Materials Science and Engineering C 38 (2014) 170–176
Contents lists available at ScienceDirect
Materials Science and Engineering C journal homepage: www.elsevier.com/locate/msec
Synthesis of nanosilver on polyamide fabric using silver/ ammonia complex Majid Montazer a,⁎, Ali Shamei b, Farbod Alimohammadi b a b
Textile Department, Functional Fibrous Structures & Environmental Enhancement (FFSEE), Amirkabir University of Technology, Hafez Avenue, Tehran, Iran Young Researchers Club, Tehran South Branch, Islamic Azad University, Tehran, Iran
a r t i c l e
i n f o
Article history: Received 9 April 2013 Received in revised form 11 January 2014 Accepted 22 January 2014 Available online 6 February 2014 Keywords: Silver nanoparticles Polyamide 6 Silver/ammonia complex Antibacterial properties
a b s t r a c t In this paper, a novel synthesis method for nanosilver has been introduced on or within the polymeric chains of polyamide 6 fabric by using silver/ammonia complex [Ag(NH3)2]+. The silver complex was reduced directly by functional groups of polyamide chains without using any additional chemical reducing agents. The polyamide fabric was also stabilized with formation of new linkages between the polymeric chains of the nylon fabric through silver nanoparticle synthesis. The presence of nanosilver on the fabric was confirmed by UV–vis spectra, EDX patterns and XRD patterns. In addition, X-ray photoelectron spectroscopy (XPS) was utilized to identify the chemical state of silver in a range of silver oxide and silver metal. The SEM images confirmed the presence of nanosilver on the polyamide within the size of 20 and 150 nm. Excellent antibacterial properties were achieved with the treated fabrics against Staphylococcus aureus and Escherichia coli. Further, the antibacterial properties of the polyamide fabric treated with 35 mg/L silver/ammonia were durable against washing as they only decreased to 98.6% after 20 washes. In addition, some other properties of the treated fabrics including color changes, dimensional stability, water droplet adsorption, and reflectance spectrum are reported and thoroughly discussed. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Silver nanoparticles are considered to be the most widely used nanoparticles in the textile industries as antibacterial. Their application increases in protective wear for medical and military personnel to reduce infection in wound dressings [1–4]. Ag ions and Ag based compounds are highly toxic to microorganisms with strong biocide effects on various species of bacteria such as Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Klebsiella mobilis [5,6]. Silver as a nonpoisonous material in low concentration with antimicrobial properties can be used in different textile fabrics [7–11]. However, few studies have been published regarding the reaction of silver nanoparticles on the human body and the possible effect of incompatibility, dispersion, accumulation in body organs and their toxicity on the body and their release to the environment requires the assessment of environmental risks associated with these particles [12,13]. Silver nanoparticles are among the most commercialized nanoparticles worldwide and clinical compounds include the treatment of external infections or in medical appliances. Wound sutures, artificial
⁎ Corresponding author at: Textile Department, Functional Fibrous Structures & Environmental Enhancement (FFSEE), Amirkabir University of Technology, Hafez Avenue, Tehran, Iran. Tel.: +98 21 65542657; fax: +98 21 66400245. E-mail address: [email protected] (M. Montazer). 0928-4931/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.msec.2014.01.044
tendons and medical packaging, which are prepared by polyamides, preferably should possess an antimicrobial efficacy to minimize the risk of device related infections. Besides, silver particles can be used as an additive or coating material for the preparation of antimicrobial polymers [14]. There are several synthesis methods introduced for the production of silver/polyamide composites or polyamide fibers containing silver nanoparticles. The preparation of polyamide/Ag nanocomposite is reported via thermal reduction of silver acetate through melting [14]. Also, syntheses of silver nanoparticles have been introduced using silver nitrate, ethylene glycol and poly(N-vinylpyrrolidone) (PVP) by electrospinning [15]. In addition, silver nanoparticles are synthesized on different fabrics including polyamide through the sonochemical method in water with ethylene glycol as a reducing agent [16–18]. In this process, a strong adhesion, and a uniform coating of silver nanoparticles on the fibers are confirmed using ultrasound irradiation [18]. Most of the reported studies on the synthesis of silver nanoparticles are based on using reducing and stabilizing agents on the textile fabrics. However, the current work is aimed to synthesize silver nanoparticles on polyamide fabric without using any reducing and/or stabilizing agents. This process was carried out in water at boil using the inherently reducing and the stabilizing properties of polyamide chains of the nylon fabric. The swelling of fabric at the boil induced Ag ions to penetrate into the intramolecular chains, and reduced the silver/ammonia complex to silver nanoparticles also oxidized the polyamide molecular chains.
M. Montazer et al. / Materials Science and Engineering C 38 (2014) 170–176
2. Materials and methods
171
between the untreated and treated samples are designated by the term ΔE which was calculated based on Eq. (3) [22–24]:
2.1. Materials Silver nitrate (AgNO3) 99.9%, sodium hydroxide (NaOH), ammonium solution 25%, Tryptic soy agar (TSA), and sodium chloride (NaCl) 99.9% were from Merck Co. (Germany), and polyamide 6 (nylon 6) knitted fabric with 85 g/m2 was purchased from the local market. Also, deionized water was used in the synthesis processing. The samples were washed in a bath containing a 2 g/L nonionic detergent with L:G (liquor to good ratio) = 50:1 at 50 °C for 15 min. Next, it was rinsed with distilled water. 2.2. Instrumentation X-ray photoelectron spectroscopy (XPS) via Twin Anode of XR3E2 (model 8025-BesTec) was applied to determine the chemical state of both silver and oxygen, and a Philips X-ray Diffraction (model X'Pert PRO MPD) was used to assess the crystallinity of the silver nanoparticles on the polyamide fabrics, the active data plot was smoothed by the average adjacent data points via OriginPro data analysis and graphing software. The SEM images were taken using a scanning electronic microscopy model XL30 from Philips Co. A spectrophotometer Varian Carry 5000 was employed to obtain the reflectance spectrum of the treated fabric. The color coordinates (L⁎, a⁎, and b⁎) of CIELAB color system were obtained using a Color eye 7000 calorimeter with observer 10°, and illuminant D65.
ΔE ¼
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 2 2 þ ao −a þ bo −b : Lo −L
ð3Þ
In this system, L⁎ shows the lightness of the fabric and a⁎ and b⁎ indicate red–green (redder if positive; greener if negative) and yellow– blue colors (yellower if positive; bluer if negative), respectively. 2.6. Dimensional stability measurement AATCC test method 179-2004 was used to specify the deformation level of the knitted fabric after washing. A square with a side of 25 cm was marked on the fabric sample and its diameters were then measured after washing. AATCC test method 124-2006 was used for washing. Finally, the deformation level was obtained from the difference in the length of diameters using Eq. (4). X ¼ 100
2ðAC−BDÞ ðAC þ BDÞ
ð4Þ
where, X is the deformation change percentage. In most garments, the acceptable shrinkage level after washing is 2– 3%. However, the type of fiber, fabric structure and final end-use influence the acceptable shrinkage level. The allowed shrinkage level for knitted fabrics is usually higher than that of woven fabrics and maximum shrinkage is up to 5% [25].
