, c bit l hin
tng cng hng plasmon b mt [35], [39], [81], [93], [102] v nhng ng dng
rng ri ca chng trong nhiu lnh vc khc nhau nh xc tc [4], [19], [87], in
ha [26], [45], [104], [105], kh nng chng oxi ha [64], pht hin v iu tr ung
th [18], [39], [40], .... Cc ht vng nano vi kch thc t 1 nm n ln hn 100
nm c tnh cht quang, in c o, khc hn so vi vt liu vng dng khi (bulk
material) [39]. Trong , s khc nhau ng ch gia vng nano v kim loi vng
dng khi l s thay i mu sc ca chng, c th l s chuyn t mu vng sang
mu ta, mu tm hoc mu xanh ph thuc vo kch thc ca ht vng nano
(hnh 1.1). S thay i mu sc ny l do hiu ng plasmon b mt to ra.
Hnh 1.1. Mu sc ca cc keo vng nano theo kch thc ht [126]
1.1.1. Tnh cht cng hng plasmon b mt
Mt trong nhng tnh cht quan trng ca vng nano l hiu ng plasmon b
mt (surface plasmon resonance: SPR). Chnh nh tnh cht ny m vng nano c
ng dng trong nhiu lnh vc khc nhau, c bit l trong chn on v iu tr
ung th [18], [39], [93].
5
Hnh 1.2. Hin tng cng hng plasmon b mt [126]
Hin tng cng hng plasmon b mt (SPR) c gii thch l: in
trng ca sng in t tc ng ln cc electron t do trn b mt ht nano, lm
electron b dn v mt pha, gy ra s phn cc (hnh 1.2) [35], [126]. Sau , di
tc dng ca lc phc hi Coulombic, cc electron s tr li v tr ban u. V c
bn cht sng, nn in trng dao ng lm cho s phn cc ny dao ng theo.
S dao ng ny c gi l plasmon. Khi tn s dao ng ca m my electron
trng vi tn s ca mt bc x in t no , s gy ra s dao ng hng lot ca
cc electron t do. Hin tng ny gi l cng hng plasmon b mt (SPR) [39],
[126]. Nh vy, hin tng cng hng plasmon b mt l s kch thch cc
electron t do bn trong vng bn dn, dn ti s hnh thnh cc dao ng ng
pha. Khi kch thc ca mt tinh th nano kim loi nh hn bc sng ca bc x
ti, khi tn s photon ti cng hng vi tn s dao ng ca electron t do b
mt s xut hin hin tng cng hng plasmon b mt. i vi ht vng nano,
dao ng cng hng plasmon dn ti s hp th mnh ca nh sng vng kh
kin. iu ny dn ti s thay i ln v mu sc ca dung dch vng nano. S
lng v v tr ca di plasmon ph thuc ch yu vo kch thc v hnh thi ca
ht vng nano. V vy, peak cng hng c th xut hin trong vng kh kin n
vng hng ngoi gn. Ngoi ra, hng s in mi ca vt liu cu trc nano, ch s
khc x ca mi trng xung quanh, trng thi ca b mt (dung mi, cht n nh)
hay khong cch gia cc ht cng nh hng n v tr v hnh dng ca cng
hng plasmon b mt [35], [102].
6
* S ph thuc tnh cht SPR vo hnh thi v kch thc ca vt liu
a) Vng nano dng cu (gold nanoparticles: GNP)
Tnh cht quang ca vng
nano dng cu c th c tnh
ton theo thuyt ca Mie [81]. Ln
u tin Mie gii thch s thay i
mu sc ca h keo vng nano
dng cu bng cch gii phng
trnh Maxwell. Bng cch ny,
ng m t tnh cht quang hc
(tn x v hp th) ca vng nano
dng cu bt k kch thc no.
Theo , i vi vng nano dng cu, SPR xy ra vng kh kin ti bc sng
khong 520-540 nm (hnh 1.3). Nu kch thc (d) ca ht tng ln th cc i hp
th ng vi SPR s dch chuyn v vng c bc sng di, tc l vng nh sng
(red-shift). Tuy nhin, khi ht cu ln n mt kch thc no , s tr thnh dng
khi (bulk) v hin tng SPR s bin mt.
b) Vng nano dng thanh (gold nanorods: GNR)
i vi vng nano dng thanh, tnh cht quang hc c th c hiu r da vo
thuyt Gans [35], [81]. Theo , trn ph UV-Vis xut hin 2 peak hp th cc i:
Mt cc i hp th tng ng vi cng hng plasmon b mt dc theo trc ngang
(transverse surface plasmon resonane: TSPR) v mt dao ng theo trc dc
(longitudinal surface plasmon resonance: LSPR) ca ht (hnh 1.4). Trong , dao
ng TSPR c cc i nm trong vng kh kin (khong 520-540 nm), cn dao ng
LSPR c cng mnh hn rt nhiu so vi dao ng TSPR v c cc i nm
trong vng c bc sng ln hn, t vng kh kin n vng hng ngoi gn ph
thuc vo t s cnh (t s gia trc dc/trc ngang hay t s di/ngang) ca vt liu.
Khi t s cnh tng, LSPR dch chuyn v vng hng ngoi gn (NIR), trong khi
TSPR gn nh khng thay i [31], [35], [81], [102]. Ngoi ra, bc sng hp th
cc i ca dao ng LSPR cn ph thuc nhiu vo ch s khc x ca mi trng
7
xung quanh n. Khi ch s khc x tng, th SPR c xu hng chuyn sang vng sng
mu v s dch chuyn SPR gn nh tuyn tnh vi ch s khc x [102]. y l
mt tnh cht quan trng c p dng trong cc ng dng v cm bin plasmon.
Cng theo thuyt Gans, cc i hp th ca dao ng LSPR t l tuyn tnh
vi t s cnh (t s di/ngang, aspect ratio: AR) theo phng trnh sau:
LSPR (nm) = 95AR + 420 (1.1)
Hnh 1.4. Hin tng SPR xy ra theo trc dc v trc ngang ca GNR
(a); ph UV-Vis tng ng ca GNR (b)
Tm li, hnh dng v kch thc ca ht vng nano nh hng ng k n
hin tng cng hng plasmon b mt ca chng, c th l: ht dng cu ch c
mt cc i hp th vi bc sng max 520 nm v khi tng kch thc (d) th
max cng tng theo (hnh 1.5) [31]. Trong khi , vng nano dng thanh c 2 cc
i hp th: 1 cc i hp th c bc sng max 520 nm v 1 cc i hp th
c bc sng nm trong vng kh kin n hng ngoi gn ty thuc vo t s
AR, c th l AR tng th cc i hp th cng dch chuyn v vng hng ngoi
gn nh minh ha hnh 1.5.
8
Hnh 1.5. S ph thuc ca hin tng SPR vo hnh dng v kch thc
ca ht vng nano [31]
1.1.2. Tng hp vng nano dng cu (GNP)
K t khi ln u tin Faraday nghin cu s to thnh keo vng bng cch
kh AuCl4- bng phospho nm 1857, c nhiu phng php tng hp keo vng
nano c cng b. Ni chung, phng php tng hp vng nano c th c chia
thnh ba nhm chnh: nhm phng php ha hc, nhm phng php bc x v
nhm phng php kh sinh hc. Phng php bc x s dng cc bc x t ngoi,
kh kin, vi sng, bc x gama, ... [1], [23], [65], [66] kh AuCl4- v Au
0 trong
s c mt ca cht n nh thch hp. Phng php ny cho hiu sut tng hp cao
nhng yu cu phi c thit b tng ng. Nguyn tc chung ca phng php kh
ha hc l s dng mt cht kh no kh Au3+
trong mui vng thnh nguyn
t Au0, trnh s kt dnh cc ht li vi nhau, cht bo v c s dng. Trong
nhm phng php ny, trc ht phi k n phng php Turkevich. Phng
php ny c pht minh bi Turkevich v cc cng s [43], [100] vo nm 1951,
sau c ci tin bi Frens [43] vo nm 1970, v l mt phng php tng hp
vng nano n gin nht cho n thi im hin ti. Nhn chung, phng php ny
to ra cc ht vng nano n phn tn dng cu tan trong nc vi kch thc t 10-
20 nm v bn cao. Cc ht ln hn cng c th c to ra bng phng php ny
nhng s mt nhiu quy trnh cng ngh hn trong vic duy tr tnh phn tn cng
nh hnh dng ht. Quy trnh to ht vng nano lin quan n phn ng gia mt
9
lng dung dch nng chloauric vi dung dch natri citrate. y, natri citrate va
ng vai tr lm cht kh va l tc nhn lm bn.
Phng php kh ha hc tip theo l phng php Brust. Phng php
ny c pht hin bi Brust v Schiffrin [15], [43] vo u nhng nm 1990. Cc
ht vng nano ch to theo phng php ny c kch thc trung bnh khong 5-6
nm. NaBH4 ng vai tr l tc nhn kh, trong khi tetraoctylammonium bromide
(TOAB) ng vai tr l cht xc tc chuyn pha v cht lm bn. Tuy nhin, TOAB
khng bc xung quanh ht nano mt cch vng chc, do dung dch s b kt ta
sau khong thi gian 2 tun. hn ch hin tng ny, mt tc nhn lm bn mnh
c s dng nh thiol (alkanethiol), c th lin kt cng ha tr vi ht vng nano.
