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\DOI{10.5802/crchim.418}
\datereceived{2024-12-08}
\dateaccepted{2025-09-04}
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\dateposted{2025-11-19}
\begin{document}

\begin{noXML}

\CDRsetmeta{articletype}{research-article}

\title{Smart fabric using continuous deposition of graphene and
aniline,  application to electromagnetic shielding}

\alttitle{Tissu intelligent utilisant le d\'{e}p\^{o}t continu de
graph\`{e}ne  et d'aniline, application au blindage
\'{e}lectromagn\'{e}tique}

\author{\firstname{Mourad} \lastname{Makhlouf}\CDRorcid{0000-0002-6157-5073}\IsCorresp}
\address{Scientific and Technological Research Directorate, Cherchell
Academy DPHB, 42000, Tipaza, Algeria}
\address{Laboratory of Energy Processes and Nanotechnology, University
of Blida, Algeria}
\email[M. Makhlouf]{makhlouf.amc@gmail.com}

\author{\firstname{Sabrina} \lastname{Bouriche}\CDRorcid{0009-0000-0037-1168}}
\addressSameAs{2}{Laboratory of Energy Processes and Nanotechnology, 
University of Blida, Algeria}

\author{\firstname{Zoubir} \lastname{Benmaamar}\CDRorcid{0000-0001-9469-7301}}
\addressSameAs{2}{Laboratory of Energy Processes and Nanotechnology, 
University of Blida, Algeria}

\author{\firstname{Didier}\nobreakauthor\lastname{Villemin}\CDRorcid{0000-0002-6266-3817}}
\address{Laboratory of Molecular and Thio-organic Chemistry, UMR CNRS
6507, INC3M, FR 3038, ENSICAEN and Research Center, University of Caen,
France}

\shortrunauthors

%\def\thanksname{}

%\thanks{}

\keywords{\kwd{Cotton fabric}
\kwd{Graphene}
\kwd{Polyaniline}
\kwd{Electromagnetic shielding}
\kwd{Conductivity}
\kwd{Recycling}}

\altkeywords{\kwd{Tissu en coton}
\kwd{Graph\`{e}ne}
\kwd{Polyaniline}
\kwd{Blindage \'{e}lectromagn\'{e}tique}
\kwd{Conductivit\'{e}}
\kwd{Recyclage}}

\begin{abstract}
This study presents the development of conductive textiles for
effective  electromagnetic interference (EMI) shielding, achieved
through the  modification of cotton fabric with graphene and
polyaniline. Graphene,  obtained by electrochemical exfoliation of
recycled graphite from spent  batteries, and polyaniline, synthesized
in situ using hydrogen peroxide as a  novel oxidant, were selectively
deposited on the cotton fibers to ensure  strong adhesion and uniform
dispersion. The electrical conductivity and EMI  shielding
effectiveness (SE) of the modified fabrics were evaluated in the  
8--9 GHz frequency range as a function of nanofiller content. Experimental 
results showed excellent electrical conductivity and significant EMI 
shielding performance, with a maximum SE value of 15.4 dB. The
synergistic  conductive network formed by the integration of
electrochemically exfoliated  graphene and chemically synthesized
polyaniline played a critical role in  enhancing the electromagnetic
wave attenuation. This work demonstrates a  sustainable approach for
the preparation of high-performance EMI shielding  textiles using
recycled materials and a novel synthesis route, and  demonstrates the
potential of graphene and polyaniline as effective  conductive
nanofillers for advanced EMI shielding applications.
\vspace*{-2pt}
\end{abstract}

\begin{altabstract}
Cette \'{e}tude pr\'{e}sente le d\'{e}veloppement de textiles
conducteurs  pour un blindage efficace contre les interf\'{e}rences 
\'{e}lectromagn\'{e}tiques (EMI), obtenu par la modification d'un tissu
de  coton avec du graph\`{e}ne et de la polyaniline. Le graph\`{e}ne,
obtenu par  exfoliation \'{e}lectrochimique de graphite recycl\'{e}
provenant de  batteries usag\'{e}es, et la polyaniline,
synth\'{e}tis\'{e}e in situ en  utilisant le peroxyde d'hydrog\`{e}ne
comme nouvel oxydant, ont \'{e}t\'{e}  d\'{e}pos\'{e}s
s\'{e}lectivement sur les fibres de coton pour assurer une  forte
adh\'{e}rence et une dispersion uniforme. La conductivit\'{e} 
\'{e}lectrique et l'efficacit\'{e} de blindage (SE) EMI des tissus 
modifi\'{e}s ont \'{e}t\'{e} \'{e}valu\'{e}es dans la gamme de 
fr\'{e}quences 8--9 GHz en fonction de la teneur en nanocharges. Les 
r\'{e}sultats exp\'{e}rimentaux ont montr\'{e} une excellente 
conductivit\'{e} \'{e}lectrique et une performance de blindage EMI 
significative, avec une valeur maximale de SE de 15,4 dB. Le r\'{e}seau
conducteur synergique form\'{e} par l'int\'{e}gration du graph\`{e}ne 
exfoli\'{e} \'{e}lectrochimiquement et de la polyaniline
synth\'{e}tis\'{e}e  chimiquement a jou\'{e} un r\^{o}le essentiel dans
l'am\'{e}lioration de  l'att\'{e}nuation des ondes
\'{e}lectromagn\'{e}tiques. Ce travail  d\'{e}montre une approche
durable pour la pr\'{e}paration de textiles de  blindage EMI haute
performance en utilisant des mat\'{e}riaux recycl\'{e}s  et une
nouvelle voie de synth\`{e}se, et met en \'{e}vidence le potentiel du 
graph\`{e}ne et de la polyaniline en tant que nanocharges conductrices 
efficaces pour des applications avanc\'{e}es de blindage EMI.
\end{altabstract}

