Multifunctional Properties of Polyester Fabrics Modified by Corona Discharge/Air RF Plasma and Colloidal TiO2 Nanoparticles
D. Mihailovic´,1 Z. Sˇaponjic´,2 R. Molina,3 M. Radoicˇic´,2 J. Esquena,3 P. Jovancˇic´,1 J. Nedeljkovic´,2 M. Radetic´1 1 Textile Engineering Department, Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11120 Belgrade, Serbia 2
Vincˇa Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, Serbia
3
Chemical and Biomolecular Nanotechnology Department Institut de Quı´mica Avanc¸ada de Catalunya (IQAC), Consejo Superior de Investigaciones Cientı´ficas (CSIC), C/ Jordi Girona 18-26, 08034 Barcelona, Spain
In this study the possibility of tailoring the textile nanocomposite materials based on the polyester fabric and TiO2 nanoparticles that can simultaneously provide desirable level of antibacterial activity, UV protection, and self-cleaning effects with long-term durability was investigated. To enhance the binding efficiency of colloidal TiO2 nanoparticles, the surface of polyester fabrics was activated by low-pressure RF air plasma, and corona discharge at atmospheric pressure. Obtained functionalized textile materials provided maximum antibacterial efficiency against gram-negative bacterium E. coli. High values of UV protection factor (UPF) indicate the maximum UV blocking efficiency (50þ) of these fabrics. The results of self-cleaning test with blueberry juice stains and photodegradation of methylene blue in aqueous solution confirmed excellent photocatalytic activity of TiO2 nanoparticles deposited on the fiber surface. POLYM. COMPOS., 32:390–397, 2011. ª 2010 Society of Plastics Engineers
INTRODUCTION Future breakthroughs in manufacturing of textiles will be mainly focused on creation of lightweight, durable, and comfortable materials that can provide protection Correspondence to: Maja Radetic´; e-mail:
[email protected] Contract grant sponsor: Ministry of Science of Republic of Serbia; contract grant numbers: TR 19007, 142066. Contract grant sponsor: Spanish Ministry of Science and Innovation; contract grant number: CTQ2008-06892-C03-01. Contract grant sponsor: Office of Science, Office of Basic Energy Sciences of the U.S. DOI 10.1002/pc.21053 Published online in Wiley Online Library (wileyonlinelibrary.com). C 2010 Society of Plastics Engineers V
POLYMER COMPOSITES—-2011
from different undesired environmental impacts. It is well known that appropriate antimicrobial and UV protection as well as self-cleaning effects can be engineered by depositing the nontoxic and inexpensive TiO2 nanoparticles (NPs) onto textile fibers, without changing the fiber bulk properties and deteriorating the textile appearance [1–4]. Developed procedures for synthesis of TiO2 NPs with welldefined crystallinity and surface properties open up possibility to control the mechanism of interaction between fiber surface and particles. However, the major problem of nanoparticle application to textile materials is the maintenance of the adequate durability of obtained effects. Recent studies revealed the great potential of TiO2 NPs synthesized by sol-gel methods at relatively low temperatures in textile processing. Although the major work so far corresponds to the application of TiO2 NPs to cotton fabrics [5–16], manmade fibers and particularly polyester (PES) fibers should receive much more attention as these fibers account for 74% share in total manmade fiber production and usage globally [17]. Additionally, it is predicted that PES fibers will continue to dominate manufactured fiber output. The deposition of TiO2 NPs onto PES fiber is highly challenging due to the lack of chemical bonding between PES and TiO2 NPs [18, 19]. The low pressure plasma treatment of textile materials is established as a well-controlled and reproducible process. However, it requires expensive vacuum pumps and more complex handling compared with systems operating at atmospheric pressure (corona discharge and dielectric barrier discharge). To increase binding between PES fibers and TiO2 NPs Bozzi et al. proposed the approach that relies on the modification of PES textiles by radio frequency (RF) plasma, microwave (MW) plasma, or vacuum
UV irradiation [18]. Plasma oxidation and plasma etching provide activation of the fiber surface i.e. formation of polar functional groups such as CO, C¼ ¼O, O C¼ ¼O, COH, COOH or OO [3] which can ensure better bonding with TiO2 NPs. Daoud et al. also confirmed the benefits of oxygen RF plasma treatment prior to loading of anatase TiO2 NPs onto PES fabrics [19]. This study discusses the possibility of using both, lowpressure RF air plasma and corona discharge at atmospheric pressure for the surface activation of PES fabrics in order to enhance the binding efficiency of colloidal TiO2 NPs. The chemical changes of PES fiber surface induced by air RF plasma/corona treatments and TiO2 NPs deposition were analyzed by XPS. Additional effort was made to tailor the properties of TiO2 NPs in such a manner that they can simultaneously provide optimum antibacterial activity, UV protection and self-cleaning properties of PES fabrics with long-term durability. The deposition of colloidal TiO2 NPs with amorphous structure onto corona activated PES fabrics in our previous studies induced an excellent UV protection and self-cleaning properties, but poor antibacterial efficiency [20, 21]. Therefore, the step forward had to be made in the procedure for the synthesis of colloidal TiO2 NPs by acidic hydrolysis method. Namely, the thermal treatment of colloidal solution prepared in accordance with previous procedure [21] ensured the formation of nanoparticles with anatase crystal structure, which in turn imparted significant improvement of antibacterial efficiency to PES fabrics. Antibacterial activity was tested against gramnegative bacterium E. coli. The UV blocking efficiency was evaluated by determining the UV protection factor (UPF). The photocatalytic activity of TiO2 NPs deposited on the PES fabrics was tested by degradation of blueberry juice stains and methylene blue in aqueous solution.
