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Design of electrically conductive superhydrophobic antibacterial cotton fabric through hierarchical architecture using bimetallic deposition
Accepted Manuscript Design of electrically conductive superhydrophobic antibacterial cotton fabric through hierarchical architecture using bimetallic deposition Thirumalaisamy Suryaprabha, Mathur Gopalakrishnan Sethuraman PII:
S0925-8388(17)32365-4
DOI:
10.1016/j.jallcom.2017.07.009
Reference:
JALCOM 42425
To appear in:
Journal of Alloys and Compounds
Received Date: 5 May 2017 Revised Date:
29 June 2017
Accepted Date: 2 July 2017
Please cite this article as: T. Suryaprabha, M.G. Sethuraman, Design of electrically conductive superhydrophobic antibacterial cotton fabric through hierarchical architecture using bimetallic deposition, Journal of Alloys and Compounds (2017), doi: 10.1016/j.jallcom.2017.07.009. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Graphical Abstract
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Design of Electrically Conductive Superhydrophobic Antibacterial Cotton Fabric through Hierarchical Architecture using Bimetallic Deposition Thirumalaisamy Suryaprabha and Mathur Gopalakrishnan Sethuraman*
Corresponding Author E. mail: [email protected].
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*
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Department of Chemistry, The Gandhigram Rural Institute – Deemed University, Gandhigram-624 302, Tamil Nadu, India.
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ACCEPTED MANUSCRIPT Abstract In view of the emerging applications of electrically conductive textiles, a simple and inexpensive method for the fabrication of superhydrophobic textiles with electrical
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conductivity and antibacterial activity has been developed through bimetallic deposition of copper and silver over cotton fabric. The as-fabricated modified cotton surface was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction studies. The antibacterial activity of the
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modified fabrics has been evaluated by disc diffusion method against Gram positive and
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Gram negative bacteria. The results of the study revealed that the strategy of the bimetallic deposition over cotton could well become the method of choice for the fabrication of superhydrophobic smart textiles with diverse applications.
Key words: Superhydrophobic textiles, bimetallic, antibacterial, hierarchical, electrical
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conductivity
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ACCEPTED MANUSCRIPT 1. Introduction Intelligent or smart textiles are new generation textiles, which have advanced built-in applications in various fields such as medicine and defence, personal electronics as sensors, data processing, energy or data storage devices and communication [1–4]. In addition to these
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applications, electrically conductive textiles have become very crucial for next generation wearable consumer electronics or smart clothings. Wearable electronics are new class of materials which have attracted extensive attention due to the novel functionalities such as electrical conductivity, flexibility, lightweight, high stretchability, electromagnetic and radio interference protection [5–7]. Portable power displays, high-performance sportswear,
Recently,
properties
like
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novel examples of these electrically conductive textiles.
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embedded health-monitoring devices, flexible heaters [8] and electrode materials [9] are few
superhydrophobicity,
superoleophobicity
or
superomniphobicity have been imparted over conductive materials in order to get multifunctional textiles. Moreover, superhydrophobicity is also an important factor to increase the electrical properties of textiles for various applications. The electrical properties of textiles are highly influenced by two parameters viz., relative humidity and high-water
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trapping properties. So, textiles with superhydrophobicity and electrical conductivity will be immense use in wearable textile systems [10].
Superhydrophobic surfaces, with a water contact angle higher than 150ᵒ and a sliding
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angle lower than 10ᵒ play a vital role in many industrial applications and also in our daily life which includes the fabrication of self-cleaning windows, anti-reflective glasses, protection of electronic devices, windshields, utensils, solar panels and micro-/nanofluidic applications
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[8,9,11]. The micro-/nano- hierarchical structure and low surface energy are the essential parameters for superhydrophobic surfaces [12]. The electrically conductive superhydrophobic textiles can be fabricated by using atomic layer deposition, dip-coating, knitting, layer by layer assembly, electroless deposition (ELD), in-situ deposition and so on. Among these methods, in-situ deposition and ELD methods are widely used since they are simple and easy to adopt [7,13]. The electrically conductive textiles have found potential applications in medical and health-care and hence, it is necessary to protect them from microbial attack also. Conductive textiles can be made by the coating of conductive polymers such as polyaniline [14], polypyrrole [15], metal and metal oxide nanoparticles such as copper, 3
ACCEPTED MANUSCRIPT nickel, silver and carbonaceous materials such as carbon nanoparticles, carbon nanotubes (CNTs) and graphene oxide (GO) [16–18]. The use of metals or metal oxides over conductive polymers prevents conductive decay which otherwise occurs [18]. The deposition of metal nanoparticles on textile substrates is a simple process and requires easy handling procedure. The metal deposited textiles not only show electrical conductivity but also have excellent
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mechanical stability, flexibility and strong attraction towards almost all types of textile fabrics [19].
However, in literature, only few work are available for the fabrication of electrically conductive superhydrophobic textiles. Shateri-Khalilabad et al., have used graphene and
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methyltrichlorosilane for the fabrication of electrically conductive superhydrophobic textiles [20]. In 2014, Caffrey et al., have prepared electrically conductive superhydrophobic film
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using the multiwalled nanotubes (MWNTs) and poly(dimethoxysilane) [21]. Similarly, Yao et al., have also used MWNTs for the synthesis of electrically conductive superhydrophobic films [22]. But in all the above reports, they had used carbon nanotubes and graphene for the conductive coatings over textiles, but after hydrophobicization of those conductive textiles, conductivity was found to be low. Moreover, Liu et al., have prepared conductive yarns using poly [2-(methacryloyloxy)ethyltrimethylammonium chloride] bridged copper particles [5].
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Atwa et al., used silver nanowire coated threads for electrically conductive textiles [19]. However, they did not have any superhydrophobic property. To the best of our knowledge, this is the first report on the fabrication of electrically conductive superhydrophobic textiles
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using bimetallic nanoparticles.