\maketitle

\twocolumngrid

\end{noXML}

\section{Introduction}\label{sec1}

Textile engineers can design fabrics with electromagnetic shielding 
properties, which are particularly valuable in aerospace, military, and
medical applications. Electrically conductive fabrics offer excellent 
electromagnetic interference (EMI) shielding capabilities, making them 
suitable for a wide range of uses~\cite{1}. Krishnasamy et~al.~\cite{2}
have developed  and characterized various EMI shielding materials,
including textiles,  designed to protect against radio waves, radar
signals, and other forms of  electromagnetic energy. Rube\v{z}ien\.{e}
et~al.~\cite{3} demonstrated that the  distribution and thickness of
poly (3,4-ethylenedioxythiophene) (PEDOT)  coatings significantly
influence the shielding effectiveness (SE) of  textiles. These fabrics
represent a promising approach to electromagnetic  shielding, with a
clear correlation established between their electrostatic  properties
and shielding performance. Patel et~al.~\cite{4} provide a 
comprehensive analysis of recent advancements in photocatalytic, 
super-hydrophobic, and EMI shielding textile treatments using
nanomaterials.  While these developments offer significant advantages
for both users and  manufacturers, it is crucial to address the
challenges and limitations  associated with the integration of
nanomaterials. The SE of treated fabrics  depends on the fabric's
geometry and the quantity of metal present. Such  textiles can be used
as protective workwear to shield individuals from  electromagnetic
radiation or as covers to block electromagnetic fields~\cite{5}. 
Recent research has focused on innovative strategies, primarily based
on  passive textile designs, to enhance thermal conductivity~\cite{6}.
Shukla  et~al.~\cite{7} optimized the thickness of a carbon layer to
develop a porous  Fe$_{3}$O$_{{4}}$/C shell, achieving an
electromagnetic wave  attenuation of 38.8 dB at a thickness of 2.1 mm.
Guo et~al.~\cite{8} successfully  created novel graphene-based foams
that are remarkably lightweight (0.011~g/cm$^3$) and exhibit
exceptional electromagnetic wave  attenuation capabilities. These foams
demonstrate an average attenuation of  37.2 dB with a graphene loading
of just 0.105{\%}, highlighting their  impressive SE.

According to Liu et~al.~\cite{9}, increasing the content of functional
particles  (such as graphite, graphene, and silver-coated copper
powder) up to 60{\%}  within the frequency range of 0.01--3.0 GHz
optimizes the shielding  properties of the coating. However, exceeding
this threshold may degrade  absorption capabilities due to the
formation of conductive structures that  alter the material's
dielectric properties. The resulting graphene nanosheet 
(GNS)/water-based polyurethane (WPU) composites exhibit exceptional EMI
shielding performance, achieving approximately 32 dB while maintaining 
flexibility and lightweight characteristics. Notably, these composites 
demonstrate high electrical conductivity, reaching 5.1 S/m at a low GNS
content of 5{\%} by volume (approximately 7.7{\%} by weight)~\cite{10}.

Sol--gel and in situ polymerization are the most commonly employed
methods  for ferrite fabrication. Polyaniline (PANI) nanocomposites,
created by  combining ferrite nanoparticles with PANI, show promising
properties for EMI  shielding~\cite{11}. Avloni et~al.~\cite{12}
demonstrated that fabrics coated with  polypyrrole (PPy) provide
effective electromagnetic shielding (37 dB),  comparable to other
conductive polymers. These fabrics allow precise tuning  of surface
resistivity, enabling control over their SE. Akif Kaynak's 
research~\cite{13} further underscores the \mbox{excellent} electromagnetic
shielding  capabilities of PPy-coated textiles. These findings
highlight that  conductive textiles based on polymers are lightweight,
high-performance  shielding materials, opening new opportunities in
this field.

Graphene-based composites are also widely used in biological
applications,  including tissue engineering, drug and gene delivery,
and bioimaging. Table~\ref{tab1} summarizes the remarkable properties
and diverse applications of various graphene-based composites in tissue
engineering. 

