nanoparticle synthesis in reverse micelles
TRANSCRIPT
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Nanoparticle Synthesis in Reverse Micelles
Nicola Pinna
Max Planck Institute of Colloids and Interfaces
e-mail: [email protected] - http://www.pinna.cx
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Plan
1. Reverse Micelles
• Surfactants in Solutions
• Reverse Micelles
• Synthesis of Particles
2. Examples
• Semiconductors
• Metals
• Oxides
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Surfactants in Solution
• Anionic
• Cationic
• Zwitterionic
• Nonionic
N+
Br-
SO
-Na
+
O
OSodium dodecylsulfate (SDS)
Cetylpyridinium bromide
O
O
P
O
OO
OCH2CH2N(CH3)3+
O-
Dipalmitoylphosphatidylcholine (lecithin)
OO
OO
OH
Polyoxyethylene(4) lauryl ether (Brij 30)
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Surfactants in Solution
4 nm4 nm
UnimersNormal micelles
spherical
cylindrical
Bilayer lamellaReverse micelles
Inverted hexagonal phase
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Surfactants in Solution
0
2
4
6
8
10
12
14
0 1Surfactant concentration
CMC
s
0
2
4
6
8
10
12
14
0 1Surfactant concentration
CMC
s
CMC
• Below CMC only
unimers are present
• Above CMC there are
micelles in equilibrium
with unimers
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Surfactants in Solution
Packing parameter (shape factor)= V/al
V Volume of the tail
a Cross sectional surface of the polar head
l Length of the hydrophobic tail
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Reverse Micelles
Water in oil microemulsion
Surfactant = AOTO
SO3
OO
O
- Na+
8A 4A
Isooctane
AOT
20%40%60%80%
AOT
20%
40%
60%
80%20%
40%
60%
80%Is
oocta
ne
H O2
H O2
L2
B
L2 + L1
L1 + B
L2 + B
H O2
Isooctane
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Reverse Micelles
W
[AOT]
[H O]2
W=
H O2
H O2
Water amount → size of the micelles
+ +
Collisions between micelles → Exchange of the water content
→ Chemical Reactions: Coprecipitation, Reduction, Hydrolysis-Condensation
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Reverse Micelles
M. Zulauf, H.-F. Eicke, J. Phys. Chem. 83, 4, 1979
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First Synthesis
First review article about particles formations in microemulsions
• Atomic and molecular clusters in membrane mimetic chemistry Janos H. Fendler, Chem. Rev.; 1987; 87(5);877-899.
• Cadmium sulfide of small dimensions produced in inverted micellesP. Lianos, J. K. Thomas, Chem. Phys. Lett. 1986, 125, 299CdS nanoparticles from AOT/H2O/Heptane reverse micelles, coprecipitation between Cd(ClO4)2 and Na2S
• Photosinsitiezed charge separation and hydrogen production in reversed micelle entrapped platinized colloidalcadmium sulfideM. Meyer, C. Wallberg, K. Kurihara, J. H. Fendler, Chem. Comm. 1984, 90CdS nanoparticles from AOT/H2O/isooctane reverse micelles, coprecipitation between CdCl2 and H2S
• Synthesis of cadmium-sulfide insitu in reverse micelles and in hydrocarbon gelsC. Petit, M. P. Pileni, J. Phys. Chem. 1988, 92, 2282CdS nanoparticles from AOT/H2O/isooctane reverse micelles, coprecipitation between Cd(NO3)2 and Na2S
• The preparation of monodisperse colloidal metal particles from microemulsionsM. Boutonnet, J. Kizling, P. Stenius, G. Maire, Colloids Surf. 1982, 5, 209Pt, Pd, Rh, Ir 3-5 nm particles prepared by reduction of metal salts in reverse micelles: Hexadecyltrimethylam-monium Chloride (CTAB)/octanol/H2O
The general approach consist on mixing 2 micellar solutions containing the cations and the anions
→ Fast reaction, spherical particles
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First Synthesis
P. Lianos, J. K. Thomas, Chem. Phys. Lett. 1986, 125, 299 M. L. Steigerwald, et al. J. Am. Chem. Soc.; 1988; 110(10);
3046-3050
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Modern Examples
Synthesis and Characterization of non spherical nanoparticles made in reverse micelles
• Semiconductors - CdS nanoparticles and nanotriangles - Coprecipitation
• Oxides - V2O5 nanorods and nanowires - Hydrolysis-Condensation
• Metals - Silver nanoparticles and nanodisks - Reduction
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Coprecipitation
N. Pinna, K. Weiss, J. Urban, M. P. Pileni, Adv. Mat, 2001, 13,261
N. Pinna, K. Weiss, H. Sack-Kongehl, W. Vogel, J. Urban, M. P. Pileni, Langmuir 2001, 17, 7982
