This document summarizes research into creating conductive and translucent materials by coating cellulose with silver particles. It discusses coating sulfonated cellulose nanocrystal (CNC) dispersions, tunicate cellulose aerogels, and carboxylated CNC dispersions with silver nanoparticles created in situ. Coating sulfonated CNC dispersions with silver was found to be the most effective method, creating a percolating conductive network observed under TEM. The concentration of silver nitrate and cellulose affected the pH and conductivity. Coating aerogels was less effective as the porous structure prevented an even coating. This research aims to develop renewable and affordable transparent conductive materials to replace indium tin oxide.

1. Conductive Cellulose Materials
Coated with Silver Particles
Karen Richards
Group Meeting 05/08/2014

2. Introduction
• Indium tin oxide (ITO)
 Translucent
 Conductive
• Uses for ITO
 Conductive layer on LCD
screens
2
• Reasons for finding a
replacement
 ITO is becoming scarce due to over
usage
 Price is steadily increasing
• Proposed ITO replacement
 Percolating network of silver in
cellulose dispersion
 Immerse polymer in dispersion
with silver
 Press into film
Solar cells
Solar cells

3. Introduction: cost projections
3
ITO (indium-tin oxide) Coating Cellulose with
Silver
 Roughly $0.25-$0.69 to
cover the LDC screen on
an iPhone 5
 Roughly $0.02 to cover
the LDC screen on an
iPhone 5
(Kalowkamo J., Baker E., 2009)

4. Models for mechanical properties
4
Percolation model
“percolation on”
Takayanagi et al. J. Polym. Sci. 1964, C5, 113.
Ouali et al. J. Plast. Rubber Comp. Process. Appl. 1991, 16, 55.
Halpin, Kardos J. Appl. Phys. 1972, 43, 2235.
Hajji et al. Polym. Comp. 1996, 17, 612.
Polymer Eng. Sci. 1997, 37, 1732.
Halpin-Kardos / Halpin-Tsai: Mean field approach
“fibers are smeared into the
matrix to form a homo-
geneous continuum”
0o
45o
90o
-45o
“mean field /
percolation off”
The first method should leads to an electrically conductive material.
“complete interconnected network
of fillers within the matrix”

5. Introduction: approach
5
Coating sulfonated
tunicate cellulose
aerogel with silver
Coating cellulose
dispersion with silver
Sulfonated
cellulose
dispersion
Carboxylated
cellulose
dispersion
Two approaches
All of these methods were tested. The sulfonated cellulose dispersion gave the best results.

6. Coating tunicate aerogel with silver
6
Tunicate cellulose aerogel
Reducing agent + surfactant
NaHBH4 (Reducing agent)
CTAB (Surfactant)
AgNO3
Reducing agent + surfactant +
tunicate cellulose aerogel
Silver covered tunicate
cellulose aerogel
Silver covered tunicate
cellulose film
+
This three step reaction produces a translucent, conductive film from a tunicate cellulose aerogel.

7. Coating c-CNC dispersion with silver
7
c-CNC dispersion
c-CNC dispersion
coated in Silver particle
AgNO3
Water, CTAB
(surfactant), NaBH4
This two step reaction produces a c-CNC dispersion coated in silver.
Sulfonated
c-CNC dispersion

8. Function of reducing agent
8
Reducing agent: NaBH4
Sodium borohydride reduces silver nitrate to create a silver particle in situ.

9. Function of surfactant
9
Surfactant (CTAB) changes the characteristics of the surface of the silver particle. This forms
an attraction between the particle and the alcohol groups of the cellulose fiber.

10. Silver coated c-CNC’s and t-CNC’s
10
Sulfonated c-CNC’s and t-CNC’s
Carboxylated c-CNC’s

11. Coating tunicate cellulose aerogel with silver
11
LyophilizeCharacterization
t-CNC aerogel Impregnate
SEM images suggest the above procedure creates a coating of silver on the aerogel.

12. Coating sulfonated c-CNC dispersion with silver
12
Sample AgNO3
conc.
(M)
Cellulose
conc.
(mg/ml)
pH before
AgNO3
addition
pH after
AgNO3
addition
1A 1.0 5.0 7.98 7.57
1B 0.5 5.0 7.98 9.09
1C 0.1 5.0 7.98 9.56
1D 10 5.0 7.98 3.28
2A 1.0 1.0 9.58 7.10
2B 0.5 1.0 9.58 8.91
2C 0.1 1.0 9.58 9.4
2D 10 1.0 9.58 5.96
Results indicate a correlation between the amount of AgNO3 added to the dispersion
with both the color and pH of that dispersion.

13. pH change with addition of AgNO3
13
0
2
4
6
8
10
12
10 M 1 M 0.5 M 0.1 M
pH
Concentration of AgNO3
pH change of 5 mg/ml cellulose dispersion
due to varying amounts of AgNO3
pH before addition
pH after addition
Sample AgNO3
conc.
(M)
Cellulose
conc.
(mg/ml)
pH before
AgNO3
addition
pH after
AgNO3
addition
1A 1.0 5.0 7.98 7.57
1B 0.5 5.0 7.98 9.09
1C 0.1 5.0 7.98 9.56
1D 10 5.0 7.98 3.28
2A 1.0 1.0 9.58 7.10
2B 0.5 1.0 9.58 8.91
2C 0.1 1.0 9.58 9.4
2D 10 1.0 9.58 5.96
The chart shows an inverse relationship between the concentration of AgNO3
and the pH of the dispersion.
As the concentration of AgNO3 decreases, the pH increases.