%tab1
\begin{table*}
\caption{\label{tab1}Properties and diverse applications of various
graphene-based composites in tissue engineering}
\begin{tabular}{llllc}
\thead
Composite &  Production &  Effects &  Applications  &  Ref. \vspace*{3pt}\\
\endthead
PLA/GO &  \parbox[t]{3.5cm}{\raggedright Fused deposition modeling} & 
\parbox[t]{5.5cm}{\raggedright Increase mechanical properties,
benefit cell proliferation} &  Tissue engineering & \cite{14} \\

PLA/PU &  - &\parbox[t]{5.5cm}{\raggedright  Remarkable improvement in
antibacterial capacity} &  Tissue engineering & \cite{15} \\

TCP/PLA &  - & \parbox[t]{5.5cm}{\raggedright Showing swelling profile, improved biomineralization
capacity, and alkaline phosphatase (ALP) activity} &  Tissue engineering
& \cite{16} \\

PE/rGO &  - & \parbox[t]{5.5cm}{\raggedright High mechanical strength, thermal stability, electrical
property, and antibacterial capacity} &  Tissue engineering & 
\cite{17}\\

Gr-ZnO & 
\parbox[t]{3.5cm}{\raggedright Depositing zinc oxide on graphene nanosheet surfaces} & 
\parbox[t]{5.5cm}{\raggedright Exhibit superior antimicrobial effects} & 
Tissue engineering & \cite{18,19}\vspace*{2pt}
\botline
\end{tabular}
\end{table*}

The table highlights the potential of graphene in tissue engineering by
combining it with other materials to create composites with enhanced 
mechanical properties, antibacterial characteristics, and improved 
biomineralization capacity, among other benefits. These attributes are 
particularly relevant for developing materials designed to interact
with  living tissues, such as implants or scaffolds for tissue
regeneration~\cite{20}.

The primary objective of our work is to develop high-performance smart 
textiles specifically designed to provide enhanced protection for
humans  against the harmful effects of electromagnetic waves. To
achieve this, we  have developed an innovative process for
functionalizing fabrics using  nanomaterials, particularly graphene
obtained through the electrochemical  exfoliation of recycled graphite
from spent batteries. Simultaneously, we  synthesized a conductive
polymer, polyaniline, using a novel alternative  oxidant, hydrogen
peroxide. By integrating these two nanomaterials into  textile fibers,
we have created composite materials that exhibit excellent  electrical
conductivity and significant electromagnetic shielding  capabilities,
particularly within the 8--9 GHz frequency range.


\section{Experimental}\label{sec2}

\subsection{Preparation of graphene}\label{sec21}

We employed an electrochemical method to exfoliate graphite rods into 
graphene using a sulfuric acid electrolyte. In this study,
electrochemical  exfoliation was carried out using graphite rods
sourced from electrical  battery units, which served as the electrodes,
along with a container filled  with a mixture of H$_{{2}}$SO$_{{4}}$
and H$_{{2}}$O as  the electrolyte. This process yielded
high-performance, large-area thin  graphene sheets. The presence of
graphene in the synthesized material was  confirmed using advanced
characterization techniques, including Raman  spectroscopy, scanning
electron microscopy (SEM), X-ray diffraction (XRD),  BET
(Brunauer--Emmett--Teller) surface area analysis, Fourier transform 
infrared spectroscopy (FT-IR), and X-ray fluorescence analysis 
(XRF)~\cite{21,22,23}.

\section{Preparation of polyaniline}\label{sec22}

The standard method for preparing polyaniline (PANI) involves the
chemical  polymerization of aniline in an acidic environment, using an
oxidant as a  catalyst. This process results in the formation of a
polymeric chain  composed of repeating aniline units, which can exist
in various oxidation  states depending on the synthesis conditions. The
production protocols for  PANI vary based on factors such as operating
conditions, including  temperature and pH of the reaction
medium~\cite{24}. Table~\ref{tab2} summarizes the  different PANI
synthesis protocols.

%tab2
\begin{table*}
\caption{\label{tab2}Production protocol for PANI}
\begin{tabular}{llllc} 
\thead
Composite name & Preparation method & Properties & Application & Ref. \\
\endthead
\parbox[t]{3.2cm}{\raggedright PANI/graphite} &
\parbox[t]{4cm}{\raggedright In situ chemical oxidative polymerization}
& \parbox[t]{2.5cm}{\raggedright Increased thermal stability} &
\parbox[t]{3cm}{\raggedright Antistatic coating} & \cite{25} \\

\parbox[t]{3.2cm}{\raggedright PANI/exfoliated graphene} &
\parbox[t]{4cm}{\raggedright In situ chemical oxidative polymerization}
& \parbox[t]{2.5cm}{\raggedright Better cyclic stability} &
\parbox[t]{3cm}{\raggedright Supercapacitor and sodium battery cathode}
& \cite{26} \\

\parbox[t]{3.2cm}{\raggedright PANI/magnetic graphene} &
\parbox[t]{4cm}{\raggedright Hydrothermal method} &
\parbox[t]{2.5cm}{\raggedright High sensitivity} &
\parbox[t]{3cm}{\raggedright Biosensors} & \cite{27} \\

