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Title: Prsentation PowerPoint


1
Vanadium oxide gels versatile precursors for
nanostructured materials
Jacques Livage
Collège de France
Uppsala 22.04.08
2
Vanadium pentoxide V2O5
a single crystalline phase made of edge sharing
double chains of VO5
3
Vanadium pentoxide V2O5 can be made
4
Vanadium coordination changes with pH
5
Vanadium (V) in aqueous solution
5
different species depending on pH and
concentration
6
Formation of vanadium oxide gels
via the acidification of aqueous metavanadates
V2O5.nH2O gels
decavanadic acid
NaVO3
7
51V NMR of the precursor solution
cationic species
anionic species
VO2
H2V10O284-
the intensity of the 51V NMR spectrum of
decavanate species decreases with time
8
Molecular precursors around the Point of Zero
Charge pH 3
9
Formation of a ribbon-like structure via the
condensation of neutral precursors
y
x
10
10
V2O5.nH2O gels are made of oxide fibres  flat
ribbons 
11
J. Legendre et al. (1983) Y. Oka et al. (1992) H.
Smyrl et al. (2000) M.G. Kanatzidis et al. (2002)
12
V2O5,nH2O gels are made of vanadium oxide
double layers
13
Layered structure of V2O5,nH2O gels
G. Kanatzidis et al. JACS, 124 (2002) 10157
double layers
Monoclinic unit cell (C2/m) a 11.722 Å
b 3.570 Å c 11.520 Å b 88.65
V2O5 ribbons
J. Legendre et al. (1983) Y. Oka et al. (1992) H.
Smyrl et al. (2000) Kanatzidis et al. (2002)
14
Acid properties of V2O5,nH2O gels
2. Acid dissociation of V-OH groups at the
oxide-solution interface
15
15
Gels remain stable for years
electrostatic repulsion between negatively
charged ribbons
16
V2O5 sols and gels lyotropic liquid crystals
Optical observation between crossed polarizers
Singular points linked by black stripes
called noyaux par G. Friedel
Schlieren structures in V2O5,400H2O sols
17
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18
Mixed conduction in V2O5,nH2O gels
19
Kodak
coating 1 mg/m2
20
20
Antistatic coatings
US Patent 4,203,769
V2O5 ? SnO2-Sb small polaron hopping does not
requires a well crystalline network
R
Percolative properties 1 mg/m2
electrical resistance of V2O5 films decreases
when the length of the nanowires increases
unaffected by changes in humidity (mixed
conduction)
t, l
21
Mixed conduction in V2O5,nH2O gels
s f(pH2O)
22
Versatile host matrix for intercalation
H2O
23
V2O5 reversible cathode for lithium batteries
24
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25
25
Electrochromic properties of V2O5,nH2O gels
Keng-Che Cheng et al. Solar Energy Materials
Solar Cells, 90 (2006) 1156
26
All gel electrochromic cell
Working electrode WO3
WO3 xLi xe- LixWO3
1V
blue
white
Counter electrode V2O5
good electrochimical reversibility
weak coloration
27
II Hybrid organic - inorganic V2O5 gels
a wide range of molecular species can be
intercalated within the layered structure of
V2O5.nH2O gels
Molecular ions (CoCp2), (FeCp2),
CnH2n1N(CH3), ... Organic molecules dyes,
pyridine, …. Polymers PEO, PVA, … Biomolecules
porphyrin, glucose oxidase, ...
28
V2O5 -Polyaniline hybrids
M.G. Kanatzidis et al. Chem. Comm. (1993) 593
Reduction of V2O5
oxygen
Oxidation of aniline
(PANI)xV2O5
29
Structure of (PANI)0.5V2O5.H2O
30
30
The conductivity of V2O5-Pani hybrids is 104
times that of V2O5
31
anisotropic conductivity
32
Glucose biosensors (diabete)
Glucose Oxydase catalysis of the oxidation of
glucose by molecular O2
electron transfer from the active site to the
electrode
molecular mediator ferrocene/ferricinium
33
V2O5 based glucose biosensor
both GOD and ferrocene can be intercalated in
V2O5,nH2O gels
V. Glezer et al. JA.C.S. 115 (1993) 2533
C.G. Tsiafoulis et al. Electrochem. Comm. 7
(2005) 781
34
PVC-V2O5 hybrids
d 12 Å
E.C. Zampronio et al. J. Non-Cryst. Solids, 332
(2003) 249
d 12.2 Å
Self-standing V2O5 films
V2O5 ribbons are dispersed into PVC no
intercalation of PVC in V2O5
Poly Vinyl Chloride reinforcing agent
35
35
R. Backov et al. Adv. Funct. Mater. 16 (2006) 1745
Vanadium oxide Fibres
via V2O5 gel extrusion
36
Vanadium oxide fibres
37
55 mm
Anisotropic fibres
Vanadium oxide fibres observed through
crossed-polarizers
38
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39
Ethanol sensing devices based on vanadium oxide
fibres
reversible adsorption of EtOH at the surface of
V2O5 fibres
40
Gaz sensing devices based on vanadium oxide fibres
40
resistance decreases rapidly upon injection of
ROH and restored its initial value when ROH is
released
41
Bio-hybrid gelatin - vanadium oxide
vanadic acid
gelatin
42
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43
visco-elastic hybrid materials
44
60C
pKa(NH3/NH2) 10,5
pKa(COOH/COO-) 4
Gelatin chains are positively charged (pH lt 4)
45
45
Formation of rubber-like gelatin-decavanadate
composites
46
Hydrothermal synthesis of vanadium oxides
from 1D to 2D structures
Nanowires - nanoribbons - nanobelts - nanosheets
47
In-situ 51V NMR
V4
V10
200C - 3 h
200C - 30 mn
100C
T
80C
V10
V4
25C
Td
Oh
Transformation of decavanadates into
metavanadates upon heating
48
transformation of decavanadates into
metavanadates
pH
T
Td
deprotonation coordination decrease
Oh
1D ribbons
2D layers
VO4 tetrahedra
49
Hydrothermal synthesis of polyvanadates in the
presence of TMA
50
50
Role of the final pH
51
TMAV8O20
pH 3
ribbon-like particles
52
TMAV4O10
pH6
layered structure
plate-like particles
53
TMAV3O7
pH 8
platelets
54
Hydrothermal synthesis in the presence of anions
V2O5 TMAOH TMAX
X I
X Cl
pH6
(TMA)8V18O42 l.4H2O
(TMA)6V15O36Cl.4H2O
octahedron
hexagonal prisms
55
55
Hollow anionic molecular clusters
anions are inserted within a negatively charged
polyvanadate cluster !