In the present work, cotton fabric is chosen as the base material due to its highcomfortness, extreme breathability and eco-friendly nature compared to other synthetic
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fabrics [23]. Copper and silver bimetallic coatings over cotton fabric are made using in-situ deposition and ELD methods. The coated fabrics also showed enhanced anti-bacterial and electrical conducting properties along with excellent superhydrophobicity. 2. Materials and Methods 2.1 Materials Copper acetate monohydrate and hydrazine hydrate purchased from Central Drug House (CDH), India, silver nitrate purchased from Sisco Research Laboratories (SRL), India were used in the present study. Cotton fabric was obtained from the local market. All the 4
ACCEPTED MANUSCRIPT chemicals used in this study were of analytical grade and used as such without any further purification process. 2.2 Methods 2.2.1 Fabrication of copper coated fabric
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The cotton fabric was thoroughly washed with detergent solution and pretreated with 0.01 N NaOH in order to remove impurities and wax coatings, if any, on the substrate. The deposition of copper on cotton fabric was achieved by the chemical reduction of copper acetate by hydrazine hydrate at room temperature in closed conditions. For the deposition of
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copper on cotton, 0.1 g of copper acetate was dissolved in 5 ml of distilled water. The piece of cotton fabric (2 cm× 2 cm) was immersed in the copper acetate solution. Then, 500 µL of
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hydrazine hydrate was added dropwise into the copper acetate solution and set aside for 12 hours under air tight conditions. Now, the color of cotton fabric turned into reddish brown due to the deposition of Cu on cotton fabric. The cotton fabric was then taken out, washed first with ethanol, then with distilled water and dried in air for a day. 2.2.2 Fabrication of hierarchical structure on cotton fabric
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The above Cu-coated cotton fabric was immersed in 0.1 mM aqueous solution of silver nitrate for about 60-80 s. The bimetallic hierarchical structure on Cu-coated cotton fabric was attained by electroless deposition of silver on copper. Then, the bimetal coated
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cotton was kept in a hot air oven for about one hour at 120º C. 2.3 Characterization of the bimetal coated cotton fabric
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Bimetal coated cotton fabric was characterized using x-ray photoelectron spectroscopy (XPS), scanning Electron Microscopy (SEM), energy dispersive x-ray spectrometer (EDAX) x-ray diffractometer (XRD) and contact angle measurements. The chemical state of elements on surface was characterized by XPS with AES Module with Ar ion as well as C60 sputter Guns (PHI 5000 Versa Probe II, FEI Inc.). The surface morphological images of pristine cotton, copper coated cotton and bimetal coated cotton fabrics along with the change in the surface morphology as a function of immersion times were obtained from SEM using VEGA3- TESCAN. The analysis of elemental composition and its distribution over the as- fabricated cotton samples was carried out using EDAXmapping (Bruker, Nano GMBH X’ Flash Detector, 5010 model, Germany). The crystallinity 5
ACCEPTED MANUSCRIPT and deposition of metals on surface was confirmed by XPERT- PRO X-ray diffractometer. The surface wettability of the as-fabricated fabrics was evaluated using goniometer (ramѐhart instrument. Co, USA). 2.4 Electrical conductivity measurements
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The electrical conductivity of the bimetal coated samples were measured by a fourprobe method [23] using Philips DM341 multimeter system and the conductivity observed in this study was only DC conductivity. The sheet resistance of bimetal coated cotton fabric mainly depends on the deposition of copper and silver on its surface. So, the effects of copper
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concentration on sheet resistance were obtained by measuring the sheet resistance at various concentration of copper solution by fixing the immersion time of silver as 60 s. Similarly, the change in the sheet resistance with respect to silver deposition was studied by varying the
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immersion time of Cu-coated cotton in silver solution by fixing the copper concentration as 0.25 mM. The conductivity was also measured for cotton samples coated with copper and silver alone for comparative purposes. 2.5 Durability of coatings
The electrical stability of all coated samples was determined by the immersion of as-
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fabricated samples at solutions of various pH such as 1.0, 4.0, 7.0, 10.0 and 13.0 at room temperature. Specimens of coated fabrics (2 cm2) were immersed in the solutions of various pH separately for 60 minutes. After that, the samples were taken out, washed first with
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ethanol then with distilled water and dried in an air oven at 120º C for one hour. The electrical conductivity and superhydrophobicity were measured for the dry coated samples.
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The washing durability is an important factor to measure the adhesion capacity of metal particles [14] on cotton surface. It was evaluated by repeated washing of as-coated samples with 0.3% of liquid detergent at constant stirring speed of 500 rpm for 30 mins at room temperature and then air-dried. The electrical conductivity is measured after each washing cycle.
2.6 Mechanical durability Mechanical durability is a very significant parameter for practical applications. The abrasion resistant ability of as-coated samples was studied by linear abrasion test using sandpaper as abradant partner with superhydrophobic surface [24,25]. It was conducted by 6
ACCEPTED MANUSCRIPT rubbing the superhydrophobic surface with 15 cm of sand paper under 100 g of load on the cotton surface. The same process was repeated for 30 times. For every 5 cycles, the WCA angle and electrical conductivity were measured to find the mechanical durability. Multiple bending and stretch tests have also been carried for the as-coated sample to evaluate the flexibility as e-textiles find wide applications in sportswear, strain sensors and
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wearable sensor [5]. 2.7 Electronic application studies
The wettability studies showed that the bimetal coated fabric had low water
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absorption/trapping property so that, the as-coated fabric could also find applications in wearable electronics and communication. Additionally, electronic textiles have found various
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applications in electronic fields such as electronic circuits, energy storage devices [6]. So, the utility of as-coated cotton sample in power circuit application was studied by constructing simple circuit through connecting the 9 V battery with one electrical contact of LED and another with bimetal coated fabric. 2.8 Antibacterial activity
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The antibacterial activity of the as-prepared samples was evaluated against Grampositive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) by disc diffusion method [26]. Exactly 100 µl of bacterial suspension was inoculated on agar plates containing nutrient broth. The coated samples were placed in the middle of plates and the
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plates were incubated at 37º C for 24 hours. The formation of clear zone around the sample indicated the antibacterial activity of each sample. The antibacterial activity was assessed by
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measuring the diameter of clear zone formed around the samples in mm.