\parbox[t]{3.2cm}{\raggedright PANI/graphene oxide} &
\parbox[t]{4cm}{\raggedright Precipitation polymerization} &
\parbox[t]{2.5cm}{\raggedright Good selectivity} &
\parbox[t]{3cm}{\raggedright Electrochemical sensor} & \cite{28} \\

\parbox[t]{3.2cm}{\raggedright PANI/reduced graphene oxide} &
\parbox[t]{4cm}{\raggedright In-situ interfacial polymerization method}
& \parbox[t]{2.5cm}{\raggedright Excellent mechanical properties} &
\parbox[t]{3cm}{\raggedright Anticorrosion, antistatic, and
antibacterial applications} & \cite{29}\\

\parbox[t]{3.2cm}{\raggedright Graphene oxide/PANI manganese oxide} &
\parbox[t]{4cm}{\raggedright In situ chemical oxidative polymerization}
& \parbox[t]{2.5cm}{\raggedright Synergic behavior of PANI} &
\parbox[t]{3cm}{\raggedright Adsorbent application} & \cite{30} \\

\parbox[t]{3.2cm}{\raggedright SnO$_{2}$/reduced graphene oxide/PANI} &
\parbox[t]{4cm}{\raggedright In situ chemical oxidative polymerization}
& \parbox[t]{2.5cm}{\raggedright  Improved chemical stability} &
\parbox[t]{3cm}{\raggedright Ammonia gas sensing} &  \cite{31} \\

\parbox[t]{3.2cm}{\raggedright PANI/graphene obtained by recycling
graphite from spent batteries} & \parbox[t]{4cm}{\raggedright In situ
chemical oxidative with H$_{2}$O$_{2}$ polymerization} &
\parbox[t]{2.5cm}{\raggedright Good screen against EMI} &
\parbox[t]{3cm}{\raggedright Continuous dyeing for intelligent fabrics}
& This work\vspace*{3pt}
\botline
\end{tabular}
\vspace*{-3pt}
\end{table*}

The synthesis protocol for PANI comprised three essential steps:

\subsection{Pretreatment of monomer (aniline)}\label{sec23}

To prevent side reactions and enhance polymerization yield, aniline 
(analytical grade, Merck) was purified using vacuum distillation. The 
purified aniline was then stored in a cool, dark environment.

\subsection{Protonation of aniline monomer}\label{sec24}

\vspace*{-2pt}

As PANI is a base-conjugated semiconductor, the dopant plays a critical
role  during polymerization. To initiate the reaction, 50 mL of
hydrochloric acid  (HCl, 37{\%}) was added dropwise to purified aniline
under continuous  mechanical stirring for one hour. This step
facilitates the cleavage of N--H  and N--C bonds in aniline, enabling
the attachment of protons (H$^+$) to  nitrogen atoms, which act as
polymerization initiators in the presence of an  oxidant.

\vspace*{-2pt}

\subsection{Polymerization}\label{sec25}

\vspace*{-2pt}

Following protonation, polymerization was initiated by slowly adding 
hydrogen peroxide (H$_2$O$_2$) as the oxidant dropwise over 4--6~h. The 
oxidant-to-monomer ratio ([H$_2$O$_2$]/[aniline]) was maintained at 1.15, and
the  reaction temperature was held at ${-}$5~\textdegree C. The resulting
dark green  PANI powder was filtered under vacuum, washed sequentially
with 0.1 N HCl,  methanol, and deionized water, and dried in an oven at
60~\textdegree C for  24~h.

\vspace*{-2pt}

\section{Continuous dyeing process}\label{sec3}

\vspace*{-2pt}

Two dispersions were prepared:

(G) Graphene dispersion: 1 g of graphene was dispersed in 100 mL of 
distilled water and sonicated for 1 h; (PANI) Polyaniline dispersion: 
1~g of  PANI was dispersed in 100 mL of acetic acid and sonicated for 
1~h. Both  dispersions were simultaneously applied to a plain-weave
cotton fabric  (properties listed in Table~\ref{tab3}), yielding three
samples:

T/G: Fabric coated with graphene.

T/PANI: Fabric coated with polyaniline.

T/G/PANI: Fabric coated with graphene and polyaniline.

%tab3
\begin{table*}
\caption{\label{tab3}Characteristics of the cotton fabric\vspace*{-1pt}}
\begin{tabular}{llllll}
\thead
Characteristic &  \parbox[t]{2.5cm}{\raggedright Weave structure} &  
\parbox[t]{2.5cm}{\raggedright Warp and weft density} &  
\parbox[t]{2.5cm}{\raggedright Thread count} & 
Weight &  \parbox[t]{1.5cm}{\raggedright Hand feel}\vspace*{2pt} \\
\endthead
Value & Plain-weave & \parbox[t]{2.5cm}{\raggedright 100 threads per inch (TPI)} & 
\parbox[t]{2.8cm}{\raggedright Approximately 60 threads per inch} & 
\parbox[t]{2.2cm}{\raggedright Approximately 150 g/m$^{2}$} & Soft \vspace*{2pt}
\botline
\end{tabular}
\vspace*{-1pt}
\end{table*}

\subsection{Conductivity measurement}\label{sec41}
To measure conductivity, a PANI sample was prepared as a film or
pellet. Two  electrodes were connected to the sample, and a voltage was
applied across  it. The conductivity $(\sigma )$ of the sample was
calculated using the  formula:
{$$
\sigma = 1/\rho \times t/A
$$}\unskip
where $\rho$ is the resistivity, $t$ is
the thickness of the sample, and $A$ is the cross-sectional area.

