beyond silica: the quest for mesoporous semiconductors...p/p o s p = 402 m2/g v p = 0.36 cm3/g (at...
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Beyond silica: the quest for mesoporous semiconductors
Funded by NSFChemistry Research Group
Mercouri KanatzidisNorthwestern UniversityArgonne National Laboratory
ISIC14, June 12-15, Seoul, S. KoreaPlenary Lecture
Chicago, Illinois
Northwestern University
Outline
Chalcogenide networksWormholes, honeycombs and labyrinths..MCM-48 type chalcogenidesMesostructured elementsGe-Cubic (NU-Ge-1)Ge-hexagonal (NU-Ge-2)Ge-hexagonal (NU-Ge-3)Conclusions
Mesoporous Oxides via Liquid Crystal Template Route
Major Breakthrough ca 1989: general synthetic
strategy to ordered mesoporous silicates by Mobil1
(MCM-41, MCM-48 etc), opened the pathway for novel
hybrid solids.
Many mesoporous metal oxides have been
synthesized based on MCM-X materials
ZrO2, V2O5, SnO2, TiO2
Tanev Pt, Pinnavaia TJ Science 267 (5199): 865-867 Feb 10 1995Huo Qs, Margolese D I, Ciesla U, et al. Nature 368 (6469): 317-321, 1994Kresge C T, Leonowicz M E, Roth W J, et al. Nature 359 (6397): 710-712, 1992
Mesoporous silica
Shunai Che, Zheng Liu, Tetsu Ohsuna, Kazutami Sakamoto, Osamu Terasaki and Takashi TatsumiNature 429, 281-284(20 May 2004)
chiral mesoporous silica
Cubic MCM-41
EgEg?Eg
An array of nanocrystalsQuantum dotsAn array of
Quantum anti-dots
Bulk semiconductor
Porous Semiconductors (non-oxidic): A challenge
Inside-out version
M. G. Kanatzidis, Advanced Materials, 2007, 19, 1165
Mesostructured Non-Oxidic Solids Based on the Tetrahedral 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, 681.4. Riley AE, Tolbert SH J. Am. Chem. Soc. 2003, 125 (15): 4551
Ge, Sn
Ge, Sn
S, Se, Te
S, Se, Te
SiO4 analogstopologically similar structures?
Synthesis+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[SnSe4]4-
[SnTe4]4-
Surfactants set the stage for inorganic framework assembly
N+ N+N+ N+ N+
R-pyridinium R-quinolinium R-TMA- Gemini-Cn-s-n
R=CnH2n+1
Examples
Mesostructured Wormholes ~35 Å
surfactant filled pores
metal chalcogenide framework
Kanatzidis et al Advanced Mater. 2000, 12, 85-91
Influence of solvent
In water: (R-NMe3)2MGe4Q10Disordered wormhole
In formamide: (R-NME3)2-xM1+xGe4Q10+δOrdered hexagonal, cubic
[Ge4Q10]4- [Ge4Q10-x]z- + xQ2-
2[SnSe4]4- [Sn2Se6]4- + 2Se2-
CP/M/Ge4S10 (CPMGeS) M=Ga, In, Zn 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
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 TEM images
Thermally stable up to 220 oC
Photoluminescence
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
Perhaps we don’t want to remove the surfactant!
Add functionality to the surfactantElectronically 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
Highly ordered CP-PtGe4Se10
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 Pt2+ / [Sn2Se6]4-
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!…?
TEM of a Cubosome: [110] direction
Unit cell edge: 95ÅV=857,375 Å3
Density 1.8 g/cm3~34000 atoms per cell
Acid stability and framework breathing
2 4 6 8 10
Inte
nsity
(arb
.uni
ts)
2θ (deg.), CuKα
(a)
(b)
(c)
(d)
21122
0(e)
SEM images of (left) as-synthesized c-C20PyPtSnSe. (right) H2SO4_C20PyPtSnSe particles showing contracted grain size yet preserved cubosome morphology.
2 4 6 8 10 12 14 16-10-505
10152025
G(r
)
Radial distance r(Å)
PDF PDF (acid)
Trikalitis PN, Ding N, Malliakas C, et al. J. Am. Chem. Soc. 2004, 126 (47): 15326.
How does cubic Pt-Sn-Se breath?A Hoberman sphere is a structure that resembles a geodesic dome, but is capable of folding down to a fraction of its normal size by the scissor-like action of its joints.