EXPERIMENTAL Sample Preparation Desized and bleached polyester (PES, 115 g/m2) fabric was used as a substrate in this study. To remove the fabric surface impurities, the cleaning procedure was carried out as described in details elsewhere [22]. Corona treatment of PES fabrics was performed at atmospheric pressure using a commercial device Vetaphone CP-Lab MK II. Fabrics were placed on the electrode roll, rotating at the minimum speed of 4 m/min. The distance between electrodes was 2 mm. The power was 900 W and the number of passages was set to 30. Glow-discharge treatment of PES fabrics was performed in a low-pressure capacitively coupled RF-induced (13.56 MHz) air plasma. The plasma system consists of a chamber, RF power supply, matching box, and vacuum pump. The chamber is cylindrical (37 cm in diameter, 50 cm DOI 10.1002/pc
in length) with a central electrode (14 mm in diameter) that is powered through the matching box. Plasma formed between the central electrode and the wall of the chamber that was grounded. Treatment time was 2.5 min, pressure 0.27 mbar with the power supply maintained at a constant level of 100 W. All the chemicals used for the synthesis of TiO2 colloid were analytical grade and used as received without further purification (Aldrich, Fluka). Milli-Q deionized water was used as a solvent. The colloids consisting of TiO2 NPs were prepared in a manner analogous to that of Rajh et al. [23]. The solution of TiCl4 cooled down to 2208C was added drop-wise to cooled water (at 48C) under vigorous stirring and then kept at this temperature for 30 min. The pH of the solution was between 0 and 1, depending on TiCl4 concentration. Slow growth of the particles was achieved by using dialysis against water at 48C until the pH of the solution reached 3.5. The concentration of TiO2 colloidal solution was determined from the concentration of the peroxide complex obtained after dissolving the particles in concentrated H2SO4 [24]. To enhance the crystallinity and overall efficiency of obtained TiO2 NPs, the colloid was thermally treated in reflux at 608C for 16 h. One gram of PES fabric was dipped into 20 mL of 0.1 M TiO2 colloid for 5 min and dried at room temperature. After 30 min of curing at 1008C, the fabrics were rinsed twice (5 min) with deionized water and dried at room temperature. METHODS The shape and size distribution of TiO2 NPs were determined using a high resolution electron microscope (HREM, Phillips CM200 with a FEG) at 200 kV. The evaluation of surface chemical changes was conducted by X-ray photoelectron spectroscopy (XPS) analysis. Samples were analyzed using a PHI Model 5500 Multitechnique System with an Al Ka monochromatic X-ray source operating at 350 W. The measurements were conducted under a take-off angle of 458. Survey scans were in the range 0–1100 eV, with pass energy of 187.85 eV. High resolution scans were obtained on the C 1s, O 1s, and Ti 2p photoelectron peaks, with pass energy of 23.5 eV. Binding energies were referenced to the C 1s photopeak position for CC and CH species at 285.0 eV. Surface composition has been estimated after a linear background subtraction from the area of the different photo-emission peaks modified by their corresponding sensitivity factors [25]. The antibacterial efficiency of fabrics was quantitatively evaluated by using a gram-negative bacterium E. coli ATCC 25922. Bacterial inoculum was prepared in the tripton soy broth (Torlak, Serbia), which was used as the growth medium for bacteria while the physiological saline solution (pH 7.0) was used as the testing medium. Bacteria were cultivated in 3 mL of tripton soy broth at POLYMER COMPOSITES—-2011 391
