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Colloids and Surfaces A: Physicochem. Eng. Aspects 427 (2013) 7– 12

Contents lists available at SciVerse ScienceDirect

Colloids and Surfaces A: Physicochemical andEngineering Aspects

jo ur nal ho me page: www.elsev ier .com/ locate /co lsur fa

V-durable superhydrophobic textiles with UV-shielding propertiesy introduction of ZnO/SiO2 core/shell nanorods on PET fibers andydrophobization

hao-Hua Xuea,b,∗, Wei Yina, Ping Zhanga, Jing Zhanga, Peng-Ting Ji a, Shun-Tian Jiaa

College of Resource and Environment, Shaanxi University of Science and Technology, Xi’an, 710021, People’s Republic of ChinaKey Laboratory of Auxiliary Chemistry and Technology for Light Chemical Industry, Ministry of Education, Shaanxi University of Science and Technology,i’an, 710021, People’s Republic of China

i g h l i g h t s

ZnO nanostructures were grown uni-formly covering around PET fibers.The ZnO structures were treated bysilica to suppress the photoactivity ofZnO.The textiles decorated withZnO/silica core/shell structureswere hydrophobized.UV-durable superhydrophobic tex-tiles with UV-shielding propertieswere obtained.

g r a p h i c a l a b s t r a c t

r t i c l e i n f o

rticle history:eceived 23 October 2012eceived in revised form 27 February 2013ccepted 6 March 2013

a b s t r a c t

ZnO nanostructures with different morphologies were grown on poly(ethylene terephthalate) fibers bya hydrothermal process at a low temperature of 93 ◦C. Then the ZnO nanorod decorated fibers werelayer-by-layer coated with silica forming ZnO/SiO2 core/shell structures on the textiles, and hydropho-bized with hexadecyltrimethoxysilane. Scanning electron microscopy showed that introduction of ZnO

vailable online 19 March 2013

eywords:urfacesurface properties

nanostructures onto fibers made the textiles roughened dramatically, favoring the formation of super-hydrophobic surfaces. Ultraviolet–visible spectrophotometry analysis and contact angle measurementof the textiles showed that growth of ZnO on the fibers enhanced the UV-blocking ability of the tex-tiles, and coating of silica improved not only the UV-shielding property but also the UV-durability of thesuperhydrophobicity on the textiles.

oatings

anostructures

. Introduction

Superhydrophobic textiles with a contact angle of above 150◦

ave got great interest in recent years for its potential applica-

ions [1–4]. Superhydrophobic surfaces were mostly fabricated by

imicking the lotus leaf in nature through roughening of substrateollowed by hydrophobization [5,6]. These functions can be added

∗ Corresponding author at: College of Resource and Environment, Shaanxi Uni-ersity of Science and Technology, Xi’an, 710021, People’s Republic of China.el.: +86 29 8616 8825; fax: +86 29 8616 8291.

E-mail addresses: xuech@zju.edu.cn, xuechaohua@126.com (C.-H. Xue).

927-7757/$ – see front matter © 2013 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.colsurfa.2013.03.021

© 2013 Elsevier B.V. All rights reserved.

to textiles via fiber modification without a detrimental influence onthe mechanical properties of textiles. Poly(ethylene terephthalate)(PET) textile is widely used for outdoor protection due to its excel-lent physical property. As markets in outdoor textiles have beenexpanded, the needs for multifunctional textiles have continuouslyincreased, in which superhydrophobic textiles with UV-shieldingproperty are appreciated very much [2,7,8]. Generally speaking,there are mainly two approaches to prepare superhydrophobic sur-faces: one is to build rough surface on hydrophobic materials, the

other is to construct rough surfaces followed by hydrophobization.Many superhydrophobic surfaces have been successfully obtained[9,10], in which nanomaterials are usually used to construct suit-able roughness, such as ZnO, TiO2, SiO2, etc. [6,8,11,12]. ZnO is a

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C.-H. Xue et al. / Colloids and Surfaces

ood candidate material due to its easily controlled morphologynd excellent UV-shielding property [13–15].

Textiles with excellent UV-shielding properties have been fab-icated by growth of ZnO nanostructures onto fibers [2,12,16–18].owever, photodegradation of organic supports or coveringsaused by ZnO and photoinduced superhydrophilicity of ZnO mate-ial under light must be seriously considered [1,3,19] in fabricationf superhydrophobic textiles with UV-shielding property using ZnOased materials. Until now, most of the reported works grew ZnOanostructures onto cotton fabrics [2,12,16,18], and only a fework took into consideration the side effects of ZnO under light

2].In this work, ZnO nanostructures were grown covering around

ET fibers to obtain stable superhydrophobic textiles withV-shielding property after coating of SiO2 followed by hydropho-ization, which coincides with the method reported by Wang [2] onuperhydrophobic cotton textiles with UV-blocking property. Dif-erently, PET fibers, instead of cotton, were pretreated by NaOH tomprove the affinity for ZnO in order to obtain full coating of ZnOeeds and then uniform covering of ZnO rods on fibers, becauseET fibers are usually smooth and inert, which disfavors seedingf ZnO. The schematic illustration of these processes was shown inig. 1. This method might expand the research on utilization of thexcellence of PET fiber, which is superior to cotton fiber for outdoorultifunctional textiles.

. Experimental

.1. Materials

Zinc nitrate hexahydrate (Zn(NO3)2·6H2O, 99% purity)nd hexamethylene tetramine (C6H12N4, 99.5%) were pur-hased from Tianjin Dengfeng Chemical Reagent Co. Ltd. Zinccetate dehydrate (Zn(CH3COO)2·2H2O, 99% purity) were

urchased from Tianjin Yaohua Chemical Reagent Co. Ltd.oly(diallyldimethylammonium chloride) (PDDA, Mw < 200,000)nd poly(sodium 4-styrenesulfonate) (PSS, Mw = 70,000)ere purchased from Shanghai Herochem Products Co., Ltd.

