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American Journal of  Smart 
Technology and Solutions (AJSTS)

Preparation and Conductivity of  Polymer-Modified Graphene Films
Md. Jewel Rana1, Khan Rajib Hossain2*, Marzan Mursalin Jami3, Md. Abu Shyeed4, Md. Kamrul Hasane5

Volume 2 Issue 1, Year 2023
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Article Information ABSTRACT

Received: December 24, 2022

Accepted: March 02, 2023

Published: March 06, 2023

The Hummers method was used to make graphite oxide, and ultrasonic exfoliation at 
25°C and 90°C was used to make graphene oxide (GO). At a low temperature, polyeth-
yleneimine (PEI) was used as a reducing and changing agent for graphene oxide (GO) to 
make dispersions of  graphene that were modified with PEI. Optoelectronics’ electron 
and infrared spectroscopy showed how temperature affected PEI’s ability to break down 
GO. The results show that PEI can partially reduce GO at 25°C. At 90°C, the grafted 
PEI gradually dissociated from the GO sheet. The graphene dispersion was filtered and 
assembled into a PEI-GO film, and its conductivity was found to be 117S.m-1, hopefully 
conductive material for graphene.

Keywords
Conductive, Graphene 
Film, Polyethyleneimine, 
Graphene Oxide

1 Department of  Applied Chemistry and Chemical Engineering, Bangabandhu Sheikh Mujibur Rahman Science and Technology  
  University, Gopalgonj 8100, Bangladesh
2 State Key Laboratory of  Solid Lubrication, Lanzhou Institute of  Chemical Physics, Chinese Academy of  Sciences, Lanzhou 730000, China
3 School of  Textile Science and Engineering, Wuhan Textile University, Wuhan, China
4 Department of  Applied Chemistry and Chemical Engineering, Rajshahi University, Rajshahi 6205, Bangladesh
5 Department of  Chemistry,Hajee Mohammad Danesh Science & Technology, Dinajpur 5200, Bangladesh
* Corresponding author’s e-mail: apexlabbd@gmail.com

INTRODUCTION
Graphene, which is only one atom thick, has a unique 
planar structure in two dimensions, a very high specific 
surface area, and great barrier properties. Graphene has 
attracted extensive attention for its electrical (Kim, et al., 
2017 and Mohan, et al., 2016) and thermal conductivity 
(Balandin, et al., 2008 and Pop, et al., 2012), optical 
(Schoche, et al., 2017) and mechanical properties (Liu, 
et al., 2012, Kordkheili, et al., 2013, Zhu, et al., 2010). 
Water could be used as a reducing agent, according to 
Stankovich S, Dikin D A et al., 2007. Hydrazine hydrate 
can turn graphene oxide (GO) into graphene with higher 
electrical conductivity. The electrical conductivity of  the 
resulting graphene is similar to that of  graphite. (Qi, X 
Y, Yan D, Jiang Z, et al., 2011) the GO made with the 
Hummer method was turned into graphene by heating 
it, and the graphene was then added to a polystyrene 
matrix. The graphene/polystyrene composite material 
was obtained. The research results found that: after 
adding a small amount of  graphene to pure polystyrene, 
its electrical conductivity changed from 6.70×10-14S.m-1 

increased to about 3.49S.m-1.
(Liu H Y, Kuila T, Kim N H, et al., 2013) reported that 
polyethyleneimine (PEI) could reduce GO, and at the 
same time, PEI was grafted to the in situ generated stone. 
A water-soluble polymer-modified graphene PEI-GO 
was obtained on the graphene sheet. According to the 
conductivity test results, the PEI mass ratio is GO. The 
conductivity of  the resulting PEI-GO can be greatly 
affected. Based on the research (Liu, H Y, Kuila T, Kim 
N H, et al., 2013), this paper looks into how the reaction 
temperature affects how PEI breaks down GO. Under 
the premise of  fixing the mass ratio of  raw materials 

PEI and GO by changing the reaction temperature, PEI-
modified graphene was prepared. The prepared PEI-
modified graphene aqueous dispersion was filtered into 
a composite film, and the graphene composite thin films 
obtained at different temperatures were investigated the 
conductivity of  the film.