2.3. Synthesis of silver nanoparticles on the polyamide knitted fabric 2.7. Water droplet adsorption time The mixture of silver nitrate solution (0.5 M) and NaOH (0.5 M) was sonicated in an ultrasonic bath for 5 min, resulting in brown Ag2O powder precipitation (Eq. (1)). Next, the precipitate was washed with deionised water for 3 times and then dried. It was subsequently mixed with 2% ammonia, molar ratio of 4:1, forming a stable aqueous solution complex [Ag(NH3)2]+ (Eq. (2)) [17,19,20]. The precautions were made for disposal of dilute acid to prevent formation of the explosive silver nitride [21]. þ
−
þ
−
2Ag þ 2NO3 þ 2Na þ 2OH →Ag2 O↓ þ 2NaNO3 þ H2 O
ð1Þ
þ Sonication Ag2 O þ NH 3 ·H2 O → AgðNH 3 Þ2 :
ð2Þ
The polyamide fabric was then treated with three diverse concentrations of Ag2O including 10 mg/L, 25 mg/L, and 35 mg/L and required ammonia in L:G = 20:1 at room temperature. The temperature was increased to boil with 4 °C/min for 30 min. The color of the treated fabric changed from white to light yellow. However, the color changes were much more intense on the fabric loaded with more silver nanoparticles. Subsequently, the treated fabrics were extracted from the bath, washed and dried at the room temperature. 2.4. Washing fastness of polyamide fabric treated by Ag-NPs The washing fastness was conducted according to AATCC 61(2A)1996 test method as each washing is equivalent to five launderings at medium or warm setting in 38 ± 3 °C. This test is used to investigate the stability of nanoparticles on the surface of the polyamide through antibacterial tests after 10, 20 and 30 washes. 2.5. Color changes of polyamide fabric treated by silver nanoparticles Three coordinates (L*, a*, and b*) of CIELAB color system were obtained using a Color eye 7000 [22]. The overall color differences
This test (BS 4554) is considered for the fabrics containing hydrophilic fibers. The necessary time by seconds taken for a water droplet or water sugar solution to be adsorbed up to 50% in the fabric is defined as wettability. In this test, the sample is closed and leveled in a frame to a diameter of 15 cm. A burette with a standard tip is placed above the horizontal level of the sample with a 6 mm interval. A light source is placed in a 45° and the vision angle is placed in a 45° direction to the light source. Once no liquid is seen on the surface, the time is recorded. Three samples are tested in 5 areas and the mean value was reported [25,26]. 2.8. Antimicrobial testing on treated polyamide fabrics Staphylococcus aureus, ATCC 6538, as Gram-positive bacteria and E. coli, ATCC 11303, as Gram-negative bacteria were tested. Some colonies of each bacterium were suspended in a physiologic saline solution (NaCl 0.9% in distilled water at pH 6.5) with a concentration of 0.5 McFarland. The vials of bacterial suspensions were then incubated with agitation at 37 °C ± 2 °C, 220 rpm for 2 h. A homogenous suspension of bacteria was prepared. Then, a serial dilution was prepared in 5 steps (dilution of 1:100 000) and a concentration of about 1.5–2 × 10 3 CFU/mL was used for the antibacterial testing. The bacteriological culture tubes containing one piece of polyamide fabric (10 mm × 10 mm) were sterilized by an autoclave device in moisturized heat (121 °C, 15 lb) for 15–20 min. Subsequently, an aliquot of 1 mL bacterial suspension and 2 mL TSB broth was added to each tube and 3 mL in each tube was detected. To ensure that any decrease in bacterial count was due to the exposure to the polyamide fabrics, one control of the saline solution with TSB broth, and one control of aliquot with the untreated fabrics including the tubes containing the polyamide fabrics treated with the bacterial suspensions and the control tubes were incubated at 37 °C for 24 h. Next, some samples of 10 μL from each tube were taken and counted by pour plate method. In this method, samples are mixed with melted agar (that decreases temperature to 45 °C) and poured. The plates were incubated at 37 °C for 24 h and the colonies of
172
M. Montazer et al. / Materials Science and Engineering C 38 (2014) 170–176
each plate were counted through colony counted device to compare and determine the bacterial reduction of the suspensions. The results of the colony numbers before and after the treatment of the fabrics were used to determine the bactericidal effect and calculate the percentage of reduction of bacteria using Eq. (5): R ð%Þ ¼ 100ðA−BÞ=A
ð5Þ
where R is the bacterial reduction, A is the number of bacterial colonies from the untreated fabrics and B is the number of bacterial colonies from the treated fabrics. In order to increase validation of the examinations, all test tubes were duplicated [4,27]. 3. Results and discussion 3.1. The effect of silver nanoparticles synthesis on the polyamide fabric Polyamides are produced from a diamine and a dicarboxylic acid. Polyamide 6 is the most important polyamide for the commercial production of fibers and resins [28,29]. Polyamide 6 contains weakly basic amino and weakly acidic carboxylic end groups, both of which are considered as weak reducing agents for silver nanoparticles [30–32]. The synthesis of silver nanoparticles in alkali media (pH = 8–9) produced negatively charge carboxylate anions (COO−) as attractive anions for [Ag(NH3)2]+ cations. Thus, the linkages between the silver/ammonia complex and carboxylates can be possibly considered (Fig. 1a) within the polyamide chains. On the other hand, amine groups with a nucleophilic property in alkali media can adsorb the silver/ammonia complex on the fabric surface and within the polymeric chains of polyamide. Also, the silver/ ammonia complex can be oxidized through the polyamide chains, and silver ions are reduced to silver metal. Furthermore, the nitrogen atoms of polyamide chains can stabilize the silver nanoparticles through coordination (Fig. 1b) [33]. The Raman spectra of the treated and untreated polyamide samples are presented in Fig. 2. Silver nanoparticles enhance the scattering cross section of Raman spectroscopy [34,35]. Accordingly, the highly sensitive surface-enhanced Raman scattering (SERS) fabric has been fabricated by synthesizing silver nanoparticles on the cotton surface. Therefore, sharp and intensive picks can be observed on the Raman spectrum. It is presumed that silver/ammonia complex (Tollens' reagent) as a mild oxidizing agent oxidizes the polyamide chains. However, this is a complex reaction and selective oxidation in a desired position is difficult. The most noticeable change in the Raman spectrum can be attributed to the carbonyl groups (aldehyde, ketone and carboxylate) as the
Fig. 2. Raman spectra of polyamide 6 samples over 500–4000 cm−1; untreated and treated samples.
broad band of 1200–1750 cm− 1 increased (Fig. 2). In addition, the Raman spectra show a decrease at 3000–3400 cm−1 (N\H stretching) [36–38] as evidence of polyamide oxidation. In addition, it should be noted through oxidation process that the carboxylic groups can react with ammonia. This reaction occurs between [RCOO]− and [NH4]+ groups where the appeared peak at 755 cm−1 is contributed to the ammonium carboxylate.
3.2. SEM micrographs The SEM pictures of the untreated and treated fabrics with Tollens' reagent are shown in Fig. 3. The clear surface of the untreated polyamide fabric is observed in Fig. 3a while the formed nanoparticles with various sizes on the fabric surface can be seen in Fig. 3b, c and d. Generally, silver nanoparticles cover between 20 and 150 nm of the surface with an average size of 90 nm. The images confirmed the homogeneous deposition of silver nanoparticles on the polyamide fabric surface. The agglomerated particles may be attributed to the thermo-migration of the nanoparticles during heating at the boiling point [19]. Fig. 3e presents the EDS spectrum of a treated sample, and both weight percentages (wt.%) and atomic percentages (at.%) of the detected elements. This also confirms the presence of Ag element on the
Fig. 1. a) A schematic view of silver nanoparticle linkage to polyamide through the intermediate agent Tollens' reagent; b) a schematic of the coordination and stabilization of silver nanoparticles.
M. Montazer et al. / Materials Science and Engineering C 38 (2014) 170–176
173
Fig. 3. SEM images of polyamide samples; a) untreated samples; b, c, d) treated samples with 35 mg/L Ag2O; e) EDX spectrum of treated polyamide fabric.
surface of fabric treated with 2.28 wt.% on the sample surface. Moreover, Ag and Au are two major elements on the treated sample. The presence of Au in the EDS spectra is related to a gold layer covering the outer layer of the sample prepared for taking SEM images.