Nm 2009, Perault v Chan [74] pht minh ra phng php mi tng
hp vng nano (phng php Perault), s dng hydroquione kh HAuCl4 trong
dung dch c cha sn cc ht vng nano. Trong phng php ny, cc ht vng
nano c th ng vai tr l cht cu ni vi hydroquinone xc tc vic kh cc
ion vng trn b mt. S tn ti cc cht n nh nh cc ion citrate c th to ra
vic mc cc ht c kim sot. Phng php ny c th to ra cc ht nano vi kch
thc rt ln, khong 30-250 nm.
Mt phng php kh ha hc khc c nhm tc gi Eah pht minh vo
nm 2010, gi l phng php Martin [59]. Phng php ny to ra cc ht vng
nano trong nc bng vic kh HAuCl4 bi NaBH4. Mc d khng s dng cc
cht hot ng b mt nh citrate, nhng cc ht vng nano c s phn tn cao.
Nhn chung, cc phng php kh ha hc to ra sn phm c phn tn
cao. Tuy nhin, nhc im ca chng l s dng cc tc nhn kh nh natri
citrate, NaBH4, l nhng ha cht c hi, gy nh hng nghim trng n mi
trng. khc phc vn ny, cc nh khoa hc nghin cu s dng phng
php xanh (green method) [13], [37], [80], [92] tng hp vt liu vng nano.
Trong phng php ny, tc nhn c s dng (dung mi, cht kh v cht bo
v) l cc ha cht khng c hi, thng l cc polymer c tnh tng hp sinh
hc. Raveendran v cng s [82] ln u tin s dng phng php xanh tng
hp vng nano vi dung mi l nc, cht kh l -D-glucose v cht n nh l
10
tinh bt. Sau , nhm tc gi ny s dng -D-glucose va lm cht kh v
cht n nh tng hp vng nano. Bn cnh glucose v tinh bt, chitosan l mt
polysaccharide c s dng nhiu cho mc ch ny bi hai l do sau: Th nht,
chitosan l dn xut ca chitin polysaccharide c mt rng ri trong t nhin. Th
hai l, s c mt ca mt lng ln cc nhm amino (-NH2) v nhm hydroxyl
(-OH) t do trong mch chitosan lm cho n c nhng c tnh ha l c bit
nh polycation, to phc v to mng. Theo Huang v cng s [38], chitosan c
s dng nhiu lm cht kh v cht n nh trong tng hp vng nano bi c cu
trc giu oxy trong nhm hydroxyl v ete. Hn na, chitosan l mt polymer c
tnh tng hp sinh hc, phn hy sinh hc, do ngy cng c nhiu cng trnh s
dng chitosan tng hp vng nano [110].
Wei v cng s [110], [111] s dng chitosan lm lm cht kh v cht
n nh tng hp nano bc v vng. Sn phm thu c c mu ta v c cc
i hp th ti bc sng 520 nm. nh TEM hnh 1.6b cho thy, c xut hin cc
ht dng cu nhng phn b km ng u.
Hnh 1.6. Ph UV-Vis (a) v nh TEM (b) ca vng nano s dng chitosan
lm cht kh v cht n nh [110]
Cng thi gian , Sun v cng s [97] cng tng hp thnh cng vng
nano dng cu ch s dng chitosan va lm cht kh va lm cht n nh. nh
TEM v phn b kch thc ht hnh 1.7 cho thy, cc ht vng nano dng cu
c hnh thnh vi kch thc trung bnh 27,58 nm nhng km ng u, th hin
gi tr sai s chun (SD) ln (SD = 12,27).
11
Hnh 1.7. nh TEM (a) v phn b kch thc ht (b) ca vng nano s
dng chitosan lm cht kh v cht n nh [97]
Gn y nht, nm 2013, Siemieniec [92] s dng phng php xanh
tng hp vng nano v bc, dng dch chit cy xanh kh HAuCl4 v AgNO3.
Nh vy, vic tng hp vng nano s dng chitosan c u im khng gy
nh hng ti mi trng. Tuy nhin, chitosan c nhc im l ch tan c trong
axit m khng tan trong nc hay mi trng trung tnh. iu ny lm hn ch
phn no kh nng ng dng ca vng nano c tng hp t chng. Trong lun n
ny, chng ti nghin cu iu ch chitosan tan trong nc t chitosan v ln u
tin s dng chng lm cht kh ng thi lm cht n nh tng hp vng
nano dng cu (GNP).
1.1.3. Tng hp vng nano dng thanh (GNR)
Trong nhng nm qua, c nhiu phng php c pht trin c th nh
hng v kim sot qu trnh pht trin bt ng hng ca vt liu vng nano. Da
trn c ch hnh thnh ca vt liu, cc phng php c th phn thnh 3 nhm
nh sau [96]:
12
1.1.3.1. Phng php kh quang ha
Phng php ny xut hin vo nhng nm 1990, bng cch s dng bc x
UV ( = 254 nm), ngi ta c th tng hp c vng nano dng thanh vi s c
mt ca cht bo v CTAB. Tuy nhin, hiu sut tng hp thp v c mt lng ln
ht dng cu to thnh trong phng php ny. Hiu sut tng hp tng ln v t s
AR c th kim sot c khi thm AgNO3 vo nh hng pht trin ng thi
thm cht ng hot ng b mt (co-surfactant) nh tetradodecylamonium
bromide (TDAB). D vy, phng php kh quang ha vn c nhc im, l
thi gian phn ng di (cn chiu bc x n 48 gi), do vy sau ngi ta ci
tin bng cch kt hp bc x UV vi s dng cht kh l axit ascorbic. Bng cch
ny, c th rt ngn thi gian kh xung cn 1 gi v tng hp c vng nano
dng thanh vi t s AR nh hn 5 [89], [96].
1.1.3.2. Phng php in ha
Phng php ny c pht minh bi Wang v cng s [108]. Theo ,
mui vng c kh trn in cc platin khi c mt hn hp hai cht hot ng b
mt l CTAB v TDAB. Phng php ny n gin, c th to ra vng nano vi t
s AR khong 1-7. Tuy nhin, cc ht vng nano c to ra theo phng php ny
c s phn b kch thc rng v cha mt lng ln ht dng cu, iu ny lm
hn ch ng dng ca chng [122].
1.1.3.3. Phng php pht trin mm
Phng php pht trin mm rt ph bin trong vic tng hp vt liu vng
nano dng thanh vi u im quy trnh n gin, hiu sut tng hp cao, thu c
sn phm vi kch c, hnh thi mong mun, n phn tn cao v c th kim
sot c t s di/ngang [67], [89], [96]. Phng php ny c pht minh u
tin vo nm 1989 khi Wiesner v Wokaun [114] nghin cu s to thnh bt ng
hng ca vng nano bng cch thm ht mm vng vo dung dch pht trin c
cha HAuCl4. Ht mm c to ra t phn ng kh HAuCl4 vi phospho v s
pht trin ca ht mm bt u bng cch thm H2O2. Tuy nhin, khi nim pht
trin mm mi tht s bt u vo nm 2001 bi Jana v cng s [42] khi h nghin
13
cu tng hp vng nano dng thanh bng cch
thm vng nano dng cu c bo v bng
natri citrate vo dung dch pht trin HAuCl2
hnh thnh do phn ng kh ca HAuCl4 vi
axit ascorbic khi c mt CTAB v ion bc.
Axit ascorbic ch c th kh c ion vng v
nguyn t vng khi c mt ht nano kim loi
xc tc. Cc ht vng nano dng thanh vi t
s AR khong bng 4 (hnh 1.8) c to thnh khi thm ht mm c
kch thc 3,5 nm vo dung dch pht trin. Sau , tng t s cnh ca ht vng
nano, nhm tc gi ny ci tin v m rng phng php pht trin mm thnh 3
giai on v khng s dng AgNO3. Trong , sn phm ca giai on th nht lm
mm cho giai on 2 v giai on 2 lm mm cho giai on 3 (hnh 1.9a). Phng
php ny to ra sn phm c t s AR cao (ln n 25) nhng c nhc im l to
ra mt lng ln ht dng cu. Ngoi ra, cng c mt s nghin cu thm axit nitric
vo giai on th 3 nhm mc ch tng t s cnh AR [115].
Hnh 1.9. S tng hp vng nano dng thanh bng phng php pht trin mm
ca Jana v cng s nm 2001(a) v c Nikoobakht ci tin nm 2003 (b) [67]
n nm 2003, Nikoobakht v El-Sayed [67] c hai ci tin mi cho
phng php ny, l: thay natri citrate bng CTAB trong qu trnh hnh thnh
[42]
14
mm v s dng ion Ag+ kim sot t s AR. Phng php ny bao gm hai giai
on (hnh 1.9b):
- Giai on to mm: s dng tc nhn kh mnh NaBH4 kh Au3+
trong
AuCl4- v Au
0. Giai on ny to ra mt lng ln ht mm trong mt thi gian
ngn (thng l 2-5 gi). Mui kim loi c kh trong nc, trong khng kh
nhit phng v to ra cc ht mm dng cu vi kch thc khong 3-4 nm v
thng c bo v bng cht hot ng b mt CTAB.