METHOD AND MATERIALS
Reagents and instruments
Sigma-Aldrich sold polyethyleneimine with an average 
relative molecular mass of  Mn≈10000. Concentrated 
sulfuric acid (the mass fraction is 98%), potassium 
permanganate, sodium nitrate, hydrogen peroxide 
(30% by mass), and hydrochloric acid (38% by mass) 
were analytically pure reagents for further purification. 
The samples were tested by an AXIS-NOVAX-ray 
photoelectron spectrometer (Kratos Analytical Ltd., 
UK) elemental composition. The structural information 
of  the samples was tested using a Nicolet 6700 infrared 
spectrometer (Thermo Scientific, USA). Product 
morphology tests were completed on the H-7650 TEM 
(Hitachi, Japan) and JSM-6701F SEM (JEOL, Japan). A 
Keithley 2000 type four-probe resistivity tester (Keithley 
Instruments Inc., USA) was used to test its electrical 
conductivity.

Preparation of  Graphene Oxide
First, graphite oxide was prepared according to the 
Hummers method (Lei, et al., 2016). Under ice-water 
bath conditions, 50 ml of  concentrated sulfuric acid 
was added to 1g of  natural graphite and 0.5g of  sodium 
nitrate and stirred to mix them evenly. Under magnetic 
stirring, take 3g of  potassium permanganate, slowly add 

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it to the system, and continue stirring. After 10 minutes, 
the ice-water bath was removed, the reaction system was 
heated to 35 °C, and the stirring was continued for 30 
minutes. At this point, the black reaction system became 
a brownish-yellow color, 40ml of  deionized water was 
added to the reaction system, the temperature was raised 
to 95 °C, and the reaction was continued for 1h to obtain 
a golden yellow dispersion. Additions of  150ml of  
deionized water and 10ml of  hydrogen peroxide with a 
mass fraction of  30% were mixed for 30 min, and then 
50ml of  5% hydrochloric acid solution was added. Last, 
wash the sample with deionized water until the solution 
is neutral. The obtained product was filtered with suction 
to remove the solvent water, and the obtained sample 
was placed in a vacuum at 40°C. Dry to obtain dry 
graphite oxide. Weigh graphite oxide and disperse it in an 
appropriate amount of  deionized water. 30 minutes of  
medium sonication to obtain 0.5 mg/ml. The graphene 
oxide solution is ready for use.

Preparation of  polyethyleneimine-modified graphene
Dissolve 0.05 g of  polyethyleneimine in 100 ml deionized 
water to obtain a PEI solution of  0.5 mg/ml. The PEI 
solution was placed in a three-necked flask, and 100 ml 
of  GO solution (0.5 mg/ml) was added dropwise to the 
PEI solution via a constant pressure drop funnel while 
magnetic stirring at 25°C. The reaction was stirred for 4h 
to obtain a brown PEI-GO dispersion.
The GO dispersions were passed through a membrane 
(a cellulose filter membrane with a pore size of  0.2 μm) 
suction filtration, with about 1 liter of  deionized water 
added to wash the sample and remove the impurities. 
Separated PEI and PEI-GO films were obtained, 
respectively.

RESULTS AND DISCUSSION
Morphology analysis of  the product
The GO sheet contains many epoxy groups, hydroxyl 
groups, carboxyl groups, and carbonyl groups at the edge 
of  the sheet, and GO has good water solubility. It can be 
spread out evenly in solvent water to make a brownish-
yellow GO solution. The GO solution was added to the 
polyethyleneimine solution at room temperature. After 
stirring for 4h, PEI-GO was obtained. In appearance, PEI-
GO was not much different from GO, both of  which were 
brown-yellow aqueous solutions. This is because, at 25 °C, 
PEI can’t reduce GO very well, so it’s grafted onto GO 
sheets instead. The amino group of  PEI reacts with the 
epoxy group of  GO to make PEI-GO with a modified 
branch linkage. When the reaction temperature was 90 °C, 
most of  the amino groups of  PEI were dissociated from 
the GO sheet, forming C=C, reducing GO. 
It is graphene, which is consistent with the mechanism of  
hydrazine hydrate reduction of  GO. (Song, P, Zhang X, 
Sun M, et al., 2012) used oxalic acid as a reducing agent 
and heated it at 75°C for 18h. The brown GO was also 
observed to transform into a black graphene dispersion.
So that the shapes of  GO and PEI-GO could be 
seen, their dispersions were taken and freeze-dried to 
make samples that looked like fluffy sponges. The field 
emission scanning electron microscope (FE-SEM) photo 
of  the surface after gold spraying is shown in Figure 1. 
For GO, there are a lot of  random wrinkles on the GO 
sheet, and the edges are easy to bend, showing that the 
GO sheet has good flexibility and toughness. Due to 
their very high specific surface area, the different GO 
sheets in PEI-GO are randomly stacked and cross over 
each other. However, the packing density of  PEI-GO is 
slightly larger than that of  GO because, at 25°C, GO has 