3. Results and discussion The fabrication of bimetallic deposition over cotton fabrics proceeds via a two-step
process (Fig. 1). The first step was the reduction of copper acetate using hydrazine hydrate and the coating of reduced Cu metal over cotton fabric. It is well known that, the cotton fabric is hydrophilic due to the presence of cellulosic hydroxyl groups which makes the adsorption/ deposition of metal/ metal oxides easy. Thus, copper particles were easily deposited in situ on cotton fabric which converted micro-structured fabric into micro-/nanostructured with rough surface. The strong adsorption of copper on cotton surface not only 7
ACCEPTED MANUSCRIPT produced roughness but also nucleated the surface for another metal deposition. Subsequently, the Cu-coated cotton fabric was immersed in 0.1mM aqueous solution of AgNO3 for about 60-80 s. The Cu0 on copper coated cotton fabric acted as a catalyst and stimulated the metallic silver (Ag0) deposition on the cotton surface. The hierarchical structure on the cotton fabric proceeds via electroless deposition of silver on copper, followed
deposition
of
silver
on
copper
increased
superhydrophobicity on cotton fabric.
surface
roughness
and
created
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3.1 Surface characterization of treated samples
the
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by thermal treatment of bimetal coated cotton fabrics at 120º C for about an hour. The
3.1.1 XPS analysis
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The XPS spectra of as-fabricated superhydrophobic cotton fabrics are shown in fig. 2. The characteristic peaks of Cu at 930.4 eV (Cu 2p3/2) and 950. 3 eV (Cu 2p1/2) and the peaks of Ag at 366.7 eV (Ag 3d5/2) and 372.6 eV (Ag 3d3/2) existed with spin-orbit separation of 20.1 and 6.1 eV respectively, strongly confirmed the existence of metallic architectures viz., copper and silver. Particularly, by comparing the standard values of bulk Cu (2p3/2= 932.1 eV) and Ag (3d5/2=367.5 eV) with bimetal in the as- fabricated coatings,
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the binding energies were found to be negatively shifted to ca. 1.7 eV and 0.8 eV for copper and silver respectively. This shift in binding energy may be due to strong bonding formation between copper and silver. Thus, XPS results clearly showed that the metals in the bimetal
surface [27].
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deposition were strongly bonded suggesting the formation of Ag-Cu bimetals on cotton
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3.1.2 SEM analysis
SEM images of pristine, Cu-coated cotton and bimetal coated cotton are shown in
fig.3. The SEM image of pristine cotton showed the wavy structure of cotton fibers (Fig.3a). Fig.3b-e showed the typical SEM images of as-fabricated cotton fabrics. The complete deposition of copper on cotton fabric has made the surface rougher which could be clearly seen in fig.3b and 3c. The deposition of silver dendrites with length 10±2 µm and width of 5±1 µm (Fig. 3e) on copper surface could be achieved at a reaction time of 60s which could be seen in fig.3d. When deposition time of silver was increased from 60s to 160s the density of silver dendrites increased and became very thick. Simultaneously, the new sub-dendrites were formed from the old dendrite branches which independently grew up (Fig. 3e and 3f). 8
ACCEPTED MANUSCRIPT These results showed the importance of Ag deposition time and the role of copper which supported the construction of the silver dendrites at 1D approach through nucleation process. As a whole, the formation of hierarchical structure on copper occurred through nucleationgrowth- renucleation process [28]. Thus, this method was found to be an effective one for the fabrication of hierarchical structure over cotton fabric which increased the surface roughness
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of the as-tailored surface. 3.1.3 EDX mapping analysis
EDX mapping analysis was used to find out the chemical elements present in the
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coated fabrics and its distribution over the cotton surface. Fig. 4a of Cu-coated fabric showed the peaks of C, O and Cu. The peaks of C and O might have come from cotton cellulose and the peak for Cu confirmed the deposition of Cu on cotton. The EDAX mapping images (fig.
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4b) of Cu-coated cotton showed that copper was uniformly deposited on cotton surface. The 91% of Ag was deposited on copper by electroless deposition which was confirmed from the fig. 4c. The absence of O peak in fig. 4b also suggested the deposition of pure metallic copper and silver. The corresponding EDAX mapping images revealed that large quantity of silver and copper were uniformly distributed in bimetal coated cotton surface which was shown in
3.1.4 XRD analysis
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fig 4d.
The XRD pattern of as-coated samples was shown in fig.5. In fig 5a, the sharp peaks at 43.8º,
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50.7º and 73.5º were observed which correspond to the lattice planes of (111), (200) and (220) of metallic copper phases on the cotton surface. In fig 5b, the pure silver peaks at 38.3º, 44.4º, 64.6º, 77.5º and 81.7º could be observed for the indices of (111), (200), (220), (311), and (222) of pure
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metallic silver particles respectively, which also strongly supported the deposition of silver over copper phase. At the same time, in fig. 5b, diffraction peaks for copper were displaced and diminished which could be due to the formation of Cu-Ag alloy on the surface [29]. The results of XRD analysis thus clearly showed the successful deposition of the pure metallic copper and silver over cotton fabric. These results agreed well with those of XPS and EDX which further confirmed the existence of metallic Cu and Ag. 3.2 Water contact angle measurements of as-fabricated cotton surface The wettable properties of as-prepared cotton samples were identified by measuring the contact angle of water on its surface. Fig. 6a shows the complete absorption of water on 9
ACCEPTED MANUSCRIPT pristine cotton fabric. The presence of hydrophilic –OH of cellulose is responsible for the water absorbance which gives WCA of 0º. After deposition of copper, the surface became rougher and the WCA rose to 126.4º (Fig. 6b) which confirmed the hydrophobicity of Cucoated cotton. But the hierarchical deposition of Ag over Cu further increased the surface
3.3 Electrical conductivity of as-coated samples
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roughness, and consequently the WCA was increased to 160.9º (Fig. 6c).
The results of electrical conductivity as- coated samples showed that pristine cotton was an electro-insulator while the copper- coated cotton fabric showed the sheet resistance of
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1.15 Ω sq-1 and bimetal deposited cotton fabric had the sheet resistance of 0.15 Ω sq-1.
A control experiment was used to identify the significance of bimetallic deposition on
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cotton fabric. In order to test the necessity of bimetallic deposition, cotton fabrics were deposited with either copper or silver alone. The conductivity of these samples was found to be very low which could be due to the partial oxidation of copper and silver on air [5,7]. But the as-prepared bimetal coated cotton did not show any noticeable change in electrical conductivity even after two weeks. It showed that the bimetal deposition on cotton fabric prevented the partial oxidation of silver and copper on the cotton surface and enhanced the
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humidity resistance of as-prepared samples with its environment. Hertleer et al., had studied the influence of relative humidity on electrical properties. Against this back drop, the electrical conductivity shown by the as-prepared superhydrophobic surface assumes
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importance [10].
Fig. 7a shows the sheet resistance of as-coated fabrics at various concentrations of copper solution ranging from 0.10 mM to 0.35 mM. The sheet resistance for 0.1 mM
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concentration was found to be very high when compared with other coated samples. This could be due to the deposition of fewer copper atoms on cotton surface. Upon increasing the copper concentration, more copper atoms could be deposited uniformly and the autocatalytic deposition of silver on its surface gets speeded up. But beyond 0.25 mM, the resistance increased slightly. This suggested that the deposition of copper phase on cotton may affect the silver deposition over it. The relationship between silver deposition on copper and electrical conductivity was studied by measuring the immersion time of Cu-coated cotton samples in aqueous AgNO3. The plot of sheet resistance vs. immersion time is shown in fig. 7b. This showed that sheet 10
ACCEPTED MANUSCRIPT resistance increased with electroless deposition time upto 200 s. But, it remained almost the same beyond 200 s. The results clearly indicated that the minimum immersion time (i.e. 60 s) is the optimum immersion time to get the cotton fabric with low sheet resistance.
