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. 2018 Apr 7;8(4):224.
doi: 10.3390/nano8040224.

Scalable Fabrication of High-Performance Transparent Conductors Using Graphene Oxide-Stabilized Single-Walled Carbon Nanotube Inks

Linxiang He  1 , Chengzhu Liao  2 , Sie Chin Tjong  3
Affiliations

Scalable Fabrication of High-Performance Transparent Conductors Using Graphene Oxide-Stabilized Single-Walled Carbon Nanotube Inks

Linxiang He et al. Nanomaterials (Basel). .

Abstract

Recent development in liquid-phase processing of single-walled carbon nanotubes (SWNTs) has revealed rod-coating as a promising approach for large-scale production of SWNT-based transparent conductors. Of great importance in the ink formulation is the stabilizer having excellent dispersion stability, environmental friendly and tunable rheology in the liquid state, and also can be readily removed to enhance electrical conductivity and mechanical stability. Herein we demonstrate the promise of graphene oxide (GO) as a synergistic stabilizer for SWNTs in water. SWNTs dispersed in GO is formulated into inks with homogeneous nanotube distribution, good wetting and rheological properties, and compatible with industrial rod coating practice. Microwave treatment of rod-coated films can reduce GOs and enhance electro-optical performance. The resultant films offer a sheet resistance of ~80 Ω/sq at 86% transparency, along with good mechanical flexibility. Doping the films with nitric acid can further decrease the sheet resistance to ~25 Ω/sq. Comparing with the films fabricated from typical surfactant-based SWNT inks, our films offer superior adhesion as assessed by the Scotch tape test. This study provides new insight into the selection of suitable stabilizers for functional SWNT inks with strong potential for printed electronics.

Keywords: aqueous dispersion; carbon nanotube; electrical conductivity; graphene oxide; ink; mechanical flexibility; optical transmittance; rod coating.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(A) UV-vis absorbance of diluted GO and GO-SWNT (weight ratio of 10:1) dispersions. Pure SWNT solution (weakly oxidized by nitric acid) is shown for comparison. The inset photo displays GO-SWNT (left) and GO (right) dispersions. (B) Absorbance of GO-SWNT dispersion for different time periods. (C,D) Raman profiles of GO-SWNT dispersion (weight ratio of 10:1), GO and SWNT.
Figure 1
Figure 1
(A) UV-vis absorbance of diluted GO and GO-SWNT (weight ratio of 10:1) dispersions. Pure SWNT solution (weakly oxidized by nitric acid) is shown for comparison. The inset photo displays GO-SWNT (left) and GO (right) dispersions. (B) Absorbance of GO-SWNT dispersion for different time periods. (C,D) Raman profiles of GO-SWNT dispersion (weight ratio of 10:1), GO and SWNT.
Figure 2
Figure 2
TEM micrographs of (A) SWNT bundles in water; (B) GO-SWNT dispersion with a GO:SWNT mass ratio of 10:1; (C) GO-SWNT dispersion with a GO:SWNT mass ratio of 20:1. The concentration of SWNT in each case is 0.2 mg/mL; (D) Effect of GO concentration on the diameter of SWNT bundles in the dispersion. The SWNT content in the ink is 0.2 mg/mL.
Figure 3
Figure 3
Contact angles for GO-SWNT ink on PET substrate: (A) before and (B) after plasma treatment. The contact angle is 59.7° and 10.2°, respectively.
Figure 4
Figure 4
Effects of the concentration of (A) SWNT and (B) GO on the viscosity of GO-SWNT ink.
Figure 5
Figure 5
SEM micrographs of rGO-SWNT films prepared from inks with different GO to SWNT mass ratios: (A) 5:1, (B) 10:1 and (C) 20:1.
Figure 5
Figure 5
SEM micrographs of rGO-SWNT films prepared from inks with different GO to SWNT mass ratios: (A) 5:1, (B) 10:1 and (C) 20:1.
Figure 6
Figure 6
XPS C-1s spectra of GO, GO-SWNT (weight ratio of 10:1) and rGO-SWNT films. Peaks relate to different carbon bonds are indicated.
Figure 7
Figure 7
Sheet resistance versus optical transmittance for rGO-SWNT films fabricated from inks with different GO to SWNT mass ratios. The SWNT content in the ink is 0.2 mg/mL.
Figure 8
Figure 8
AFM height (A, C and E) and amplitude (B, D and F) microgrqaphs of rGO-SWNT films prepared from inks with different GO to SWNT mass ratios: (A) 5:1, (B) 10:1 and (C) 20:1.
Figure 8
Figure 8
AFM height (A, C and E) and amplitude (B, D and F) microgrqaphs of rGO-SWNT films prepared from inks with different GO to SWNT mass ratios: (A) 5:1, (B) 10:1 and (C) 20:1.
Figure 9
Figure 9
Comparison of electrical properties of rGO-SWNT film with those films contained other dispersing agents. (A) Transmittance versus sheet resistance profiles; (B) Comparison of figure of merit (FoM) CMC: sodium carboxymethyl cellulose; SDS: sodium dodecyl sulphate; FS: fluorosurfactant (FC-4430).
Figure 10
Figure 10
(A) Relative sheet resistance vs. benching cycles for rGO-SWNT films. R0 is the electrical resistance of samples before bending, and R is the electrical resistance that changes with bending cycles. Error bars reflect standard deviation for five measurements; (B,C) Mechanical stability of rGO-SWNT/PET film: before and after the Scotch tape test; (D) Sheet resistance vs. transparency before and after Scotch tape peeling test.
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