- Giai on pht trin mm: s dng cht kh yu axit ascorbic (vitamin C)
kh ion kim loi vng trong s c mt ca cht nh hng cu trc v cht n
nh. Qu trnh kh xy ra chm trn b mt ht mm. Trong giai on ny, cht
nh hng cu trc (thng l Ag+) ng vai tr quyt nh ti s pht trin bt
ng hng ca ht mm to ra dng thanh. Bc nitrate c thm vo dung dch
pht trin trc khi thm mm kim sot hnh thi ca ht vng nano dng thanh
v thu c sn phm vi t l cnh mong mun.
Phng php ny cho sn phm vng nano dng thanh vi hiu sut cao
(99%) v t s cnh AR khong 1,5 n 4,5. Ngoi ra, tng t s AR, ngi ta
cn s dng cht ng hot ng b mt (co-surfactant) nh benzyl
dimethylhexadecyl ammonium chloride (BDAC) [93], [96] hoc hp cht vng
thm [121].
Hiu sut tng hp, n phn tn, hnh thi v kch thc ca vt liu c
th c kim sot bng cch iu chnh cc thng s nh: nng , kch thc v
lng mm, nng mui vng, nng axit ascorbic, nng cht hot ng b
mt, nhit , pH, ...
Trong lun n ny, chng ti tng hp vng nano dng thanh bng phng
php pht trin mm, nghin cu nh hng ca cc yu t nh t l mol
[Ag+]/[Au
3+], t l mol [AA]/[Au
3+], nng Au
3+, nng CTAB cng nh gi tr
pH n tnh cht plasmon v t s AR ca sn phm to thnh.
1.1.4. Cu trc ca vng nano dng thanh
15
Nghin cu c tnh cu trc ca vng nano l mt nhn t rt quan trng bi
hai nguyn nhn. Th nht l hiu c c im cu trc tinh th th mi c th
hiu c c ch hnh thnh ca vng nano. Hn na, c tnh ca vt liu ph
thuc rt nhiu vo hng pht trin ca vng nano dng thanh [35], [71], [93],
[96], [94], [118].
xc nh cu trc tinh th ca vng nano dng thanh, ngi ta thng s
dng cc phng php hin vi in t truyn qua (TEM), hin vi in t truyn qua
c phn gii cao (HRTEM), ph nhiu x in t chn lc (SAED) [47], [71].
Theo Sisco [93] v Susanne [96], c s khc nhau v cu trc ca vng nano
dng thanh tng hp bng phng php in ha v phng php pht trin mm.
Cc tinh th kim loi lp phng thng cha cc mt (111), (100) v (110). S kt
hp ca cc mt ny s kim sot hnh dng ca chng.
Cu trc tinh th ca vng nano dng thanh tng hp bng phng php in
ha c Wang v cng s [108] nghin cu s dng k thut TEM, HRTEM v
ph nhiu x electron. Theo nhm tc gi, cc ht vng nano dng thanh vi t s
AR t 3 n 7 c cu trc n tinh th, u n, khng c khuyt tt hay dnh li
vi nhau. Hng pht trin ca nano dng thanh l hng [001] v c thit din bt
din. Mt bn c gii hn bi cc mt (100) v (110) xen k nhau v do u
mt ca vng nano dng thanh c gii hn ln lt bi cc mt (100) v (111)
(hnh 1.10a).
Trong khi , Gai v Harmer [30] a ra m hnh cu trc tinh th ca vng
nano c t s AR cao tng hp bng phng php pht trin mm ba giai on, s
dng mm bao bc bi citrate v khng c bc nitrate trong dung dch pht trin.
Theo m hnh ny, ht vng nano pht trin theo hng [100], cc mt bn s l
(110) v (100) v kt thc l 5 mt (111) ging nhau (pentatwinned) (hnh 1.10b).
Ngoi ra, Murphy v cng s [42] cho rng, cc ht vng nano dng thanh
tng hp bng phng php pht trin mm 2 giai on, s dng ht mm c bao
bc bng CTAB v c mt AgNO3 trong dung dch pht trin l cc n tinh th vi
cc mt bn l (110) v mt kt thc l (100) (hnh 1.10c).
16
Hnh 1.10. M hnh cu trc vng nano ca Wang v cng s (a) [108], Gain v
Harmer (b) [30], Murphy v cng s (c) [42] v Liz-Marzn v cng s (d) [21]
Gn y, Liz-Marzn v cng s [21] thit lp m hnh cu trc mi cho
ht vng nano dng thanh c t l AR nh c tng hp trong s c mt ca bc
nitrate v cht hot ng b mt. Da vo nh TEM phn gii cao ca ht vng
nano dng thanh thng ng, nhm tc gi ny cho rng cc mt bn ca cc ht
vng nano dng thanh u l cc mt c ch s cao (higher-index) (250). Cc ht
vng nano pht trin theo hng [001] v cc mt u mt khng khc so vi m
hnh ca Wang v cng s, gm cc mt (111) v (110) (hnh 1.10d).
1.1.5. C ch pht trin ca ht vng nano dng thanh
C ch pht trin ca vng nano dng thanh v ang c nhiu nh khoa
hc quan tm nghin cu. Theo , tn ti nhiu quan im khc nhau khi gii
thch c ch hnh thnh ca ht vng nano dng thanh. Nhn chung, c th chia
thnh hai nhm chnh:
1.1.5.1. C ch pht trin ca vng nano dng thanh trong trng hp khng
thm bc nitrate
17
Trn c s m hnh cu trc tinh th ca vng nano dng thanh a ra,
Gai v Harmer [30] cho rng c ch pht trin ca vng nano dng thanh da trn
qu trnh ti thiu ha nng lng b mt. Theo nhm tc gi, u tin trong giai
on to mm, c nhiu ht mm dng 5 cnh ghp i (pentatwinned) c to
thnh. Trong qu trnh pht trin mm, lin kt gia cc phn t cht hot ng b
mt vi mt (110) mnh hn do nng lng b mt t do ca mt ny thp hn so
vi cc mt cn li. V vy, mt (110) c bo v bng CTAB, do ht mm s
pht trin theo hng [100] v kt qu l vng nano dng thanh c hnh thnh
(hnh 1.11).
Hnh 1.11. C ch hnh thnh ht vng nano dng thanh trong trng hp
khng c AgNO3 [96]
Mc d xut m hnh cu trc khc cho vng nano nhng Murphy v
cng s [42] ngh c ch pht trin vng nano dng thanh tng t nh Gai v
Hamer. Theo , s pht trin ca ht vng nano dng thanh da trn s hp ph
ca cht hot ng b mt ln cc mt ca ht mm vi mc u tin khc nhau.
H cho rng, phn t CTAB s u tin hp ph ln mt bn (100). Do , qu trnh
pht trin s b gii hn theo mt hng no dn n s hnh thnh dng thanh.
Trong khi , Liz-Marzn v cng s [21] cho rng, ban u c s hnh
thnh phc gia CTA+ v AuCl4
-. Vic thm axit ascorbic dn n s hnh thnh
phc AuI-CTAB. Au
I to lin kt mnh hn vi mixen CTAB, do tn s va chm
vi ht mm vng l cc nh, chnh iu ny lm gim tc pht trin tinh th.
18
1.1.5.2. C ch pht trin ca ht vng nano dng thanh trong trng hp c
thm bc nitrate
C hai c ch pht trin ht vng nano dng thanh c ngh trong trng
hp ny. C ch th nht da vo s hnh thnh phc gia ion Ag+ v CTAB [67],
[69], [71]. Phc ny s hp ph u tin ln mt mt tinh th no v s hn ch s
pht trin theo hng ny. Do , ht mm s pht trin theo nhng hng khc
khng cha phc ny, dn ti s pht trin bt ng hng ca ht vng nano. S
c mt ca phc CTAB-Ag c th c xc nh bng phng php ph quang in
t tia X (X-ray photoelectron spectroscopy, XPS) hoc khi ph (mass
spectrometry, MS). Ngoi ra, bng k thut XPS v 1H-NMR, mt s tc gi cho
rng, phc CTAB-Ag hp ph ln b mt nguyn t vng mnh hn so vi CTAB.
C ch th hai da trn s kh di th (underpotential deposition, UPD)
ca ion Ag+ thnh Ag
0 [40], [47], [67], [71], [96]. Qu trnh kh Ag
I u tin xy ra
trn mt (110), do to thnh mt lp n nguyn t Ag0 trn mt (110), lm hn
ch s pht trin theo hng ny, kt qu l to ra s pht trin bt ng hng ca
ht vng v hnh thnh vng nano dng thanh. S kh di th l qu trnh kh xy
ra mt th m hn rt nhiu so vi th kh thc t ca n.
Ngoi ra, Liu v Guyot-Sionnest [53] cho rng, cu trc ca ht mm ban
u s xc nh cu trc tinh th ca ht vng nano dng thanh. Ht mm c iu
ch vi cht bo v l CTAB c cu trc n tinh th trong khi ht mm c bao
bc bng citrate c cu trc a song tinh (ghp hp) (multiply twinned). V vy, hai
loi ht mm ny s to nn hai dng nano thanh khc nhau. Ht mm a song tinh
(multiply twinned) s pht trin thnh dng thp i 5 mt ging nhau (penta-
twinned bipyramids) (hnh 1.12b). S hnh thnh cc ht vng nano n tinh th s
dng ht mm n tinh th l do s pht trin chm ca ht nano dng thanh khi c
mt ion Ag+ (hnh 1.12a).
