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1. Characterization of Hybrid Reduced Graphene Oxide - Silver
Nanoparticles Conductive Ink for Flexible Electronics Applications
Nora’zah Abdul Rashid*, Nur Diyana Syazwani Zambri, Aiman Sajidah Abd Aziz, Syed
Muhammad Hafiz Syed Mohd Jaafar, Suraya Sulaiman
Flexible Electronics Laboratory, Research and Development, MIMOS Berhad,Technology Park
Malaysia, Bukit Jalil 57000 Kuala Lumpur, Malaysia
*Corresponding author’s phone: +603-8995 5000
E-mail: norazah@mimos.my
ABSTRACT
Hybrid ink of reduced graphene
oxide (RGO) decorated with silver
nanoparticles (AgNPs) hasattracted much
attention in the development of conductive
inks for the application of flexible
electronics. In this work, we characterized
the synthesized RGO-AgNPs and
demonstrated their ability to perform inkjet
printing on a flexible substrate
polyethylene terephthalate (PET). X-ray
Photoelectron Spectroscopy (XPS)
confirmed that the intensity of oxygenated
functional groups has been dramatically
reduced,and silver nanoparticles are
decorated on the RGO sheet.Transmission
Electron Microscopy (TEM) shows that
the particle size distribution of AgNPs is in
the range of 10-25 nm,and the lattice
fringe spacing is 0.24 nm. The hybrid of
RGO-AgNPs inkjet printing film has
achieved a high conductivity of 1.50 × 104
S/cm, which provesthe improvement of the
electrical performance. The developed ink
could be used in numerous electrical and
electronic applications such as RFID tags.
Keywords— reduced graphene oxide;
silver nanoparticles; hybrid inks; high
conductivity; flexible electronics
1.0 INTRODUCTION
Conductive ink is a vital substance
in inkjet printing for producing printed
electronics. The development of
conductive inks with high conductivity,
low resistivity, environmentally friendly
and low-cost preparation methods has
become a key challenge [1]. Existing
conductive inks such as that from
polymer-based materials [2], carbon
nanotubes, metal- based nanoparticles and
etc. have some disadvantages due to their
limited utilization. For example, polymer-
based inks and carbon nanotubes have
poor conductivity and poor dispersion,
respectively. Metal-based nanoparticles
that act as filler such as Au, Ag, Pt and Cu
have great conductivity, but they do have
some of their drawbacks such as Au and Pt
which are too costly for mass production
[2] while Cu is easy to oxidize. According
to reports, due to its high conductivity and
strong oxidation resistance, silver
nanoparticles are the most commonly used
conductive ink [3]. However, due to the
high cost, it is still not recommended for
large-scale production.
Graphene, which was discovered in
2004 has become an interesting research
topic to produce printed electronics.
However, due to the poor solubility of
pure graphene or pristine in water, it is not
an ideal formulation for producing
conductive inks [4]. In view of this,
reduced graphene oxide (RGO) is an ideal
ink material for flexible electronic
products, because it is easy to
Proceedings of the 4th International Symposium on Advanced Materials and Nanotechnology 2020
(i-SAMN2020), December 1-3, 2020
131

2. functionalize due to some residual defects
and organic groups on its surface.
However, the conductivity of the RGO ink
printed film is still very low, so it is
necessary to further modify or improve the
RGO ink to support the application in the
field of printed electronics.
2.0 MATERIALS
Graphene oxide water dispersion
was purchased from Graphenea, USA.
Silver nitrate (AgNO3), was purchased
from Merck, Germany. The water used in
all reactions was deionized water. All
chemicals were of analytical grade and
utilized without further purification.
3.0 EXPERIMENTAL
3.1 Synthesis of Hybrid
Reduced Graphene Oxide-Silver
Nanoparticles (RGO-AgNPs)
Hybrid reduced graphene oxide
(RGO)-silver nanoparticles
(AgNPs)composite was prepared using
chemical reduction method. Graphene
oxide (GO) was used as a precursor for
graphene synthesis, while silver nitrate
was usedas the source of metallic silver. A
reducing agent and an encapsulating agent
were added to reduce GO and silver
nitrate, and the latter was used for the
silver protective coating.The mixed
solution was left overnight to allow for the
growth process of silver nanoparticles. A
black composite was collected after
centrifuging process. Finally, the
composite was crushed and deionized
water was added to produce a hybrid
RGO-AgNPs colloid. The colloid was
stored in a tight sealed bottle for further
use.
3.2 Inkjet Printing
Hybrid RGO-AgNPs ink was
filtered and injected into an empty
disposable cartridge and attached to a 16
chip nozzle head. Patterns were printed
usinga square design (10 mm × 10 mm) on
Polyethylene Terephthalate (PET)
substrate as shown in Fig. 1. Dimatix
Fujifilm
Materials Printer DMP 2850 was used for
the inkjet printing processes. Fig. 2 shows
a disposable cartridge with nozzle head
and Dimatix inkjet printer for precise
printing of hybrid RGO-AgNPs ink. The
printer settings are shown in Table 1.
3.3 Characterization
X-ray photoelectron spectroscopy
(XPS) by Phi Quantera II was used to
analyze the surface chemical bonding of
organic and inorganic species.