56
Structure of (TMA)6V15O36Cl
Cl-
anions behave as templates
Cl- anions are inside the negative V15O365-
clusters
V15O36Cl6-
TMA just behave as a counter-ions
TMA cations are outside the V15O365- clusters
55
57
Anions behave as templates
highly labile water molecule lifetime t
10-10 s
driving force for condensation oxolation
58
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59
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60
Nanostructured vanadium oxides
60
foams
nano-urchins
nano-flowers
G. Gonzales et al. Chem. Mater. 18 (2006) 3016
J. Livage et al. unpublished
G.T. Chandrappa et al. Nature, 416 (2002) 702
61
Vanadium oxide nanotubes from gels
Hydrothermal treatment of vanadium oxide with
long chain alkyl amines
62
Vanadium oxide nanotubes from gels (G.T.
Chandrappa et al. JSST (2003)
63
VOx nanotubes
R. Nesper et al. Angew. Chem. 37 (1998) 1263
length up to 15 mm
outer diameter 15 - 150 nm
inner diameter 5 - 50 nm
wall thicknes 5 - 25 nm
5 - 30 layers
64
Structure of VOx-NT
CnH2n1NH2
Two sets of diffraction peaks
do not change with the amine
depends on the amine
d lt 2l
Dd f(n) 1.7 - 3.8 nm
n gt 12 large overlap of alkyl chains
R. Nesper et al. Chimia 53 (1999) 336
65
65
Structural model of C12-VOx-NT
BaV7O16,nH2O
2 sheets of VO5 square pyramids pointing in
opposite directions with VO4 tetrahedra
Intercalated amines
R. Nesper et al. Chimia 53 (1999) 336
66
How do VOx-NT form ?
K.J. Rao
67
Most nanotubes are open
Scroll-like morphology
R. Nesper et al. JACS. 121 (1999) 8324
68
1st step Intercalation of long chain alkyl
amines ageing at room temperature long enough (1
to 3 days) to get intercalated layers before the
formation of nanotubes
69
2nd step Hydrothermal heating around 180C
VO5
V7O16 layers
VO4
VO5
70
70
exfoliation during the hydrothermal treatment
71
Formation of VOx nanotubes from V2O5.nH2O gels
180C
from layers to nanotubes
72
3rd step Formation of vanadium oxide scrolls
73
flexible layers corner sharing ? edge sharing
rolling
74
V2O5 nanofibre sheet actuators
Gang Gu et al. Nature Materials, 2 (2003) 316
Two V2O5 sheets separated by a flexible substrate
Expansion of V2O5 ribbons upon electron injection
75
75
Vanadium oxide Nanorings
G.T. Chandrappa et al.
76
Nanorings are formed via hydrothermal heating
around pH 4
77
From nanotubes to nanorings
78
Vanadium oxide nano-urchins
C.O Dwyer et al. Chem. Mater. 18 (2006) 3016
Vanadium oxide gels formed via the hydrolysis of
vanadium alkoxides
79
Formation of vanadium oxide nano-urchins
formation of VOx layers
TMAV4O10
80
80
Formation of vanadium oxide nano-urchins
curvature with NT axis parallel to the layers
radial growth of NT
81
Urchin-like nanostructures made of spherical
VOx-NT radial arrays
d 10 mm
82
Growth stages of VOx nano-urchins
83
Vanadium oxide foam
G.T. Chandrappa et al. Nature, 416 (2002) 702
1g of V2O5 gives 2.5 liters of foam
84
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85
85
20 m
MEB
10 m
50 m
86
Crystalline vanadium oxide foams
TEM
TEM
layered structure d 33Å
87
Macroporous vanadium oxide foams R. Backov et al.
Adv. Mater. (2006)
Non ionic surfactant tergitol
88
The pore size depends on the foaming conditions
89
600 µm
90
90
Vanadium oxide nanotubes can be formed via the
hydrothermal treatment of foams
Intercalation ageing 0 days ? 3
days Hydrothermal at 180C 2 days ? 7 days
91
Vanadium oxide gels Versatile precursors for
nanostructured materials
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