Liquid Phase Exfoliation of Graphene and Inorganic Layered Compounds

– a Route to Diverse Applications

Dr. Mustafa Lotya on behalf of Prof. Jonathan Coleman

School of Physics & CRANN, Trinity College Dublin

lotyam@tcd.ie, colemaj@tcd.ie

NSF/AFORSF Workshop May 30, 2012

Graphene! How much do we need?

Graphite ~ $/kg

Mechanical props: Composites - ????kg

Electronic props: wafer scale - ~10-7 kg/m2

Graphene! How much do we need?

Need large scale production!

Key – Solvent exfoliation of graphene

Nature Nano, 3, 563 ACS Nano, 4, 3455

Small , 6, 864 Small, 6, 458

New J. Phys. 12, 125008 Langmuir, 26, 3208

JACS, 131, 3611 Adv. Func. Mater. 19, 3680

NMP

What about oxides/defects?

0 1 2 30.0

0.2

0.4

0.6

0.8

<I D

/IG>

1/<L> (m-1)

Powder

1000 1500 2000 2500 3000

G2D

Raman shift (cm-1)

D284 286 288

282 284 286 288 290

Binding energy (eV)

Graphene

C=OC-N

CRing

C-C

•XPS says no oxides

Hernandez, Nature Nanotechnology 2008, 3, (9), 563-568 Khan, SMALL 2010, 6, (7), 864-871

•Raman suggests few basal plane defects

Can we extend liquid exfoliation to layered compounds?

Boron Nitride Metal oxides

Metal chalcogenides

Bi2Te3 Sb2Te3

Bi2Se3 Sb2Se3

Transition metal dichalcogenides (TMDs)

2

METALLIC

SEMICONDUCTING

BOTH, depends on X

Mechanically Exfoliated MoS2

Transistors (Ion/Ioff ~ 108) 1

Photocurrent effect 2

1 B. Radisavljevic et. al. Nature Nanotechnology 2011, 6, (3), 147-150 2 Z. Yin et. al. ACS Nano 2011

Liquid Phase MoS2/WS2

Li-ion intercalation in water Distortion: 2H -> 1T octahedral

Semiconductor ->metallic

WS

2 (N

MP

) B

N (IP

A)

10 µm

MoS2

5 µm

WS2

5 µm

BN

100 nm

500 nm

500 nm J. Coleman, M. Lotya, A. O’Neill, S. Bergin,

V. Nicolosi et. al., Science, 331, 568-571, 2011

MoS

2 (N

MP

)

Other inorganic materials…

Mo

Se2

Mo

Te2

TaSe

2

Nb

Se2

Bi 2T

e 3

NiT

e 2

MoSe2MoTe2 TaSe2

NbSe2 Bi2Te3 NiTe2

A

C

400 600 800 1000 1200 1400 1600

TaSe2

MoSe2

NbSe2

MoTe2

Bi2Te

3

Absorb

ance (

au)

Wavelength (nm)

NiTe2

B

Mo

Se2

Mo

Te2

TaSe

2

Nb

Se2

Bi 2T

e 3

NiT

e 2

MoSe2MoTe2 TaSe2

NbSe2 Bi2Te3 NiTe2

A

C

400 600 800 1000 1200 1400 1600

TaSe2

MoSe2

NbSe2

MoTe2

Bi2Te

3

Absorb

ance (

au)

Wavelength (nm)

NiTe2

B

Bi2Te3

200 nm

Bi2Te3

What governs dispersion?

22

, NSSE

atomV

atomV/1

Hamaker approach: extended monatomic systems, solely London interactions….

Polarisability

Atom density

2

,,

,

2

8exp NSSSS

NSS

NS EEkTE

DC

Simple, crude model:

• Depends on surface energy ES

• Solvent and nanosheet values

must match • Why similar?

0.0

0.5

1.0

MoTe2

MoSe2

MoS2

WS2

0.0

0.5

1.0

Co

nce

ntr

atio

n (

au

)

0.0

0.5

1.0

50 60 70 80 900.0

0.5

1.0

Solvent surface tension (mJ/m2)

Cunningham, ACS Nano 2012, 6, (4), 3468-3480

Increase concentration?

More starting material

Longer sonication

10 1001

10

100

C (

mg/m

l)

tSonic

(hrs)

C (

mg/m

l)

600 700 800 900

103

104

20 mg/ml

Wavelength (nm)

A/l (

m-1)

-2.7

10 mg/ml

100 mg/ml

50 mg/ml

600 700 800 900

140 hrs

94 hrs

A/l (

m-1)

Wavelength (nm)

-4.2

72 hrs

10 100

0.1

1

CI (mg/ml)

200 nm 200 nm 200 nm

E) 23 hr F) 70 hrs G) 106 hrs

MoS2

Hybrid materials

Sufficiently good properties of inorganic material alone? e.g. MoS2 – poor electrical conductor Hybrid materials -> new/unusual properties? Much potential for devices Easy with liquid dispersions….