The conductivity of PANI can vary significantly depending on factors
such as  the synthesis method, doping level, and sample purity.
The conductivity of various materials is summarized in Table~\ref{tab4}.

%tab4
\begin{table}
\caption{\label{tab4}Conductivity of various materials}
\begin{tabular}{ccc}
\thead
Material & \parbox[t]{2cm}{\centering Conductivity (S${\cdot}$cm$^{-1}$)} & Ref. \vspace*{3pt}\\
\endthead
Silver, gold, iron & ${\sim}10^{5}$ & \morerows{4}{\cite{32}}  \\
Silicon, germanium & ${\sim}10^{1}$ &  \\
Doped polyaniline & ${\sim}10^{1}$ &  \\
Undoped polyaniline & ${\sim}10^{-8}$ &  \\
Nylon & ${\sim}10^{-14}$ &  \\
PANI &  4.$7\times 10^{-1}$ & This work
\botline
\end{tabular}
\end{table}

\subsection{Structural characterization by FT-IR}\label{sec42}

During FT-IR analysis, PANI is exposed to infrared radiation, which
causes  the polymer's chemical bonds to absorb specific wavelengths of
the  radiation. The resulting spectrum reveals absorption frequencies
that  correspond to vibrational modes of functional groups within PANI.
These  vibrational modes are compared to standard reference bands to
identify  functional groups and confirm their presence in the polymer
structure. The  FT-IR spectrum of the as-synthesized PANI is shown in
Figure~\ref{fig1}. A  quinoid-ring stretching vibration appears as a
band at about 1560  cm$^{{-1}}$, and the peak around 1325 cm$^{{-1}}$
is  attributed to the C--N stretching vibration between the benzenoid
and  quinoid units~\cite{33}. The band at 1475 cm$^{{-1}}$ is due to
the C--C  stretching vibration in the benzene ring. Another peak
appears around 1290  cm$^{{-1}}$, associated with the delocalization of
$\uppi $-electrons  due to protonation or C--N stretching vibration,
while a high absorption  band near 1246 cm$^{{-1}}$ is observed due to
the deformation of the  polaron structure from the C--N stretching
mode~\cite{34,35}. The band between  1145 and 1601 cm$^{{-1}}$
corresponds to in-plane C--H bending  (N${=}$Q${=}$N and B--NH$^{{+}}$--B
where Q ${=}$ NH$^{{+}}$--B and  B represents the aromatic ring)
resulting from protonation~\cite{36}. Researchers  refer to this as the
``electronic-like band'', indicating electron  delocalization in
PANI~\cite{37}.

In addition, the peak at 1090 cm$^{{-1}}$ is attributed to the 
in-plane bending of aromatic C--H in the 1,4-disubstituted aromatic
ring~\cite{38}. Researchers have identified the band at 860 cm$^{{-1}}$
as the  out-of-plane bending vibration mode of C--H, as previously
discussed for  single-walled carbon nanotubes (SWCNTs)~\cite{39}. The
band at 640~cm$^{{-1}}$ corresponds to the S--O stretching vibration of
sulfonate  substituents in aromatic rings, indicating that PANI
nanotubes have been  doped~\cite{40}. The characteristic bands are
\mbox{consistent} for all PANI salts,  confirming the presence of the
emeraldine salt phase in each compound~\cite{41}.  The differences in
the intensities of the 1350--1000 cm$^{{-1}}$  peaks among the PANI
salts can be explained by the different degrees of 
protonation~\cite{42}.

\begin{figure}
\includegraphics{fig01}
\caption{\label{fig1}Fourier transform infrared (FTIR) spectrum of the
conducting polyaniline (PANI).}
\end{figure}

\subsection{Contact angle measurement}\label{sec43}

Contact angle measurements are used to characterize the 
hydrophilic/hydrophobic nature of a material, enabling the evaluation
of the  influence of nanofillers on the wetting properties of the
fabric~\cite{43,44}.  This technique involves depositing a liquid
droplet onto the fabric and  measuring the angle formed between the
tangent to the droplet surface and  the solid surface at any point
during the process. This angle, known as the  contact angle or sessile
angle, describes the interaction between the  liquid, solid, and
air~\cite{45}. We characterized the shape of the droplets at 
equilibrium on our substrates using the sessile-drop method and imaging
software (Figure~\ref{fig2}).

\begin{figure*}
\includegraphics{fig02}
\caption{\label{fig2}Contact angle degrees: (T) fabric 
66.749\textdegree, (T/PANI) fabric coated with polyaniline
137.643\textdegree, (T/G/PANI) fabric coated with graphene and
polyaniline 108.635\textdegree.}
\end{figure*}

The researchers used these measurements to determine whether the
modified  fabric exhibited hydrophilic or hydrophobic properties. The
contact angles  of the samples are summarized in Table~\ref{tab5}.