more accurately. The full width at half maximum (FWHM) was used to estimate the size of the crystals [42]. The average crystal size based on the Scherrer's equation (Eq. (6)) was obtained around 90 nm, which confirmed the nanoparticle size by SEM images [43]:
3.3. XRD pattern
K λ 180 ¼ Crystal size Å : FWHM π cosθ
XRD pattern of silver nanoparticles on the polyamide fabric is shown in Fig. 4a that confirmed the Bragg's reflections in the face-centered cubic (fcc) phase structure [39,40]. All the prominent peaks on 2θ scale 38.03°, 44.23°, 64.39°, and 77.32° are attributed to the lines with reflections including (1 1 1), (2 0 0), (2 2 0), and (3 1 1) for silver particles. Small changes in the position of peaks indicated the presence of strain in the crystal structure as the characteristics of nanocrystals [40,41]. Clearly the silver metal was dominated and intense peaks due to Ag2O were not observed at 32°, and 54°, which correspond to (1 1 1) and (2 2 0) planes. The Ag2O peak can overlap in (1 1 1) to silver metal, thus XPS analysis was used to investigate silver components
ð6Þ
3.4. X-ray photoelectron spectroscopy (XPS) X-ray photoelectron spectroscopy (XPS) provides a sensitive measure of the chemical state in the near surface region of materials. This has been applied to determine silver metal and silver oxide states. The high resolution XPS Ag-3d spectrum is shown in Fig. 4b indicating the binding energy of AgO (367.4 eV), Ag2O (367.8 eV), and Ag (368.2 eV) [42,43]. On the other hand, Fig. 4c shows the high resolution XPS O1s spectrum, the peak with the binding energy of 531 eV related to sub
174
M. Montazer et al. / Materials Science and Engineering C 38 (2014) 170–176
Fig. 4. a) XRD pattern of polyamide sample containing silver nanoparticles; b, c) the XPS analysis of treated fabric.
surface oxygen, and the peak with the binding energy of 528 eV attributed to oxygen in silver oxide [44–46]. A small amount of silver oxide is shown in Fig. 4b and c which also supports XRD results.
3.5. Reflectance spectrum of samples The surface plasmon bands appearing in the visible region are a characteristic of the noble metal nanoparticles. Silver nanoparticles have a surface plasmon resonance absorption in the UV–visible region [47,48]. Diffuse reflectance spectroscopy analysis has been obtained on the untreated and treated fabrics containing 10 mg/L, 25 mg/L and 35 mg/L silver nanoparticles (Fig. 5). The reflection percentage generally decreased in the nanosilver treated fabrics. However, more decrements are obtained on the higher concentration of nanosilver. Thus, the lower reflectance was obtained by the treated fabric with 35 mg/L nanosilver solution around 200–900 nm. The sharp and intense peak
at 250 nm is related to the polyamide fabric and the reflectance is more than 80% for the untreated polyamide fabric, which decreased to 30% after treating by nanoparticles. As a result, it can be useful for blocking UV radiation. On the other hand, a slight peak at 400– 430 nm appeared that is due to surface plasmon of the silver nanoparticles. However, the weakness of the peak was considered as overlapping of the reflectance peak related to silver nanoparticles and polyamide fiber while sharper peaks appeared for the fabrics treated with the higher nanosilver. Thus, it is proposed that the nanosilver on the polyamide fabric acts as an absorber on the wavelengths raging from UV to IR from 200 to 900 nm.
3.6. Color changes of fabrics In order to evaluate the color variation of the treated samples, three indices of the CIELAB color system were measured using a
M. Montazer et al. / Materials Science and Engineering C 38 (2014) 170–176
175
Table 2 Number of colonies after 24 h and antibacterial reduction percentages of the polyamide samples treated with diverse concentrations of nanosilver. Washing cycles
0 10 20 30
10 mg/L Reduction (%)
25 mg/L Reduction (%)
30 mg/L Reduction (%)
E. coli
S. aureus
E. coli
S. aureus
E. coli
S. aureus
99.99 99.99 99.86 99.5
98.43 87.47 82.61 69.32
99.99 99.99 99.99 99.7
99.67 97.72 94.69 76.65
99.99 99.99 99.99 99.99
99.99 99.99 99.3 86.93
3.8. Water absorption time
Fig. 5. The reflection spectra of polyamide samples.
spectrophotometer (Color eye 7000). The CIELAB color system is widely used in the color measurement of the textile fabrics [49]. The values of L⁎, a⁎, b⁎ and ΔE for 10 mg/L, 25 mg/L and 35 mg/L silver nanoparticles are presented in Table 1. The fabric lightness decreased while b⁎ (blueness, yellowness) increased with the more silver nanoparticles. On the other hand, a⁎ (redness–greenness) increased upon the higher silver nanoparticle loading. The amounts of color changes (ΔE) of different treated fabrics are: 12.85, 24.55 and 25.42 for 10, 25 and 35 mg/L nanosilver respectively. The differences among the absorption peaks of the various silver nanoparticle loaded fabrics are a clear sign of fabric yellowing. This can be attributed to the performance conditions and the formed silver nanoparticles on the fabric surfaces due to surface plasmon property of particles.
3.7. Dimensional stability The dimensional change percentages of different fabrics were obtained by AATCC test method 197-2004. This test method assesses change in the skewness in woven and knitted fabrics or twist in fabrics. The deformation of the untreated sample and the one treated with 35 mg/L silver nanoparticles were 4.8% and 2.43%, respectively. Deformation of polyamide knitted fabric of about 2.37% results in a better resistance to deformation and improving elastic recovery from deformation. Decreasing knitted fabric deformation can be due to the silver nanoparticle entrapment and filling gaps within the intramolecular chains of polyamide fabric and also the possible formation of chemical linkages between the polymeric chains and nanosilver. These mentioned factors may be considered as effective ones on the dimensional stability of the treated samples, so the deformation properties have been improved. Furthermore, the increasing nanosilver on the fabric surface led to a reduction of fabric deformation. Overall, in situ synthesis of silver nanoparticles on the polyamide knitted fabric reduces fabric deformation to the acceptable standard percentage of woven fabrics (max. 3%).
Table 1 The color difference of samples containing different amounts of silver nanoparticles in comparison with untreated sample based on CIELAB color system. Samples
L⁎
a⁎
b⁎
ΔE
Untreated fabric Treated with 10 mg/L Treated with 25 mg/L Treated with 35 mg/L
78.9 73.4 66.3 70.1
−0.1 −0.5 1.5 1.1
−1.4 10.1 19.4 22.3
– 12.85 24.55 25.42
The time taken for water absorption on the untreated and treated fabrics with 35 mg/L silver nanoparticles was 8.8 s and 4.2 s respectively. The fabric wettability of the nanosilver treated samples improved considerably. The treatment of polyamide fabric with silver/ammonia complex led to the forming of the silver nanoparticles and also fabric oxidation. This can be contributed to the increased hydrophilic properties of the treated fabrics. 3.9. Anti-bacterial properties The anti-bacterial activity of the treated polyamide fabric can be influenced by treatment with silver/ammonia complex even with a low concentration. Antimicrobial properties were evaluated on E. coli and S. aureus with 10, 25 and 35 mg/L (Table 2). Subsequently, the washing fastness is assigned according to the variation of their antimicrobial property after each washing cycle. An efficient antimicrobial property is achieved on the fabrics due to the presence of nanoparticles. Both bacteria showed different resistance against silver nanoparticles. The differential response/susceptibility of bacteria towards treated fabric is higher for S. aureus as a Gram-positive than that of E. coli as a Gram-negative. This corresponds to a thick peptidoglycan layer of Gram-positive cell wall [4,43]. The antibacterial properties of the fabric reduced with repeated washings however, the reduction is within the acceptable limit and an acceptable stability was indicated during laundry even after 30 cycles on both bacteria. Thus, Ag particles are synthesized into the intramolecular polymeric chains and are entrapped within them [50–52]. In fact, the antibacterial activity is a required feature for a wide range of applications including wound dressing, bed lining and medicinal bandages; thus, this treatment can be the subject of further interest [53,54]. 4. Conclusion In situ synthesis of silver nanoparticles was successfully performed on the polyamide fabric using silver/ammonia complex at boil. The performance of the treated fabrics showed excellent antibacterial properties even after repeated washings. The polymeric chains of polyamide were effective as the reducing and stabilizing agents to synthesis and stabilize silver nanoparticles on/within the polymeric chains of the fabric without using other chemicals as stabilizer or reducing agents. This method is considered as in-situ synthesis method for nanosilver on polyamide fabric in addition to obtain other useful properties such as dimensional stability, UV-blocking, and hydrophilicity. In conclusion, this develops the use of silver nanoparticles on the textile fabrics. References [1] M.B. Dickerson, C.L. Knight, M.K. Gupta, H.R. Luckarift, L.F. Drummya, M.L. Jespersena, G.R. Johnsonb, R.R. Naik, Mater. Sci. Eng. C 31 (2011) 1748–1758. [2] X. Zan, Z. Sue, Thin Solid Films 518 (2010) 5478–5482. [3] Q. Li, S. Mahendra, D.Y. Lyon, L. Brunet, M.V. Liga, D. Li, P.J.J. Alvarez, Water Res. 42 (2008) 4591–4602. [4] M. Montazer, F. Alimohammadi, A. Shamei, M.K. Rahimi, Colloids Surf. B 89 (2012) 196–202.