378C and left overnight (late exponential stage of growth). Afterwards, 70 mL of sterile physiological saline solution was added to sterile beaker (400 mL), which was then inoculated with 0.7 mL of the bacterial inoculum. The zero counts were made by removing 1 mL aliquots from the flask with inoculum, and making 1:10 and 1:100 dilutions in physiological saline solution. 0.1 mL of the 1:100 solution was placed onto a tripton soy agar (Torlak, Serbia) and after 24 h of incubation at 378C, the zero time counts (initial number of bacterial colonies) of viable bacteria were made. One gram of sterile PES fabric cut into small pieces was put in the beaker (70 mL of sterile physiological saline solution inoculated with 0.7 mL of the bacterial inoculum) and shaken for 2 h under UV illumination (TL-D lamp, 18 W, Philips). Two-hour counts were made in accordance with an above described procedure. The percentage of bacteria reduction (R, %) was calculated using the Eq. 1: R¼
C0 C 100 C0
(1)
where: C0 (CFU, colony forming units) is the number of bacterial colonies on the control fabric (fabric without TiO2 NPs) and C (CFU) is the number of bacterial colonies on PES fabric loaded with TiO2 NPs [26–28]. The UV transmission of PES fabrics was determined using an UV/VIS spectrophotometer Cary 100 Scan (Varian). The UV protection factor (UPF) values were automatically calculated on the basis of the recorded data in accordance with Australia/New Zealand standard AS/ NZS 4399:1996 using a Startek UV fabric protection application software version 3.0 (Startek Technology). For the examination of self-cleaning properties of PES fabrics blueberry juice was used. Control PES fabric and fabrics loaded with TiO2 NPs were cut into 5 cm 3 5 cm pieces. The fabrics were stained with 50 lL of blueberry juice. After drying at room temperature, the fabrics were illuminated by ULTRA-VITALUX lamp, 300 W (Osram) for 24 h. To determine the color change after 24 h of illumination, color coordinates of the stained fabrics (CIE L*, a*, b*) were determined with Datacolor SF300 spectrophotometer under illuminant D65 using the 10o standard observer. On the basis of measured CIE color coordinates, color difference (DE*) was determined as: qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi (2) DE ¼ ðDa Þ2 þðDb Þ2 þ ðDL Þ2 where: DL*, the color lightness difference between treated (stained PES fabric loaded with TiO2 NPs) and control fabrics (stained UPES fabric); Da*, red/green difference between treated and control fabrics; Db*, yellow/blue difference between treated and control fabrics. Always the same position on the stained fabric (where the color intensity of the stain was the strongest - the central part) was analyzed. 392 POLYMER COMPOSITES—-2011
FIG. 1. HREM image of TiO2 NPs (inset: SAED pattern). [Color figure can be viewed in the online issue, which is available at wileyonlinelinbrary. com.]
Photocatalytic activity of TiO2 NPs deposited on PES fabrics was evaluated by degradation of methylene blue (MB). Totally, 0.5 g of PES fabric was immersed in 25 mL of MB solution (10 mg L21, pH 5.81) and illuminated by ULTRA-VITALUX lamp, 300 W (Osram) for 2, 4, 6, 8, and 24 h. The MB concentration was determined by measuring absorption intensity at 664 nm using an UV/ VIS spectrophotometer Cary 100 Scan (Varian).