Transmission Electron Microscope (TEM)
by Technai G2-200 kV was used to
observe the size and the morphology of
RGO-AgNPs hybrid ink. The electrical
data was collected using a four-point probe
meter (Loresta-GP MCP T700 Mitsubishi
Chemical Analytech).
Fig. 1: Printed film of RGO-AgNPs
Fig. 2: (a) Disposable cartridge with nozzle head
(b) Dimatix Fujifilm Materials Printer DMP2850
TABLE I: Printer and Cartridge Setting
Parameter Setting
Jetting voltage 40 V
Substrate
Temperature
40 °C
Cartridge
Temperature
30 °C
Cartridge print height 0.450 mm
a b
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3. 4.0 RESULTS AND DISCUSSION
4.1 The Study of X-ray
Photoelectron Spectroscopy
(XPS)
The X-ray photoelectron
spectroscopy (XPS) was employed to
analyze the nature of binding energy
which can be characterized by oxygen
containing groups in GO, RGO-AgNPs
and also small molecules [5]. As shown in
Fig. 3(a), there were four main peaks in
XPS spectrum of GO; C-C at 284.7 eV, C-
O at 286.4 eV, C=O at 287.0 eV, and
carboxylate carbon HO-C=O at 288.4 eV.
Meanwhile,as shown in Fig.3(b)
RGO-AgNPs, the oxygenated functional
groups intensity decreased significantly
upon reduction, which indicates that the
reduction of GO by removing some
oxygen function group was successful.
The remaining carboxylic acid functional
groups indicate the presence of
encapsulating polymers as a coating
mechanism for silver nanoparticles.
Furthermore, Fig.3(c) shows the binding
energies of AgNPs at 367.9eV and
373.9eV for Ag 3d5/2 and Ag
3d3/2respectively. It was proven that
AgNPs was effectively decorated on the
surface of RGO sheets. The increase of
binding energy by 6eV was due to the
electron transfer from metallic Ag to the
RGO sheets.
Fig. 3: XPS spectra of (a) GO, (b) RGO-AgNPs
and (c) AgNPs
4.2 The Study of Transmission
Electron Microscopy (TEM)
Shown in Fig. 4 is a typical TEM
micrographs to confirm the distribution of
AgNPs on RGO nanosheets. It is clearly
shown in Fig. 4(a) and 4(b) that an
abundant spherical shape of AgNPs was
decorated on the surface and at the edge of
the RGO, which is consistent with
previous studies[2].The particle size
distribution of AgNPs is found to be in the
range of 10-25 nm (Fig. 4c) and the
measured lattice fringe spacing is 0.24 nm
(Fig. 4d) which matches the FCC lattice of
(111) crystal plane. These results therefore
confirmed the formation of silver
nanoparticles on the RGO sheets.
4.3 The Study of Electrical Data
In this work, RGO-AgNPs ink was
developed with average viscosity obtained
was 4.43 cP whereas the optimum range of
desired viscosity of inks for inkjet printing
is 1-10 cP [6], hence the average viscosity
are in close agreement with each other.
A four-point probe electrical
testing was performed to evaluate the
performance of theinkjet printing film. The
data of resistance, sheet resistance,
resistivity and conductivity were presented
in Table II.Conductivity of 1.50 × 104
S/cm was achieved with hybrid RGO-
AgNPs inkjet printing film as compared to
conductivity of only 2.5 × 102
S/cm of
graphene ink [7].
a b
c
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4. Fig. 4: TEM images of RGO-AgNPs
Table II: Electrical Data of RGO-AgNPs
Printed Film
Parameters 1 2 Average
Resistance
(Ω)
1.90 × 10-1
1.56 × 10-1
1.73 × 10-1
Sheet
resistance
(Ω/‫)ם‬
7.39 × 10-1
6.05 × 10-1
6.72 × 10-1
Resistivity
(Ω.cm)
7.39 × 10-5
6.05 × 10-5
6.72 × 10-5
Conductivity
(S/cm)
1.35 × 104
1.65 × 104
1.50 × 104
This comparison proved that the
hybrid RGO with Ag nanoparticles
apparently have improved the printed film
conductivity.
5.0 CONCLUSION
In this work, we had successfully
demonstrated thecharacteristic of hybrid
RGO-AgNPs.XPS spectrum was observed
as RGO and the existence of metallic
silver nanoparticles. TEM result confirmed
that the size of nanoparticles was in the
range of 10-25 nm. The hybrid of RGO-
AgNPs has been proven to improve the
conductivity. In summary, hybrid RGO-
AgNPs ink characterized in this work
could be useful for future flexible
electronic application with further
optimization, i.e. to improve the quality of
the inkjet printing.
ACKNOWLEDGEMENTS
This work was supported
financiallyby Ministry ofScience,
Technology and Innovation (MOSTI)
through the 11th
Malaysia Plan
development expenditure (DE) funding.
All the microscopy analysis were carried
out at Failure Analysis and Material
Analysis Laboratory, MIMOS Berhad.
Meanwhile, the inkjet printing was
performed at Research and Development
(R&D) Flexible Electronics Laboratory,
MIMOS Berhad.
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