176
M. Montazer et al. / Materials Science and Engineering C 38 (2014) 170–176
[5] H. Barani, M. Montazer, T. Toliyat, N. Samadi, J. Liposome Res. 20 (2010) 323–329. [6] R. Yoksana, S. Chirachanchai, Mater. Sci. Eng. C 30 (2010) 891–897. [7] A. Nazari, M. Montazer, A. Rashidi, M. Yazdanshenas, M. Anary-Abbasinejad, Appl. Catal. A 371 (2009) 10–16. [8] R. Dastjerdi, M. Montazer, S. Shahsavan, Colloids Surf. A 354 (2009) 202–210. [9] A. Moazami, M. Montazer, A. Rashidi, M.K. Rahimi, J. Appl. Polym. Sci. 118 (2010) 253–258. [10] R. Badulescu, V. Vivod, D. Jausovec, B. Voncina, Carbohydr. Polym. 71 (2008) 85–91. [11] H. Barani, M. Montazer, N. Samadi, T.H. Toliyat, Colloids Surf. B 92 (2012) 9–15. [12] X. Chen, H.J. Schluesener, Toxicol. Lett. 176 (2008) 1–12. [13] R. Dastjerdi, M. Montazer, Colloids Surf. B 79 (2010) 5–18. [14] C. Damm, H. Munstedt, A. Resch, Mater. Chem. Phys. 108 (2008) 61–66. [15] L. Francis, F. Giunco, A. Balakrishnan, E. Marsano, Curr. Appl. Phys. (2010) 1005–1008. [16] V.K. Sharma, R.A. Yngard, Y. Lin, Adv. Colloid Interface Sci. 145 (2009) 83–96. [17] G. Xu, Q. Xue-liang, Q. Xiao-lin, C. Jian-guo, Colloids Surf. A 320 (2008) 222–226. [18] I. Perelshtein, G. Apderot, N. Perkas, G. Guibert, S. Mikhailov, A. Gedanken, Nanotechnology 19 (2008) 1–6. [19] H.H. Nersisyan, J.H. Lee, H.T. Son, C.W. Won, D.Y. Maeng, Mater. Res. Bull. 38 (2003) 949–956. [20] R.T. Morrison, R.N. Boyd, Organic Chemistry, 4th ed. Allyn and Bacon/New York University, 1983. 503–504 (752–753). [21] A.I. Vogel, G. Svehla, Vogel's Qualitative Inorganic Analysis, 7th ed. Addison Wesley Longman, 1996. [22] J. Hu, Fabric Testing, Number 76, Woodhead Publishing in Textiles, Cambridge, England, 2008. 183. [23] A. Nazari, M. Montazer, M.B. Moghadam, M. Anary-Abbasineja, Carbohydr. Polym. 83 (2011) 1119–1127. [24] R. Dastjerdi, M. Montazer, S. Shahsavan, Colloids Surf. B 81 (2010) 32–41. [25] F. Dadashian, G. Goudarzi, Fabric Physical Tests, University Jihad Publications, Amir Kabir Technological Unit, 2005. 119–230. [26] M. Montazer, E. Pakdel, M.B. Moghadam, Colloids Surf. A 375 (2011) 1–11. [27] K. Saengkiettiyut, P. Rattanawaleedirojn, S. Sangsuk, CMU J. Nat. Sci. Spec. Issue Nanotechnol. 7 (1) (2008) 33–36. [28] M. Lewin, Handbook of Fiber Chemistry, Third edition Taylor & Francis Group, 2007. [29] A.D. Broadbent, Basic Principles of Textile Coloration, Society of Dyers and Colourists, 2001. [30] A. Akbari, J.C. Remigy, P. Aptel, Chem. Eng. Prog. 41 (2002) 601–609. [31] M. Montazer, S.B. Malekzadeh, J. Polym. Res. 19 (2012) 9980–9986. [32] Z. Jia, H. Sun, Q. Gu, Colloids Surf. A 419 (2013) 174–179.
[33] A. Travan, C. Pelillo, I. Donati, E. Marsich, M. Benincasa, T. Scarpa, S. Semeraro, G. Turco, R. Gennaro, S. Paoletti, Biomacromolecules 10 (6) (2009) 1429–1435. [34] K. Wong-ek, P. Eiamchai, M. Horprathum, V. Patthanasettakul, P. Limnonthakul, P. Chindaudom, N. Nuntawong, Thin Solid Films 518 (2010) 7128–7132. [35] N. Nuntawong, M. Horprathum, P. Eiamchai, K.k. Wong-ek, V. Patthanasettakul, P. Chindaudom, Vacuum 84 (2010) 1415–1418. [36] L.L. Cho, Forensic Sci. J. 6 (1) (2007) 55–62. [37] M.N. Grigg, Thermo-oxidative Degradation of Polyamide 6, (Ph.D. Thesis at) Queensland University of Technology, 2006. [38] D.L. Pavia, G.M. Lampman, G.S. Kriz, J.R. Vyvyan, Introduction to Spectroscopy, Fourth edition Brooks/Cole, Cengage Learning, 2009. [39] M. Montazer, A. Behzadnia, E. Pakdel, M.K. Rahimi, M.B. Moghadam, J. Photochem. Photobiol. B 103 (2011) 207–214. [40] Y. Zhao, Y. Jiang, Y. Fang, Spectrochim. Acta A 65 (2006) 1003–1006. [41] G.E. Burunkayaa, O. Kesmeza, N. Kiraza, H. Erdem, C. Amurluc, M. Asilturka, E. Arpac, Mater. Chem. Phys. 120 (2010) 272–276. [42] M. Montazer, E. Pakdel, M.B. Moghadam, Fibers Polym. 11 (7) (2010) 967–975. [43] M. Montazer, F. Alimohammadi, A. Shamei, M.K. Rahimi, Carbohydr. Polym. 87 (2012) 1706–1712. [44] X.Y. Gao, S.Y. Wang, J. Li, Y.X. Zheng, R.J. Zhang, P. Zhou, Y.M. Yang, L.Y. Chen, Thin Solid Films 455–456 (2004) 438–442. [45] T.C. Kaspar, T. Droubay, S.A. Chambers, P.S. Bagus, J. Phys. Chem. C 114 (2010) 21562–21571. [46] P.L. Taylora, O. Omotosob, J.B. Wiskela, D. Mitlina, R.E. Burrell, Biomaterials 26 (2005) 7230–7240. [47] H. Itani, P. Keil, D. Lützenkirchen-Hecht, U. Haake, H. Bongard, A. Dreierc, C.W. Lehmann, G. Grundmeier, Surf. Coat. Technol. 205 (2010) 2113–2119. [48] M. Lismont, L. Dreesen, Mater. Sci. Eng. C 32 (2012) 1437–1442. [49] F. Schwarz, B. Stritzker, Surf. Coat. Technol. 12–13 (2010) 1875–1879. [50] M. Parvinzadeh Gashti, F. Alimohammadi, G. Song, A. Kiumarsi, Characterization of nanocomposite coatings on textiles: a brief review on microscopic technology, in: A. Méndez-Vilas (Ed.), Current Microscopy Contributions to Advances in Science and Technology, vol. 2, Formatex Research Center, Spain, 2012, pp. 1424–1437. [51] R. Dastjerdi, M. Montazer, Colloids Surf. B 88 (2011) 381–388. [52] R. Dastjerdi, M.R.M. Mojtahedi, A.M. Shoshtari, A. Khosroshahi, A.J. Moayed, Text. Res. J. 79 (2009) 1099–1107. [53] F. Alimohammadi, M. Montazer, A. Shamei, M. Karim Rahimi, Iran. J. Polym. Sci. Technol. 25 (2012) 265–275. [54] M. Montazer, A. Shamei, F. Alimohammadi, Prog. Org. Coat. 75 (2012) 379–385.
