Embed Size (px)
Citation preview
LIONS/ CEA-DAE Indo-French Workshop 2008
Nanoparticles at interfaces
D. Carrière
A. Thill, D. Kopetzki, Y. Michina (LIONS)
P. Barboux (ENSCP)
LIONS/ CEA-DAE Indo-French Workshop 2008
The principle
phase A
phase B
R
R’
Two non-miscible reactive phases
Confinement of the reaction
Control by the interface
Growth
Controlled growth of nanoparticles
LIONS/ CEA-DAE Indo-French Workshop 2008
The context
Brust-Schiffrin « two phase » reaction
toluene
water
AuCl4-
BH4-
N+
Au
SH
Au SH
SH
SH
Brust1994
LIONS/ CEA-DAE Indo-French Workshop 2008
The context
Works fine with metals but:- limited success with chalcogenides- no success with oxydes (> 20 nm)
Pan2004&2007Abu Bakar2007, Vorobyova2004
Control
LIONS/ CEA-DAE Indo-French Workshop 2008
SHSH
SH
SH
Mechanism intellectually appealing but:- film vs nanoparticle?- contact angle vs “transfer agent”?- shear?
Rautaray2003Patil2000, Rao2005, Fan2007, Sanyal2008
The context
LIONS/ CEA-DAE Indo-French Workshop 2008
Our systems
Microemulsions(Separate reactive phases!)
Dynamic interfacesby microfluidics
Towards « smart »surfactant vesicles
10 nm
100 µm
5 µm
LIONS/ CEA-DAE Indo-French Workshop 2008
Reactive microemulsions
Oil: 2-ethyl hexanoic acidvery weak acid hydrophobic
COOH
Organic metal precursor:2-ethyl hexanoates hydrophobic M2+
-OOC
COO-
Surfactant:CTACl N+
Cl-
LIONS/ CEA-DAE Indo-French Workshop 2008
Phase diagram
2 phases
Isotropicmicroemulsion
Birefringentmicroemulsion
LIONS/ CEA-DAE Indo-French Workshop 2008
Stabilization mechanism
Cosurfactant: none!
N+
COO-H+
“Catanionic” film at the oil/water interface
surfactant
N+
Cl-
Cl-
LIONS/ CEA-DAE Indo-French Workshop 2008
Microemulsion
Effect of metal precursor
Microemulsion
Metal precursor in oil phase:Contraction of the microemulsion
LIONS/ CEA-DAE Indo-French Workshop 2008
Effect of metal precursor
Water-in-oil microemulsionBicontinuous emulsion?
LIONS/ CEA-DAE Indo-French Workshop 2008
SAXS in W/O domain
Water-in-oil ~ 6 nm independent on Cu concentration
LIONS/ CEA-DAE Indo-French Workshop 2008
Reaction triggering (1)
Cu2+(L-)2 + 2 OH- CuO + 2L- + H2O
No more W/O domain
LIONS/ CEA-DAE Indo-French Workshop 2008
Reaction triggering (2)
70°C : reaction triggering
LIONS/ CEA-DAE Indo-French Workshop 2008
No structural change in the microemulsion upon reaction
SAXS
LIONS/ CEA-DAE Indo-French Workshop 2008
ICPMS
Less low-Mw metal precursorMn reactivity > Cu reactivity
TEM: amorphous growth?
LIONS/ CEA-DAE Indo-French Workshop 2008
Mechanism
M2+
-OOC
COO-
HH
O
HH
O
M2+COO-
COO-
HH
O
HH
O
M2+COO-
COO-
HH
O
HH
O
M2+COO-
COO-
HH
O
HH
O
M2+COOH
COOHOH-
OH-
OH- generated in situ by heating?Also works with NaCl addition: equilibrium M2+ Na+
LIONS/ CEA-DAE Indo-French Workshop 2008
Original growth triggering (temperature, salt addition)
Mechanism to be clarified:
- Time-resolved ESR- SAXS
From amorphous to crystalline nanoparticles?
Conclusion
OK for materials, too complex for mechanism studies
simplification
LIONS/ CEA-DAE Indo-French Workshop 2008
Dynamic interfacesby microfluidics100 µm
LIONS/ CEA-DAE Indo-French Workshop 2008
Oil/Water dynamic interfaces
1 mm ~ 20 µsec
Mn2+(2EH)2in toluene
NaOHin water
Time-resolved SAXS (Soleil, SWING)
LIONS/ CEA-DAE Indo-French Workshop 2008
NaOH = 0.1 mol/L-1
No NaOH
Short times (~ 20 µs)
Longer times (~ 200 µs)
NaOH 0.1 M: increase then decreaseTo be assigned to amorphous growth
LIONS/ CEA-DAE Indo-French Workshop 2008
NaOH = 1 mol/L-1
NaOH 1 M: inhibition of the reaction at short times?
No NaOH
Longer times (~ 200 µs)
Short times (~ 20 µs)
LIONS/ CEA-DAE Indo-French Workshop 2008
Mechanism
M2+
-OOC
COO-
H+
O
COO-
COO-
O
M2+COO-
COO-
O
M2+COO-
COO-
M2+
OH-
OH-
Cation reaction favorable at high NaOHLigand release/reprotonation not favorable
H+
LIONS/ CEA-DAE Indo-French Workshop 2008
Microfluidics powerful tool for time-resolved SAXS (µs vs ms)
Conclusion
Inhibition of the reaction at short times despiteexpected higher reactivity
LIONS/ CEA-DAE Indo-French Workshop 2008
Towards « smart »surfactant vesicles5 µm
LIONS/ CEA-DAE Indo-French Workshop 2008
+X-
H+
+
+ H+X-
+X-
Critical molar fraction:No surfactant extraction
Catanionic mixtures
LIONS/ CEA-DAE Indo-French Workshop 2008
20 µm
Vesicles at the critical molar fractionResistant to dialysis
Catanionic vesicles
LIONS/ CEA-DAE Indo-French Workshop 2008
pH measurement
dialysis
Encapsulation of a pH-sensitive probe
LIONS/ CEA-DAE Indo-French Workshop 2008
pH gradient accross the vesicle membrane
pH measurement
LIONS/ CEA-DAE Indo-French Workshop 2008
Spontaneous uptake of cationsTransmembrane potential (from permeabilities) ~ -33 mV
Spontaneous uptake
LIONS/ CEA-DAE Indo-French Workshop 2008
Size dependence
C α S/V = 1/R
Control of the uptake and pH by the size of the vesicles
Br- = 0.74 mM Br- = 1.80 mM
LIONS/ CEA-DAE Indo-French Workshop 2008
First attempts
+ AgNO3
Uptake of Ag+
Formation of [AgCl]No vesicle destruction
LIONS/ CEA-DAE Indo-French Workshop 2008
Conclusion
More elaborate inorganic particlesControl of diffusion rates by the size of vesicles
Sorting of the particle size by the vesicles
LIONS/ CEA-DAE Indo-French Workshop 2008
Three different soft-matter systems:
- microemulsions: original growth triggering
- microfluidics: mechanistic studies
- vesicles: selection of growth conditions
LIONS/ CEA-DAE Indo-French Workshop 2008
Acknowledgements
P. Barboux (ENSCP): SERA. Thill (CEA, LIONS): SAXSC. Mariet (CEA, LPS): ICPMS
SAXS at Soleil
D. Kopetzki, Y. Michina (CEA, LIONS)T. Gustavsson (CEA, LFP)
Microemulsions
Vesicles
O. Taché, P. Haltebourg, C. Blot, J. Daillant, O. Spalla, A. Thill,Swing
