The paper expands the information present in the poster

1. In situ production of silver nanoparticles on cotton fabric
for antimicrobial properties
Alvaro Y. Gómez Peñuela, Jaime A. Gómez Montealegre
Abstract -- In the last few decades, there has been
increased interest in antibacterial coatings on textile
materials because of a variety of environmental
pollutants. Silver at nanoscale present known
bactericidal properties, that’s why in this paper a simple
and environmentally-acceptable approach for the in situ
forming silver nanoparticles (AgNPs) on cotton fabrics
has been used. The fabrics were characterized by FTIR,
SEM, EDS and its antimicrobial property was evaluated
against E. coli and S. aureus according to AATCC 100
standard. The presence of nanoparticles on the cotton
fabric was checked and the results of antimicrobial
studies reveal an excellent and durable antimicrobial
effect. This study presents an advance in the efficient
development of antimicrobial fabrics.
Keywords – Silver nanoparticles, Antimicrobial Cotton
fabric, In situ loading
1. Introduction
The textile industry in recent decades has ventured
into the development of fabrics with antibacterial
properties capable of inhibiting the formation of
pathogens present in our body and in the
environment [1]. They have invested part of their
resources in the investigation of methods and
processes that allow reproducing this emerging
technology on a large scale and efficiently.
Cotton fabrics are some of the most used for the
manufacture of clothes due to their mechanical
properties, biodegradability, hygroscopicity and
softness. However, these properties facilitate the
rapid growth and spread of bacteria, owing to its
ability to retain moisture [2]. Therefore, numerous
chemicals have been used to improve the
antimicrobial activity of cotton textiles [3]. Silver
nanoparticles are well known for their antimicrobial
activity that can be used in microbial protective
textiles [1], some research has shown that silver
nanoparticles is skin friendly and does not cause skin
irritation [4],therefore, it have great potential.
The aim of the present work is to grow silver
nanoparticles onto cotton fabric to prepare
antimicrobial cotton fabric in a simple, low cost and
time-saving way. The fabric obtained was subjected
to tests of washing cycles, morphological and
compositional analysis, coating resistance and
antimicrobial property. As results, the fabric with
silver nanoparticles obtained have demonstrated
continuous antibacterial efficacy after several
washing cycles, finally, the method used could be
applied to the large-scale manufacture of
antibacterial textiles with potential uses in industry.
2. Materials and methods
2.1 Cotton fabric and chemicals.
Cotton fabrics (plain woven, 280 g/m2
) purchased in
Fabricato (Colombia) were used in this study. The
fabric was washed in warm water using a nonionic
detergent to ensure removal of residual chemicals.
After washing, the fabric was rinsed with warm
water several times and then with cold water and
finally dried in an oven. Silver nitrate (AgNO3,
#101512), sodium hydroxide (NaOH, # 106469) in
pellets form and acetic acid (#159166) were of
analytical grade and provided by Sigma-Aldrich.
2.2 Formation of silver nanoparticle on cotton fabric.
The procedure for the synthesis of silver
nanoparticles was taken from [5] and involves three
processing steps shown in Fig. 1.
Fig. 1. Diagram of the in-situ synthesis of Ag NPs on cotton fabric, adapted from [5].