Contents lists available at ScienceDirect
Materials Science and Engineering C journal homepage: www.elsevier.com/locate/msec
Synthesis of nanosilver on polyamide fabric using silver/ ammonia complex Majid Montazer a,⁎, Ali Shamei b, Farbod Alimohammadi b a b
Textile Department, Functional Fibrous Structures & Environmental Enhancement (FFSEE), Amirkabir University of Technology, Hafez Avenue, Tehran, Iran Young Researchers Club, Tehran South Branch, Islamic Azad University, Tehran, Iran
a r t i c l e
i n f o
Article history: Received 9 April 2013 Received in revised form 11 January 2014 Accepted 22 January 2014 Available online 6 February 2014 Keywords: Silver nanoparticles Polyamide 6 Silver/ammonia complex Antibacterial properties
a b s t r a c t In this paper, a novel synthesis method for nanosilver has been introduced on or within the polymeric chains of polyamide 6 fabric by using silver/ammonia complex [Ag(NH3)2]+. The silver complex was reduced directly by functional groups of polyamide chains without using any additional chemical reducing agents. The polyamide fabric was also stabilized with formation of new linkages between the polymeric chains of the nylon fabric through silver nanoparticle synthesis. The presence of nanosilver on the fabric was confirmed by UV–vis spectra, EDX patterns and XRD patterns. In addition, X-ray photoelectron spectroscopy (XPS) was utilized to identify the chemical state of silver in a range of silver oxide and silver metal. The SEM images confirmed the presence of nanosilver on the polyamide within the size of 20 and 150 nm. Excellent antibacterial properties were achieved with the treated fabrics against Staphylococcus aureus and Escherichia coli. Further, the antibacterial properties of the polyamide fabric treated with 35 mg/L silver/ammonia were durable against washing as they only decreased to 98.6% after 20 washes. In addition, some other properties of the treated fabrics including color changes, dimensional stability, water droplet adsorption, and reflectance spectrum are reported and thoroughly discussed. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Silver nanoparticles are considered to be the most widely used nanoparticles in the textile industries as antibacterial. Their application increases in protective wear for medical and military personnel to reduce infection in wound dressings [1–4]. Ag ions and Ag based compounds are highly toxic to microorganisms with strong biocide effects on various species of bacteria such as Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Klebsiella mobilis [5,6]. Silver as a nonpoisonous material in low concentration with antimicrobial properties can be used in different textile fabrics [7–11]. However, few studies have been published regarding the reaction of silver nanoparticles on the human body and the possible effect of incompatibility, dispersion, accumulation in body organs and their toxicity on the body and their release to the environment requires the assessment of environmental risks associated with these particles [12,13]. Silver nanoparticles are among the most commercialized nanoparticles worldwide and clinical compounds include the treatment of external infections or in medical appliances. Wound sutures, artificial
⁎ Corresponding author at: Textile Department, Functional Fibrous Structures & Environmental Enhancement (FFSEE), Amirkabir University of Technology, Hafez Avenue, Tehran, Iran. Tel.: +98 21 65542657; fax: +98 21 66400245. E-mail address: [email protected] (M. Montazer). 0928-4931/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.msec.2014.01.044
tendons and medical packaging, which are prepared by polyamides, preferably should possess an antimicrobial efficacy to minimize the risk of device related infections. Besides, silver particles can be used as an additive or coating material for the preparation of antimicrobial polymers [14]. There are several synthesis methods introduced for the production of silver/polyamide composites or polyamide fibers containing silver nanoparticles. The preparation of polyamide/Ag nanocomposite is reported via thermal reduction of silver acetate through melting [14]. Also, syntheses of silver nanoparticles have been introduced using silver nitrate, ethylene glycol and poly(N-vinylpyrrolidone) (PVP) by electrospinning [15]. In addition, silver nanoparticles are synthesized on different fabrics including polyamide through the sonochemical method in water with ethylene glycol as a reducing agent [16–18]. In this process, a strong adhesion, and a uniform coating of silver nanoparticles on the fibers are confirmed using ultrasound irradiation [18]. Most of the reported studies on the synthesis of silver nanoparticles are based on using reducing and stabilizing agents on the textile fabrics. However, the current work is aimed to synthesize silver nanoparticles on polyamide fabric without using any reducing and/or stabilizing agents. This process was carried out in water at boil using the inherently reducing and the stabilizing properties of polyamide chains of the nylon fabric. The swelling of fabric at the boil induced Ag ions to penetrate into the intramolecular chains, and reduced the silver/ammonia complex to silver nanoparticles also oxidized the polyamide molecular chains.
M. Montazer et al. / Materials Science and Engineering C 38 (2014) 170–176
2. Materials and methods
171
between the untreated and treated samples are designated by the term ΔE which was calculated based on Eq. (3) [22–24]:
2.1. Materials Silver nitrate (AgNO3) 99.9%, sodium hydroxide (NaOH), ammonium solution 25%, Tryptic soy agar (TSA), and sodium chloride (NaCl) 99.9% were from Merck Co. (Germany), and polyamide 6 (nylon 6) knitted fabric with 85 g/m2 was purchased from the local market. Also, deionized water was used in the synthesis processing. The samples were washed in a bath containing a 2 g/L nonionic detergent with L:G (liquor to good ratio) = 50:1 at 50 °C for 15 min. Next, it was rinsed with distilled water. 2.2. Instrumentation X-ray photoelectron spectroscopy (XPS) via Twin Anode of XR3E2 (model 8025-BesTec) was applied to determine the chemical state of both silver and oxygen, and a Philips X-ray Diffraction (model X'Pert PRO MPD) was used to assess the crystallinity of the silver nanoparticles on the polyamide fabrics, the active data plot was smoothed by the average adjacent data points via OriginPro data analysis and graphing software. The SEM images were taken using a scanning electronic microscopy model XL30 from Philips Co. A spectrophotometer Varian Carry 5000 was employed to obtain the reflectance spectrum of the treated fabric. The color coordinates (L⁎, a⁎, and b⁎) of CIELAB color system were obtained using a Color eye 7000 calorimeter with observer 10°, and illuminant D65.
ΔE ¼
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 2 2 þ ao −a þ bo −b : Lo −L
ð3Þ
In this system, L⁎ shows the lightness of the fabric and a⁎ and b⁎ indicate red–green (redder if positive; greener if negative) and yellow– blue colors (yellower if positive; bluer if negative), respectively. 2.6. Dimensional stability measurement AATCC test method 179-2004 was used to specify the deformation level of the knitted fabric after washing. A square with a side of 25 cm was marked on the fabric sample and its diameters were then measured after washing. AATCC test method 124-2006 was used for washing. Finally, the deformation level was obtained from the difference in the length of diameters using Eq. (4). X ¼ 100
2ðAC−BDÞ ðAC þ BDÞ
ð4Þ
where, X is the deformation change percentage. In most garments, the acceptable shrinkage level after washing is 2– 3%. However, the type of fiber, fabric structure and final end-use influence the acceptable shrinkage level. The allowed shrinkage level for knitted fabrics is usually higher than that of woven fabrics and maximum shrinkage is up to 5% [25].