%tab5
\begin{table*}
\caption{\label{tab5}Contact angles of our samples}
\begin{tabular}{cccc}
\thead
Fabric type &  Contact angle  &  Interval of young  &  Nature of sample\\
\endthead
T &  \066.749 & $\upalpha <90$ & Hydrophilic \\
T/PANI & 137.643 & $90<\upalpha<150$ & Hydrophobic\\
T/G/PANI & 108.635 & $90<\upalpha<150$ & Hydrophobic
\botline
\end{tabular}
\end{table*}

Our observation was that the contact angle increased with the
conductivity  of the coating filler, indicating a trend toward a more
hydrophobic surface.  This shift toward hydrophobicity suggests a
change in the surface's polar  characteristics. Generally, hydrophilic
surfaces (low contact angles) are  more polar, exhibiting stronger
interactions with \mbox{polar} liquids like water  through hydrogen bonding
and dipole--dipole interactions. 
Conversely, \mbox{hydrophobic} \mbox{surfaces}
(high contact angles) are typically less polar, with  weaker
interactions with water, favoring interactions through London 
dispersion forces. Therefore, our finding that higher conductivity
fillers  led to higher contact angles implies that these fillers, when
integrated  into the fabric, resulted in a less polar surface. This
could be attributed  to the nature of the conductive materials
used---graphene and  polyaniline---which, in their deposited form,
present a less polar surface  compared to the untreated fabric.

\section{Shielding effectiveness}\label{sec5}

A network analyzer is an instrument used to characterize devices in 
microwave circuits, such as amplifiers, attenuators (both fixed and 
variable), and cables, among others. It integrates the system and
evaluates  its impact on signal transmission or reception. This
instrument enables the  quantification of the S-parameters (short for
scattering parameters). These  parameters provide critical information,
including power, gain and/or  attenuation, return loss, and impedance.
The rectangular waveguide, based on  a quadrupole structure, is a
technique used to determine key parameters such  as the reflection
coefficient and transmission coefficient using a network  analyzer. To
measure the electromagnetic shielding effectiveness (SE), we  placed
fabric samples into the waveguide support of a Keysight N5222A vector 
network analyzer, as illustrated in Figure~\ref{fig3}.

\begin{figure*}
\vspace*{-2pt}
\includegraphics{fig03}
\vspace*{-3pt}
\caption{\label{fig3}(a) Sample holder; (b) Fabrics (4 cm$^{2}$); (c)
Waveguide holder; (d) Vector network analyzer.}
\vspace*{-3pt}
\end{figure*}

The SE experiments were conducted within the frequency range of 
8--9~GHz, which is commonly used in both military and civilian
communications. Using a two-port vector network analyzer, the
S-parameters were measured and analyzed. These parameters are defined
as: $S_{11}=b_1/a_1$ (reflection coefficient), $S_{21}=b_2/a_1$
(transmission coefficient), where $a$ and $b$ represent the normalized
incident and reflected waves, respectively. The process involves
measuring the reflected signal ($S_{11}$) and the transmitted signal
($S_{21}$), as well as calculating the absorbance using the following
equations:
{\begin{eqnarray}
\mbox{Transmittance }T &=& | S_{21}|^2 \label{eq1}\Seqnsplit
\mbox{Reflection }R &=& | S_{11}|^2 \label{eq2}\Seqnsplit
\mbox{Absorbance }A &=& 1-R -T \label{eq3}\Seqnsplit
\mbox{SER }&=& 10{\cdot}\log_{10}(1-R) \label{eq4}\Seqnsplit
\mbox{SEA }&=& 10{\cdot}\log_{10}|T/(1-R)| \label{eq5}\Seqnsplit
\mbox{SE }&=& \mbox{SER} + \mbox{SEA} \label{eq6}
\end{eqnarray}}\unskip