Se
Sn
Se
PtSe
Sn
SeSeSe
Se
SnSe
PtSe
SeSeSn
SeSeSe
TEM images of C16N(CH3)(CH2CH2OH)2Pt_SnTe4
Extremely air sensitive.
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
Mesoporous elements…Group IV: Si, Ge and Sn
Mg2Ge + GeCl4 + EMBHEAB EMBHEA-(Ge)m
1 1 1.5 (molar ratio)
Preparation of mesostructured Preparation of mesostructured GeGe
Mg2Ge/FM at 750C
+Surfactant (3h)GeCl4 at 65oC
Aged at 85oC for 18h
EMBHEAB = C20N(CH3)(C2H4OH)2Br
K4Ge9 + GeCl4 + CnMBHEAB CnMBHEA-(Ge9Ge)m
1 1 6 (molar ratio)
in en/FM solution at 80oC for 18h
[Ge9]-4=
NU-Ge-1
NU-Ge-2
After purification in CHClAfter purification in CHCl33
EMBHEA-(Ge)m(s) in CHCl3(l) (1 mg/1 ml) for 1h
EDS Analysis
formula: C20N(CH3)(C2H4OH)2-[Ge]7.3
2 4 6 8 100
1000
2000
3000
4000
5000
6000
Inte
nsity
(arb
. uni
ts)
2Θ (deg.)
x3
211
220
321 40
042
0 332
422
431
PXRD of PXRD of EMBHEA-(Ge)7.3: NU-Ge-1
a0= 84 Å
d3Iα
From Mg2Ge cubic
TEM Images of Cubic EMBHEATEM Images of Cubic EMBHEA--(Ge)(Ge)7.37.3
[111]
[311][110]
[100]
NU-Ge-1
0 100 200 300 400 500 60040
50
60
70
80
90
100
-6
-4
-2
0
2
4
6
Wei
ght l
oss (
%)
Temperature (oC)
42.5%
DC
S (m
W)
TGA/DSC & CHN AnalysisTGA/DSC & CHN Analysis
1.615.9732.24
N (%)H (%)C (%)
formula: C20N(CH3)(C2H4OH)2-[Ge]7.3
Crystalline Ge
NU-Ge-1
C18MBHEA0.91-(Ge9Ge)
C20MBHEA0.92-(Ge9Ge)
[100]
[100]
[110]
[110]
Hexagonal
NU-Ge-2
Porous silicon versus mesoporous Ge
Porous siliconAnodizing Si
mesoporous GeSelf-assembly
0.0 0.2 0.4 0.6 0.8 1.00
50
100
150
200
250
300
350
Volu
me
of N
2 (cm
3 /g)
P/Po
Sp= 402 m2/g
Vp= 0.36 cm3/g (at P/Po=0.97)
0 5 10 15 200.00
0.05
0.10
0.15
0.20
0.25
dV/d
D (c
m3 /g
-nm
)
D (nm)
Dp= 2.3 nmt ~ 2.2 nm
Mesoporosity of (C20-1)-[(Ge9)m]: NU-Ge-2
Linking Ge atom
Optical Properties of mesoporous-Ge: NU-Ge-2
0 1 2 3 4 5 60.01
0.1
1
Ab
sorp
tio
n,
α/
s (a
rb.
un
its)
Energy (eV)
EMBHA-[Ge]7.3 under N2 (Eg= 1.22 eV) EMBHA-[Ge]7.3 under O2 (Eg= 1.5 eV)
Bulk Ge
15 16 17 18 191.68
1.74
1.80
1.86
1.92
E g (eV
)
Wall thickness (D)
Oxidation
24 28 32 36 40Ph
otoe
lect
ron
Inte
nsity
(a.u
.)
Binding Energy (eV)
GeO2Ge
MSU-Ge-2
26 28 30 32 34 36 38 40
MSU-Ge-1(b)
Phot
oele
ctro
n In
tens
ity (a
.u.)
Binding Energy, eV
31.5
31.429.3
Cubic 1 nm wall hexagonal 2 nm wall
X-ray photoelectron spectroscopy
Mg2Ge From [Ge9]4-
binding energy of Ge 3d peaks
Is mesoporous Ge really a new form of Ge?