2.3. Synthesis of silver nanoparticles on the polyamide knitted fabric 2.7. Water droplet adsorption time The mixture of silver nitrate solution (0.5 M) and NaOH (0.5 M) was sonicated in an ultrasonic bath for 5 min, resulting in brown Ag2O powder precipitation (Eq. (1)). Next, the precipitate was washed with deionised water for 3 times and then dried. It was subsequently mixed with 2% ammonia, molar ratio of 4:1, forming a stable aqueous solution complex [Ag(NH3)2]+ (Eq. (2)) [17,19,20]. The precautions were made for disposal of dilute acid to prevent formation of the explosive silver nitride [21]. þ
−
þ
−
2Ag þ 2NO3 þ 2Na þ 2OH →Ag2 O↓ þ 2NaNO3 þ H2 O
ð1Þ
þ Sonication Ag2 O þ NH 3 ·H2 O → AgðNH 3 Þ2 :
ð2Þ
The polyamide fabric was then treated with three diverse concentrations of Ag2O including 10 mg/L, 25 mg/L, and 35 mg/L and required ammonia in L:G = 20:1 at room temperature. The temperature was increased to boil with 4 °C/min for 30 min. The color of the treated fabric changed from white to light yellow. However, the color changes were much more intense on the fabric loaded with more silver nanoparticles. Subsequently, the treated fabrics were extracted from the bath, washed and dried at the room temperature. 2.4. Washing fastness of polyamide fabric treated by Ag-NPs The washing fastness was conducted according to AATCC 61(2A)1996 test method as each washing is equivalent to five launderings at medium or warm setting in 38 ± 3 °C. This test is used to investigate the stability of nanoparticles on the surface of the polyamide through antibacterial tests after 10, 20 and 30 washes. 2.5. Color changes of polyamide fabric treated by silver nanoparticles Three coordinates (L*, a*, and b*) of CIELAB color system were obtained using a Color eye 7000 [22]. The overall color differences
This test (BS 4554) is considered for the fabrics containing hydrophilic fibers. The necessary time by seconds taken for a water droplet or water sugar solution to be adsorbed up to 50% in the fabric is defined as wettability. In this test, the sample is closed and leveled in a frame to a diameter of 15 cm. A burette with a standard tip is placed above the horizontal level of the sample with a 6 mm interval. A light source is placed in a 45° and the vision angle is placed in a 45° direction to the light source. Once no liquid is seen on the surface, the time is recorded. Three samples are tested in 5 areas and the mean value was reported [25,26]. 2.8. Antimicrobial testing on treated polyamide fabrics Staphylococcus aureus, ATCC 6538, as Gram-positive bacteria and E. coli, ATCC 11303, as Gram-negative bacteria were tested. Some colonies of each bacterium were suspended in a physiologic saline solution (NaCl 0.9% in distilled water at pH 6.5) with a concentration of 0.5 McFarland. The vials of bacterial suspensions were then incubated with agitation at 37 °C ± 2 °C, 220 rpm for 2 h. A homogenous suspension of bacteria was prepared. Then, a serial dilution was prepared in 5 steps (dilution of 1:100 000) and a concentration of about 1.5–2 × 10 3 CFU/mL was used for the antibacterial testing. The bacteriological culture tubes containing one piece of polyamide fabric (10 mm × 10 mm) were sterilized by an autoclave device in moisturized heat (121 °C, 15 lb) for 15–20 min. Subsequently, an aliquot of 1 mL bacterial suspension and 2 mL TSB broth was added to each tube and 3 mL in each tube was detected. To ensure that any decrease in bacterial count was due to the exposure to the polyamide fabrics, one control of the saline solution with TSB broth, and one control of aliquot with the untreated fabrics including the tubes containing the polyamide fabrics treated with the bacterial suspensions and the control tubes were incubated at 37 °C for 24 h. Next, some samples of 10 μL from each tube were taken and counted by pour plate method. In this method, samples are mixed with melted agar (that decreases temperature to 45 °C) and poured. The plates were incubated at 37 °C for 24 h and the colonies of
172
M. Montazer et al. / Materials Science and Engineering C 38 (2014) 170–176
each plate were counted through colony counted device to compare and determine the bacterial reduction of the suspensions. The results of the colony numbers before and after the treatment of the fabrics were used to determine the bactericidal effect and calculate the percentage of reduction of bacteria using Eq. (5): R ð%Þ ¼ 100ðA−BÞ=A
ð5Þ
where R is the bacterial reduction, A is the number of bacterial colonies from the untreated fabrics and B is the number of bacterial colonies from the treated fabrics. In order to increase validation of the examinations, all test tubes were duplicated [4,27]. 3. Results and discussion 3.1. The effect of silver nanoparticles synthesis on the polyamide fabric Polyamides are produced from a diamine and a dicarboxylic acid. Polyamide 6 is the most important polyamide for the commercial production of fibers and resins [28,29]. Polyamide 6 contains weakly basic amino and weakly acidic carboxylic end groups, both of which are considered as weak reducing agents for silver nanoparticles [30–32]. The synthesis of silver nanoparticles in alkali media (pH = 8–9) produced negatively charge carboxylate anions (COO−) as attractive anions for [Ag(NH3)2]+ cations. Thus, the linkages between the silver/ammonia complex and carboxylates can be possibly considered (Fig. 1a) within the polyamide chains. On the other hand, amine groups with a nucleophilic property in alkali media can adsorb the silver/ammonia complex on the fabric surface and within the polymeric chains of polyamide. Also, the silver/ ammonia complex can be oxidized through the polyamide chains, and silver ions are reduced to silver metal. Furthermore, the nitrogen atoms of polyamide chains can stabilize the silver nanoparticles through coordination (Fig. 1b) [33]. The Raman spectra of the treated and untreated polyamide samples are presented in Fig. 2. Silver nanoparticles enhance the scattering cross section of Raman spectroscopy [34,35]. Accordingly, the highly sensitive surface-enhanced Raman scattering (SERS) fabric has been fabricated by synthesizing silver nanoparticles on the cotton surface. Therefore, sharp and intensive picks can be observed on the Raman spectrum. It is presumed that silver/ammonia complex (Tollens' reagent) as a mild oxidizing agent oxidizes the polyamide chains. However, this is a complex reaction and selective oxidation in a desired position is difficult. The most noticeable change in the Raman spectrum can be attributed to the carbonyl groups (aldehyde, ketone and carboxylate) as the
Fig. 2. Raman spectra of polyamide 6 samples over 500–4000 cm−1; untreated and treated samples.
broad band of 1200–1750 cm− 1 increased (Fig. 2). In addition, the Raman spectra show a decrease at 3000–3400 cm−1 (N\H stretching) [36–38] as evidence of polyamide oxidation. In addition, it should be noted through oxidation process that the carboxylic groups can react with ammonia. This reaction occurs between [RCOO]− and [NH4]+ groups where the appeared peak at 755 cm−1 is contributed to the ammonium carboxylate.
3.2. SEM micrographs The SEM pictures of the untreated and treated fabrics with Tollens' reagent are shown in Fig. 3. The clear surface of the untreated polyamide fabric is observed in Fig. 3a while the formed nanoparticles with various sizes on the fabric surface can be seen in Fig. 3b, c and d. Generally, silver nanoparticles cover between 20 and 150 nm of the surface with an average size of 90 nm. The images confirmed the homogeneous deposition of silver nanoparticles on the polyamide fabric surface. The agglomerated particles may be attributed to the thermo-migration of the nanoparticles during heating at the boiling point [19]. Fig. 3e presents the EDS spectrum of a treated sample, and both weight percentages (wt.%) and atomic percentages (at.%) of the detected elements. This also confirms the presence of Ag element on the
Fig. 1. a) A schematic view of silver nanoparticle linkage to polyamide through the intermediate agent Tollens' reagent; b) a schematic of the coordination and stabilization of silver nanoparticles.
M. Montazer et al. / Materials Science and Engineering C 38 (2014) 170–176
173
Fig. 3. SEM images of polyamide samples; a) untreated samples; b, c, d) treated samples with 35 mg/L Ag2O; e) EDX spectrum of treated polyamide fabric.
surface of fabric treated with 2.28 wt.% on the sample surface. Moreover, Ag and Au are two major elements on the treated sample. The presence of Au in the EDS spectra is related to a gold layer covering the outer layer of the sample prepared for taking SEM images.
more accurately. The full width at half maximum (FWHM) was used to estimate the size of the crystals [42]. The average crystal size based on the Scherrer's equation (Eq. (6)) was obtained around 90 nm, which confirmed the nanoparticle size by SEM images [43]:
3.3. XRD pattern
K λ 180 ¼ Crystal size Å : FWHM π cosθ
XRD pattern of silver nanoparticles on the polyamide fabric is shown in Fig. 4a that confirmed the Bragg's reflections in the face-centered cubic (fcc) phase structure [39,40]. All the prominent peaks on 2θ scale 38.03°, 44.23°, 64.39°, and 77.32° are attributed to the lines with reflections including (1 1 1), (2 0 0), (2 2 0), and (3 1 1) for silver particles. Small changes in the position of peaks indicated the presence of strain in the crystal structure as the characteristics of nanocrystals [40,41]. Clearly the silver metal was dominated and intense peaks due to Ag2O were not observed at 32°, and 54°, which correspond to (1 1 1) and (2 2 0) planes. The Ag2O peak can overlap in (1 1 1) to silver metal, thus XPS analysis was used to investigate silver components
ð6Þ
3.4. X-ray photoelectron spectroscopy (XPS) X-ray photoelectron spectroscopy (XPS) provides a sensitive measure of the chemical state in the near surface region of materials. This has been applied to determine silver metal and silver oxide states. The high resolution XPS Ag-3d spectrum is shown in Fig. 4b indicating the binding energy of AgO (367.4 eV), Ag2O (367.8 eV), and Ag (368.2 eV) [42,43]. On the other hand, Fig. 4c shows the high resolution XPS O1s spectrum, the peak with the binding energy of 531 eV related to sub
174
M. Montazer et al. / Materials Science and Engineering C 38 (2014) 170–176
Fig. 4. a) XRD pattern of polyamide sample containing silver nanoparticles; b, c) the XPS analysis of treated fabric.
surface oxygen, and the peak with the binding energy of 528 eV attributed to oxygen in silver oxide [44–46]. A small amount of silver oxide is shown in Fig. 4b and c which also supports XRD results.