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TEM
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HRTEM
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Shape Determination
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Optical Properties
t=0
t=48h
t=0
t=48h
t=0
t=48h
t=0
t=48h
t=0
t=48h
t=0
t=48h
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Optical Properties
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Hydrolysis-Condensation
2VO(OR)3 + 3H2O → V2O5 + 6ROH R=CH(CH3)2
VO(OCH(CH ) )3 2 3
in isooctane
t=24h-100dt=0
H O2
+
N. Pinna, U. Wild, J. Urban, R. Schlogl. Adv. Mat. 15(4), 329, 2003
N. Pinna, M. Willinger, K. Weiss, J. Urban, R. Schlogl, Nano Lett, 3, 1131, 2003
M. Willinger, N. Pinna, D.S. Su, R. Schlogl, Phys. Rev. B, 69, 155114, 2004
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V2O5 Nanorods and Nanowires
500 nm
25 nm
50 nm
50 nm
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XPS
514516518520Binding Energy (eV)
0
2000
4000
6000
8000
1∗104
1.2∗104
Inte
nsity
(cps
)
V2p3/2
VOx
528530532534536Binding Energy (eV)
0
0.05
0.1
0.15
Inte
nsity
(cps
)
O1sAOTVOxVOx - AOT
512514516518520Binding Energy (eV)
0
0.05
0.1
0.15
0.2
Inte
nsity
(cps
)
V2p 3/2VOx
528530532534536Binding Energy (eV)
0
0.05
0.1
0.15
0.2
0.25
Inte
nsity
(cps
)
O1sAOTVOxVox-AOT
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XRD
IN(b) =∑N
n,m6=n fnfmsin(2πbrnm)
2πbrnmb = 1
d= 2sinϑ
λ
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Structures
α-V2O5 γ-V2O5
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Structures
α-V2O5 γ-V2O5
Atom1 Atom2 Distance (A)
V O1 1.5759V O2 1.7783V O3 2.0176V O3 1.8776
Atom1 Atom2 Distance (A)
V1 O1 1.7257V1 O3 1.5468V1 O4 1.8914V1 O4 1.9861V2 O1 1.8479V2 O2 1.5810V2 O5 1.8984V2 O5 1.9671
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FT-IR
- - - AOT · · · α-V2O5 Bulk — γ-V2O5 24h – – γ-V2O5 100d
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Band structure
α-V2O5 γ-V2O5
Γ X S Y Γ Z U R T Z
E F
Ene
rgy
(eV
)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
-1.0
-2.0
-3.0
-4.0
-5.0
-6.0 Γ X S Y Γ Z U R T Z
E F Ene
rgy
(eV
)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
-1.0
-2.0
-3.0
-4.0
-5.0
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DOS
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Electron Energy Loss Spectrometry
α-V2O5 γ-V2O5
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Electron Energy Loss Spectrometry
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Reduction
1 - 60% Ag(AOT) - 40% Na(AOT) O.1 M - W=2
2 - Na(AOT) O.1 M - N2H4 - [N2H4]/[AOT]=1.44
2 N2H4 + 4Ag+ → N2 + 4H+ + 4Ag0
A. Taleb, C. Petit, M. P. Pileni, Chem. Mater. 1997, 9, 950
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Silver Nanoparticles
N. Pinna, M. Maillard, A. Courty, V. Russier, and M. P. Pileni, Phys. Rev. B 2002, 66, 045415
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Optical Properties
Maxwell-Garnett
2D Generalisation
Dipolar Fields:∑
x = 12S0 ;
∑z = −S0 ; S0 =
∑′
j = 1(rij/d)3
εxeffεm
= 1−(λα/8)(S0/2)+2γ(2a/d)2α1−(λα/8)(S0/2) ;
εzeffεm
= 1+(λα/8)S01+(λα/8)S0−2γ(2a/d)2α
λ = (2a/d)3 ; α = εs(ω)−εm
εs(ω)+2εm; γ = fs/(2a/d)2
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Optical Properties
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Optical Properties
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Silver Nanodisks
1 - 60% Ag(AOT) - 40% Na(AOT) O.1 M - W=2
2 - Na(AOT) O.1 M - N2H4 - 4.1 < [N2H4]/[AOT] < 16.5
2 N2H4 + 4Ag+ → N2 + 4H+ + 4Ag0
M. Maillard, S. Giorgio, M.P. Pileni, Adv. Mater. 14, 1084, 2002
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Optical Properties
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Conclusion
• The reverse micelle technique permits the synthesis of many inorganic materials
• Size and shape control
• Homogeneous products
• Low polydispersity
• Small quantities and difficult to scale up
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Acknowledgements
• M. Willinger - First DFT calculations of γ-V2O5 Structure
• K. Weiss, H. Sack-Kongehl - Transmission electron microscopy
• U. Wild - XPS mesurements
• Dr. M. Maillard, Dr. V Russier - Optical properties of silver nanoparticles
• Prof. J. Urban, Prof. R. Schlogl, Prof. M. P. Pileni