Mesostructured cubic and hexagonal Genot a new elemental form..They are compounds:
{C20N(CH3)(C2H4OH)2} (Ge7.3){C20N(CH3)(C2H4OH)2}0.9(Ge10)
Mesoporous hexagonal Ge: ~Ge8H
GeGe
HGe
Ge
Ge
OHGeGe
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
GeGe
Ge
GeGe
Ge
Ge
Ge
Ge
H
Ge
GeGe
Ge
Ge
GeGe O
Ge
Ge
Ge
GeGe
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
GeGe
Ge
Ge
GeGe
H OGe
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
GeGe
HGe
O
HGe Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
Ge
GeGe
Ge
GeH
O
OH
H
O
Ge
Ge
GeGeGe
Ge Ge
GeH
Ge
H
GeH
Ge
Ge
OH
GeH
HGe
HHOH
H
H O
H
HO
H
H
HGe
Ge
Ge
H
H
~2nm
Formula: ~ Ge6(H,OH,O) to Ge10(H,OH,O)CaZn13, AlB12
Network structure unknown
Comparison to Ge nanocrystals May not be valid (unless size <2 nm)
unkn
own
Mesoporous Ge from the oxidative self-polymerization of the deltahedral [Ge9]4-
cluster
No linking Ge atoms NU-Ge-3
NU-Ge-2
EDMHEABr + K4Ge9 (EDMHEA)x[Ge9] + KBren/FM
(EDMHEA)x[Ge9] + NH4NO3 (NH4+)y[Ge9]
1 10‐times excess
(NH4+)y[Ge9] H+_[Ge9] + NH3
calcination at 75oC under vacuum
EtOH at RT
(2‐times)
EDMHEABr: C20H41N(CH3)2(C2H4OH)Br
Oxidative self-polymerization of mesoporous (Ge9)-polymer: NU-Ge-3
Chemical composition of (Ge9)-polymer: NU-Ge-3
0 100 200 300 400 500 600
65
70
75
80
85
90
95
100
-0.35
-0.30
-0.25
-0.20
-0.15
-0.10
-0.05
0.00
Wei
ght l
oss
(%)
Temperature (oC)
DTG
(wt./
deg)
31.6%
6.7%
(EDMHEA)0.81[Ge9] (EDMHEA)0.13[H_Ge9]
NH4+ NH3
0.1 0.2 0.3 0.4 0.5 0.60
1000
2000
3000
4000
5000
Inte
nsity
(arb
. uni
ts)
q (1/ )
(EDMHEA)0.81[Ge9] a0=5.04 nm
(EDMHEA)0.13[H_Ge9] a0=4.94 nm
SAXS diffraction and TEM images of mesoporous (Ge9)-NU-Ge-3
[100] [110]
0 2 4 6 8 10 120
500
1000
1500
2000
2500
3000
3500
4000
Inte
nsity
(a.u
.)
Energy (keV)
CO
Ge
Ge
Ge
Cu
Cu
EDS spectrum
0.0 0.2 0.4 0.6 0.8 1.00
50
100
150
200
250
300
350
Abs
orbe
d Vo
lum
e (c
m3 /g
)
P/Po
0 2 4 6 8 10 12 14 16 18 200.0
0.2
0.4
0.6
0.8
Diff
eren
tial p
ore
volu
me
(cm
3 /g)
Pore width (nm)
N2 adsorption-desorption isotherm at 77K
NLDFT pore size distribution
Sp= 402 m2/gVp= 0.34 cm3/g
Vmeso= 0.31 cm3/gVmicro= 0.03 cm3/g
1.08
nm
3.05nm
Pore blocking or cavitations effects?
0.0 0.2 0.4 0.6 0.8 1.00
50
100
150
200
250
300
350
Abs
orbe
d Vo
lum
e (c
m3 /g
)
P/Po
0.44
0.0 0.2 0.4 0.6 0.8 1.00
50
100
150
200
250
300
Abs
orbe
d Vo
lum
e (c
m3 /g
)
P/Po
0.25
N2 at 77K Ar at 77K
Adsorptive N2 ArCross-section area
16.2 Å2 14.2 Å2
Surface area 402 m2/g 385 m2/g
0.00 0.04 0.08 0.12 0.16 0.20
0.1
1
10
100
1000
adsorption desorption
Abs
olut
e pr
essu
re (m
mH
g)
weight %H2
0 200 400 600 8000
4
8
12
16
20
24
adsorption desorption
Qua
ntity
ads
orbe
d (c
m3 /g
)
Absolute pressure (mmHg)
0.19 wt. %H2
Hydrogen adsorption at 77K
(EDMHEA)0.13[Ge9] (EDMHEA)0.13(H2)1.3[Ge9] 0.19 wt. %H2
Small angle x-ray scattering (SAXS) analysis: NU-Ge-3
10-2 10-1 100
10-1
100
101
102
103
104
105
Inte
nsity
(arb
. uni
ts)
q (1/D)
I(q) = f(q) (q=4π/λ sin(θ))
K – Porod’s constant
φ – fraction of pores (porosity)
ρ,ρς – bulk and skeleton densities
⎟⎟⎠
⎞⎜⎜⎝
⎛⋅
⋅⋅=⎟⎟⎠
⎞⎜⎜⎝
⎛⋅
−⋅⋅=Q
KQ
KSsρ
φπρ
φφπ )1(
max
2max
min
))((qKdqqbqIQ
q
q
+−= ∫
SAXS unit cell, a0‡
49.4 Å (50.4 Å of
as-prepared)
Surface area, SBET† 402 m2/g
Surface area, SSAXS 417 m2/g
Surface area, SNLDFT 400 m2/g
Gurvich pore volume (at
P/Po=0.95)0.34 cm3/g
SAXS mesopore width, DSAXS 29.9 Å
Wall thickness, WTSAXS§ 19.5 Å
FTIR spectra of as-prepared (A) and mesoporous (B) materials
3500 3000 2500 2000 1500 1000 500
897
2075
Tran
smis
sion
(a.u
.)