RESULTS AND DISCUSSION Characterization of TiO2 NPs and PES Fabrics Loaded With TiO2 NPs HREM image of thermally treated, irregularly shaped TiO2 NPs with average dimension of 6 nm is shown in Fig. 1. The NPs tend to be single crystalline, although the multiple twinned particles having the haring-bone structure were also observed. The electron diffraction pattern indicates the formation of anatase crystal structure (Fig. 1 inset). The chemical changes on the outer surface of PES fibers induced by corona/plasma treatment were discussed in detail in our earlier studies [20-22, 29-30]. Higher O/C atomic ratio found on the corona treated (CPES) and air RF plasma-treated (PPES) PES fibers compared to untreated (UPES) fibers is primarily attributed to plasma oxidation of fiber surfaces [29, 30]. The appearance of new oxygen-containing functionalities on the fiber surface resulted in improved hydrophilicity of PES fibers. Consequently, PES fibers became more accessible to different hydrophilic species, including colloidal Ag and TiO2 NPs, DOI 10.1002/pc
TABLE 1. Elemental composition of the UPES, CPES, and PPES fibers loaded with TiO2 NPs. Sample UPESþTiO2 CPESþTiO2 PPESþTiO2
C (atom %)
O (atom %)
Ti (atom %)
78.99 66.43 60.51
19.67 26.34 30.58
1.34 7.23 8.91
as shown in our previous work [20-22, 29, 30]. Similar observations after oxygen plasma treatment of PES fabrics were reported by Qi et al. [19]. The results of XPS measurements clearly imply that corona/plasma pretreatment of PES fabrics positively influenced the loading of thermally treated colloidal TiO2 NPs. The elemental composition of the UPES, CPES and PPES fabrics loaded with TiO2 NPs (UPESþTiO2, CPESþTiO2, PPESþTiO2) is presented in Table 1. Five to seven times higher Ti content detected in the CPESþTiO2 and PPESþTiO2 fibers compared to UPESþTiO2 fibers is likely due to plasma-induced chemical and morphological changes [19, 29]. However, detected Ti content is lower compared with Ti content in the equivalent CPES and particularly UPES samples loaded with amorphous TiO2 NPs [29]. Namely, higher number of reactive undercoordinated surface defect sites on the amorphous TiO2 NPs provided better binding efficiency of NPs to PES fibers. The decrease of defect sites on the crystalline anatase TiO2 NPs makes them less reactive. Hence, less thermally treated TiO2 NPs was expected to be deposited on the UPES and CPES fabrics. The high resolution XPS spectra of Ti 2p and O 1s photoelectron peaks for the UPES þ TiO2,CPES þ TiO2, and PPES þ TiO2 fibers are shown in Figs. 2 and 3, respectively. The Ti 2p1/2 and Ti 2p3/2 spin-orbital splitting electrons are located at binding energies of 464.2 eV and 458.6 eV, respectively (see Fig. 2). The O 1s spectrum of analyzed fibers was deconvoluted with three com-
FIG. 3. High-resolution spectra of O 1s photoelectron peaks for the UPESþTiO2, CPESþTiO2, and PPESþTiO2 fibers.
ponents (Table 2). The peaks at binding energies of 529.8 ¼O eV, 531.6 eV, and 532.9 eV are assigned to TiO2, C¼ and CO groups, respectively. The clear peak that appears in each spectrum at 529.8 eV confirms the presence of TiO2 NPs on the surface of each sample.
Antibacterial Efficiency Antibacterial properties of PES fabrics loaded with TiO2 NPs were tested against gram-negative bacterium E. coli. The values of bacterial reduction are given in Table 3. The UPESþTiO2 fabric provided bacterial reduction of only one order of magnitude compared with control UPES fabric showing the unsatisfactory antibacterial efficiency. Treatment of PES fabrics with corona or air RF plasma prior to loading of TiO2 NPs positively influenced the antibacterial efficiency. Both the CPESþTiO2 and PPESþTiO2 fabrics reached maximum bacterial reduction, which was preserved after five washing cycles (Table 3). This indicates excellent laundering durability of obtained antibacterial effects. Better antibacterial properties of the CPESþTiO2 and the PPESþTiO2 fabrics in comparison with UPESþTiO2 fabric is attributed to higher amount of deposited TiO2 NPs. Achieved results clearly demonstrate that thermal treatment of colloid and the formation of nanocrystalline anatase TiO2 imparted the desirable level of antibacterial activity to PES fabrics. TABLE 2. Relative intensity data of the deconvoluted O 1s spectra of the UPESþTiO2, CPESþTiO2, and PPESþTiO2 fibers. Atomic ratio (%) Sample
FIG. 2. High-resolution spectra of Ti 2p photoelectron peaks for the UPESþTiO2, CPESþTiO2, and PPESþTiO2 fibers.
DOI 10.1002/pc
UPESþTiO2 CPESþTiO2 PPESþTiO2
TiO2 529.8 eV
C¼ ¼O 531.6 eV
C O 532.9 eV
18.6 66.5 76.2
36.9 9.8 5.0
44.5 23.7 18.8
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TABLE 3. Antibacterial efficiency of PES fabrics loaded with TiO2 NPs.