200 nm 500 nm

Hybrid materials

500 nm

MoS2

10s of nm thick to freestanding

25 mm

Gra/MoS2 SWNT/WS2

200 nm 500 nm

Homogenous – Graphene/MoS2 hybrids

10 µm 10 µm

Graphene MoS2

Dispersion excellent on length scale of flake size

0 500 1000 1500 2000 2500 3000

Inte

nsity (

a.u

.)

Raman Shift (cm-1)

300 350 400 450 500

MoS2

Gra

Electrical properties: Graphene/MoS2 hybrids

0.1 10.1

1

10

100

D

C (

S/m

)

-c

Below percolation

Above percolation

t

c

cGraDC

1

s

c

cMoSDC

2

s=5.3 t=2.1 c=22%

0.0 0.2 0.4 0.6 0.8 1.010

-7

10-5

10-3

10-1

101

103

DC (

S/m

)

Volume fraction,

0.3 0.2 0.110

-7

10-6

10-5

10-4

10-3

10-2

D

C (

S/m

)

c-

0.05

Cunningham, J Materials Chem, under review.

Application: Supercaps, Thermoelectrics

0.0 0.5 1.0-2

0

2 MnO

2

MnO2/SWNT

I (m

A)

Voltage (V)

Super-cap electrodes

10 100

80

120

160

0 50 100

0

50

100

150

200

Mass fraction, (%)Mass fraction, (%)

D

C (

S/c

m)

Mass fraction, (%)

SWNTs

WS2/SWNT

WS2/SWNT

S2

DC (W

/K2m

)0 20 40 60 80 100

0

20

40

60

80

100

S (V

/K)

2

DCSzT T

Thermo-electric materials

Application: Li-ion batteries Good energy density but poor stability: electrode cracks on cycling

Required:

• Good Li intercalation,

• Conductivity

• mechanical robustness

Devices tested at Uni Sydney by Prof A Minett

Solution: MoS2/Nanotube hybrid MoS2/SWNT hybrid cathode

Graphite anode

LiPF6 electrolyte

xLi+MoS2 ↔ LixMoS2

Application: Polymer Composites

25 mm

PU Exfoliated layers easily formed into composites

Y=270 GPa, B=23 GPa

Reinforcement?

MoS2/Polyvinylalcohol films

2.0

2.5

3.0

3.5

4.0

4.5

0.0 0.1 0.2 0.3 0.4 0.5100

120

140

160

180

Expected:

dB/dV

f=23 GPa

dY/dVf=700 GPa

Y (

GP

a)

Expected:

dY/dVf=270 GPa

Volume fraction (%)

B (

MP

a)

0 5 10 15 20 25 30

0

50

100

150

Str

ess (

MP

a)

Strain (%)

PVA

0.14%

0.24%

Stress transfer >5 MPa

Flake L/t~2000

Solvents? Use Surfactant/water

0 2 4 6 8 10 12 14

-60

-40

-20

0

(

mV

)

pH

-100 -50 0

MoS2/SC

(mV)

SC

400 600 800 100010

-2

10-1

100

1500 rpm

1250 rpm

1000 rpm

A

Wavelength (nm)

750 rpm

600 700 800 900

0.00

0.05

0.10

MoS2/Sodium Cholate in H2O

Smith, Advanced Materials 2011, 23, (34), 3944-3948

TEM & AADF-TEM

5 n m5 n m

200 nm 200 nm 50 nm 10 nm

100 nm

2 n m2 n m

2 nm

0 2 4 6 80

1

2

I (a

u)

nm

100 nm

Good quality few layer flakes

Smith, Advanced Materials 2011, 23, (34), 3944-3948

Other materials in water?

BN

WS 2

Mo

Te2

Mo

Se2

TaSe

2

Nb

Se2

BN TaSe2 WS2

MoTe2 NbSe2 MoSe2

MoSe2

200 nm

NbSe2 TaSe2

MoTe2

WS2

200 nm

200 nm 200 nm

200 nm

BN

200 nm

~1g MoS2 in 1L water ~1015 flakes

Next steps – layered oxides?

100 nm 500 nm

MoO3 TiO2 MnO2

100 nm

Supercaps, Li ion batteries etc

Surfactant / solvent exfoliation?

MoO3

Acknowledgements

Collaborators: Prof. Valeria Nicolosi (CRANN, TCD) Prof. Andy Minett (Univ of Sydney)

Dr. Sukante De Dr. Umar Khan Dr. Phil Lyons Marguerite Hughes Karen Young Evelyn Doherty Paul King

Arlene O’Neill Sophie Sorel Peter May Ronan Smith Graeme Cunningham Conor Boland Sebastian Barwich

Chemical Physics of 1D Nanostructures Group

Prof. Jonathan Coleman