19
Hnh 1.12. C ch hnh thnh ht vng nano dng thanh t ht mm n tinh th
(a) v ht mm multiply twinned (b) di s nh hng ca Ag+ [96]
1.1.6. Mt s khi nim lin quan n GNR
Thng thng, nh gi tnh cht ca vt liu GNR, ngi ta thng xem
xt cc kt qu thu c t ph UV-Vis v nh TEM, l:
a. Ph UV-Vis ca vt liu GNR s c 2 peak hp th c trng, bao gm
mt peak tng ng vi dao ng TSPR (~ 520 nm) c cng yu v mt peak
ng vi dao ng LSPR c cng ln hn nm trong vng kh kin hoc hng
ngoi gn ty thuc vo t s cnh ca vt liu [10], [17], [86].
b. Cc i hp th ng vi dao ng LSPR ca GNR: Theo ti liu [28],
[30], [39], [40], LSPR lin quan n t s cnh AR. Nu LSPR cng dch v vng
hng ngoi gn th t s cnh cng ln v ngc li.
c. T s hp th quang ca dao ng LSPR/dao ng TSPR (t s
LSPR/TSPR, k hiu R) [39], [40]. T s ny cho bit hiu sut ca qu trnh tng
hp GNR. Hiu sut thp ng ngha vi mt lng ln cc ht vng nano dng cu
hnh thnh, do s lm tng hp th quang dao ng TSPR. iu ny c
gii thch l do dao ng SPR ca vng nano dng cu v dao ng TSPR ca GNR
u c cc i hp th nm trong khong 520 nm. V vy, s c mt ca vng nano
dng cu s lm tng hp th quang ca dao ng TSPR, lm t s R gim.
20
d. T s cnh: l t s gia chiu di v chiu ngang ca ht vng nano dng
thanh, k hiu AR. Theo cc ti liu tham kho [40], [67], [89] c mi quan h
tuyn tnh gia t s cnh v bc sng hp th cc i ca dao ng LSPR, c th
l khi AR tng th bc sng cc i hp th s dch chuyn v vng bc sng di
(chuyn dch ). Ngoi ra, mt s nghin cu [9], [40] cn cho thy t s cnh c
nh hng ng k n kh nng ng dng ca ca vng nano dng thanh, c bit
l kh nng pht hin v iu tr ung th.
1.2. GII THIU V CHITOSAN
1.2.1. Cu trc ca chitosan
Chitosan (k hiu l CTS) l mt polysaccharide mch thng cu to t cc
mt xch D-glucosamine lin kt ti v tr -(1-4), l sn phm deacetyl ha ca
chitin, trong nhm (-NH2) thay th mt phn nhm (-NHCOCH3) v tr C2 ph
thuc vo deacetyl (A) [27], [83], [84].
Hnh 1.13. Cu trc ca chitosan [27]
1.2.2. deacetyl ha ca chitosan
deacetyl ha (A) cho bit mc acetyl ha ca chitosan. Qu trnh
deacetyl ha l qu trnh loi nhm acetyl khi chui phn t chitin v hnh thnh
phn t CTS vi nhm amino hot ng ha hc cao. acetyl ha l mt c tnh
quan trng ca qu trnh sn xut CTS bi v n nh hng n tnh cht ha l v
kh nng ng dng ca sn phm.
C nhiu phng php khc nhau xc nh A ca CTS bao gm: Ph
cng hng t ht nhn 1H-NMR, ph hng ngoi, chun bng HI,[25], [46],
[50]. Trong khun kh lun n, chng ti ch trnh by phng php 1H-NMR v
ph IR xc nh A ca chitosan.
21
Xc nh A bng phng php 1H-NMR [25], [50]: y l mt trong nhng
phng php chnh xc nht xc nh A. T ph 1H-NMR, A c xc
nh theo mt trong cc cng thc sau:
HAc
(H2-H6)
1I
3A (%) = 1 1001
I6
(1.2)
HAc
(H1-GlnNAC)
IA (%) = 1 100
3 I
(1.3)
HAc
(H2-GlnN)
1I
3A (%) = 1 100I
(1.4)
1(H GlnN)
(H1-GlnN) (H1-GlnNAC)
IA (%) = 1 100
I I
(1.5)
1(H GlnN)
(H1-GlnN) HAc
IA (%) = 1 100
1I I
3
(1.6)
Trong : + IHAc l cng peak ca 3 hydro trong nhm CH3
+ IH2-H6: l tng cng peak ca H2, H3, H4, H5 v H6
+ IH1-GlnNAc: l cng peak ca H1(N-Acetylglucosamine)
+ IH1-GlnN: l cng peak ca H1 (D-glucosamine)
+ Cng thc (1.2) v (1.6) c p dng cho tt c chitosan
+ Cng thc (1.3) c p dng cho chitosan c A=79-98%
+ Cng thc (1.4) c p dng cho chitosan c A > 40%
+ Cng thc (1.5) c p dng cho chitosan c A < 90%
Xc nh A bng phng php IR [25], [46]: y l mt trong nhng
phng php c s dng ph bin xc nh A. T ph IR, A c xc
nh theo mt trong cc cng thc sau:
22
33,1
100100(%)
3450
1655
A
AA (1.7)
33,1
100100(%)
2870
1655
A
AA (1.8)
115100(%)
3450
1655
A
AA (1.9)
03133,0
03822,0
100(%) 1420
1320
A
A
A (1.10)
Trong : A1655, A3450, A2870, A1320 v A1420 ln lt l hp th ti cc v
tr s sng tng ng.
1.2.3. Phn ng N-acetyl ha chitosan to chitosan tan
Chitosan, mt dn xut ca chitin, l mt polymer c s dng rng ri
trong nhiu lnh vc khc nhau bi chng c nhng u im nh kh nng khng
khun, tng hp sinh hc, kh nng phn hy sinh hc, kh nng hp ph kim loi
nng trong nc, lm lnh vt thng, ... c bit chng c xem l mt vt liu
sinh hc [83]. Tuy nhin, chitosan c nhc im l ha tan km trong nc v cc
dung dch c pH trung tnh [50]. iu ny lm hn ch kh nng ng dng ca
chng trong i sng. Do vy, nhiu cng trnh nghin cu bin tnh chitosan
tng ha tan nh lm gim khi lng phn t chitosan. Lu v cng s [57],
Wang v cng s [107] nghin cu ct mch chitosan bng phng php bc x
kt hp vi tc nhn H2O2 thu c chitosan c ha tan tt hn. Trong khi ,
Abdel-Aziz v cng s [6] nghin cu ct mch chitosan c khi lng phn t
88.000 Da to chitosan c khi lng phn t thp hn (5000 Da) bng enzyme t
vi khun c li Bacuillus alvei nhm mc ch tng ha tan ca chitosan. Ngoi
ra, mt s tc gi cn bin tnh chitosan thnh cc dn xut c kh nng ha tan tt
nh cacboxylmetyl chitosan, chitosan-g-poly(etilen glycol), N-phthaloyl chitosan.
Tuy nhin, nhng phng php ny vn cn hn ch bi v to ra chitosan c khi
lng phn t thp hoc l oligochitosan ch tan trong dung dch c pH < 7. Mt
23
khc, cc bin i ha hc hay ct mch c th lm thay i cu trc ca chitosan
dn n chitosan b mt i nhng tnh cht ha l ban u ca chng.
khc phc nhng hn ch trn, Lu v cng s [56] nghin cu iu
ch chitosan tan trong nc (water soluble chitosan: WSC) bng phng php
N-acetyl ha s dng anhydrid acetic vi nhiu u im l quy trnh n gin,
nhanh, t tc nhn, hiu sut iu ch cao v c bit l to ra chitosan c kh nng
tan tt trong nc. Sn phm to thnh l chitosan acetyl c A dao ng t 37%
n 62% ph thuc vo cc yu t nh nng H+, thi gian acetyl ha, dung mi,
lng andehyde, ... Sau , Nguyn Ngc Duy v cng s [64] ci bin quy trnh
ca Lu v cng s, s dng bc x hoc tc nhn oxi ha l H2O2 m khng s
dng dung mi c l pyridin iu ch chitosan tan, to ra c chitosan c
kh nng ha tan tt trong nc.
Trong lun n ny, chng ti s dng phng php acetyl ha chitosan bng
anhydrid acetic theo quy trnh ca Nguyn Ngc Duy v cng s [64] iu ch
chitosan tan trong nc v s dng sn phm tng hp vng nano.