We calculate the SEA and the SER of each sample by measuring the 
$S_{{11}}$ and $S_{{21}}$ parameters of our various samples  using a
vector network analyzer. \mbox{Figures~\ref{fig4}} and~\ref{fig5} present the
results of the  SE measurements, illustrating the variation in the
effectiveness of the  shielding for reflection SER and absorption SEA.
It is evident from the  plots that the SEA and SER values exhibit a
proportional relationship with  the frequency at low frequencies, as
well as with the type of nanofiller  added. Furthermore, the addition
of conductive nanofillers primarily  contributes to the increases in
SEA and SER. The purpose of these tests was  to evaluate the
electromagnetic SE and obtain values for S-parameters  $S_{{11}}$
(reflected incident) and $S_{{21}}$ (transmitted  incident). These
findings indicate that the SE of the composite fabrics  increases with
a higher surface conductive charge. For instance, a fabric  coated with
graphene displayed $S_{{21}}$ and $S_{{11}}$  (S-parameters) values of
5.2 and 10.95 dB, respectively, compared to 9.2 and  7.24 dB for a
PANI-coated fabric. On the other hand, a fabric coated with  both PANI
and graphene displayed $S_{{21}}$ and $S_{{11}}$  values of 11.9 and
10.24 dB, respectively. The increase in conductive  loading also led to
an increase in the $S_{{21}}$ transmission  parameter from 3.15 dB
(fabric) to 5.2 dB (graphene-coated fabric), 9.2 dB  (PANI-coated
fabric), and 11.9 dB (T/G/PANI). In addition, the  $S_{{11}}$
reflection parameter increased from 5.2 dB (fabric) to  10.24 dB
(graphene and PANI-coated fabric). The S-parameters of different 
fabrics are summarized in {Table~\ref{tab6}}.\looseness=-1

\begin{figure}
\includegraphics{fig04}
\caption{\label{fig4}Shielding effectiveness for reflection (SER) in
the 8--9~GHz range.}
\vspace*{-2pt}
\end{figure}

\begin{figure}
\vspace*{-1pt}
\includegraphics{fig05}
\vspace*{-3pt}
\caption{\label{fig5}Shielding effectiveness for absorption (SEA) in
the 8--9~GHz range.}
\end{figure}

%tab6
\begin{table}
\caption{\label{tab6}S-parameters of different fabrics\vspace*{-3pt}}
\begin{tabular}{ccc}
\thead
{Fabric} & $S_{21}$ {(dB)} & $S_{11}$ (dB) \\
\endthead
T/G & {\05.2}  & {10.95}  \\
T/PANI & {\09.2}  & {\07.24}  \\
T/G/PANI & {11.9}  & {10.24}
\botline
\end{tabular}
\vspace*{-3pt}
\end{table}

%tab7
\begin{table*}
\caption{\label{tab7}EMI shielding effectiveness of carbon-coated fabrics\vspace*{-1pt}}
\begin{tabular}{ccccccccc}
\thead
Substrates & Medication routes & Carbon-based materials
& EMI SE (dB)  & Ref.\vspace*{3pt} \\
\endthead
Cotton & Dip-drying process & MWCNTs$^{\mathrm{a}}$ & \09.0 & \cite{46} \\
Vinylon & Blade coating method & Graphite nanosheets & 28.0 & \cite{47} \\
Polyester & Pad-dry-cure method & Nano carbon black & \07.7 & \cite{48} \\
Polyester & Plasma-assisted dip-drying & NH$_{2}$--MWCNTs & 18.2 & \cite{49} \\
Cotton & Knife-over-roll coating & Carbon black & 31\0 & \cite{50} \\
Nonwoven fabric  & Knife-over-roll coating & Graphene nanotube & 15\0 & \cite{51} \\
Cotton & Continuous dyeing & Graphene ${+}$ PANI & 15.4  & This work
\botline
\end{tabular}
\tabnote{$^{\mathrm{a}}$Multiwall carbon nanotubes.}
\end{table*}