Figure 1: Field Emission Scanning Electron Microscopes photos of  GO and PEI-GO.
a higher packing density. PEI partially restored it. It can 
be observed that the graphene sheets have corrugated 
wrinkles due to their close packing with each other. This 
is because GO is effectively reduced to graphene by PEI 
at 90°C, due to the π-π interaction leading to Graphene 
sheets being tightly packed together.
To better show the morphology of  the samples, another 
dispersion liquid was taken, dropped on the carbon film, 
and dried for transmission electron microscopy (TEM) 
analysis. The obtained TEM photos are shown in Figure 

2. Figure 2a shows a TEM image of  GO divided into 
two parts. It can be seen that graphene oxide has a 
finely layered structure with a large number of  irregular 
wrinkles at the edges, which can reduce graphene oxide. 
The specific surface area reduces its surface energy, 
thereby making it stable. The TEM image of  PEI-GO is 
shown in Figure. 2b with graphene oxide.
In contrast, PEI-GO is still a finely layered structure, and 
its darker color may be due to the PEI grafted on the 
surface of  GO. The folded state of  graphene at the edge 

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Figure 2: TEM view of  GO and PEI-GO

is clearly seen in the graphene sheet, and there are more 
random wrinkles. This is because the graphene sheets 
π-π interact, making wrinkles more likely. More wrinkles 
also indicate that the graphene oxide sheets are reduced 
to graphene sheets. (Xu, L Q, Liu Y L, Neoh K G, et al., 
2011) reported that due to the modification of  graphene 
sheets and graphene oxide sheets showed similar TEM 
morphologies.

Structural Analysis of  the Product
X-ray photoelectron spectroscopy (XPS) was done on the 
samples to determine how the temperature affected PEI’s 
ability to break down GO. Figure 3 depicts the spectrum 
of  a spectroscope (XPS) analysis. For GO, its XPS spectra 
have two main peaks, corresponding to sp. carbon (281.4 
eV) and oxygen (530.5 eV), which is consistent with the 
conclusion of  the (Chua, C K et al., 2012). Except for the 
carbon and oxygen peaks, the XPS spectrum of  PEI-GO 
is at 398 eV. A nitrogen peak appeared at the position of  
GO, which means that the polyethyleneimine molecular 
chain was grafted onto the GO sheet. Carbon and oxygen 
peaks of  PEI-GO and GO are compared. It has been 
found that the former oxygen peak is less strong than it 
used to be. This may be because the PEI molecular chain 
absorbs the oxygen from the epoxy group in the GO 
sheet. The nitrogen of  the amino group is substituted 
to form a nitrogen-containing three-membered ring. It 

means that even at 25°C, the amino group of  the PEI 
molecular chain can interact with the GO sheet. PEI-GO 
was created by reacting the epoxy groups and grafting 
them onto the GO sheet. In (Li, X et al., 2009), GO was 
heated in a nitrogen atmosphere to prepare nitrogen-
doped graphene, also found a nitrogen peak at 398 eV in 
the XPS spectrum.
Figure 4 shows the three samples’ Fourier transform 
infrared (FT-IR) spectra. For GO, the broad and strong 
blunt peak at 3100-3500cm-1 is the stretching vibration 
peak of  the associated hydroxyl group, and the peak 
in the 1734cm-1 figure is the C=O stretching vibration 
peak at 1640 cm-1. The spikes correspond to the C=C 
stretching vibration peak, 1388 cm-1. The absorption 
peak is the bending vibration peak of  the hydroxyl group 
at 1246 cm-1. The absorption peak is the CO stretching 
vibration peak of  the epoxy group. The appearance of  
these oxygen-containing functional groups is consistent 
with the (Gao, Y, Liu L Q, Zu S Z, et al., 2011), which 
says that Ming graphite was successfully oxidized, and 
graphene oxide was obtained after ultrasonic exfoliation.
In contrast, the FT-IR curves of  PEI-GO are not related. 
The hydroxyl stretching vibration peak was replaced by 
the PEI molecular chain. The N-H stretching vibration 
peak is strong and sharp, indicating that the PEI molecular 
chain is branched to the GO sheets. It is worth noting 
that in PEI-GO 1734 cm-1. Still exist C=O vibration 