1.3. NG DNG VNG NANO XC NH MELAMIN TRONG SA
1.3.1. Gii thiu v melamin
Melamin (tn y 1,3,5-triazine-2,4,6-triamine) l mt baz hu c c
cng thc ha hc C3H6N6 v c cng thc cu to nh sau [12], [20], [22], [32]:
Hnh 1.14. Cng thc cu to ca melamin
Melamin tr thnh ti c bn lun nhiu vo nm 2007 khi cc nh
khoa hc xc nh rng nguyn nhn lm cho hng trm con vt nui cht l do
nhim bn melamin trong thc n [33]. c bit l v mt s loi sa Trung Quc
b nhim bn melamin lm t nht 6 tr em t vong v hn 54000 tr em phi nhp
vin v b bnh lin quan n thn [32], [36], [44], [49].
24
Trong phn t melamin, nit chim 66% khi lng. V hm lng nit cao
nn melamin c mt s nh sn xut a vo trong thc phm, c bit l trong
sa nhm mc ch tng hm lng protein. C s h thc hin iu ny l
nhng phng php kim tra nh phng php Kjeldahl v phng php Dumas o
hm lng protein trong thc phm thng qua vic xc nh hm lng nit [33],
[44], [51], [58], [75].
Bn thn melamin khng c c tnh liu thp nhng khi vo trong c th,
melamin d dng kt hp vi axit cyanuric qua lin kt hydro to kiu lin kt phn
t hnh mi ngi, lng ng, gy si thn v thm ch dn n t vong [33].
Hnh 1.15. S kt hp gia melamin v axit cyanuric
1.3.2. S dng vng nano xc nh hm lng melamin trong sa
Vic xc nh melamin trong thc phm ni chung v trong sa ni ring l
iu v cng cn thit. Cho n nay, c nhiu phng php khc nhau nh
tnh v nh lng melamin trong thc phm nh: sc k lng ghp ni khi ph
(LC-MS) [44], [95], sc k kh ghp ni khi ph (GC-MS) [44], sc k lng hiu
nng cao (HPLC) [85], xt nghim hp th min dch lin kt vi enzym (ELISA)
[49], ... Tuy nhin, nhng phng php ny c nhc im l phi dng nhng thit
b t tin, phc tp, tn thi gian v phi c chuyn vin thc hin [33], [57]. V
vy, vic pht trin mt phng php n gin, nhanh v r xc nh melamin
ang thu ht s quan tm ca cc nh khoa hc.
Gn y, c mt s cng trnh trn th gii nghin cu s dng cc ht
vng nano xc nh melamin trong sa v cc sn phm t sa [12], [20], [22],
http://vi.wikipedia.org/wiki/S%E1%BA%AFc_k%C3%ADhttp://en.wikipedia.org/wiki/High_performance_liquid_chromatographyhttp://en.wikipedia.org/wiki/High_performance_liquid_chromatography
25
[32], [33], [36], [51], [112]. u im chnh ca phng php ny l c th nh tnh
melamin trong mu sa bng mt thng da vo s thay i mu ca dung dch t
ta sang xanh ti (hay mu tm) khi thm melamin vo vng nano. Do , khng
cn n cc thit b phc tp, tn km. Phng php ny pht hin melamin vi
nhy cao. Cao v cng s [20] da vo lin kt hydro gia melamin v 1-(2-
mercaptoethyl)-1,3,5-triazinane-2,4,6-trione (MTT) xc nh melamin trong sa
s dng vng nano c bo v bng MTT. Tuy nhin, phng php ny kh phc
tp v trc ht phi tng hp MTT, sau tng hp vng nano s dng MTT.
Sau , mt s tc gi s dng vng nano tng hp t cc phng php
khc nhau xc nh melamin trong sa vi gii hn pht hin thp hn.
Mc d c mt s cng b trn th gii s dng vng nano xc nh
melamin nhng theo s tm hiu ca chng ti th ti Vit Nam, cha c nghin cu
no cho mc ch ny. Trn c s , trong lun n ny chng ti s dng vng
nano dng cu tng hp c nh tnh v nh lng melamin trong sa.
1.4. NG DNG IN CC BIN TNH VNG NANO XC NH
HM LNG AXIT URIC BNG PHNG PHP VON-AMPE HA TAN
1.4.1. Gii thiu phng php von-ampe ha tan
Phng php von ampe ha tan (SV) l mt phng php c nhy,
chnh xc cao, xc nh nhanh cc cht c nng thp, thit b khng phc tp
[106]. Vi nhng u im trn, hin nay phng php von-ampe ha tan ang c
s dng rng ri xc nh lng vt cc kim loi cng nh cc hp cht hu c.
Nguyn tc: Qu trnh phn tch cng bao gm hai giai on: giai on lm
giu v giai on ha tan [106].
- Giai on lm giu: Bn cht ca giai on ny l tp trung cht cn phn
tch trong dung dch ln trn b mt in cc lm vic (WE) mt th v thi gian
xc nh. Trong giai on lm giu, dung dch c khuy trn u bng khuy t
hoc dng in cc rn a quay. Qu trnh tp trung cht phn tch ln trn b mt
WE c th bng hai cch, l in phn lm giu hoc hp ph lm giu.
26
Sau giai on ny, th trn WE c gi nguyn nhng ngng khuy hoc
ngng quay in cc trong khong thi gian t 2 s n 30 s cht phn tch phn
b u trn b mt in cc lm vic.
- Giai on ha tan: Thc cht ca giai on ny l ha tan cht phn tch ra
khi b mt WE bng cch qut th v pha dng hn (gi l qut anot).
1.4.2. Cc in cc s dng trong phng php von-ampe ho tan
Cc loi in cc c s dng trong phng php von-ampe ha tan gm:
- in cc lm vic (WE): nh in cc rn a quay bng kim loi hoc vt
liu nn l cacbon, in cc git thy ngn tnh (SMDE), in cc git thy ngn
treo (HMDE), in cc mng kim loi (MeFE) hoc in cc bin tnh, [98]
- in cc so snh: thng l in cc calomen hoc bc-clorua bc
- in cc ph tr: thng dng l mt in cc platin.
C nhiu loi in cc lm vic c s dng [106]. y, chng ti ch
cp n loi in cc bin tnh bng nano kim loi v mng polymer mt loi in
cc c quan tm nghin cu nhiu trong nhng nm gn y bi chng c ng
dng rng ri trong lnh vc bin tnh in cc [26], [45], [62], [106], [109].
Trong s cc nano kim loi s dng cho mc ch ny, vng nano ang c
quan tm nhiu v nhng tnh cht c bit ca n nh c th nng cao dn,
thun li cho vic chuyn in t v nng cao gii hn pht hin ca phng php
von - ampe do s bt thng ca chng v tnh cht vt l v ha hc [34], [45],
[62], [98], [109]. Ngoi ra, cc ht nano kim loi vng c din tch b mt cao, hiu
qu chuyn khi, hot ng in xc tc cao v thn thin vi mi trng [109].
Tuy nhin, vn t ra l cc lp nano kim loi vng trn b mt in cc thng
d trc v do khng n nh in, hn ch ng dng ca n trong cm bin. V
vy, cn c mt cht kt dnh c nh ht vng nano trn b mt in cc. Da
trn s n nh ca mng hu c, in cc ph mng hu c c th c s dng
nh mt cht nn cho s kt bm ca ht vng nano, phn phi n nh v ng
nht ht vng nano trn b mt in cc, nhiu im hot ng in hn c th dn
n phn tch tn hiu ln hn.
27
Trong s cc loi polymer dn in v cc cht kt dnh thng c s
dng, L-cystein (k hiu l L-cys) l 1 -axit amin vi cng thc ha hc
HO2CCH(NH2)CH2SH, L-cys, c bit hu ch cho vic bin tnh in cc [109].
O
OH
SH
H2N
Hnh 1.16. Cng thc cu to ca L-cystein [109]
L -cys c nhiu tnh nng ni tri, nh lp mng ny rt n nh v kh c
th loi b ra khi b mt; phn t L-cys cha nhm thiol c i lc mnh vi kim
loi nh Au, c th hnh thnh lin kt S-Au bng lin kt cng ha tr. Do , c
th phn tn cc ht nano kim loi (nh Au) ln b mt in cc v to ra cc im
in xc tc [34], [109].
in cc bin tnh bi L-cys v vng nano c s dng xc nh axit
ascorbic, dopamin, axit uric [34], [109], v nhiu hp cht hu c khc vi u
im l lm tng nhy v khong tuyn tnh ca in cc.
1.4.3. S dng in cc bin tnh vng nano xc nh axit uric bng phng
php von-ampe ha tan anot
1.4.3.1. Gii thiu v axit uric
Axit uric (2,6,8-trioxypurine) l hp cht khng mu, khng mi v khng v,
vi cng thc phn t C5H4N4O3 [26], [45], [61].
Hnh 1.17. Cng thc cu to v cu trc phn t ca axit uric [61]
Phn ln axit uric trong mu dng t do, ch c khong t hn 4% gn vi
protein huyt thanh. Nng axit uric trung bnh trong mu nam l 5,1 1,0
mg/dL (420 mol/L), n l 4,0 1,0 mg/dL (360 mol/L) [34], [61]. Khi nng
7
9
1 6
3
28
axit uric trong mu cao (trn 420 mol/L i
vi nam hay trn 380 mol/L i vi n) th
chng c th kt ta thnh cc tinh th di
hnh kim, u nhn tch t trong khp xng
v l nguyn nhn ca bnh gout (vim khp,
sng khp) [26], [61] (hnh 1.18).