3.5. Reflectance spectrum of samples The surface plasmon bands appearing in the visible region are a characteristic of the noble metal nanoparticles. Silver nanoparticles have a surface plasmon resonance absorption in the UV–visible region [47,48]. Diffuse reflectance spectroscopy analysis has been obtained on the untreated and treated fabrics containing 10 mg/L, 25 mg/L and 35 mg/L silver nanoparticles (Fig. 5). The reflection percentage generally decreased in the nanosilver treated fabrics. However, more decrements are obtained on the higher concentration of nanosilver. Thus, the lower reflectance was obtained by the treated fabric with 35 mg/L nanosilver solution around 200–900 nm. The sharp and intense peak
at 250 nm is related to the polyamide fabric and the reflectance is more than 80% for the untreated polyamide fabric, which decreased to 30% after treating by nanoparticles. As a result, it can be useful for blocking UV radiation. On the other hand, a slight peak at 400– 430 nm appeared that is due to surface plasmon of the silver nanoparticles. However, the weakness of the peak was considered as overlapping of the reflectance peak related to silver nanoparticles and polyamide fiber while sharper peaks appeared for the fabrics treated with the higher nanosilver. Thus, it is proposed that the nanosilver on the polyamide fabric acts as an absorber on the wavelengths raging from UV to IR from 200 to 900 nm.
3.6. Color changes of fabrics In order to evaluate the color variation of the treated samples, three indices of the CIELAB color system were measured using a
M. Montazer et al. / Materials Science and Engineering C 38 (2014) 170–176
175
Table 2 Number of colonies after 24 h and antibacterial reduction percentages of the polyamide samples treated with diverse concentrations of nanosilver. Washing cycles
0 10 20 30
10 mg/L Reduction (%)
25 mg/L Reduction (%)
30 mg/L Reduction (%)
E. coli
S. aureus
E. coli
S. aureus
E. coli
S. aureus
99.99 99.99 99.86 99.5
98.43 87.47 82.61 69.32
99.99 99.99 99.99 99.7
99.67 97.72 94.69 76.65
99.99 99.99 99.99 99.99
99.99 99.99 99.3 86.93
3.8. Water absorption time
Fig. 5. The reflection spectra of polyamide samples.
spectrophotometer (Color eye 7000). The CIELAB color system is widely used in the color measurement of the textile fabrics [49]. The values of L⁎, a⁎, b⁎ and ΔE for 10 mg/L, 25 mg/L and 35 mg/L silver nanoparticles are presented in Table 1. The fabric lightness decreased while b⁎ (blueness, yellowness) increased with the more silver nanoparticles. On the other hand, a⁎ (redness–greenness) increased upon the higher silver nanoparticle loading. The amounts of color changes (ΔE) of different treated fabrics are: 12.85, 24.55 and 25.42 for 10, 25 and 35 mg/L nanosilver respectively. The differences among the absorption peaks of the various silver nanoparticle loaded fabrics are a clear sign of fabric yellowing. This can be attributed to the performance conditions and the formed silver nanoparticles on the fabric surfaces due to surface plasmon property of particles.
3.7. Dimensional stability The dimensional change percentages of different fabrics were obtained by AATCC test method 197-2004. This test method assesses change in the skewness in woven and knitted fabrics or twist in fabrics. The deformation of the untreated sample and the one treated with 35 mg/L silver nanoparticles were 4.8% and 2.43%, respectively. Deformation of polyamide knitted fabric of about 2.37% results in a better resistance to deformation and improving elastic recovery from deformation. Decreasing knitted fabric deformation can be due to the silver nanoparticle entrapment and filling gaps within the intramolecular chains of polyamide fabric and also the possible formation of chemical linkages between the polymeric chains and nanosilver. These mentioned factors may be considered as effective ones on the dimensional stability of the treated samples, so the deformation properties have been improved. Furthermore, the increasing nanosilver on the fabric surface led to a reduction of fabric deformation. Overall, in situ synthesis of silver nanoparticles on the polyamide knitted fabric reduces fabric deformation to the acceptable standard percentage of woven fabrics (max. 3%).
Table 1 The color difference of samples containing different amounts of silver nanoparticles in comparison with untreated sample based on CIELAB color system. Samples
L⁎
a⁎
b⁎
ΔE
Untreated fabric Treated with 10 mg/L Treated with 25 mg/L Treated with 35 mg/L
78.9 73.4 66.3 70.1
−0.1 −0.5 1.5 1.1
−1.4 10.1 19.4 22.3
– 12.85 24.55 25.42
The time taken for water absorption on the untreated and treated fabrics with 35 mg/L silver nanoparticles was 8.8 s and 4.2 s respectively. The fabric wettability of the nanosilver treated samples improved considerably. The treatment of polyamide fabric with silver/ammonia complex led to the forming of the silver nanoparticles and also fabric oxidation. This can be contributed to the increased hydrophilic properties of the treated fabrics. 3.9. Anti-bacterial properties The anti-bacterial activity of the treated polyamide fabric can be influenced by treatment with silver/ammonia complex even with a low concentration. Antimicrobial properties were evaluated on E. coli and S. aureus with 10, 25 and 35 mg/L (Table 2). Subsequently, the washing fastness is assigned according to the variation of their antimicrobial property after each washing cycle. An efficient antimicrobial property is achieved on the fabrics due to the presence of nanoparticles. Both bacteria showed different resistance against silver nanoparticles. The differential response/susceptibility of bacteria towards treated fabric is higher for S. aureus as a Gram-positive than that of E. coli as a Gram-negative. This corresponds to a thick peptidoglycan layer of Gram-positive cell wall [4,43]. The antibacterial properties of the fabric reduced with repeated washings however, the reduction is within the acceptable limit and an acceptable stability was indicated during laundry even after 30 cycles on both bacteria. Thus, Ag particles are synthesized into the intramolecular polymeric chains and are entrapped within them [50–52]. In fact, the antibacterial activity is a required feature for a wide range of applications including wound dressing, bed lining and medicinal bandages; thus, this treatment can be the subject of further interest [53,54]. 4. Conclusion In situ synthesis of silver nanoparticles was successfully performed on the polyamide fabric using silver/ammonia complex at boil. The performance of the treated fabrics showed excellent antibacterial properties even after repeated washings. The polymeric chains of polyamide were effective as the reducing and stabilizing agents to synthesis and stabilize silver nanoparticles on/within the polymeric chains of the fabric without using other chemicals as stabilizer or reducing agents. This method is considered as in-situ synthesis method for nanosilver on polyamide fabric in addition to obtain other useful properties such as dimensional stability, UV-blocking, and hydrophilicity. In conclusion, this develops the use of silver nanoparticles on the textile fabrics. References [1] M.B. Dickerson, C.L. Knight, M.K. Gupta, H.R. Luckarift, L.F. Drummya, M.L. Jespersena, G.R. Johnsonb, R.R. Naik, Mater. Sci. Eng. C 31 (2011) 1748–1758. [2] X. Zan, Z. Sue, Thin Solid Films 518 (2010) 5478–5482. [3] Q. Li, S. Mahendra, D.Y. Lyon, L. Brunet, M.V. Liga, D. Li, P.J.J. Alvarez, Water Res. 42 (2008) 4591–4602. [4] M. Montazer, F. Alimohammadi, A. Shamei, M.K. Rahimi, Colloids Surf. B 89 (2012) 196–202.
