organic/inorganic nanocomposites from confined...
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Controlling Organic Phase Architecture via Templating with the Inorganic Phase and vice versa.
http://www.cem.msu.edu/~kanatzid/
Organic/Inorganic Nanocompositesfrom confined polymerization
Our work exploits confined polymerization and self-assembly, to organize inorganic and organic building-units into nanocomposite materials with targeted structural features spanning Å to µm length scales.
The techniques involve concepts in
supramolecular, host-guest inclusion templatingbiomimetic chemistry
our work has contributed to the idea that inorganic materialscan be synthesized by molecular design, self-assembly and crystal engineering.
NanocompositesNanocomposites of interestof interest
lamellar
delaminated
porous
Potential ApplicationsPotential Applications
Tough structural materialsTough structural materials
Smart membrane systemsSmart membrane systems
Battery cathode materialsBattery cathode materials
Sensor applicationsSensor applications
EMI shieldingEMI shielding
Electronic device components Electronic device components
Polymerization ofPolymerization of pyrrolepyrrole
NH NH
NHNH
NHH
H
NH
NH
NH
NH
NH NH
NH
NH
H NH NH NH
NHH
Ò
Ò
deprotonation
p-doped polypyrrole+ 2H +
.
+ 2H +
chain propagation primarily through 2,5 coupling
2,5 coupling
n
oxidation
+ .+'
at the 2,5 positions
+ 2H +
strongly acidic
+
+
dimerization
radical cation
oxidation+e-
+ '
+ '
disorderedbranched
Ordered parallel
N H
+ FeOCl
N H
+ FeOCln
INTERCALATIVE POLYMERIZATIONINTERCALATIVE POLYMERIZATION IN IN FeOCl FeOCl and Vand V22OO552H2H22OO
O2 H2O2
mw=5000~55 units
CH3CN
Kanatzidis, Marks et al JACS 109, 3797 (1987)
Also NH2
S
V2O5 Xerogel
0
10
20
30
40
50
60
0 1 2 3 4 5
Oxygen Depletion (%)
Aniline/V2O5 Xerogel Molar Ratio
2θ, degrees
PANI-V2O5
Inte
nsity
XX--ray Diffraction from PANIray Diffraction from PANI--FeOCl FeOCl ““single crystalsingle crystal””
a-axis
Ordering of polyaniline in FeOCl (Endotaxy)
c-axis
Cl
Fe
2x2 supercell
VV22OO55••nHnH22O O xerogelxerogelStructure of V2O5 xerogel
water
100-200 Å
1000-3000 Å
001
003004 005
2θ degrees (CuKα)
NaVO 3 to HVO 3Polymerization of HVO 3 Sol-Gel Transition
gel
wet gel
xerogel
V2O5.nH 2O
SALIENT FEATURES OF NANOCOMPOSITESSALIENT FEATURES OF NANOCOMPOSITES
Diverse Components Mixed at the Molecular Diverse Components Mixed at the Molecular ScaleScale
compoundcompound--likelikeclassical composite classical composite --likelike
Potential Polymer Chain Ordering in Potential Polymer Chain Ordering in IntralamellarIntralamellarSpaceSpace
polymer structure polymer structure enhanced propertiesenhanced properties
Maximization of Interface InteractionsMaximization of Interface Interactionsmodel systems for interface studiesmodel systems for interface studiesInteractions at interface responsible for advanced propertiesInteractions at interface responsible for advanced properties
Hybrid materials Hybrid materials …….. new properties.. new properties
Phyllosilicates, clays: montmorillonite, hectorite, fluorohectorite
Oxides: V2O5 xerogel, MoO3
Oxyhalides: FeOCl
Dichalcogenides: MoS2, TiS2, TaS2, NbSe2, WS2
MPS3: MnPS3, CdPS3, NiPS3
metal phosphates: α-Zr(HOPO3)2·H2O, α-Ti(HOPO3)2 ·H2O,
HUO2PO4·4H2O
Layered Double Hydroxides: [Ca2Al(OH)6]+[(OH).3H2O]-
Giannelis, Ruiz-Hitzky, Kanatzidis, Nazar, Lemmon, Jones, others...