Ngoi ra, vic tng axit uric trong mu
cn dn ti mt s bnh l khc nh: bo ph, i tho ng, tng huyt p, x va
ng mch, nhi mu c tim, [34], [61], [98], [109].
1.4.3.2. Xc nh axit uric bng phng php in ha s dng in cc bin
tnh vng nano
Vic xc nh axit uric trong huyt thanh v nc tiu l iu ht sc cn
thit. Cc phng php thng c s dng l phng php hunh quang,
phng php trc quang, sc k lng hiu nng cao (HPLC), sc k ion v enzym
[72], [94], [119], Tuy nhin, a s cc phng php ny thng phc tp, tn
km v hn ch v nhy, chn lc v thu hi. Phng php in ha ra i
c th cung cp mt phng php r, n gin v nhanh chng trong vic xc nh
axit uric. Trong s cc phng php in ha hin i th phng php von-ampe
ha tan l phng php c nhy v chnh xc cao, cho php xc nh hm
lng vt nhiu kim loi, cng nh hp cht hu c, trong c axit uric.
Du v cng s [26] tin hnh bin tnh in cc si cacbon vi graphit v
vng nano xc nh dopamin v axit uric, vi khong tuyn tnh cho axit uric l
12,6 413,62 M vi chi ph thp, d ch to v hon ton kh thi. in cc glassy
cacbon bin tnh bi polyimidazole v ht vng nano c Wang v cng s
[105] nghin cu ch to v pht trin xc nh axit ascorbic, dopamine, axit uric
bng phng php von-ampe ha tan anot xung vi phn (DV), vi khong tuyn
tnh cho axit uric l 6,0 486,0 M; gii hn pht hin (LOD) l 0,5 M. in cc
c ng dng trong phn tch mu thc: vin Vitamin C, mu huyt thanh, mu
nc tiu, thu c nhiu kt qu kh quan, vi thu hi nm trong khong
95,0% n 108,6%.
Hnh 1.18. Tinh th axit uric
kt ta trong khp xng [64]
29
Trong lun n ny, chng ti s nghin cu ch to in cc bin tnh bng
ht vng kch thc nano trn nn glassy cacbon (GC) c ph lp mng L-cys v s
dng in cc ny phn tch axit uric trong huyt thanh v nc tiu bng
phng php von-ampe ha tan anot.
1.5. NGHIN CU KH NNG KHNG KHUN CA VNG NANO
1.5.1. Gii thiu v vi khun
Vi khun l sinh vt c kch thc b nh tn ti dng n bo, c cu to
gm lp mng bn ngoi v bn trong l ADN [16], [24]. C hai nhm vi khun
chnh: vi khun gram dng v vi khun gram m. y, chng ti ch gii thiu
mt s loi vi khun gy ng c thc phm, c s dng nghin cu kh nng
khng khun ca vng nano, l:
- Vi khun Escherichia coli (E. Coli) O157:H7 (E20/ E29): E. coli l vi
khun sng trong ng rut ngi v ng vt, c bit tru b. C nhiu loi vi
khun E. coli. a s cc vi khun ny khng nguy him. Tuy nhin, E. coli
O157:H7 c th gy bnh trm trng ngi nh gy tiu chy nghim trng v h
hi thn [128].
- Vi khun Salmonella typhimurium (S1) hoc Salmonella enteritidis (S4):
Trc khun Salmonella thuc b Eubacteriales, h Enterobacteriaceae. Ging
Salmonella gm 2 loi: S. enterica v S. bongori c phn chia thnh trn 2000
serotyp theo bng phn loi Kauffmann-White trn c s cu trc ca khng
nguyn thn O, khng nguyn lng H v i khi cc khng nguyn v (khng
nguyn K). Vi khun ny gy ng c thc phm, vim rut [128].
- Vi khun Listeria monocytogenes (L. monocytogenes) l mt vi khun
Gram dng k kh ty nghi. y l vi sinh vt gy ng c thc phm nguy him,
chng c th pht trin trong nhng iu kin nhit (4C) m mt s vi khun
khc khng pht trin c. Tuy t l mc bnh khng cao (khong 0,7 ca/100.000
ngi) nhng t l t vong li rt cao, c th ti 20 30%, c bit ph n c
thai, tr s sinh, ngi gi v nhng ngi suy gim min dch [128].
http://vi.wikipedia.org/w/index.php?title=Vi_khu%E1%BA%A9n_Gram_d%C6%B0%C6%A1ng&action=edit&redlink=1http://vi.wikipedia.org/w/index.php?title=Vi_khu%E1%BA%A9n_Gram_d%C6%B0%C6%A1ng&action=edit&redlink=1http://vi.wikipedia.org/w/index.php?title=K%E1%BB%8B_kh%C3%AD_t%C3%B9y_ti%E1%BB%87n&action=edit&redlink=1
30
- Vi khun Staphylococcus aureus l mt loi t cu khun Gram dng k
kh ty nghi v l nguyn nhn thng thng nht gy ra nhim khun trong cc
loi t cu. N l mt phn ca h vi sinh vt sng thng tr da c tm thy
c mi v da. Khong 20% dn s loi ngi l vt mang lu di ca S. aureus. Sc
t carotenoid staphyloxanthin lm nn tnh cht mu vng ca S. aureus, vn c th
thy c t cc khm cy trn thch ca vi khun ny [128].
1.5.2. ng dng khng khun ca vng nano
Thng thng, tiu dit cc vi khun, ngi ta thng s dng cc khng
sinh. Tuy nhin, nhc im ca vic s dng khng sinh l gy ri lon h tiu ha
ca ngi v ng vt. Quan trng hn l hin nay, cc nghin cu [16], [24], [52],
[55] cho thy, cc chng vi sinh vt (vi khun) c hin tng khng thuc do vic
s dng thuc khng sinh mt cch ba bi v iu ny ang tr thnh mi e da
ln i vi sc khe ca con ngi. Do , vic tm ra mt con ng mi gii
quyt vn trn l iu cn thit. Mt trong nhng con ng c nhiu ha hn
thnh cng, l s dng cc ht nano kim loi. Do c u im l kch thc nh,
din tch b mt ln nn cc ht nano kim loi c th d dng tip xc vi cc vi
khun [55], [76], [78]. iu ny lm tng kh nng khng khun ca cc ht nano
kim loi. Trong s cc nano kim loi th vng nano c s dng rng ri bi v n
c din tch b mt ln [24] v c kh nng chng oxi ha b mt [76]. Cc nghin
cu kh nng khng khun ca vng nano cho thy mc khng khun ph thuc
rt nhiu vo hnh dng v kch thc ht ca chng [16], [76], [78].
Nm 2011, Zawrah v cng s [124] th nghim s dng ht vng nano
dng cu nghin cu kh nng khng khun ca 6 loi vi khun khc nhau. Kt
qu l vng nano c kh nng c ch c s pht trin ca vi khun vi ng
knh vng v khun khong 13 mm.
Sau , n nm 2012, Liny v cng s [52] tng hp vng nano s dng
dch chit hoa hng dng kh AuCl4- v s dng vng nano ny nghin
cu kh nng khng khun ca 3 loi vi khun A. Flavus, E. Coli v Strpetobcillus.
thu c kt qu kh quan vi ng knh ca vng khng khun t 15-31 mm.
http://vi.wikipedia.org/wiki/T%E1%BB%A5_c%E1%BA%A7u_khu%E1%BA%A9nhttp://vi.wikipedia.org/w/index.php?title=Gram-d%C6%B0%C6%A1ng&action=edit&redlink=1http://vi.wikipedia.org/w/index.php?title=Sinh_v%E1%BA%ADt_k%E1%BB%B5_kh%C3%AD_t%C3%B9y_nghi&action=edit&redlink=1http://vi.wikipedia.org/w/index.php?title=Sinh_v%E1%BA%ADt_k%E1%BB%B5_kh%C3%AD_t%C3%B9y_nghi&action=edit&redlink=1http://vi.wikipedia.org/w/index.php?title=Nhi%E1%BB%85m_khu%E1%BA%A9n_do_t%E1%BB%A5_c%E1%BA%A7u&action=edit&redlink=1http://vi.wikipedia.org/w/index.php?title=H%E1%BB%87_vi_sinh_v%E1%BA%ADt_s%E1%BB%91ng_th%C6%B0%E1%BB%9Dng_tr%C3%BA_%E1%BB%9F_da&action=edit&redlink=1http://vi.wikipedia.org/w/index.php?title=S%E1%BA%AFc_t%E1%BB%91&action=edit&redlink=1http://vi.wikipedia.org/w/index.php?title=S%E1%BA%AFc_t%E1%BB%91&action=edit&redlink=1http://vi.wikipedia.org/wiki/Carotenoidhttp://vi.wikipedia.org/w/index.php?title=Staphyloxanthin&action=edit&redlink=1
31
Gn y, nm 2013, Prema v cng s [78]
tng hp vng nano t phn ng kh HAuCl4
bng natri citrate vi cc tc nhn lm bn khc
nhau nh tinh bt, chitosan v nghin cu kh
nng c ch ca chng vi 8 loi vi khun khc
nhau. Kt qu vng v khun nhn c t 7 n
30 mm (hnh 1.19).