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3.4 Durability of coated samples The chemical durability and electrical stability are important for commercial applications. The as-fabricated samples were found to maintain their sheet resistances and contact angle in all pH ranges (Fig 8a & 8b). These results indicated that the coatings were
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durable and had good electrical stability and superhydrophobicity in all pH solutions. But the hierarchical structure on cotton fabric was completely disrupted after immersion in acidic
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(4.0) and basic (9.0) pH solutions as evident from SEM images (Fig 9).
The washing test results showed that the sheet resistance was almost same after repeated washings. These results indicate that coating had strong adhesion and showed the chemical and washing durability of as-coated samples (Fig 10).
3.4 Mechanical stability of electrically conductive superhydrophobic cotton fabric
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The linear abrasion study revealed that even after 30 cycles the as-coated samples did not show any noticeable change in the electrical conductivity. But after 20 cycles, the superhydrophobic surface changed into hydrophobic surface. The results of change in WCA
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and electrical conductivity with respect to abrasion cycles were shown in fig 11 which indicated that the as-coated samples possessed high electrical conductivity even after multiple
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abrasion but has limited superhydrophobicity. The bending test showed the bent fabric has higher sheet resistance than the unbent
one. For example, the sheet resistance decreased from 0.15 Ω sq-1 to 0.12 Ω sq-1 during the bending process. But the resistance was almost the same even after 200 bent cycles. In the case of stretching and relaxing process, the sheet resistance was low (0.13 Ω sq-1) while stretching and showed high sheet resistance (0.18 Ω sq-1) while relaxing. This process can be explained by the fact that bending and stretching cause some mechanical forces on coated surface which reduce the junction resistance by improving the connections between the overlapping fibres of cotton. However, the sheet resistance was relatively constant after multiple stretching and relaxing cycles. 11
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shows the digital image of electronic circuits for powering LED. 3.6 Antibacterial activity of bimetal coated cotton
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The LED was found to be turned on and off continuously without loss of fidelity. Fig. 12
The anti-bacterial activity of superhydrophobic bimetallic coated cotton samples was
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evaluated using zone of inhibition on agar medium. The normal cotton did not show any antibacterial activity against both Gram negative and Gram positive bacteria, while the bimetallic
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coated cotton showed an inhibition zone of 14 mm in the case of S. aureus and 17 mm in the case of E. Coli (Fig. 13). This observation suggested that the bimetallic deposited coated cotton fabric acts as an effective inhibitor for bacterial growth on cotton fabric against both Gram positive and Gram negative organisms. 4. Conclusions
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In conclusion, the electrically conductive superhydrophobic cotton fabric with antibacterial activity could be successfully developed by bimetallic deposition. From this study, it is clear that metal particles can be used to introduce superhydrophobicity by the creation of roughness on the cotton surface. Thus, the present method is a simple strategy of
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preparing electrically conductive, antibacterial and superhydrophobic fabric using less-toxic materials. The electrical conductivity measured in this study was only DC conductivity and
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due to low sheet resistance and high conductivity, the as-coated sample could be employed for higher frequency range applications such as development of wearable electronics and communication. The proposed method is bound to have widespread applications in health monitoring systems, hospitals, defense and textile related fields and in the development of sensors.
Acknowledgement This work was supported by the UGC-RFSMS (Research Fellowship in Sciences for Meritorious Students), No: F.No.25-1/2014-15/(BSR)/7-225/2008/(BSR), dt: 7th October 2015; UGC-SAP for their support and authorities of GRI for their encouragement. 12
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[22] H. Yao, C.C. Chu, H.J. Sue, R. Nishimura, Electrically conductive superhydrophobic octadecylamine-functionalized multiwall carbon nanotube films, Carbon N. Y. 53 (2013) 366–373. doi:DOI 10.1016/j.carbon.2012.11.023.
[23] J. Ren, C. Wang, X. Zhang, T. Carey, K. Chen, Y. Yin, F. Torrisi, Environmentally-
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friendly conductive cotton fabric as flexible strain sensor based on hot press reduced graphene oxide, Carbon N. Y. 111 (2017) 622–630. doi:10.1016/j.carbon.2016.10.045. [24] X. Tian, T. Verho, R.H.A. Ras, Moving superhydrophobic surfaces toward real-world
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applications, Science (80-. ). 352 (2016) 142–143. doi:10.1126/science.aaf2073. [25] X. Zhu, Z. Zhang, Y. Song, J. Yan, Y. Wang, G. Ren, A waterproofing textile with
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robust superhydrophobicity in either air or oil surroundings, J. Taiwan Inst. Chem. Eng. 71 (2017) 421–425. doi:10.1016/j.jtice.2016.11.029.