Layered Inorganic Compounds as Host Materials
Methods for Polymer IntercalationMethods for Polymer Intercalation
inin--situsitu intercalativeintercalative redoxredox polymerizationpolymerizationpolypyrrolepolypyrrole//FeOClFeOCl, PANI/V, PANI/V22OO5 5 ((KanatzidisKanatzidis et al)et al)polypyrrolepolypyrrole//zeolitezeolite ((BeinBein et al)et al)polypyrrolepolypyrrole/clay (/clay (GiannelisGiannelis et al)et al)
monomer intercalation followed by induced monomer intercalation followed by induced topotactic polymerizationtopotactic polymerizationpostpost--intercalative intercalative nylon/clay (nylon/clay (KamigaitoKamigaito, , UsukiUsuki et al)et al)aniliniumanilinium/V/V22OO5 5 ((KanatzidisKanatzidis et al) et al)
direct polymer intercalationdirect polymer intercalation (solution/solid interface)(solution/solid interface)PPV/MoOPPV/MoO33 ((NazarNazar et al) (precursor polymer)et al) (precursor polymer)PEO/VPEO/V22OO5 5 ((KanatzidisKanatzidis et al) et al) PEO/clay (RuizPEO/clay (Ruiz HitzkyHitzky,, GiannelisGiannelis))PEO/CdPSPEO/CdPS33 (Clement et al)(Clement et al)PAN/PAN/zeolitezeolite ((BeinBein et al)et al)
……more methodsmore methods
direct polymer intercalation from the meltdirect polymer intercalation from the meltPEO/clay, polystyrene/clay (PEO/clay, polystyrene/clay (GiannelisGiannelis et al)et al)
polymer polymer encapsulationencapsulation by flocculation of a colloidal single layer by flocculation of a colloidal single layer suspension of the host suspension of the host
(nano(nano--composite self assembly) composite self assembly) PANI/MoSPANI/MoS22 ((KanatzidisKanatzidis et al)et al)
simultaneous polymerization/polymer simultaneous polymerization/polymer encapsulationencapsulation by flocculation of a by flocculation of a colloidal single layer suspension of the host colloidal single layer suspension of the host
(nano(nano--composite self assembly)composite self assembly)polypyrrolepolypyrrole/MoS/MoS22 ((KanatzidisKanatzidis et al)et al)
Alternating Alternating layer by layerlayer by layer deposition of one phase on top of anotherdeposition of one phase on top of anotherMalloukMallouk, , DecherDecher othersothers
Others...Others...
POLYMER ENCAPSULATIONPOLYMER ENCAPSULATION
waterLi
Li+
polymer solution
nanocomposite
dispersion
exfoliation
polymer
Host material
Exfoliated layers of MoSExfoliated layers of MoS22 , WS, WS22 , NbSe, NbSe22 and TaSand TaS22 have been have been used for the first time to produce plasticused for the first time to produce plastic--likelikenanocompositesnanocomposites
The exfoliation method applies to a large variety of soluble polThe exfoliation method applies to a large variety of soluble polymersymersEnables tuning of the mechanical properties in these materialsEnables tuning of the mechanical properties in these materials
PolyethylenePolyethylene
PolyethylenePolyethylene--oxide, PEOoxide, PEO
poly(propylene glycol) , poly(propylene glycol) ,
methyl cellulose, methyl cellulose,
poly(poly(ethylenimineethylenimine), PEI), PEI
Nylon Nylon
etc.etc.