Sample UPES UPESþTiO2 UPES CPESþTiO2 UPES PPESþTiO2 After washing UPES CPESþTiO2 UPES PPESþTiO2
Initial number of bacterial colonies (CFU)
Number of bacterial colonies (CFU)
3.7 3 105
1.5 3 105 1.3 3 104 1.4 3 104 \10 1.2 3 104 \10
1.8 3 105 3.9 3 105 1.8 3 105
1.4 3 104 \10 1.2 3 104 \10
3.9 3 105
R, %
91.3 99.9 99.9
99.9 99.9
Unlike them, amorphous TiO2 NPs deposited on the CPES fabrics exhibited poor antibacterial activity [21].
UV Protection Effect The level of UV protection provided by PES fabrics was estimated by measuring the spectral transmittance across the wavelength range from 280 to 400 nm and by calculating the UV protection factor (UPF) according to Australian/New Zealand Standard. The minimum recommended UPF for garments should be 40 to 50þ. The UPF values of the control PES fabric and PES fabrics loaded with TiO2 NPs are given in Table 4. The UPF value of 43.0 and corresponding UPF rating of 40 categorize the UPES fabric to fabrics with excellent UV protection. The deposition of TiO2 NPs onto PES fabrics led to a remarkable increase of UPF values, which satisfy the UPF rating of 50þ, implying the maximum UV protection. In fact, the ability of deposited TiO2 NPs to absorb UV light was efficiently utilized for enhancement of UV blocking. More efficient UV filtering ability of the CPESþTiO2 and PPESþTiO2 samples compared with UPESþTiO2 fabric is due to higher amount of deposited TiO2 NPs. It is also evident that the CPESþTiO2 and PPESþTiO2 fabrics provided equal UV protection. Although the UPF of both fabrics decreased after five washing cycles, it was still higher than that related to the UPESþTiO2 fabric. Preserved desirable level of UV protection (50þ) indicates again excellent laundering durability of achieved effects. TABLE 4. UPF values of PES fabrics loaded of with TiO2 NPs. Sample
UPF value
UPF rating
43.0 91.6 112.6 112.3 66.2 101.8 97.4
40 50þ 50þ 50þ 50 50þ 50þ
UPES UPESþTiO2 CPESþTiO2 PPESþTiO2 UPESþTiO2 (after washing) CPESþTiO2 (after washing) PPESþTiO2 (after washing)
394 POLYMER COMPOSITES—-2011
FIG. 4. Blueberry juice stains on the UPES fabric and PES fabrics loaded with TiO2 NPs before and after 24 h of UV illumination. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
Photocatalytic Activity of TiO2 NPs on the PES Fabrics The self-cleaning efficiency of PES fabrics loaded with TiO2 NPs was followed by decoloration of blueberry juice stains. Figure 4 shows the images of all samples after blueberry juice staining (zero time of illumination) and after 24 h of UV illumination. It is noticeable that great color difference between UPES fabric and all fabrics modified with TiO2 NPs occurred immediately after staining. Additionally, the shape of stains on corona/plasma pretreated PES fabrics significantly differ from those on the UPES fabrics. The shape of the stain on the UPES fabric was clearly defined. Although slightly lighter than the one on the UPES fabric, the stain on the UPESþTiO2 had irregular but still quite definite shape. In contrast, blueberry juice stains on the CPESþTiO2 and PPESþTiO2 fabrics were more spread over. This is due to corona or RF plasma treatment and consequent increase in hydrophilicity of the PES fibers surface. DOI 10.1002/pc
TABLE 5. Color difference between blueberry juice stained UPES fabric and UPES, CPES and PPES fabrics loaded with TiO2 NPs after 0 and 24 h of UV illumination. Time, h 0
24
Sample
DE*
DL*
Da*
Db*
Description
UPESþTiO2 CPESþTiO2 PPESþTiO2 UPESþTiO2 CPESþTiO2 PPESþTiO2
4.680 7.236 5.654 9.585 11.612 8.410
0.255 20.497 21.000 4.142 5.409 5.073
24.671 27.061 24.535 27.452 28.508 26.457
20.117 1.504 3.225 4.381 5.761 1.818
Lighter, less red, bluer Darker, less red, less blue Darker, less red, less blue Lighter, less red, less yellow Lighter, less red, less yellow Lighter, less red, less yellow
Blueberry juice stain on the UPES fabric was almost not altered even after 24 h of UV illumination, showing that UPES fabric itself does not posses any photocatalytic activity. The loading of UPES fabric with TiO2 NPs caused significant decolorization of blueberry stain. However, much better self-cleaning efficiency was obtained on the fabrics that were pretreated by corona/plasma. Figure 4 indicates that the CPESþTiO2 and PPESþTiO2 fabrics exhibited similar self-cleaning effects. All the fabrics loaded with TiO2 NPs became lighter, less red, and less yellow after 24 h of UV illumination compared with equivalently illuminated UPES fabric. Quantitative determination of color difference between stained UPES fabric and PES fabrics loaded with TiO2 NPs (UPESþTiO2, CPESþTiO2, PPESþTiO2) expressed via DE*, DL*, Da*, and Db* values confirmed the visual observations (Table 5). All the fabrics loaded with TiO2 NPs became lighter, less red and less yellow after 24 h of UV illumination compared with equivalently illuminated UPES fabric. Achieved photodegradation effects can find practical applications that are based on the possibility of daylight irradiation of stains making the stained fabrics more prone to the action of detergents during household washing [11, 18]. Such opportunity would lead to a considerable energy cost saving. The photocatalytic activity of TiO2 NPs deposited on the PES fabrics was also evaluated by examining the pho-
FIG. 5. MB photodegradation by TiO2 nanoparticles on differently modified PES fabrics under UV illumination.