[26] M. Zhang, P. Wang, H. Sun, Z. Wang, Superhydrophobic surface with hierarchical architecture and bimetallic composition for enhanced antibacterial activity, ACS Appl. Mater. Interfaces. 6 (2014) 22108–22115. doi:10.1021/am505490w. [27] G. Fu, C. Liu, Q. Zhang, Y. Chen, Y. Tang, Polyhedral Palladium – Silver Alloy Nanocrystals as Highly Active and Stable Electrocatalysts for the Formic Acid Oxidation Reaction, Nat. Publ. Gr. (2015) 1–9. doi:10.1038/srep13703. [28] H. Dong, Y. Wang, F. Tao, L. Wang, Electrochemical fabrication of shape-controlled 15
ACCEPTED MANUSCRIPT copper hierarchical structures assisted by surfactants, J. Nanomater. 2012 (2012). doi:10.1155/2012/901842. [29] S.H.H. Rahaghi, R. Poursalehi, R. Miresmaeili, Optical Properties of Ag-Cu Alloy Nanoparticles Synthesized by DC Arc Discharge in Liquid, Procedia Mater. Sci. 11
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Figure Captions:
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Fig. 1 Schematic representation for the fabrication of superhydrophobic cotton Fig. 2 XPS spectra of a) Cu 2p b) Ag 3d of superhydrophobic cotton fabrics
Fig. 3 SEM microscopic images of a) pristine, b) low magnification and c) high
e) and f) formation of silver dendrites on copper at 160s
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magnification image of Cu-coated cotton, d) formation of silver dendrites on copper at 60s,
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Fig. 4 a) EDX spectrum of Cu-coated cotton and b) its corresponding elemental mapping images, c) EDX spectrum of bimetal coated cotton and d) its corresponding elemental mapping images
Fig. 5 XRD pattern of a) Cu-coated and b) Ag/Cu coated cotton fabric
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Fig. 6 Water Contact Angle of a) pristine, b) Cu-coated and c) superhydrophobic cotton Fig. 7 Sheet resistance of bimetal coated cotton as function of a) various concentrations of Cu solution b) immersion time in silver
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Fig. 8 Chemical durability of bimetal coated cotton fabric a) sheet resistance b) wettability against various pH solutions
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Fig. 9 SEM images of bimetal coated cotton fabric in a) acidic pH b) basic pH Fig. 10 Washing durability of as- coated samples after repeated washings Fig. 11 Mechanical durability of as- coated samples after 30 abrasion cycles Fig. 12 Digital image of electronic circuit to power LED Fig. 13 Antibacterial activity of as-fabricated cotton samples against a) Gram positive b) Gram negative bacteria
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Cu (COOCH3)2.H2O Hydrazine Hydrate
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ACCEPTED MANUSCRIPT Highlights Cotton fabric with electrically conductivity and superhydrophobicity is prepared
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A method of highly conductive cotton fabric using bimetal deposition is proposed
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The as-fabricated cotton fabric showed excellent mechanical and chemical durability
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The as-fabricated cotton also showed excellent anti-bacterial activity
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Due to high electrical conductivity, it can be used for power circuit applications
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S0925-8388(17)32365-4
DOI:
10.1016/j.jallcom.2017.07.009
Reference:
JALCOM 42425
To appear in:
Journal of Alloys and Compounds
Received Date: 5 May 2017 Revised Date:
29 June 2017
Accepted Date: 2 July 2017
Please cite this article as: T. Suryaprabha, M.G. Sethuraman, Design of electrically conductive superhydrophobic antibacterial cotton fabric through hierarchical architecture using bimetallic deposition, Journal of Alloys and Compounds (2017), doi: 10.1016/j.jallcom.2017.07.009. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Graphical Abstract
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Design of Electrically Conductive Superhydrophobic Antibacterial Cotton Fabric through Hierarchical Architecture using Bimetallic Deposition Thirumalaisamy Suryaprabha and Mathur Gopalakrishnan Sethuraman*
Corresponding Author E. mail: [email protected].
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*
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Department of Chemistry, The Gandhigram Rural Institute – Deemed University, Gandhigram-624 302, Tamil Nadu, India.
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ACCEPTED MANUSCRIPT Abstract In view of the emerging applications of electrically conductive textiles, a simple and inexpensive method for the fabrication of superhydrophobic textiles with electrical
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conductivity and antibacterial activity has been developed through bimetallic deposition of copper and silver over cotton fabric. The as-fabricated modified cotton surface was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction studies. The antibacterial activity of the
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modified fabrics has been evaluated by disc diffusion method against Gram positive and
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Gram negative bacteria. The results of the study revealed that the strategy of the bimetallic deposition over cotton could well become the method of choice for the fabrication of superhydrophobic smart textiles with diverse applications.
Key words: Superhydrophobic textiles, bimetallic, antibacterial, hierarchical, electrical
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conductivity
2
ACCEPTED MANUSCRIPT 1. Introduction Intelligent or smart textiles are new generation textiles, which have advanced built-in applications in various fields such as medicine and defence, personal electronics as sensors, data processing, energy or data storage devices and communication [1–4]. In addition to these
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applications, electrically conductive textiles have become very crucial for next generation wearable consumer electronics or smart clothings. Wearable electronics are new class of materials which have attracted extensive attention due to the novel functionalities such as electrical conductivity, flexibility, lightweight, high stretchability, electromagnetic and radio interference protection [5–7]. Portable power displays, high-performance sportswear,
Recently,
properties
like
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novel examples of these electrically conductive textiles.
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embedded health-monitoring devices, flexible heaters [8] and electrode materials [9] are few
superhydrophobicity,
superoleophobicity
or
superomniphobicity have been imparted over conductive materials in order to get multifunctional textiles. Moreover, superhydrophobicity is also an important factor to increase the electrical properties of textiles for various applications. The electrical properties of textiles are highly influenced by two parameters viz., relative humidity and high-water
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trapping properties. So, textiles with superhydrophobicity and electrical conductivity will be immense use in wearable textile systems [10].
Superhydrophobic surfaces, with a water contact angle higher than 150ᵒ and a sliding
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angle lower than 10ᵒ play a vital role in many industrial applications and also in our daily life which includes the fabrication of self-cleaning windows, anti-reflective glasses, protection of electronic devices, windshields, utensils, solar panels and micro-/nanofluidic applications
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[8,9,11]. The micro-/nano- hierarchical structure and low surface energy are the essential parameters for superhydrophobic surfaces [12]. The electrically conductive superhydrophobic textiles can be fabricated by using atomic layer deposition, dip-coating, knitting, layer by layer assembly, electroless deposition (ELD), in-situ deposition and so on. Among these methods, in-situ deposition and ELD methods are widely used since they are simple and easy to adopt [7,13]. The electrically conductive textiles have found potential applications in medical and health-care and hence, it is necessary to protect them from microbial attack also. Conductive textiles can be made by the coating of conductive polymers such as polyaniline [14], polypyrrole [15], metal and metal oxide nanoparticles such as copper, 3
ACCEPTED MANUSCRIPT nickel, silver and carbonaceous materials such as carbon nanoparticles, carbon nanotubes (CNTs) and graphene oxide (GO) [16–18]. The use of metals or metal oxides over conductive polymers prevents conductive decay which otherwise occurs [18]. The deposition of metal nanoparticles on textile substrates is a simple process and requires easy handling procedure. The metal deposited textiles not only show electrical conductivity but also have excellent
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mechanical stability, flexibility and strong attraction towards almost all types of textile fabrics [19].
However, in literature, only few work are available for the fabrication of electrically conductive superhydrophobic textiles. Shateri-Khalilabad et al., have used graphene and
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methyltrichlorosilane for the fabrication of electrically conductive superhydrophobic textiles [20]. In 2014, Caffrey et al., have prepared electrically conductive superhydrophobic film
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using the multiwalled nanotubes (MWNTs) and poly(dimethoxysilane) [21]. Similarly, Yao et al., have also used MWNTs for the synthesis of electrically conductive superhydrophobic films [22]. But in all the above reports, they had used carbon nanotubes and graphene for the conductive coatings over textiles, but after hydrophobicization of those conductive textiles, conductivity was found to be low. Moreover, Liu et al., have prepared conductive yarns using poly [2-(methacryloyloxy)ethyltrimethylammonium chloride] bridged copper particles [5].
