The Fundamental Interactions of 2D
Nanomaterial Powders and Surfactants
Curtis Heishman, Richard Livingston, Dale Brown, and David Estrada
Abstract
Techniques
High yield and affordable production of graphene and other two-dimensional
(2D) crystals has been a topic of considerable research in multiple disciplines.
Liquid exfoliation utilizing ionic surfactants has proven to be an effective way
to create 2D materials with potential uses such as lithium ion battery
electrodes, printable electronics, and thermal interface materials. The focus of
this research is the examination of the relationship between surfactants used in
the exfoliation process and the quality of the resultant 2D nanoflakes of
graphene and transition metal dicalchogenides (TMDs). To do this we first create
MoSe2, MoS2, and graphene suspended flakes via liquid exfoliation in an aqueous
solution of ionic surfactant. We then create dry powders of randomly stacked 2D
crystals for further use in device applications by freeze drying the solutions.
Finally we perform DOSY NMR Spectroscopy, IR Spectroscopy, Raman
Spectroscopy, Thermogravimetric Analysis, and Inductively Coupled Plasma
Atomic Emission Spectroscopy to elucidate the fundamental interactions of
surfactants with our 2D crystals.
Characterization
Single Layer MoS2, MoSe2, Graphene Solutions Preparation
•80mg Bulk Powders
•40mL Soldium Cholate Solution (2% w/v)
•Tip Sonication in Ice Bath 30 min
•Centrifuge 25 min @ 4500 rpm
•Creates 2D Materials in Surfactant Micelles
e.g. Jonathan Coleman 5
Lyophilization to Create 2D Powders
•0.110 mBar, -53 C, 24 hours
IR Spectroscopy
Sodium Cholate
Ionic Surfactant
Fig 4
MoSe2 + NaCh overlayed w/ Sodium Cholate
1H
Lyophilization Data
Research Relevance
Create a pellet of mixed 2D nanomaterials
• Cheap, Efficient, High Reproducibility, Easy To Work With
• MoSe2, MoS2, Graphene, WS2, WSe2
• Achieve a high quality ZT Value
Material
MoSe2
MoS2
Graphene
Graphene + MoS2
Volume of Solution
15mL
15mL
15mL
14mL
Mass Yield
0.1820 g
0.2930 g
0.2550 g
0.2677 g
Density of Solution
12.133 g/L
19.533 g/L
17.000 g/L
19.121 g/L
ZT = s2 σ T λ-1
(Thermoelectric Figure of Merit)
s = Seebeck coefficient (converting temperature to current)
σ = Electrical Conductivity
λ = Thermal Conductivity
MoS2/Graphene Heterostructured Nonvolatile Memory
T = Temperature
NaCh MoSe2
06/23/14
NaCh MoSe2
06/13/14
NaCh
06/13/14
Future Work
Van der Waals Heterostructures
Labconco FreeZone 4.5L
Graphene & Surfactant Flakes
MoSe2 Flakes Heated to 575 C
Characterization
Thermogravimetric Analysis 6
Fig 2
Funded by:
National Science Foundation, Office of Special Programs,
Division of Materials Research
•Grant Number DMR 1359344
Fig 3
NMR Spectroscopy
Evidence of Hydrolysis
Fig 1
Common TMDs
MoSe2 after heating to 575 C
To Remove Surfactant
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•
•
•
•
MoS2 & MoSe2 + Surfactant Powders
Heated to 1100 C, 50 C per minute, 21 minutes
~ 71% of Powder is NaCh Surfactant
Surfactant Digests at Min 390 ̊C - Max 550 ̊C
Yield @ ~20%, but does Sodium remain? Preliminary ICP MS anaylsis suggests yes
TGA of MoS2 + Sodium Cholate Surfactant Powder
•
•
•
•
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ICP MS Analysis to determine levels of sodium doping
Raman Spectroscopy to determine thickness of flakes
Investigate potential to bind molecules to 2D flakes
Find non-ionic surfactants that can be lyophilized
Heat Flakes in Inert Atmosphere of Tube Furnace and analyze
TGA of MoS2 + Sodium Cholate Surfactant Powder
Acknowledgements
1. A. K. Geim and I. V. Grigorieva, Nature 499 (7459), 419425 (2013).
2. Q. H. Wang, K. Kalantar-Zadeh, A. Kis, J. N. Coleman and
M. S. Strano, Nature Nanotechnology 7 (11), 699-712
(2012).
3. A. K. Geim and I. V. Grigorieva, Nature 499 (7459), 419425 (2013).
4. Seong, Maen-Je, Journal of Korean Physical Society Vol
58, No 4
5. Science 331, February 4, 2011, DOI:
10.1126
6. Dr. Jerry Harris, NNU