PEOCH2CH2
On
NH
O nnylon
O
OO OMeO
OMe
O
MeOOMe
OMen
Some Encapsulated PolymersSome Encapsulated Polymers
PVP
PPG
PE
Methyl-cellulose
CHCH2
O
CH3
nCH2CH2
n
O
OOO
MeO
OMe
O
MeOOMe
OMe
n
PEOCH2
CH2
On
NO
CHCH2
n
CH2
CH2
NHn
PEINylon-6
NH
O nnylon
volts
mic
roam
ps
RectifyingRectifying polypyrrolepolypyrrole/ V/ V22OO55 xerogelxerogel junctionsjunctions
N H
H N
N H
H N
(polypyrrole)xV2O5
Conductivity type changes with xAt low x system is n-typeAt high x system is p-type
substrateV2O5 xerogel
drop of pyrrole
graded composition(ppy)xV2O5
rectifying junction
(ppy)xV2O5
(+) (-)
-6
-5
-4
-3
-2
-1
0
1
2
-300
-250
-200
-150
-100
-50
0
50
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
(polypyrrole)xV
2O
5
Log(cond), S/cm Thermopower, µV/K
Log(
cond
), S
/cm
Thermopow
er, µV/K
x value
I-V
(PEO)(PEO)xxVV22OO55 nanocompositesnanocomposites
-5 10 -5
0 10 0
5 10 -5
1 10 -4
1.5 10 -4
0 0.5 1 1.5 2 2.5 3 3.5
(PEO)xV
2O
5
Con
duct
ivity
(S/c
m)
x
2 6 10 14 18 22 26 30
Inte
nsity
V2O
5-nH
2O xerogel
2θ, degrees
(PEO)0.5
V2O
5-nH
2O
(PEO)1.5
V2O
5-nH
2O
0
1
2
3
4
5
0 500 1000 1500 2000 2500 3000
abso
rban
ce
λ, nanometers
Saturated with N2H4Optical Spectrum of PEO/V
2O
5
10
12.5
15
17.5
20
0 1 2 3 4 5 6
Interlayer Distance (Å)
Molar Ratio (x)
(PEO)xV
2O
5 -nH
2O
Response to NH3Response to N2H4
(PEO)xV2O5 as a sensitive N2H4 sensor
Time (sec)
Highly oriented filmsHighly oriented films
0 20 40 60 80 100 120 140
XRD Pattern of LixTaS
2•PEO Film
(M.W. = 100,000)
Inte
nsity
2-theta (deg)
001
002
003004005
006007008009
00100011
00120013001400150016 0017
0 0.2 0.4 0.6 0.8 1
One-Dimensional Electron-Density Maps of Li
xTaS
2¥PEO Nanocomposite
Ele
ctro
n de
nsity
z-axis
Experimental data
Type II PEO-HgCl2
complex comformation
Planar zigzag comformation,parallel arrangement
Planar zigzag comformation, perpendicular arrangement
Li -PEO-TaS2
-5
0
5
10
0 0.2 0.4 0.6 0.8 1
experimentmodel
elec
tron
dens
isty
c-axis
0
1000
2000
3000
4000
5000
6000
-100 -50 0 50 100
Line
wid
th (H
z)
Temperature (oC)
Li0.2TaS 2
Li-PEO-TaS 2
Type-II PEO-HgCl2 complex
PEO conformation in TaS2 and NbSe2 and Li-ion mobility
Li NMR static
Superconductivity in TaS2 and NbSe2
Free standing film of TaS2Meissner effect in NbSe2
Phyllo-morphous
EgEg?Eg
An array of nanocrystalsQuantum dotsAn array of
Quantum anti-dots
Bulk semiconductor
Porous Semiconductors (non-oxidic): A challenge
Inside-out version
MesoporousMesoporous Oxides via Liquid Crystal Oxides via Liquid Crystal Template RouteTemplate Route
Major Breakthrough ca 1989Major Breakthrough ca 1989: :
general synthetic strategy to general synthetic strategy to
orderedordered mesoporousmesoporous silicates by silicates by
MobilMobil1 1 (MCM(MCM--41, MCM41, MCM--48 etc), 48 etc),
opened the pathway for novel hybrid opened the pathway for novel hybrid
solids.solids.
ManyMany mesoporousmesoporous metal oxides metal oxides
have been synthesized based on have been synthesized based on
MCMMCM--X materialsX materials2,32,3..
ZrOZrO22, V, V22OO55, SnO, SnO22, TiO, TiO221. C.T. Kresge, M.E. Leonowicz, W.J. Roth, J.C. Vartuli,
J.S. Beck, Nature 1992, 359, 710.
