Graphene hydrogels: from fundamentals to applications · Carbon gels Graphene gel Chemistry of...

Carbon gels Graphene gel Chemistry of gelation Shell-less gels Composite gels

Graphene hydrogels: from

fundamentals to applications

Kaiwen Hua, Xingyi Xiea,b, Thomas Szkopekc, Marta Cerrutia

aMaterials Engineering, McGill University, CanadabCollege of Polymer Science and Engineering, Sichuan University, China

cElectrical and Computer Engineering , McGill University, Canada


Porous materials in our life

2

Electrochemical energy storage

Filtration, ion exchangeTissue engineering

CO2 / pollutant capture


Traditional carbon gels

3

Antonietti. Markus et al. Chemistry of Materials 26.1 (2013): 196-210.

Polymerization

Classical Resorcinol-formaldehyde (RF) system (1989)

Phase Separation

Al‐Muhtaseb, Shaheen A., and James A. Ritter. Advanced Materials 15.2 (2003): 101-114.

• Complex system• Need of pyrolysis and post activation• Low mechanical properties

Solution Colloidal suspension Gel


Graphene oxide as gel building block

4

Graphene oxide (GO)

• High colloidal stability in solvents (Mw=106-107 g/mol)

• Rich chemistry for crosslinking

• High surface area material (~750 m2/g)

• Restoration of graphene structure


Hydrothermal gelation of GO (2011)

5

Graphene oxide (GO)

Hydrothermal reduction

Reduced graphene oxide (RGO)

Increasing Hydrophobic interaction

• Simple system• Strong and conductive gels


Today’s talk

• How does hydrothermal reduction chemistry work?

• What is the structure of the gels?

• Can we use this information to rationally design new gels?

6


• Low pH: Gas entrapment

• High pH: Absorbed by ammonia

CO2 formation?

• Acidic solution after gelation:

Formation of acidic species?

Identifying gelation products

7Hu, K., Xie, X., Szkopek, T., & Cerruti, M. 28.6 (2016). Chemistry of Materials 1756-1768.

Increasing NH4OH 11

GHG-N-0 GHG-N-60 GHG-N-170 GHG-N-290


a) b)



a) b)



a) b)



a) b)

3pH


Quantification of products

8

0 4 8 12 16 20 24

3

4

5

6

7

8

9

10

11

pH

Volume (ml)

GHG-N-0(A)

GO

GO-supernatant

314.062

328.091

358.138

652.452490.322

288.003

0.000.000.00

150127-02-SSdhb-Cerruti-GHG0D-cal NPpepmix neg 0:G3 MS

314.029

330.055

476.307359.069

287.997

177.723

652.416

150127-03-SSdhb-Cerruti-G0D-cal NPpepmix neg 0:G13 MS

200 300 400 500 600 700m/z

GHG-N-0(A)

GO-supernatant

314.062

328.091358.138

288.003 490.322 652.452

314.029

330.055

359.069 476.307

652.416

287.997

177.723

200 300 400 500 600 700

m/z

0 2 4 6 8 10 12 14 16

3

4

5

6

7

8

9

10

I

IIpH

Volume (ml)

GHG-N-0(A)

GHG-N-60(A)

GHG-N-170(A)

GHG-N-290(A) III

20 30 40 50 600

50

100

150

200

250

300

(1010)

(116)

(018)(202)

(013)

(110)

(104)

Inte

nsity

2 (degree)

CaCO3 (Calcite)

(012)

RGO

CO2

organic fragments

H2O

others

26%

9%

12%

8%

45%

Hu, K., Xie, X., Szkopek, T., & Cerruti, M. 28.6 (2016). Chemistry of Materials 1756-1768.


Impact on structure and properties

9

0 50 100 150 200 250 3000

100

200

300

400

500

600

700 GHG-N-0

GHG-N-60

GHG-N-170

GHG-N-290

Ela

stic m

od

ulu

s (

kP

a)

Ammonia addition (l)

0 50 100 150 200 250 3000.0

0.4

0.8

1.2

1.6

2.0GHG-N-290

GHG-N-170GHG-N-60

Volu

me (

cm

3)

V(ammonia) (l)

GHG-N-0




a) b)



a) b)

Compression

Hu, K., Xie, X., Szkopek, T., & Cerruti, M. 28.6 (2016). Chemistry of Materials 1756-1768.