%tab8
\begin{table*}
\caption{\label{tab8}Microwave absorption properties of various
PANI-based composites}
\begin{tabular}{ccccc}
\thead
Absorber &  Thickness (mm) &  Max RL (frequency) &  Bandwidth (GHz) & Ref. \\
\endthead
PANI nanoparticles &  2.0 &  18.8~dB (17.2~GHz ) &  14.1--18.0 & \cite{52} \\
BaFe$_{12}$O$_{19}$/PANI &  2.0 &  19.7~dB (14.6~GHz) &  13.0--16.9 &  \cite{53} \\
Ba(CoTi)$_{x}$Fe$_{12-2x}$O$_{19}$/PANI &  2.0 &  33.7~dB (14.6~GHz) & 12.0--17.3 &  \cite{54} \\
Fe$_{3}$O$_{4}$ microspheres/PANI &  2.0 &  18.6~dB (14.0~GHz) & 12.1--16.0 &  \cite{55} \\
Fe$_{3}$O$_{4}$/MWCNT/PANI &  2.0 &  8.0~dB (14.7~GHz) &  Undetected & \cite{56} \\
graphite/CoFe$_{2}$O$_{4}$/PANI &  2.0 &  11.0~dB (3.8~GHz) &  3.4--4.0&  \cite{57} \\
graphene/PANI &  2.0 &  25.3~dB (16.5~GHz) &  13.9--18.0 &  \cite{58}  \\
${\upalpha}$-MoO$_{3}$/PANI &  2.0 &  33.7~dB (16.9~GHz) &  14.2--18.0&  \cite{59} \\
Fe$_{3}$O$_{4}$/PANI &  2.0 &  13.8~dB (16.7~GHz) &  16.3--17.2 & \cite{60} \\
Fe$_{3}$O$_{4}$ microspheres/PANI &  2.0 &  37.4~dB (15.4~GHz) & 13.0--18.0 &  \cite{61} \\
NiZn ferrite/PANI &  2.0 &  20.0~dB (14.0~GHz) &  12.0--16.6 & \cite{62} \\
Fe$_{3}$O$_{4}$/CIP/PANI &  2.0 &  25.5~dB (10.1~GHz) &  7.1--9.9 & \cite{63} \\
BaTiO$_{3}$/PANI &  2.0 &  13.8~dB (11.6~GHz) &  10.7--12.5 & \cite{64} \\
MnO$_{2}$/PANI &  2.0 &  20.9~dB (13.5~GHz) &  11.4--16.8 &  \cite{65}\\
graphene@Fe$_{3}$O$_{4}$@SiO$_{2}$@PANI &  2.0 &  19.4~dB (16.4~GHz) & 10.4--18.0 &  \cite{66} \\
Ni/C/PANI &  2.0 &  7.5~dB (10.0~GHz) &  Undetected &  \cite{67} \\
PPy@PANI-0.8 &  2.0 &  23.3~dB (15.8~GHz) &  13.5--18.0 &\morerows{2}{\cite{68}}  \\
PPy@PANI-1.2 &  2.0 &  34.8~dB (13.9~GHz) &  11.9--16.6 & \\
PPy@PANI-1.6 &  2.0 &  31.5~dB (13.6~GHz) &  11.7--16.4 &  \\
Textile &  2.0 &  9.53~dB (8.17~GHz) & \morerows{3}{8--9}  &\morerows{3}{This work}  \\
Textile/Graphene &  2.0 &  11.17~dB (8.17~GHz) &  &  \\
Textile/PANI &  2.0 &  9.98~dB (8.17~GHz) &  &  \\
Textile/Graphene/PANI &  2.0 &  15.4~dB (8.17~GHz) &  &
\botline
\end{tabular} 
\end{table*}

However, the PANI/G composite fabric showed a lower $S_{{11}}$ 
reflection parameter of 10.24 dB compared to the graphene-coated
fabric,  which had an $S_{{11}}$ value of 10.95 dB~\cite{22}. This
decrease can be  attributed to the way PANI/graphene is absorbed and
retained on the fabric  surfaces and within its interstices. Despite
this, researchers notably found  that all the composite fabrics studied
could serve as effective materials  for constructing electromagnetic
shielding. Figure~\ref{fig6} presents the SE of  various samples as a
\mbox{function} of frequency within the 8--8.6 GHz range. The  data reveals a
clear frequency dependence of SE, indicating that both the  conductive
charge and the specific nature of the fabric's coating  significantly
influence its shielding capabilities.

Table~\ref{tab7} summarizes the electromagnetic interference (EMI) SE
of fabrics  coated with carbon-based materials.

Table~\ref{tab8} lists the electromagnetic SE of some typical
PANI-based composites.  Max RL (Frequency) refers to the maximum
attenuation in decibels (dB),  indicating the peak absorption
efficiency at a given frequency. Bandwidth  (GHz) indicates the
frequency range over which absorption exceeds a certain  threshold.

The results show that the modification of the fabric coating with
graphene  nanofillers improves SE. The conductive PANI coating on the
fabric achieved  a SE of 9.98 dB, while graphene used as a coating
material increased this  effect to 11.17 dB. The effective shielding
properties were further improved  to a SE of 15.4 dB when the fabric
was coated with PANI/graphene. 

\begin{figure}
\includegraphics{fig06}
\vspace*{-4pt}
\caption{\label{fig6}Electromagnetic
shielding effectiveness (SE) for various samples in the 8 to 8.6~GHz
range.}
\vspace*{-2pt}
\end{figure}

\vspace*{-4pt}
\section{Conclusion}\label{sec6}

\vspace*{-3pt}

In this work, we report the use of graphene as filler uniformly
distributed  in the fabric matrix with polyaniline coating to improve
its electromagnetic  shielding effectiveness up to 15.4 dB from
simulation results. The trade-off  between the attenuation of
electromagnetic waves and reflection loss results  in a conductive
network with a higher graphene content. Changing the type of  carbon
nanofillers within the matrix affects the shielding effectiveness, 
which may be due to the conductivity enhancement in each doped device. 

\vspace*{-4pt}

\section*{Authorship contributions} 

\vspace*{-3pt}

Authors equally contributed to this work. 

\vspace*{-4pt}

\section*{Ethics approval}

\vspace*{-3pt}

There are no ethical issues with the publication of this manuscript.

\vspace*{-4pt}

\section*{Data availability statement} 

\vspace*{-3pt}

The authors confirm that the data that supports the findings of this
study are available within the article. Raw data that support the
findings of this study are available from the corresponding author,
upon reasonable request. 

\section*{Declaration of interests}

The authors do not work for, advise, own shares in, or receive funds
from any organization that could \mbox{benefit} from this article, and
have declared no affiliations other than their research organizations.

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