G. D. Stucky et al, Chem. Mater. 1996, 8, 1147
AdamantaneAdamantane based frameworksbased frameworks
z
x y
S
Mn
Ge
Yaghi et alOzin et al
(Me4N)2MnGe4S10 microporous
MesostructuredMesostructured Wormholes ~35 Wormholes ~35 ÅÅ
surfactant filled pores
metal chalcogenide framework
Kanatzidis et al Advanced Mater. 2000, 12, 85-91
(R(R--NMeNMe33))22M(GeM(Ge44QQ1010) Q= S, Se) Q= S, Se
0 20 40 60 80 100
Inte
nsity
(arb
. uni
ts)
2θ (deg), CuKα
C14ZnGeS
30
35
40
45
12 13 14 15 16 17 18
CnCdGeSCnCdGeSe
d p (Å)
Surfactant Chain Length (n)
Diffuse scatteringAdjustable pore size
Non-periodic inorganic framework
Optical PropertiesOptical Properties
Diffuse scattering and Pair Distribution Diffuse scattering and Pair Distribution Functions Functions (with S. J . L.(with S. J . L. BillingeBillinge, M. F. Thorpe), M. F. Thorpe)
Influence of solventInfluence of solvent
In water: In water: (R(R--NMeNMe33))22MGeMGe44QQ1010
•• Disordered wormholeDisordered wormhole
InIn formamideformamide: : (R(R--NMENME33))22--xxMM1+x1+xGeGe44QQ10+10+δδ
•• Ordered hexagonal, cubicOrdered hexagonal, cubic
[Ge4Q10]4- [Ge4Q10-x]z- + xQ2-
2[SnSe4]4- [Sn2Se6]4- + 2Se2-
Biologically inspired nanocomposites (Fe4S4 ferredoxinoids)Fe4S4-MSU-1 and Fe4S4-M�SU-2 Angew Chemie 2000, 39, 4558
1
10
0 1 2 3 4 5
Cpy/Fe4S
4/Ge
4S
10
log(
a/s)
Energy, eV
Eg=1 eV
Fe
S
S
SFeFe
Fe
S
S
S
S
S
Q
GeQ
Ge
QGe
Q
GeQ Q
Q
Q Q
Q
Q=S, Se
Tra
nsm
ittan
ce
(i)
(ii)
(i)
(ii)
(iii)
423
(a) (b)
Wavenumber (cm-1)Velocity (mm/sec)
Rel
ativ
e T
rans
mis
sion
(%)
Characterization ofCharacterization of Fe4S4Fe4S4--MSUMSU--1 and Fe4S41 and Fe4S4--M�SUM�SU--22
Fe Mössbauer Infrared spectroscopy Fe4S4 cluster extractionUV/vis spectra
0
0.5
1
1.5
2
400 450 500 550 600 650 700 750 800
Fe4S4-MSU-1
Fe4S4-MSU-2
Abs
orba
nce
Wavelength (nm)
λmax
= 445 nm
MesostructuredMesostructured NonNon--OxidicOxidic Solids Based on the Solids Based on the Tetrahedral Clusters and Metal IonsTetrahedral Clusters and Metal Ions
1. M. Wachhold, K.K. Rangan, S.J.L. Billinge, V. Petkov, J. Heising, M.G. Kanatzidis, Adv. Mater. 2000, 12(2) 85-91.2. K. K. Rangan, S. J. L. Billinge, V. Petkov, J. Heising, M. G. Kanatzidis, Chem. Mater. 1999, 10, 2629.3. M.J. MacLachlan, N. Coombs, G.A. Ozin, Nature 1999, 397, 681.
Ge, Sn
Ge, Sn
S, Se, Te S, Se, Te
SiO4 analogstopologically similar structures?
SynthesisSynthesis+NR
R : CH3-(CH2)15-
Formamide : 20 ml
Surfactant : 10 mmol
K4SnSe4 : 1 mmol
Temperature : 75 oC
Supramolecular organization Slow addition of
M2+/FM solution
M2+ : Mn2+, Fe2+, Co2+, Zn2+, Cd2+, Hg2+
Immediate precipitation
aging for 24h
Mesostructured Chalcogenide Phases
wormhole
cubic