Cng thi gian , Lokina v cng s [55]
nghin cu kh nng khng khun ca vng
nano c tng hp s dng dch chit qu nho
lm cht kh. Theo , 6 loi vi khun c
chn nghin cu v kt qu thu c nng c ch ti thiu (MIC) t 0,08 n
1,25 mg/mL.
Ha cng xu hng trn, trong lun n ny, chng ti nghin cu kh nng
khng khun ca hai loi vng nano dng cu v dng thanh vi bn loi vi khun
khc nhau c lit k trn.
Hnh 1.19. Kh nng khng khun
ca vng nano [78]
32
CHNG 2
NI DUNG, PHNG PHP NGHIN CU
V THC NGHIM
2.1. MC TIU
Tng hp vng nano dng cu, dng thanh v kho st mt vi ng dng ca
chng.
2.2. NI DUNG NGHIN CU
- Nghin cu tng hp vng nano dng cu (GNP) bng phng php kh s
dng WSC lm cht kh ng thi lm cht n nh.
- Nghin cu tng hp vng nano dng thanh (GNR) bng phng php pht
trin mm s dng cetyltrimethylammonium bromide (CTAB) lm cht bo v.
- Nghin cu s dng vng nano xc nh melamin trong sa.
- Nghin cu ch to in cc bin tnh vng nano phn tch axit uric
trong huyt thanh v nc tiu.
- Nghin cu kh nng khng khun ca vng nano.
2.3. CC PHNG PHP NGHIN CU
2.3.1. Phng php ph t ngoi kh kin (UVVis) [2], [5]
Ph UV-Vis l loi ph electron, ng vi mi electron chuyn mc nng
lng ta thu c mt vn ph rng, l mt phng php nh lng xc nh nng
ca cc cht thng qua hp th nh sng ca dung dch.
C
----------------
I0 I
l
33
Nguyn tc: Cho chm nh sng c di bc sng xc nh trong vng
kh kin (Vis) hay trong vng t ngoi gn (UV) i qua vt th hp th (thng
dng dung dch). Da vo lng nh sng b hp th bi dung dch m suy ra
nng (hm lng) ca dung dch .
Cng tia ti: Io = I
A + I
r + I (2.1)
Trong : Io
l cng ban u ca ngun sng; I l cng nh sng sau
khi i qua dung dch; IA l cng nh sng b hp th bi dung dch v I
r l
cng nh sng phn x bi thnh cuvet v dung dch, gi tr ny c loi b
bng cch lp li 2 ln o.
Cng hp th bc x ca 1 cht c xc nh da trn s gim cng
chm bc x khi chiu qua dung dch cha cht kho st v c chng minh
bi nh lut hp th nh sng ca Bouguer-Lambert-Beer.
0I
A = lg lCI (2.2)
Trong : A l hp th hoc mt quang; C l nng mol cht ban u
(mol/L); l l b dy lp dung dch m nh sng i qua (cm); l h s hp th (nu
C = 1 mol/L, l = 1 cm th c gi l h s hp th phn t gam; nu C = 1%
(v/v), l = 1 cm th c gi l h s hp th ring (E)).
Nh vy, hp th ca dung dch t l vi nng (C) v b dy (l) ca
lp cht kho st.
Chng ti s dng ph UV-Vis xc nh bc sng hp th cc i ca
vng nano. Vng nano c tnh cht cng hng plasmon b mt, nh n c th
hp th cc tia bc x thch hp. Ngoi ra, cc ht vng nano dng thanh (GNR) c
t s cnh (chiu dc/chiu ngang) cng ln th bc sng hp th cc i cng
dch chuyn v vng hng ngoi gn. Chnh v vy, chng ti dng ph UV-Vis
nh gi s b t s cnh, hnh thi cng nh hiu sut tng hp GNR.
Trong lun n ny, ph UV-Vis c ghi trn thit b Jasco V-630 UV-Vis
spectrophotometer.
2.3.2. Phng php hin vi in t truyn qua (TEM) [2], [3], [5]
34
Knh hin vi in t truyn qua l mt thit b nghin cu vi cu trc vt rn,
s dng chm in t c nng lng cao chiu xuyn qua mu vt rn mng v s
dng cc thu knh t to nh vi phng i ln (c th ti hng triu ln).
nh c th c to ra trn mn hunh quang, hay trn mng quang hc, hay c
ghi nhn bng cc my chp k thut s.
Phng php TEM cho bc nh chn thc v kch thc ht ca vt liu.
Nh cch to nh nhiu x, vi nhiu x v nano nhiu x, k thut hin vi in t
truyn qua cn cho bit nhiu thng tin chnh xc v cch sp xp cc nguyn t
trong mu, theo di c cch sp xp trong chi tit tng ht, tng din tch c
micromet vung v nh hn. Nguyn l hot ng ca phng php o TEM c
trnh by trn hnh 2.1.
Hnh 2.1. S nguyn l hot ng ca thit b hin vi in t truyn qua
Trong lun n ny, nh TEM c o trn my Jeol-JEM 1010 transmision
elecctron microscope (Nht).
2.3.3. Phng php quang ph hng ngoi (IR) [3], [5]
Ph hng ngoi l php phn tch ph bin cho bit cc lin kt v cc nhm
chc trong vt liu phn tch. Phng php IR da trn s tng tc ca cc bc x
in t trong min hng ngoi (400 - 4000 cm-1
) vi cc phn t nghin cu. Qu
trnh tng tc c th dn n s hp th nng lng, c lin quan cht ch n
cu trc ca cc phn t.
http://vi.wikipedia.org/wiki/%C4%90i%E1%BB%87n_t%E1%BB%ADhttp://vi.wikipedia.org/wiki/Th%E1%BA%A5u_k%C3%ADnh_t%E1%BB%ABhttp://vi.wikipedia.org/wiki/Quang_h%E1%BB%8Dc
35
Nguyn tc chung: Khi chiu mt chm tia n sc c bc sng nm trong
vng hng ngoi qua mu phn tch, mt phn nng lng b hp th lm gim
cng tia ti. S hp th ny tun theo nh lut Lambert-Beer.
A= lg(I0/ I) =lC (2.3)
Trong : + A: mt quang
+ T = I0/I: truyn qua
+ : h s hp th
+ l: chiu dy cuvet (cm)
+ C: nng cht nghin cu (mol/L)
Phng trnh (2.3) l phng trnh c bn cho cc phng php phn tch
ph hp th nguyn t cng nh phn t. ng cong biu din s ph thuc mt
quang v chiu di bc sng kch thch gi l ph.
Hu ht cc phn t khi dao ng c gy ra s thay i moment lng cc
in, c kh nng hp th bc x hng ngoi cho hiu ng ph hng ngoi hay
(ph dao ng). Theo quy tc ny, cc phn t c hai nguyn t ging nhau khng
cho hiu ng ph hng ngoi .
Khi tn s dao ng ca nhm nguyn t no trong phn t t ph thuc
vo cc thnh phn cn li ca phn t th tn s dao ng c gi l tn s c
trng cho nhm . Cc tn s c trng cho nhm (hay cn gi l tn s nhm)
thng c dng pht hin cc nhm chc trong phn t.
Da vo tn s c trng, cng nh trong ph hng ngoi, ngi ta c
th phn on trc tip v s c mt ca cc nhm chc, cc lin kt xc nh trong
phn t nghin cu, t xc nh c cu trc ca cht nghin cu.
Trong lun n ny, ph IR c o trn my IR-Prestige-21 (Shimadzu)
trong vng 400-4000 cm-1
.
2.3.4. Phng php nhiu x tia X (XRD) [5]
Chiu mt chm tia X n sc c bc sng ti mt tinh th cht rn. Theo
l thuyt cu to tinh th, mng tinh th c xy dng t cc nguyn t hay ion
36
phn b u n trong khng gian theo mt trt t nht nh, cc mt tinh th s
cch nhau mt khong u n d. Khi chm tia X ti b mt tinh th v i su vo
bn trong mng li th tinh th mng li ny ging nh mt cch t nhiu x c
bit to ra hin tng nhiu x ca cc tia X.
Mi quan h ca khong cch gia hai mt phng tinh th song song (d), gc
gia phng tia X ti v mt phng tinh th () v bc sng tia X () c biu
din bi phng trnh Vulf-Bragg [4]:
2dsin = n (2.4)
Trong : n l bc nhiu x (n = 1, 2, 3, )
T nh lut Bragg c th xc nh khong cch gia cc mt mng dhkl khi
bit v gc nhiu x tng ng vi vch nhiu x thu c. Mi mt cht tinh
th khc nhau s c c trng bng cc gi tr dhkl khc nhau. So snh gi tr dhkl
thu c vi gi tr dhkl ca mu chun cho php ta xc nh c mu nghin cu
c cha cc loi khong vt no. Do vy, phng php nhiu x tia X c th xc
nh c thnh phn pha tinh th ca vt liu. Kim tra s n pha ( tinh khit)
ca vt liu, xc nh c kch thc tinh th, cu trc tinh th,
Hnh 2.2. Cc tia X nhiu x trn cc mt tinh th cht rn
Gin XRD ca cc mu nghin cu c o trn thit b Brucker D8
Advance, ng pht tia X vi anod bng Cu c bc sng (CuK)= 1,5406 .