DOI 10.1002/pc
todegradation of dye methylene blue (MB) in aqueous solution. The dependence of C/C0 versus time of UV illumination for the UPES, UPESþTiO2, CPESþTiO2, and PPESþTiO2 fabrics is shown in Fig. 5. The adsorption of MB on the UPES fabric got saturated after 6 h. Further prolongation of UV illumination time caused no change of the dye concentration in the solution. The color of the UPES fabric turned from white to blue. However, adsorbed dye
FIG. 6. Changes in relative concentration of MB after repeated photodegradation processes under the UV illumination for the (a) CPESþTiO2 fabric and (b) PPESþTiO2 fabric.
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was not decomposed under the UV illumination, confirming that PES fabric itself posses no photocatalytic ability. The loading of the UPES fabric with TiO2 NPs led to a significant progress in photodegradation of MB. However, even after 24 h of the UV illumination, the whole amount of dye did not degrade. Additionally, after multiple rinsing in water, the color of fabric remained pale blue. This sample did not provide the total photodegradation neither in the solution nor on the fabric. On the contrary, TiO2 NPs deposited onto the CPES and PPES fabrics ensured complete removal of MB from solution after 24 h of UV illumination. The fabrics remained white, confirming the complete photodegradation of MB. To establish the durability of photocatalytic activity of the CPESþTiO2 and PPESþTiO2 fabrics, the photodegradation process under the UV illumination was repeated two more times on the same samples as shown in Fig. 6. Figure 6a reveals that photodegradation of MB on the CPESþTiO2 fabric even improved during the 2nd and the 3rd photodegradation cycle. In fact, nearly complete removal of MB was obtained already after 8 h of UV illumination. The PPESþTiO2 fabric showed almost the same photocatalytic activity during the 1st and the 2nd photodegradation cycle (Fig. 6b). However, the photodegradation of MB was significantly enhanced during the 3rd cycle and almost complete removal of dye was reached after 8 h as in the case of the CPESþTiO2 fabric. Increased photodegradation of dyes after repeated cycles was also observed by other researchers [15]. Higher photocatalytic activity of TiO2 NPs in repeated cycles appears as a consequence of particles surface cleaning from impurities during the first photodegradation cycle. CONCLUSIONS Air RF plasma and corona discharge pretreatments of polyester fabrics positively influenced the deposition of colloidal TiO2 nanoparticles. XPS and AAS measurements confirmed the higher amounts of Ti on these fabrics compared with fabrics that were only loaded with TiO2 nanoparticles. Consequently, plasma/corona pretreated fabrics loaded with TiO2 nanoparticles provided considerably better UV protection, antibacterial, and photocatalytic activity. These fabrics ensured desirable level of antibacterial efficiency against gram-negative bacterium E. coli. Maximum UV protection with high UPF rating (50þ) was reached. All obtained effects were preserved after five washing cycles, indicating their good laundering durability. Excellent photocatalytic activity of TiO2 nanoparticles on the fabric surface resulted in efficient self-cleaning of blueberry juice stains and decoloration of methylene blue in aqueous solution under UV illumination. The results also implied that thermal treatment of colloid and formation of anatase TiO2 nanoparticles significantly contributed to multifunctionality of studied nanocomposite textile materials. Similar antibacterial, UV protective and photocatalytic effects provided by PES fabrics modified by air RF 396 POLYMER COMPOSITES—-2011
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