Wavenumbers (cm-1)
1977
a.
b.
3500 3000 2500 2000 1500 1000 500
Wavenumbers (cm-1)
1989
2085
898
922
c.
Tran
smis
sion
(a.u
.)
1979b.
a.
A
B
Ge‐H
Ge‐0GeOGe‐H
~20min air exposure
~5min air exposure
2days air exposure
(EDMHEA)0.81[Ge9]
(EDMHEA)0.13[Ge9]
GeOGe‐H Ge‐0
Ge‐H
X-ray photoelectron spectroscopy (XPS) analysis of mesoporous NU-Ge-3
20 24 28 32 36 40
Energy (eV)
c.
Phot
oele
ctro
n in
tens
ity (a
.u.)
b.
a.
29.0 eV
29.4 eV
29.2 eV
After surface Sputtering with Ar+ ion beam
Ge0 3d5/2 = 29.0 eV
GeO2 3d5/2 = 32.5 eV
Ge‐H and
possibly Ge‐OH (?)
High‐resolution Ge 3d photoelectron spectra
Time-of-Flight secondary ion mass spectroscopy (ToF-SIMS) analysis
of mesoporous NU-Ge-3
0 5 10 15 20 25 301E-3
0.01
0.1
1
74GeOH+
74GeO+
74GeH+
Nor
mal
ized
inte
nsity
(a.u
.)Cycle
74Ge+
89 90 91 920
20
40
69 70 71 72 73 74 75 76 770
50
100
150
200
250
300
Cou
nts
m/z
m/z
Cou
nts
GeO+GeOH+
74GeH+
74Ge+
*analysis time of 28s and sputtering time of 5s
Depth profile*
Ge
m/z777675747372717069
norm
alis
ed in
tens
ity
Ge calculated spectrum
Pair distribution function (PDF) analysis
2.5 Å 6.0 Å
3.9 Å
2 4 6 8 10 12 14 16 18
-4-202468
r ( )
-202468
10
G(r
)
-100
10203040
2.5
3.95.9
‐(Ge9‐Ge9)‐
cryst‐Ge2.44.0
4.7
n(Ge9)4‐ 2∞{Ge9}0 + 4ne‐
EDMHEAB + nGe94‐ + 2nNH2(CH2)2NH2 (EDMHEA)x[1∞{Ge9}2n‐] + 2n(NH2(CH2)2NH)1‐ + nH2
(EDMHEA)x[1∞{Ge9}2n‐] + 2nNH2(CH2)2NH2 (EDMHEA)x[2∞{Ge9}0] + 2n(NH2(CH2)2NH)1‐ + nH2
Oxidation coupling of (Ge9)4-: Possible mechanism
(EDMHEA)0.81[Ge9] (668nm, 1.86eV)
(EDMHEA)0.13[Ge9] (663nm, 1.87eV)
0 1 2 3 4 5
log(
α/s
)ads
orpt
ion
(a.u
.)
Energy (eV)
S
S S
S
CN
CNNC
NC
TTF
TCNE
CN
CNNC
NC
S
S S
S
donor
acceptor
anthracene
Optical properties of mesoporous Ge: NU-Ge-3
Mesoporous non-oxidic solids are a realityAll known forms for mesostructured materials can be prepared.The scope and diversity of materials possible with non-oxide systems is wider than oxides.Mesoporous Ge: first porous elemental semiconductorUnique absorption as well as electronic and optical properties anticipated.
Conclusions
Kanatzidis group