2. In the first step, in order to activate cotton fabric, a
piece (15 cm x 25 cm) of cotton fabric was immersed
in aqueous solution of 5% NaOH with liquid ratio
1:10, taking into account the weight of dry fabric,
and left there for 5 min at room temperature. In the
second step, the fabric was immersed in 0.4 mM
AgNO3 with a liquid ratio of 1:10 as follow: started
with vigorous stirring at room temperature for 5 min;
after that the temperature was increased, with a rate
of 4°C/min, to 70 °C and it remained there for
additional 5 min. This step was performed in an IR
dyeing machine, in which the treated cotton fabric
was obtained together with a waste solution with
silver nanoparticles (see Fig. 1).
Finally, the third stage of the process involved
washing with 1 g/L non-ionic detergent (CORY)
with a liquid ratio 1:30 at 90°C for 5 min and
neutralization with treatment in acetic acid solution
(1 mL/L) with a liquid ratio of 1:30 for 5 min. The
samples were washed again with water to 25°C for
5 min, after that it was dried in an oven at 65 ° C for
60–90 min. The obtained fabric was called Cotton-
Ag.
2.3 Characterization
UV-visible spectrum was used to qualitatively
confirm the presence of silver in nanometer size in
the waste solution using Shimadzu UV-1800
spectrophotometer (Japan) in the range from 200 to
900 nm. Also the waste solution was analyzed in
dispersion light scattering (DLS) equipment,
Microtrack Zettatrack (United State), to determine
the size and dispersion of the nanoparticles.
In addition, scanning electron microscopy (SEM)
and energy-dispersive spectroscopy (EDS), JEOL
JEM6000plus (Japan), was used to establish the
morphology and composition of coated and
uncoated cotton fabrics. The specimens were
mounted on the SEM’s specimen stabs and coated
with thin film of gold by the sputtering method
during 60s at 30mA. Fourier transform infrared
spectroscopy (FTIR), Shimadzu FTIR-8400S
spectrometer (Japan), was performed to clarify the
interaction of silver nanoparticles with cotton
fabric.
The antibacterial efficiencies of treated samples
were quantitatively estimated against Gram-positive
bacteria S. aureus (29212) and Gram-negative
bacteria E. coli (8739) according to the AATCC
100-2004 standard as follow (before this step the
samples was washed five times):
The samples was inoculated with 1.0 mL of
inoculums. After incubation 24 h, the bacteria were
eluted from the samples by shaking in 50 mL of
sterilized water for 1 min, 0.1 mL of these
suspensions and diluted suspensions with
physiological solution were plated on soy agar and
incubated for 24 h. Afterwards the number of
bacteria was counted and the reduction of bacteria,
R, was calculated as follows:
% 𝑅 =
𝐵−𝐴
𝐵
∗ 100
Where A is the number of bacteria incubated during
24 h and B is the number of bacteria immediately
after inoculation (at “0” contact time).
3. Results and discussion
We presented an easy method to produce an
antibacterial cotton fabric via in situ fabrication,
silver nanoparticles were deposited on the surface of
fabrics by direct reduction of silver ions obtained
from the dissociation of silver nitrate (AgNO3→Ag+
+NO3
-
the reduction of silver ions typically produces
silver nanoparticles [2]). A visible color change was
observed in the cotton fabric after the process that
indicated the formation of silver nanoparticles, the
color change is the most used indicator for the
formation of metal nanoparticles [4].
In water, NaOH dissociates into Na+
and OH-
ions,
when cotton fabric is introduced into the alkaline
solution, Na+
ions bind to the hydroxyl groups of
cellulose (the main component of cotton). Therefore,
alkaline treatment disrupts intermolecular hydrogen
bonds between cellulose chains loosening their
structure as shows in Fig. 2. This allows easier
access of Ag+
to the interior of the fibers. The OH-
produced in the dissociation of NaOH and the
hydroxyl groups of the cellulose reduce the silver
ions that produce silver atoms (Ag+
→Ag0
), after that
they accumulate into oligomeric clusters, which
eventually produce silver nanoparticles inside and
on the cotton fabric [6].The treatment in a NaOH
solution with a high enough concentration ensures
the introduction of additional OH-
groups inside the
fibers, which facilitates the growth of nanoparticles
in the internal structure of the fiber.

3. Fig. 2. NaOH treatment disrupting intermolecular hydrogen bonds between cellulose chains. The Na+
ions
opens up the surface and internal pores of cellulose fibers, allowing Ag+
to penetrate into the fibers prior to
its reduction into silver nanoparticles.
The waste solution was examined to detect the
presence of nanoparticles using UV-vis
spectrometry, the spectrum obtained is shown in Fig.
3. An adsorption peak with a maximum at 415 nm is
observed, this corresponds to the resonance peak of
the surface plasmon of silver nanoparticles with
spherical geometry [7].Therefore it is very likely
that the cotton fabric contains silver nanoparticles.
The DLS was used to determine the hydrodynamic
diameter of the nanoparticles, the number
distribution (Fig. 4) showed that the average
diameter observed to be 223.7 nm
Fig 3. Uv-vis spectrum of the waste solution
Fig 4. Nanoparticle size distribution
SEM images of blank cotton and cotton-Ag fabrics
are presented in Fig. 5. There are no morphological
changes in cotton fabric caused by in-situ deposition
of silver nanoparticles, nor are nanoparticles
observed on the surface, probably due to the
resolution of the equipment used. Therefore, to
provide additional information of silver coated
cotton fabric, energy-dispersive spectroscopy (EDS)
was used to map the presence silver nanoparticles in
the cotton-Ag fabric.