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Atwa et al., used silver nanowire coated threads for electrically conductive textiles [19]. However, they did not have any superhydrophobic property. To the best of our knowledge, this is the first report on the fabrication of electrically conductive superhydrophobic textiles
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using bimetallic nanoparticles.
In the present work, cotton fabric is chosen as the base material due to its highcomfortness, extreme breathability and eco-friendly nature compared to other synthetic
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fabrics [23]. Copper and silver bimetallic coatings over cotton fabric are made using in-situ deposition and ELD methods. The coated fabrics also showed enhanced anti-bacterial and electrical conducting properties along with excellent superhydrophobicity. 2. Materials and Methods 2.1 Materials Copper acetate monohydrate and hydrazine hydrate purchased from Central Drug House (CDH), India, silver nitrate purchased from Sisco Research Laboratories (SRL), India were used in the present study. Cotton fabric was obtained from the local market. All the 4
ACCEPTED MANUSCRIPT chemicals used in this study were of analytical grade and used as such without any further purification process. 2.2 Methods 2.2.1 Fabrication of copper coated fabric
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The cotton fabric was thoroughly washed with detergent solution and pretreated with 0.01 N NaOH in order to remove impurities and wax coatings, if any, on the substrate. The deposition of copper on cotton fabric was achieved by the chemical reduction of copper acetate by hydrazine hydrate at room temperature in closed conditions. For the deposition of
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copper on cotton, 0.1 g of copper acetate was dissolved in 5 ml of distilled water. The piece of cotton fabric (2 cm× 2 cm) was immersed in the copper acetate solution. Then, 500 µL of
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hydrazine hydrate was added dropwise into the copper acetate solution and set aside for 12 hours under air tight conditions. Now, the color of cotton fabric turned into reddish brown due to the deposition of Cu on cotton fabric. The cotton fabric was then taken out, washed first with ethanol, then with distilled water and dried in air for a day. 2.2.2 Fabrication of hierarchical structure on cotton fabric
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The above Cu-coated cotton fabric was immersed in 0.1 mM aqueous solution of silver nitrate for about 60-80 s. The bimetallic hierarchical structure on Cu-coated cotton fabric was attained by electroless deposition of silver on copper. Then, the bimetal coated
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cotton was kept in a hot air oven for about one hour at 120º C. 2.3 Characterization of the bimetal coated cotton fabric
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Bimetal coated cotton fabric was characterized using x-ray photoelectron spectroscopy (XPS), scanning Electron Microscopy (SEM), energy dispersive x-ray spectrometer (EDAX) x-ray diffractometer (XRD) and contact angle measurements. The chemical state of elements on surface was characterized by XPS with AES Module with Ar ion as well as C60 sputter Guns (PHI 5000 Versa Probe II, FEI Inc.). The surface morphological images of pristine cotton, copper coated cotton and bimetal coated cotton fabrics along with the change in the surface morphology as a function of immersion times were obtained from SEM using VEGA3- TESCAN. The analysis of elemental composition and its distribution over the as- fabricated cotton samples was carried out using EDAXmapping (Bruker, Nano GMBH X’ Flash Detector, 5010 model, Germany). The crystallinity 5
ACCEPTED MANUSCRIPT and deposition of metals on surface was confirmed by XPERT- PRO X-ray diffractometer. The surface wettability of the as-fabricated fabrics was evaluated using goniometer (ramѐhart instrument. Co, USA). 2.4 Electrical conductivity measurements
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The electrical conductivity of the bimetal coated samples were measured by a fourprobe method [23] using Philips DM341 multimeter system and the conductivity observed in this study was only DC conductivity. The sheet resistance of bimetal coated cotton fabric mainly depends on the deposition of copper and silver on its surface. So, the effects of copper
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concentration on sheet resistance were obtained by measuring the sheet resistance at various concentration of copper solution by fixing the immersion time of silver as 60 s. Similarly, the change in the sheet resistance with respect to silver deposition was studied by varying the
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immersion time of Cu-coated cotton in silver solution by fixing the copper concentration as 0.25 mM. The conductivity was also measured for cotton samples coated with copper and silver alone for comparative purposes. 2.5 Durability of coatings
The electrical stability of all coated samples was determined by the immersion of as-
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fabricated samples at solutions of various pH such as 1.0, 4.0, 7.0, 10.0 and 13.0 at room temperature. Specimens of coated fabrics (2 cm2) were immersed in the solutions of various pH separately for 60 minutes. After that, the samples were taken out, washed first with
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ethanol then with distilled water and dried in an air oven at 120º C for one hour. The electrical conductivity and superhydrophobicity were measured for the dry coated samples.
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The washing durability is an important factor to measure the adhesion capacity of metal particles [14] on cotton surface. It was evaluated by repeated washing of as-coated samples with 0.3% of liquid detergent at constant stirring speed of 500 rpm for 30 mins at room temperature and then air-dried. The electrical conductivity is measured after each washing cycle.
2.6 Mechanical durability Mechanical durability is a very significant parameter for practical applications. The abrasion resistant ability of as-coated samples was studied by linear abrasion test using sandpaper as abradant partner with superhydrophobic surface [24,25]. It was conducted by 6
ACCEPTED MANUSCRIPT rubbing the superhydrophobic surface with 15 cm of sand paper under 100 g of load on the cotton surface. The same process was repeated for 30 times. For every 5 cycles, the WCA angle and electrical conductivity were measured to find the mechanical durability. Multiple bending and stretch tests have also been carried for the as-coated sample to evaluate the flexibility as e-textiles find wide applications in sportswear, strain sensors and
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wearable sensor [5]. 2.7 Electronic application studies
The wettability studies showed that the bimetal coated fabric had low water
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absorption/trapping property so that, the as-coated fabric could also find applications in wearable electronics and communication. Additionally, electronic textiles have found various
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applications in electronic fields such as electronic circuits, energy storage devices [6]. So, the utility of as-coated cotton sample in power circuit application was studied by constructing simple circuit through connecting the 9 V battery with one electrical contact of LED and another with bimetal coated fabric. 2.8 Antibacterial activity
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The antibacterial activity of the as-prepared samples was evaluated against Grampositive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) by disc diffusion method [26]. Exactly 100 µl of bacterial suspension was inoculated on agar plates containing nutrient broth. The coated samples were placed in the middle of plates and the
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plates were incubated at 37º C for 24 hours. The formation of clear zone around the sample indicated the antibacterial activity of each sample. The antibacterial activity was assessed by
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measuring the diameter of clear zone formed around the samples in mm.