hexagonal
Surfactants set the stage for Surfactants set the stage for inorganic framework assemblyinorganic framework assembly
N+ N+N+ N+ N+
R-pyridinium R-quinolinium R-TMA- Gemini-Cn-s-n
R=CnH2n+1
Examples
CP/M/GeCP/M/Ge44SS1010 ((CPMGeSCPMGeS)) M=M=GaGa, In, In J. Am. Chem. Soc. 2000, 122, 10230
1.5 2 2.5 3 3.5 4 4.5 5
CPGaGeSCPInGeSCPBr
Inte
nsity
(arb
. uni
ts)
Energy (eV)
Excitation
Emission77 K
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
0.08
2 4 6 8 10 12 14
CPInGeS
CPGaGeS
Red
uced
PD
F G
(r)
r (�)
Ge-SM 3+ -S
Ge-Ge
S-S (2nd)Ge-S(2nd)
2 3 4 5 6 7 8 9 100
500
1000
1500
2000
Inte
nsity
(arb
. uni
ts)
2θ (deg), CuKα
100
110
200
Diffraction patternHexagonal 6mm
Walls are amorphous
Radial distribution function
TEM images
CPMGeSCPMGeS materials: CP/M/Gematerials: CP/M/Ge44SS1010
4 8 12 16 20 24
Inte
nsity
(arb
. uni
ts)
2θ (deg), CuKα
100
110
200
CPSbGeS
h k l d (�)1 0 0 35.521 1 0 20.012 0 0 17.33
M=Zn, Cd, Hg, Sb, In, Ga
(CP)2M1+x(Ge4S10)Sx
0 10 0
2 10 4
4 10 4
6 10 4
2 2.5 3 3.5 4
Cp_SbGe4S
10In
tens
ity
Energy, eV
2.88 ev
Hexagonal Hexagonal CPZnGeSCPZnGeS
1.2 1.6 2 2.4 2.8 3.2 3.6 4
CQZnGeSCPZnGeS
0
1 105
2 105
3 105
4 105
5 105
Inte
nsity
(arb
. uni
ts)
Energy (eV)
1.9 eV 2.4 eV
(CP)2Zn2(Ge4S10)S
Thermally stable up to 220 oC
Perhaps we donPerhaps we don’’t want to remove the t want to remove the surfactant!surfactant!
Add functionality to the surfactantAdd functionality to the surfactant•• Electronically active head groups or tailsElectronically active head groups or tails
S S
S S
S S
S S
S S
S S
S S
S S
electroluminescence
conduction band
valence band
š* band
radiative recombination
inorganic organic
PhotoluminescencePhotoluminescence
1.5 2 2.5 3 3.5
CPCdGeS4
CPCdSnS4
0
1 10 5
2 10 5
3 10 5
4 10 5
5 10 5
Inte
nsity
(arb
. uni
ts)
Energy (eV)
2.1 eV 2.4 eV
VB
CB
primarily S
primarily Ge
š*
š
hν
metal-sulfide network
organic head
1.2 1.6 2 2.4 2.8 3.2 3.6 4
CQZnGeSCPZnGeS
0
1 10 5
2 10 5
3 10 5
4 10 5
5 10 5
Inte
nsity
(arb
. uni
ts)
Energy (eV)
1.9 eV 2.4 eV
N
R
N
R
S
GeSGe
S Ge
S
GeS S
S
S
S
SS
SnSSn
S Sn
S
SnS S
S
S
S
S
Chemical Formula : (CP)Chemical Formula : (CP)44--2x2xMMxxSnSeSnSe44 (1.0<x<1.3)(1.0<x<1.3)
Sample Sn:Se4 M:Se4 % C, H, NM:Se4
Calc.Color
Mn 1.01 0.90 44.71, 7.10, 2.25 1.03 Orange
Fe 0.91 1.22 38.40, 6.23, 2.05 1.28Dark-
brown
Co 0.98 0.94 48.35, 6.64, 2.36 1.19Dark-
brown
Zn
(cubic)0.99 0.86 40.28, 6.17, 2.18 1.20
Yellow-
orange
Zn
(Hex)0.96 0.85 41.58, 6.44,2.29 1.15 Yellow
Cd 0.92 1.23 36.90, 6.01, 2.28 1.23 Yellow
Hg 1.03 1.09 34.65, 5.52, 1.92 1.20Dark
orange
Transmission Electron MicroscopyTransmission Electron MicroscopySurf / Zn2+ / SnSe4