176
M. Montazer et al. / Materials Science and Engineering C 38 (2014) 170–176
[5] H. Barani, M. Montazer, T. Toliyat, N. Samadi, J. Liposome Res. 20 (2010) 323–329. [6] R. Yoksana, S. Chirachanchai, Mater. Sci. Eng. C 30 (2010) 891–897. [7] A. Nazari, M. Montazer, A. Rashidi, M. Yazdanshenas, M. Anary-Abbasinejad, Appl. Catal. A 371 (2009) 10–16. [8] R. Dastjerdi, M. Montazer, S. Shahsavan, Colloids Surf. A 354 (2009) 202–210. [9] A. Moazami, M. Montazer, A. Rashidi, M.K. Rahimi, J. Appl. Polym. Sci. 118 (2010) 253–258. [10] R. Badulescu, V. Vivod, D. Jausovec, B. Voncina, Carbohydr. Polym. 71 (2008) 85–91. [11] H. Barani, M. Montazer, N. Samadi, T.H. Toliyat, Colloids Surf. B 92 (2012) 9–15. [12] X. Chen, H.J. Schluesener, Toxicol. Lett. 176 (2008) 1–12. [13] R. Dastjerdi, M. Montazer, Colloids Surf. B 79 (2010) 5–18. [14] C. Damm, H. Munstedt, A. Resch, Mater. Chem. Phys. 108 (2008) 61–66. [15] L. Francis, F. Giunco, A. Balakrishnan, E. Marsano, Curr. Appl. Phys. (2010) 1005–1008. [16] V.K. Sharma, R.A. Yngard, Y. Lin, Adv. Colloid Interface Sci. 145 (2009) 83–96. [17] G. Xu, Q. Xue-liang, Q. Xiao-lin, C. Jian-guo, Colloids Surf. A 320 (2008) 222–226. [18] I. Perelshtein, G. Apderot, N. Perkas, G. Guibert, S. Mikhailov, A. Gedanken, Nanotechnology 19 (2008) 1–6. [19] H.H. Nersisyan, J.H. Lee, H.T. Son, C.W. Won, D.Y. Maeng, Mater. Res. Bull. 38 (2003) 949–956. [20] R.T. Morrison, R.N. Boyd, Organic Chemistry, 4th ed. Allyn and Bacon/New York University, 1983. 503–504 (752–753). [21] A.I. Vogel, G. Svehla, Vogel's Qualitative Inorganic Analysis, 7th ed. Addison Wesley Longman, 1996. [22] J. Hu, Fabric Testing, Number 76, Woodhead Publishing in Textiles, Cambridge, England, 2008. 183. [23] A. Nazari, M. Montazer, M.B. Moghadam, M. Anary-Abbasineja, Carbohydr. Polym. 83 (2011) 1119–1127. [24] R. Dastjerdi, M. Montazer, S. Shahsavan, Colloids Surf. B 81 (2010) 32–41. [25] F. Dadashian, G. Goudarzi, Fabric Physical Tests, University Jihad Publications, Amir Kabir Technological Unit, 2005. 119–230. [26] M. Montazer, E. Pakdel, M.B. Moghadam, Colloids Surf. A 375 (2011) 1–11. [27] K. Saengkiettiyut, P. Rattanawaleedirojn, S. Sangsuk, CMU J. Nat. Sci. Spec. Issue Nanotechnol. 7 (1) (2008) 33–36. [28] M. Lewin, Handbook of Fiber Chemistry, Third edition Taylor & Francis Group, 2007. [29] A.D. Broadbent, Basic Principles of Textile Coloration, Society of Dyers and Colourists, 2001. [30] A. Akbari, J.C. Remigy, P. Aptel, Chem. Eng. Prog. 41 (2002) 601–609. [31] M. Montazer, S.B. Malekzadeh, J. Polym. Res. 19 (2012) 9980–9986. [32] Z. Jia, H. Sun, Q. Gu, Colloids Surf. A 419 (2013) 174–179.
[33] A. Travan, C. Pelillo, I. Donati, E. Marsich, M. Benincasa, T. Scarpa, S. Semeraro, G. Turco, R. Gennaro, S. Paoletti, Biomacromolecules 10 (6) (2009) 1429–1435. [34] K. Wong-ek, P. Eiamchai, M. Horprathum, V. Patthanasettakul, P. Limnonthakul, P. Chindaudom, N. Nuntawong, Thin Solid Films 518 (2010) 7128–7132. [35] N. Nuntawong, M. Horprathum, P. Eiamchai, K.k. Wong-ek, V. Patthanasettakul, P. Chindaudom, Vacuum 84 (2010) 1415–1418. [36] L.L. Cho, Forensic Sci. J. 6 (1) (2007) 55–62. [37] M.N. Grigg, Thermo-oxidative Degradation of Polyamide 6, (Ph.D. Thesis at) Queensland University of Technology, 2006. [38] D.L. Pavia, G.M. Lampman, G.S. Kriz, J.R. Vyvyan, Introduction to Spectroscopy, Fourth edition Brooks/Cole, Cengage Learning, 2009. [39] M. Montazer, A. Behzadnia, E. Pakdel, M.K. Rahimi, M.B. Moghadam, J. Photochem. Photobiol. B 103 (2011) 207–214. [40] Y. Zhao, Y. Jiang, Y. Fang, Spectrochim. Acta A 65 (2006) 1003–1006. [41] G.E. Burunkayaa, O. Kesmeza, N. Kiraza, H. Erdem, C. Amurluc, M. Asilturka, E. Arpac, Mater. Chem. Phys. 120 (2010) 272–276. [42] M. Montazer, E. Pakdel, M.B. Moghadam, Fibers Polym. 11 (7) (2010) 967–975. [43] M. Montazer, F. Alimohammadi, A. Shamei, M.K. Rahimi, Carbohydr. Polym. 87 (2012) 1706–1712. [44] X.Y. Gao, S.Y. Wang, J. Li, Y.X. Zheng, R.J. Zhang, P. Zhou, Y.M. Yang, L.Y. Chen, Thin Solid Films 455–456 (2004) 438–442. [45] T.C. Kaspar, T. Droubay, S.A. Chambers, P.S. Bagus, J. Phys. Chem. C 114 (2010) 21562–21571. [46] P.L. Taylora, O. Omotosob, J.B. Wiskela, D. Mitlina, R.E. Burrell, Biomaterials 26 (2005) 7230–7240. [47] H. Itani, P. Keil, D. Lützenkirchen-Hecht, U. Haake, H. Bongard, A. Dreierc, C.W. Lehmann, G. Grundmeier, Surf. Coat. Technol. 205 (2010) 2113–2119. [48] M. Lismont, L. Dreesen, Mater. Sci. Eng. C 32 (2012) 1437–1442. [49] F. Schwarz, B. Stritzker, Surf. Coat. Technol. 12–13 (2010) 1875–1879. [50] M. Parvinzadeh Gashti, F. Alimohammadi, G. Song, A. Kiumarsi, Characterization of nanocomposite coatings on textiles: a brief review on microscopic technology, in: A. Méndez-Vilas (Ed.), Current Microscopy Contributions to Advances in Science and Technology, vol. 2, Formatex Research Center, Spain, 2012, pp. 1424–1437. [51] R. Dastjerdi, M. Montazer, Colloids Surf. B 88 (2011) 381–388. [52] R. Dastjerdi, M.R.M. Mojtahedi, A.M. Shoshtari, A. Khosroshahi, A.J. Moayed, Text. Res. J. 79 (2009) 1099–1107. [53] F. Alimohammadi, M. Montazer, A. Shamei, M. Karim Rahimi, Iran. J. Polym. Sci. Technol. 25 (2012) 265–275. [54] M. Montazer, A. Shamei, F. Alimohammadi, Prog. Org. Coat. 75 (2012) 379–385.