3. Results and discussion The fabrication of bimetallic deposition over cotton fabrics proceeds via a two-step
process (Fig. 1). The first step was the reduction of copper acetate using hydrazine hydrate and the coating of reduced Cu metal over cotton fabric. It is well known that, the cotton fabric is hydrophilic due to the presence of cellulosic hydroxyl groups which makes the adsorption/ deposition of metal/ metal oxides easy. Thus, copper particles were easily deposited in situ on cotton fabric which converted micro-structured fabric into micro-/nanostructured with rough surface. The strong adsorption of copper on cotton surface not only 7
ACCEPTED MANUSCRIPT produced roughness but also nucleated the surface for another metal deposition. Subsequently, the Cu-coated cotton fabric was immersed in 0.1mM aqueous solution of AgNO3 for about 60-80 s. The Cu0 on copper coated cotton fabric acted as a catalyst and stimulated the metallic silver (Ag0) deposition on the cotton surface. The hierarchical structure on the cotton fabric proceeds via electroless deposition of silver on copper, followed
deposition
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3.1 Surface characterization of treated samples
the
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by thermal treatment of bimetal coated cotton fabrics at 120º C for about an hour. The
3.1.1 XPS analysis
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The XPS spectra of as-fabricated superhydrophobic cotton fabrics are shown in fig. 2. The characteristic peaks of Cu at 930.4 eV (Cu 2p3/2) and 950. 3 eV (Cu 2p1/2) and the peaks of Ag at 366.7 eV (Ag 3d5/2) and 372.6 eV (Ag 3d3/2) existed with spin-orbit separation of 20.1 and 6.1 eV respectively, strongly confirmed the existence of metallic architectures viz., copper and silver. Particularly, by comparing the standard values of bulk Cu (2p3/2= 932.1 eV) and Ag (3d5/2=367.5 eV) with bimetal in the as- fabricated coatings,
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the binding energies were found to be negatively shifted to ca. 1.7 eV and 0.8 eV for copper and silver respectively. This shift in binding energy may be due to strong bonding formation between copper and silver. Thus, XPS results clearly showed that the metals in the bimetal
surface [27].
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deposition were strongly bonded suggesting the formation of Ag-Cu bimetals on cotton
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3.1.2 SEM analysis
SEM images of pristine, Cu-coated cotton and bimetal coated cotton are shown in
fig.3. The SEM image of pristine cotton showed the wavy structure of cotton fibers (Fig.3a). Fig.3b-e showed the typical SEM images of as-fabricated cotton fabrics. The complete deposition of copper on cotton fabric has made the surface rougher which could be clearly seen in fig.3b and 3c. The deposition of silver dendrites with length 10±2 µm and width of 5±1 µm (Fig. 3e) on copper surface could be achieved at a reaction time of 60s which could be seen in fig.3d. When deposition time of silver was increased from 60s to 160s the density of silver dendrites increased and became very thick. Simultaneously, the new sub-dendrites were formed from the old dendrite branches which independently grew up (Fig. 3e and 3f). 8
ACCEPTED MANUSCRIPT These results showed the importance of Ag deposition time and the role of copper which supported the construction of the silver dendrites at 1D approach through nucleation process. As a whole, the formation of hierarchical structure on copper occurred through nucleationgrowth- renucleation process [28]. Thus, this method was found to be an effective one for the fabrication of hierarchical structure over cotton fabric which increased the surface roughness
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of the as-tailored surface. 3.1.3 EDX mapping analysis
EDX mapping analysis was used to find out the chemical elements present in the
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coated fabrics and its distribution over the cotton surface. Fig. 4a of Cu-coated fabric showed the peaks of C, O and Cu. The peaks of C and O might have come from cotton cellulose and the peak for Cu confirmed the deposition of Cu on cotton. The EDAX mapping images (fig.
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4b) of Cu-coated cotton showed that copper was uniformly deposited on cotton surface. The 91% of Ag was deposited on copper by electroless deposition which was confirmed from the fig. 4c. The absence of O peak in fig. 4b also suggested the deposition of pure metallic copper and silver. The corresponding EDAX mapping images revealed that large quantity of silver and copper were uniformly distributed in bimetal coated cotton surface which was shown in
3.1.4 XRD analysis
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fig 4d.
The XRD pattern of as-coated samples was shown in fig.5. In fig 5a, the sharp peaks at 43.8º,
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50.7º and 73.5º were observed which correspond to the lattice planes of (111), (200) and (220) of metallic copper phases on the cotton surface. In fig 5b, the pure silver peaks at 38.3º, 44.4º, 64.6º, 77.5º and 81.7º could be observed for the indices of (111), (200), (220), (311), and (222) of pure
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metallic silver particles respectively, which also strongly supported the deposition of silver over copper phase. At the same time, in fig. 5b, diffraction peaks for copper were displaced and diminished which could be due to the formation of Cu-Ag alloy on the surface [29]. The results of XRD analysis thus clearly showed the successful deposition of the pure metallic copper and silver over cotton fabric. These results agreed well with those of XPS and EDX which further confirmed the existence of metallic Cu and Ag. 3.2 Water contact angle measurements of as-fabricated cotton surface The wettable properties of as-prepared cotton samples were identified by measuring the contact angle of water on its surface. Fig. 6a shows the complete absorption of water on 9
ACCEPTED MANUSCRIPT pristine cotton fabric. The presence of hydrophilic –OH of cellulose is responsible for the water absorbance which gives WCA of 0º. After deposition of copper, the surface became rougher and the WCA rose to 126.4º (Fig. 6b) which confirmed the hydrophobicity of Cucoated cotton. But the hierarchical deposition of Ag over Cu further increased the surface
3.3 Electrical conductivity of as-coated samples
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roughness, and consequently the WCA was increased to 160.9º (Fig. 6c).
The results of electrical conductivity as- coated samples showed that pristine cotton was an electro-insulator while the copper- coated cotton fabric showed the sheet resistance of
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1.15 Ω sq-1 and bimetal deposited cotton fabric had the sheet resistance of 0.15 Ω sq-1.