Surf / Hg2+ / SnSe4
CubicCubic mesoporous chalcogenidemesoporous chalcogenide CPZnSnSeCPZnSnSe44
211
220
321420 332
h k l d (Å) 211 35.5 220 31.2 321 23.2 420 19.97 332 19.14
I a-3d a=87 Å
X-ray diffraction pattern
Ia-3d
P. N. Trikalitis, K. K. Rangan, T. Bakas and M. G. Kanatzidis, Nature 2001, 410, 671-675.
BandBand--gaps andgaps and Sn MSn Möössbauer ssbauer SpectroscopySpectroscopy
Rel
ativ
e Tr
ansm
issi
on, %
(A)
MnK4SnSe4
(B)
(C) (D)
(E) (F)
Velocity (mm/sec) Velocity (mm/sec)
Fe Zn
Cd Hg
Highly ordered CPHighly ordered CP--PtGePtGe44SeSe1010
4 8 12 16 20
Inte
nsity
(arb
. uni
ts)
2θ, Cu Kα
CP/Pt/Ge4Se
10
x 6
100
110
200
210
ao=39.98 �
hkl d(�)100 34.5110 20.0200 17.29210 13.0
The system PtThe system Pt2+2+ / [Sn/ [Sn22SeSe66]]44--
Se
Sn
[PtCl4]2- + [Sn2Se6]4-0
1000
2000
3000
4000
5000
6000
2 4 6 8 100
200
400
600
800
1000
1200
Inte
nsity
(arb
. uni
ts)
2θ (deg)
210
220
321 40
042
0 332
422
431
x 5
611
543
(C20Py)2PtSn2Se6
Single Crystals!Single Crystals!……??
TEM of a TEM of a CubosomeCubosome: [110] direction: [110] direction
Unit cell edge: 95ÅV=857,375 Å3
Density 1.8 g/cm3~34000 atoms per cell
ConclusionsConclusions
LamellarLamellar nanocompositesnanocomposites with electrically conductive and with electrically conductive and conventional polymers are large class of novel materialsconventional polymers are large class of novel materials
Conductive polymers can be encapsulated in porousConductive polymers can be encapsulated in porous solids directly by solids directly by inin situsitu intercalativeintercalative redoxredox polymerizationpolymerization
Exfoliated solids are superior for the synthesis of polymerExfoliated solids are superior for the synthesis of polymernanocompositesnanocomposites via via encapsulative precipitationencapsulative precipitation
The physical properties of lamellarThe physical properties of lamellar nanocompositesnanocomposites are affected by the are affected by the intercalated polymers.intercalated polymers.
ConclusionsConclusions
It is possible to construct organicallyIt is possible to construct organically templatedtemplated structures with heavier SiOstructures with heavier SiO44--analogs to produceanalogs to produce semiconductingsemiconducting solids with wellsolids with well--defineddefined mesoporesmesopores. .
The surfactantThe surfactant templated supramoleculartemplated supramolecular assembly of the assembly of the [SnSe[SnSe44]]44-- and and [Ge[Ge44QQ1010]]44-- anions with transition metals leads toanions with transition metals leads to mesostructuredmesostructured materials of materials of the general formulae the general formulae CPMGeQCPMGeQ and and (CP)(CP)44--2x2xMMxxSnSeSnSe44 (M=(M=MnMn, Fe, Co, Zn, , Fe, Co, Zn, CdCd, Hg)., Hg).
The The cc--(CP)(CP)44--2x2xZnZnxxSnSeSnSe44 represents the first example of cubic, nonrepresents the first example of cubic, non--oxidic oxidic mesophasemesophase..
NonNon--oxidicoxidic solids promise to produce solids promise to produce functionalfunctional mesostructuredmesostructured materials materials with novel electronic andwith novel electronic and photonicphotonic properties.properties.
Further work involving otherFurther work involving other chalcogenidechalcogenide building blocks e.g. building blocks e.g. [GeSe[GeSe44]]44--,,[GeTe[GeTe44]]44--, [SnTe, [SnTe44]]44-- and other metals ions e.g. Agand other metals ions e.g. Ag++, Pb, Pb2+2+, Bi, Bi3+3+, Sb, Sb3+3+ is needed.is needed.
Dr. Pantelis Trikalitis
Dr. Kasthuri K Rangan
Chung-Guey Wu
Yu-Ju Liu
Dr. Carl R. Kannewurf (NWU)Dr. Carl R. Kannewurf (NWU)Prof. Thomas Prof. Thomas BakasBakas,, IoanninaIoannina, Greece (, Greece (MMöössbauerssbauer))
Prof. VProf. V PapaefthymiouPapaefthymiou,, IoanninaIoannina, Greece (, Greece (MMöössbauerssbauer))
Students/Research AssociatesStudents/Research Associates
AcknowledgmentsAcknowledgments
National Science Foundation National Science Foundation
DMR-96-32472, CHE 99CHE 99--03706 (Chemistry Research Group).03706 (Chemistry Research Group).
Center for Advanced Microscopy, MSU for SEM and TEM facilities.Center for Advanced Microscopy, MSU for SEM and TEM facilities.