14. pH change with addition of AgNO3
14
0
2
4
6
8
10
12
10 M 1.0 M 0.5 M 0.1 M
pH
Concentration of AgNO3
pH change of 1 mg/ml cellulose dispersion
due to varying amounts of AgNO3
pH before addition
pH after addition
The chart shows an inverse relationship between the concentration of AgNO3
and the pH of the dispersion.
As the concentration of AgNO3 decreases, the pH increases.
Sample AgNO3
conc.
(M)
Cellulose
conc.
(mg/ml)
pH before
AgNO3
addition
pH after
AgNO3
addition
1A 1.0 5.0 7.98 7.57
1B 0.5 5.0 7.98 9.09
1C 0.1 5.0 7.98 9.56
1D 10 5.0 7.98 3.28
2A 1.0 1.0 9.58 7.10
2B 0.5 1.0 9.58 8.91
2C 0.1 1.0 9.58 9.4
2D 10 1.0 9.58 5.96

15. Transmission Electron Microscope (TEM)
15
2
µ
m
TEM images of sample 2A with 1.0 M AgNO3
and 1.0 mg/ml sulfonated c-CNC’s.

16. Coating sulfonated c-CNC dispersion with silver
16
Sample Conc. of
cellulose
(mg/ml)
Conc. Of
AgNO3
(M)
Filter
(0.22 mM)
pH before
AgNO3
addition
pH after
AgNO3
addition
4A 1 0.5 No 8.4 8.3
4B 1 0.5 No 8.4 8.3
4C 0.1 0.5 Yes 8.4 8.2
4D 0.1 0.5 Yes 8.4 8.2
Results from previous samples show aggregated cellulose. Lower
concentrations of cellulose and AgNO3 were tested. The pores in the 0.22mM
filter were too small to let any cellulose through.

17. Coating sulfonated c-CNC dispersion with silver
17
Sample AgNO3
conc.
(M)
Cellulose
conc.
(mg/ml)
Filter
(0.45
mM)
pH
before
AgNO3
addition
pH after
AgNO3
addition
6A 1.0 1.0 No 9.4 9.0
6B 1.0 1.0 Yes 9.4 8.7
6C 0.5 1.0 No 9.4 9.1
6D 0.5 1.0 Yes 9.4 9.1
6E 0.5 0.1 No 9.66 9.8
6F 0.5 0.1 Yes 9.66 7.8
Results indicate a correlation
between the amount of AgNO3
added to the dispersion with
both the color and pH of that
dispersion.
Video is 1.5x its original speed.

18. Transmission Electron Microscope (TEM)
18
The top two images display different
concentrations of silver and cellulose
from samples 6B and 6F.
Silver particles are formed in different
concentrations.
The bottom image displays the
anisotropic silver particles from
sample 2A.

19. Coating carboxylated c-CNC’s with silver
Sample Conc. of
cellulose
(mg/ml)
Conc. Of
AgNO3
(M)
Filter
(0.22 mM)
pH before
AgNO3
addition
pH after
AgNO3
addition
5A 1 0.5 No 8.4 8.8
5B 1 0.5 Yes 8.4 8.9
5C 0.1 0.5 No 8.4 9.0
5D 0.1 0.5 Yes 8.4 7.9
5E 0.01 0.5 No 8.4 8.3
5F 0.01 0.5 Yes 8.4 8.9
19
Sulfonated c-CNC’s seem to be a
better template for this project.
TEM images were
inconclusive. It was too
difficult to differentiate
the silver particles. The
pore size of the filter was
too small.

20. Conclusion
20
Sulfonated c-CNC dispersion
 The best method to create a percolating network of silver on CNC’s
 TEM images
Carboxylated c-CNC dispersion
 TEM images were inconclusive
Tunicate cellulose aerogel
 The aeorgel did not have an even coating of silver
Cause:
 light-weight porous aerogel floats in solution and is not fully
immersed
 The pores caused solution to be trapped and did not circulate
throughout the aerogel

21. Future plan
21
• Find a polymer that is both conductive
and translucent when condensed into film
with dispersion
 Possible polymers: LiClO4-doped
ethylene oxide-epichlorohydrin (EO-
EPI)
(Schroers M., et. al, 2004)
• Coat polymer with silver sulfonated c-CNC
dispersion
• Condense material into thin film
• Characterize material

22. A special thanks to…
22
Prof. Chris Weder
Prof. E. Johan Foster
Dr. Mehdi Jorfi
Sandra C. Espinosa
Jens Natterodt
Silvana Muller
Carola Endes
Janak Sapkota
Apiradee Nicharat
Sara Turner
And everyone at AMI

23. 23
Thank you for your attention!