A control experiment was used to identify the significance of bimetallic deposition on
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cotton fabric. In order to test the necessity of bimetallic deposition, cotton fabrics were deposited with either copper or silver alone. The conductivity of these samples was found to be very low which could be due to the partial oxidation of copper and silver on air [5,7]. But the as-prepared bimetal coated cotton did not show any noticeable change in electrical conductivity even after two weeks. It showed that the bimetal deposition on cotton fabric prevented the partial oxidation of silver and copper on the cotton surface and enhanced the
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humidity resistance of as-prepared samples with its environment. Hertleer et al., had studied the influence of relative humidity on electrical properties. Against this back drop, the electrical conductivity shown by the as-prepared superhydrophobic surface assumes
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importance [10].
Fig. 7a shows the sheet resistance of as-coated fabrics at various concentrations of copper solution ranging from 0.10 mM to 0.35 mM. The sheet resistance for 0.1 mM
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concentration was found to be very high when compared with other coated samples. This could be due to the deposition of fewer copper atoms on cotton surface. Upon increasing the copper concentration, more copper atoms could be deposited uniformly and the autocatalytic deposition of silver on its surface gets speeded up. But beyond 0.25 mM, the resistance increased slightly. This suggested that the deposition of copper phase on cotton may affect the silver deposition over it. The relationship between silver deposition on copper and electrical conductivity was studied by measuring the immersion time of Cu-coated cotton samples in aqueous AgNO3. The plot of sheet resistance vs. immersion time is shown in fig. 7b. This showed that sheet 10
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3.4 Durability of coated samples The chemical durability and electrical stability are important for commercial applications. The as-fabricated samples were found to maintain their sheet resistances and contact angle in all pH ranges (Fig 8a & 8b). These results indicated that the coatings were
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durable and had good electrical stability and superhydrophobicity in all pH solutions. But the hierarchical structure on cotton fabric was completely disrupted after immersion in acidic
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(4.0) and basic (9.0) pH solutions as evident from SEM images (Fig 9).
The washing test results showed that the sheet resistance was almost same after repeated washings. These results indicate that coating had strong adhesion and showed the chemical and washing durability of as-coated samples (Fig 10).
3.4 Mechanical stability of electrically conductive superhydrophobic cotton fabric
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The linear abrasion study revealed that even after 30 cycles the as-coated samples did not show any noticeable change in the electrical conductivity. But after 20 cycles, the superhydrophobic surface changed into hydrophobic surface. The results of change in WCA
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abrasion but has limited superhydrophobicity. The bending test showed the bent fabric has higher sheet resistance than the unbent
one. For example, the sheet resistance decreased from 0.15 Ω sq-1 to 0.12 Ω sq-1 during the bending process. But the resistance was almost the same even after 200 bent cycles. In the case of stretching and relaxing process, the sheet resistance was low (0.13 Ω sq-1) while stretching and showed high sheet resistance (0.18 Ω sq-1) while relaxing. This process can be explained by the fact that bending and stretching cause some mechanical forces on coated surface which reduce the junction resistance by improving the connections between the overlapping fibres of cotton. However, the sheet resistance was relatively constant after multiple stretching and relaxing cycles. 11
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shows the digital image of electronic circuits for powering LED. 3.6 Antibacterial activity of bimetal coated cotton
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The LED was found to be turned on and off continuously without loss of fidelity. Fig. 12
The anti-bacterial activity of superhydrophobic bimetallic coated cotton samples was
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evaluated using zone of inhibition on agar medium. The normal cotton did not show any antibacterial activity against both Gram negative and Gram positive bacteria, while the bimetallic
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coated cotton showed an inhibition zone of 14 mm in the case of S. aureus and 17 mm in the case of E. Coli (Fig. 13). This observation suggested that the bimetallic deposited coated cotton fabric acts as an effective inhibitor for bacterial growth on cotton fabric against both Gram positive and Gram negative organisms. 4. Conclusions
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In conclusion, the electrically conductive superhydrophobic cotton fabric with antibacterial activity could be successfully developed by bimetallic deposition. From this study, it is clear that metal particles can be used to introduce superhydrophobicity by the creation of roughness on the cotton surface. Thus, the present method is a simple strategy of
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preparing electrically conductive, antibacterial and superhydrophobic fabric using less-toxic materials. The electrical conductivity measured in this study was only DC conductivity and
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due to low sheet resistance and high conductivity, the as-coated sample could be employed for higher frequency range applications such as development of wearable electronics and communication. The proposed method is bound to have widespread applications in health monitoring systems, hospitals, defense and textile related fields and in the development of sensors.
Acknowledgement This work was supported by the UGC-RFSMS (Research Fellowship in Sciences for Meritorious Students), No: F.No.25-1/2014-15/(BSR)/7-225/2008/(BSR), dt: 7th October 2015; UGC-SAP for their support and authorities of GRI for their encouragement. 12
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Figure Captions:
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Fig. 1 Schematic representation for the fabrication of superhydrophobic cotton Fig. 2 XPS spectra of a) Cu 2p b) Ag 3d of superhydrophobic cotton fabrics
Fig. 3 SEM microscopic images of a) pristine, b) low magnification and c) high
e) and f) formation of silver dendrites on copper at 160s
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magnification image of Cu-coated cotton, d) formation of silver dendrites on copper at 60s,
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Fig. 4 a) EDX spectrum of Cu-coated cotton and b) its corresponding elemental mapping images, c) EDX spectrum of bimetal coated cotton and d) its corresponding elemental mapping images
Fig. 5 XRD pattern of a) Cu-coated and b) Ag/Cu coated cotton fabric
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Fig. 6 Water Contact Angle of a) pristine, b) Cu-coated and c) superhydrophobic cotton Fig. 7 Sheet resistance of bimetal coated cotton as function of a) various concentrations of Cu solution b) immersion time in silver
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Fig. 8 Chemical durability of bimetal coated cotton fabric a) sheet resistance b) wettability against various pH solutions
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Fig. 9 SEM images of bimetal coated cotton fabric in a) acidic pH b) basic pH Fig. 10 Washing durability of as- coated samples after repeated washings Fig. 11 Mechanical durability of as- coated samples after 30 abrasion cycles Fig. 12 Digital image of electronic circuit to power LED Fig. 13 Antibacterial activity of as-fabricated cotton samples against a) Gram positive b) Gram negative bacteria
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Cu (COOCH3)2.H2O Hydrazine Hydrate
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ACCEPTED MANUSCRIPT Highlights Cotton fabric with electrically conductivity and superhydrophobicity is prepared
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A method of highly conductive cotton fabric using bimetal deposition is proposed
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The as-fabricated cotton fabric showed excellent mechanical and chemical durability
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The as-fabricated cotton also showed excellent anti-bacterial activity
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Due to high electrical conductivity, it can be used for power circuit applications
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