Figure 3: XPS spectra survey of  the GO and PEI-GO Figure 4: FT-IR spectra survey of  the GO and PEI-GO

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peak, only the intensity compared to the decrease of  
GO shows that PEI can only partially reduce GO at 25 
°C but cannot completely reduce GO to graphene. The 
C-O stretching vibration of  the epoxy group in the GO 
curve’s dynamic peak (1246 cm-1) disappeared completely 
in PEI-GO, proving that the epoxy group of  GO was not 
affected by the reaction of  the amino group of  PEI. The 
effect of  reaction temperature means that PEI molecular 
chains can also be grafted onto GO at 25°C.

Conductivity Analysis of  the Product
The degree of  reduction of  GO has a lot to do with how 
well graphene conducts electricity. Because the GO sheet 
contains many hydroxyl, epoxy, and carbonyl groups, 
the carboxyl group destroys the conjugated structure of  
graphene, so GO is a non-conductive substance. When 
the reducing agent is added, the oxygen-containing groups 
of  the GO sheet undergo partial or full reduction, and 
graphene restores the conjugated structure, thus helping 
to improve the electrical conductivity of  the product. The 
higher the GO reduction degree, the better the graphene 
obtained and the higher the conductivity. Graphene’s 
electrical conductivity, on the other hand, can demonstrate 
the degree of  reduction in GO. It means that the degree of  
GO reduction is greater. GO and PEI-GO were assembled 
into membranes by suction filtration, respectively. The 
acupuncture method was used to calculate the electrical 
conductivity according to the method (Jun, et al., 2015).
Since GO is a non-conductive substance, the conductivity 
of  the obtained GO thin film is 0.002 S·m-1. Such a 
low conductivity also explains why the graphene oxide 
prepared by this method is rich in oxygen-containing 
functional groups, which is consistent with the results of  
FT-IR and XPS. At 25°C, GO was added dropwise to 
PEI, and PEI was grafted onto the GO sheet through 
the reaction between the amino group of  PEI and the 
GO epoxy group, resulting in a PEI-GO dispersion 
liquid. It was assembled into a PEI-GO film by suction 
filtration, and its conductivity was 0.103 S.m-1. The 
specific conductivity of  GO has increased, indicating 
that PEI reduced the oxygen-containing groups. (XU, Z, 
Bando y, Liu L, et al., 2011) found that the influence of  
epoxy groups on the electrical conductivity of  graphene 
materials is much greater than that of  hydroxyl groups, 
and the dissociation of  epoxy groups from the GO sheet 
is preferential to that of  the hydroxyl group, which is 
consistent with the results in this paper. At 25°C, due to 
the amino groups in the PEI molecular chain and the GO 
sheet. The layer epoxy group reaction made GO more 
conductive. Still, since the surface-grafted PEI molecular 
chain was not conductive, the increase in conductivity 
of  PEI-GO was not very high. Conjugated structure of  
graphene, due to the departure of  the non-conductive 
substance PEI and the recovery of  the conjugated 
structure.

CONCLUSION
The temperature of  the reaction has a big effect on how 

well polyethyleneimine can break down graphene oxide. 
At 25°C, PEI can only partially reduce GO and connect. 
At 90°C, PEI effectively reduced GO to graphene, 
resulting in surface-modified graphene PEI-GO. This 
conclusion has some implications for reducing GO with 
other reducing agents. The films assembled from PEI-
GO dispersions have, it has high electrical conductivity 
and is expected to be used in graphene-conductive 
composites.

Declaration of  Interests
The authors declare that they have no known competing 
financial interests or personal relationships that could 
have appeared to influence the work reported in this 
paper.

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