A closer look at the gel structure

10

Graphene hydrogel

50 μm

Shell

Bulk

Shell

Bulk

RGO Bulk

RGO Shell

Shell Bulk • Compact shell vs. porous bulk

• Forms at interfaces

Hu, K., Xie, X., Cerruti, M., & Szkopek (2015) Langmuir, 31(20), 5545-5549.

20 μm 20 μm 20 μm

100 μm 100 μm 500 μm

a) b) c)

d) e) f)Liquid-glass

20 μm 20 μm 20 μm

100 μm 100 μm 500 μm

a) b) c)

d) e) f)Liquid-Teflon

100 µm 2 µm

a) b)Liquid-air

20 μm 20 μm 20 μm

100 μm 100 μm 500 μm

a) b) c)

d) e) f)

GO dispersion Conventional GHG

Hydrothermal @ 1800C for 6 hours

a)

Freeze drying for 2 days

Graphene aerogel

Top shell

Side shell

Bottom shell


Difference between bulk and shell

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Shell

10 nm

70 layers

10 nm

4 to 7 layers

4 6 8 10 12 14 16

0.01

0.1

1

10

100

1000

Vitamin C

HIGHG Shell

NaBH4

Co

nd

uctivity (

S/c

m)

C/O atomic ratio

GHG Bulk

Shell:

1. Highly order multilayer up to 70 layers

2. 4 orders more conductive



Mechanism and ways to remove shell

12

GO dispersion Conventional GHG

RGO

GO

Bulk

Shell

Hydrothermal @ 1800C for 6 hours

Freeze drying

1800C in air for 1hr

RedisperseRGO in water

Hydrothermal @ 1800C for 6 hrs

GO dispersion GO sponge RGO sponge RGO suspension Shell-less GHG

a)

b)

Resuspend RGO in water

Hydrothermal @ 1800C for 6 hrs

GO suspension RGO suspension Shell-less GHGRGO

Thermal /chemical reduction

a)

b)

100 µm 100 µm

a) b) e)c)GHG Shell-less GHG Shell-less GHG

d)

100 µm 100 µm

a) b) e)c)GHG Shell-less GHG Shell-less GHG

d)

Shell-less hydrogel:• Lower density • Homogenous open structure



Three step method:

I. Homogeneous citrate-Hydroxyapatite (HA)/GO suspension

II. Hydrothermal hydrogel formation

III. Dialysis induced HA deposition on graphene

Free standing HA-RGO hydrogel

Homogenous nanoparticle composite gel

13Xie, X., Hu, K., Fang, D., Shang, L., Tran, S. D., & Cerruti, M. 2015.Nanoscale, 7(17), 7992-8002.


Dialysis?

14

shell


Distribution of HA on gel

15

40% HA loading

Homogenous HA nano-needles on graphene!


Good biocompatibility

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>93% of live cells on both rGO and G/HA-40

TCP rGO G/HA-40


Cell morphology

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More elongated cells on G/HA

Filamentous extensions on G/HA


Summary

• Conductive, elastic gels can be produced by hydrothermal reduction of GO

• Mechanical and electrical properties can be tuned by changing pH or other reduction conditions (pre-reduction)

• Nanocomposite porous, biocompatible, conductive, elastic structures for tissue engineering…. And what more?

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Acknowledgements

• NSERC

• Centre of Self Assembled Chemical Structures (CSACS)

• Canada Research Chair Foundation

• Fonds de recherche Nature et technologies Quebec

• McGill University: MEDA scholarshipCSACSFEMR and Dr. X. LiuBiointerface and Nanoelectronic devices and material lab members

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Thank you!

Graphene hydrogels: from fundamentals to applications · Carbon gels Graphene gel Chemistry of...

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