4. Fig. 5. SEM images of a) uncoated cotton fabric and b) coated cotton fabric
Fig 6. shows the EDX spectrum of cotton-Ag fabric
proving the existence of silver element on the
surface of the fabric treated, the atomic percentage
of carbon, oxygen, and silver in the present study
observed to be 51.22%, 48.71%, and 0.07%,
respectively. This way is confirmed the existence of
the low amount of silver nanoparticles on the surface
of the treated fabrics.
After confirming the presence of silver nanoparticles
in the fabric, the interaction of the nanoparticles with
cellulose was elucidated through an FTIR
analysis. Fig. 7 shows FTIR spectra for cotton fabric
and cotton-Ag fabric, The characteristic peaks of
cotton due to cellulose macromolecule, which
appear at 3,334 cm-1 (O–H stretching), 2,900 cm-1
(C–H stretching), 1,430 cm-1 (C–H wagging), 1,368
cm-1 (C–H bending) and 1,029 cm-1 (C–O
stretching) [5] have lost intensity for silver coated
cotton fabric. This result indicates binding of silver
nanoparticles with O in cellulose macromolecule.
Fig. 6. Compositional spectrum of cotton-Ag
fabric.
On the other hand, the spectra of cotton-Ag fabric
doesn’t reveal new peaks different from the case of
blank sample, which means that no chemical
reaction on cellulose takes place during the in situ
coating [5].
Fig. 7. FT-IR transmission spectra of the cotton fabric and the cotton-Ag fabric

5. Finally, antibacterial activity of cotton-Ag fabric
was determined according to AATCC 100
standard. To evaluate the durability of the imparted
antibacterial activity after repeated washings, the
antibacterial activity of the cotton fabric was studied
after five washings cycles. The antibacterial activity
was tested quantitatively against two different
bacterial strains: S. aureus as an example of Gram
positive bacteria and E. coli as an example of Gram
negative bacteria, and results were reported in Table
1.
Table 1. Antibacterial activity of cotton fabric and
cotton-Ag fabric after five washing cycles.
Cotton
fabric
Cotton-Ag
fabric
Reduction E. Coli -600,00% 98,30%
Reduction S.
Aureus
-34,48% 99,9%
The data shown in Table 1 reveal that the silver
coating shows good fixation after five wash cycles
since the reduction rate remained high. For the
untreated fabric, the number of bacteria increased
600 and 35 times more for S. aureus and E. coli
respectively. On the contrary, the fabric treated
presented an excellent antibacterial action with
reduction percentage close to 100%.
There is certainly no doubt about the antimicrobial
efficiency of the silver-coated cotton fabric. Silver,
which is well-known to effectively destroy
numerous microorganisms [1], also inhibited all two
chosen microorganisms with the reduction
amounted to > 98%. The excellent antimicrobial
activity proves that enough of Ag+
ions is still
present and released during performance. Due to the
procedure proposed is not complicated, inexpensive
and environmentally-acceptable, it is suitable for
industrial production and straight integration in
already existing setups for textile industry. The
fabric obtained could be used in several applications
such as wound dressing, bed lining, medicinal
bandages, purification of medical and food
equipment, and domestic cleaning, etc.
4. Conclusion
The antibacterial cotton fabrics were successfully
fabricated by in situ direct reduction of silver nitrate
on cellulose molecules using a practicable and eco-
friendly preparation method. The loading level of
silver nitrate on cotton fabric could be easily
controlled by controlling the amount of silver nitrate
precursor. Uv-vis spectroscopy demonstrated the
present on silver nanoparticles in waste solution, on
the other hand EDS analysis confirmed the existence
of silver nanoparticles on the surface of cotton
fabrics. FTIR study ensure that cellulose's functional
groups played role in reduction of silver ions to
silver metal, also that the interaction between
cellulose fibers and metallic silver nanoparticles
only results from physical adsorption of silver
nanoparticles on surface of treated fabrics. The
silver nanoparticles imparted an excellent
antibacterial property to the cotton fabric with an
excellent washing durability. The advantages of this
process are its ease to carry out and its efficiency
which could have strong application for the
development of antimicrobial fabrics for several
applications.
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