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

PDF

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

PDF

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