2.3.5. Phng php sc k thm thu gel (GPC)
Bc sng 1
Bc sng 2
Mt
phng
nguyn
t
Gc ti Gc phn
x
37
Phng php sc k thm thu gel c dng tch cc cu t da vo
khi lng phn t ca chng. V vy, ngi ta c th dng phng php ny
xc nh khi lng phn t ca cht cn phn tch.
Nguyn l hot ng: GPC l mt thit b sc k c th xc nh c khi
lng phn t ca cc hp cht cao phn t. Hn hp c tch da theo kch
thc ca phn t cc cht phn tch c phn b khc nhau vo trong cc mao
qun ca pha tnh. Cc phn t c kch thc nh s di chuyn vo bn trong mao
qun nn c ra gii ra sau, v ngc li.
Loi sc k ny c p dng tch hn hp cc cht c khi lng phn
t ln v khng c kh nng phn ly thnh ion. N c p dng xc nh khi
lng cc cht c khi lng phn t ln phc v cho cc ngnh cng nghip sn,
ch to polymer trong i sng,...
xc nh khi lng phn t ca chitosan (CTS) bng phng php GPC,
ngi ta bm dung dch CTS vo ct ca thit b GPC, ra gii bng m acetate.
Sau so snh thi gian lu ca cu t ra gii c vi cht chun, t suy ra
khi lng phn t ca CTS.
Trong lun n ny, khi lng phn t ca CTS v WSC c xc nh trn
my GPC 110, detector RI, Agilent -M.
2.3.6. Phng php ph tn x nng lng tia X (EDX) [2], [3], [5]
Ph tn x nng lng tia X (thng c k hiu l EDX, EDS hoc
XEDS) (t y gi l ph EDX) l k thut phn tch thnh phn ha hc ca vt
rn da vo vic ghi li ph tia X pht ra t vt rn do tng tc vi chm in t
c nng lng cao.
Nguyn tc ca phng php EDX l da trn s tng tc gia ngun tia X
kch thch v mu cn phn tch. Mi nguyn t ho hc c mt thnh phn nguyn
t xc nh to ra cc vch ph c trng cho nguyn t . to bc x c trng
t mu, mt dng nng lng cao ca cc ht tch in nh in t, photon, hay
chm tia X c chiu vo mu cn phn tch. Thng thng, cc in t trong
mu cc trng thi c bn (cha b kch thch) v chng xoay quanh ht nhn
38
cc mc nng lng khc nhau. Khi kch thch bng mt chm tia X, in t s
nhy ln mt mc nng lng cao hn, to nn mt l trng in t, mt in t
khc t lp bn ngoi c nng lng cao hn nhy vo in vo l trng .
Bc nhy ny gii phng nng lng di dng nng lng tia X tn x.
Hnh 2.3. Nguyn tc tn x tia X dng trong ph EDX
Trong lun n ny, phng php EDX c s dng xc nh thnh phn
nguyn t ca vng nano dng cu v dng thanh, c o trn my JEOL-6490-JED-
2000.
2.3.7. Phng php ph cng hng t ht nhn (NMR) [5]
Ph cng hng t ht nhn (NMR) c xy dng trn nguyn tc spin ht
nhn. Trong nguyn t, ht nhn t quay quanh trc c moment ng lng ring
v to ra spin ht nhn, di tc dng ca t trng ngoi th c th chia thnh 2
mc nng lng. NMR hot ha spin ht nhn khi nguyn t c s proton hoc
neutron l. Nh th 1H nhy vi nguyn t hydro nht.
Trong mt phn t, mt ht nhn c bao bc bi cc in t v cc ht
nhn c t tnh khc ln cn. Do tc dng thc ca t trng ngoi vo ht
nhn nghin cu khng hon ton ging vi tng ht nhn c lp. Khi , c 2 yu
t nh hng n tc dng ca t trng ngoi ln ht nhn nghin cu l s che
chn ca m my in t xung quanh ht nhn v nh hng ca cc ht nhn bn
cnh c trong phn t. Trong mt phn t, ty theo cu trc m tn s cng hng
ca proton (hay 13
C) khc nhau. Tng s cc peak cng hng to thnh ph
NMR ca phn t. Phn t vi cu trc khc nhau s c ph NMR c trng khc
nhau. Hai yu t quan trng trong ph cng hng t ht nhn l v tr peak (cho
Ht nhn
in t nhy ra
Kch thch ngoi
http://upload.wikimedia.org/wikipedia/commons/9/9f/EDX-scheme.svg
39
bit dch chuyn ha hc) v hnh dng peak (cho bit tng tc ca ht nhn
ang xt vi cc ht nhn k cn). V tr v hnh dng peak trong ph NMR cho bit
cu trc phn t ang xt.
Trong lun n ny, chng ti ghi ph 1H-MNR trn my JEOL JNM
CMX300, Japan, Nht Bn vi dung mi l HOD.
2.3.8. Ph phn x khuch tn t ngoi kh kin (UV-Vis/DR) [2], [3], [5]
Khi dng nh sng va p vo mu rn c hai loi phn x xy ra: Phn x
gng v phn x khuch tn. Phn x gng (specular reflectance) lin quan n
qu trnh phn x ca dng tia ti v tia phn x c cng gc (nh gng phng).
Phn x khuch tn (diffuse reflectance) lin quan n dng tia ti phn x theo tt
c mi hng. Phn x khuch tn v phn x gng c minh ha hnh 2.4.
Hnh 2.4. Phn x gng v phn x khuych tn t b mt nhm
Bc x phn x khuch tn nm vng t ngoi, kh kin hay vng hng
ngoi cn gi l ph phn x khuch tn t ngoi kh kin (t y gi l ph UV-
Vis/DR). i vi vt liu hp th nh sng, khi dng tia ti c cng (Io) chiu
vo vt liu hp th i qua mt lp mng c dy l l, vi h s hp th ().
Cng (I) ca tia l c tnh theo nh lut hp th Lambert bit:
-l
oI I e (2.5)
Vic o s phn x khuch tn c thc hin bi mt ph k UV-Vis gn
vi mt thit b phn x khuch tn (cn gi l qu cu tch phn) c kh nng tp
hp dng phn x. Qu cu tch phn l mt qu cu rng c ph bn trong vt
liu trng c mc phn x khuch tn xp x 1. Qu cu c mt khe c th cho
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dng nh sng i qua v tng tc vi vt liu cn o v vt liu so snh. Vt liu
trng vi h s khuch tn cao thng l polytetrafluoroethylene (PTFE) hay
barium sulfate (BaSO4).
Trong lun n ny ph UV Vis/DR c o trn my GBC Instrument -
2885 trong vng t 200 n 800 nm.
2.3.9. Phng php sc k lng hiu nng cao (HPLC) [85]
Phng php HPLC l phng php chia tch trong pha ng l cht lng
cn pha tnh cha trong ct l cht rn c phn chia di dng tiu phn hoc
mt cht lng ph ln mt cht mang rn hay l mt cht mang c bin i
bng lin kt ha hc vi cc nhm chc hu c. Qu trnh sc k lng da trn c
ch hp ph, phn b, trao i ion hay phn loi theo kch c (ry phn t).
Trong lun n ny, chng ti s dng phng php HPLC phn tch hm
lng melamin, s dng my Series 20A Shimadzu (Nht) vi cc iu kin sc k
nh sau: Qu trnh tch c thc hin trn mt ct C18 (150mm x 3.2mm ID, kch
thc ht 5 m). Pha ng (0,1% Trifluoroacetic - TFA / methanol l 90:10) c
bm vi tc dng 0.3 mL/ pht vi bc sng pht hin 240 nm. Melamin
c tch ra thi gian lu l 13,6 pht.
2.3.10. Phng php o nht
Trong lun n ny, chng ti tin hnh o nht ca hn hp dung dch
WSC v HAuCl4 trc v sau phn ng vi dung mi l H2O bng nht k
Ubbelohde 50113/Ic (ng knh mao qun 0,84 mm). Qu trnh c thc hin
qua cc bc sau:
1. Chun b 20 mL hn hp dung dch gm WSC 0,5% + Au3+
0,5 mM,
2. Xc nh thi gian chy ca dung mi H2O (0),
3. Xc nh thi gian chy ca hn hp dung dch WSC 0,5% + Au3+
0,5
mM trc phn ng (1),
4. Xc nh thi gian chy ca hn hp dung dch WSC 0,5% + Au3+
0,5
mM sau phn ng (2),
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Mi gi tr thi gian chy c o 3 ln ri ly gi tr trung bnh.
Qu trnh o c tin hnh 25C. Nhit c n nh bng my n
nhit vi sai s nhit l 0,1C.
5. Tnh ton nht
nht tng i c tnh theo phng trnh (2.6).
t = /o = /o (2.6)
nht ring c tnh theo phng trnh (2.7).
r = (-o)/o = t-1 = /o-1 (2.7)
2.3.11. Phng php phn tch in ha
Trong lun n ny, chng ti s dng phng php von-ampe vng v von-
ampe ha tan anot phn tch axit uric.
- Phng php von-ampe vng: c s dng nhm nghin cu c tnh ca
axit uric trn in cc bin tnh bng vng kch thc nano.