Fig. 1. Illustration of fabrication of superhydropho

sicochem. Eng. Aspects 427 (2013) 7– 12

Hexadecyltrimethoxysilane (HDTMS) was purchased fromHangzhou Silong Material Technology Co., Ltd. Tetraethyl orthosili-cate (TEOS), sodium chloride (NaCl), absolute ethanol, 2-propanoland aqueous ammonia solution (28 wt%) were purchased fromTianjin Chemical Reagent Co. (China). PET textiles were obtainedcommercially. Deionized water was used throughout all theexperiments.

2.2. Synthesis of seed ZnO nanoparticles

A solution of 0.087 mM Zn(CH3COO)2 was first prepared in2-propanol at 10 ◦C, then 20 ml of 20 mM sodium hydroxide in2-propanol was dropwise added into the cool solution under con-tinuous stirring. The mixture was then kept in a temperaturecontrolled water bath at 60 ◦C for 2 h to prepare seed ZnO nanopar-ticles [20,21].

2.3. Hydrothermal growth of ZnO

PET textiles were treated with ethanol and acetone for clean-ing. Then the textiles were pretreated by 20% NaOH for 2 min at100 ◦C to obtain hydrolyzed PET, as reported previously [1]. Thetextiles were seeded by dipping the hydrolyzed PET into the as-prepared seed ZnO nanoparticles sol for 15 min, then dry heated at80 ◦C for 20 min to ensure that the seeds were securely attached.These processes were repeated three times to load enough seed ZnOon the textiles. The ZnO nanostructures were grown in a sealed con-ical flask containing an equimolar solution of Zn(NO3)2·6H2O andC6H12N4 at 93 ◦C with continuously oscillation for 3 h. Differentconcentrations of the precursor solution, as shown in Table 1, wereused to control the structure of the grown ZnO.

2.4. Coating of SiO2 shell on ZnO

Silica coating on ZnO was conducted by a layer-by-layer depo-sition method [22]. Firstly, the textile was dipped into an aqueoussolution of PSS (1 g L−1, containing 0.5 M NaCl) for 10 min withintermediate water washing in order to render the surface of ZnO

bic PET textiles with UV-shielding property.

C.-H. Xue et al. / Colloids and Surfaces A: Phy

Table 1Water contact angles on the obtained PET textile surfaces.

Sample IDa Zn(NO3)2·6H2O C6H12N4 Na2SiO3 WCA WCAc

mol L−1 mol L−1 mol L−1 ◦ ◦

A0b 157 ± 5 156 ± 3A1 0.250 0.250 158 ± 3 115 ± 5A2 0.150 0.150 158 ± 5 109 ± 4A3 0.100 0.100 162 ± 4 86 ± 3A4 0.050 0.050 161 ± 3 82 ± 4A5 0.040 0.040 161 ± 6 73 ± 5A6 0.035 0.035 162 ± 5 56 ± 2A7 0.030 0.030 165 ± 3 72 ± 4A8 0.025 0.025 162 ± 5 76 ± 3B1 0.250 0.250 0.04 157 ± 5 145 ± 4B2 0.150 0.150 0.04 158 ± 3 144 ± 3B3 0.100 0.100 0.04 162 ± 4 147 ± 5B4 0.050 0.050 0.04 160 ± 3 145 ± 3B5 0.040 0.040 0.04 157 ± 5 146 ± 4B6 0.035 0.035 0.04 160 ± 4 145 ± 3B7 0.030 0.030 0.04 161 ± 5 146 ± 2B8 0.025 0.025 0.04 156 ± 5 148 ± 4

a All the samples were hydrophobized with HDTMS (1 wt%).b Sample A0 stands for the hydrolyzed PET.

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of samples A3, A5, and A7, all the obtained ZnO crystals are of

c The samples were exposed to UV lamp for 40 h.

egatively charged. After that, the sample was dipped into an aque-us solution of PDDA (1 g L−1, containing 0.5 M NaCl) for 10 minith intermediate water washing in order to render the surface

f ZnO positively charged. These steps were repeated four timeso modify the ZnO nanostructures with rich polyelectrolytes. Thenhe textile was alternatively dipped into the aqueous solutions ofDDA (1 g L−1, containing 0.5 M NaCl) and sodium silicate solutions40 mM, pH 7.5) for 10 min with intermediate water washing. Byhese procedures PDDA/silica bilayer was conformably preparedn the surface of ZnO. The deposition of the PDDA/silica bilayeras repeated three times so as to prepare multilayered structure

f (PDDA/silica)3. The multilayer-coated ZnO was baked at 150 ◦Cor 2 h to form a dense SiO2 shell on the surface of ZnO. The thick-ess of the silica shell can be controlled by regulate the coatingimes of the PDDA and Na2SiO3.

.5. Hydrophobization of PET textiles with HDTMS

Textiles were immersed in an HDTMS ethanol solution (1 wt%),nd reacted for 20 min at room temperature. Excess HDTMS solu-ion on the fibers was removed with a padder. Then the PET textilesere air-dried at 80 ◦C for 10 min, these steps were repeated three

imes. At last, the textiles were baked at 170 ◦C for 5 min.

.6. Characterization

.6.1. MorphologyA scanning electron microscope (SEM JSM-6700, JEOL, Japan)

as used to observe the PET textiles. Samples were sputter-coatedith gold prior to examination. A transmission electron micro-

cope (TEM H-600, HITACHI, Japan) was employed to observe theorphologies of ZnO/SiO2 core/shell nanostructures. The modified

ET fabrics were cut into pieces at first and then the pieces weremmersed in absolute ethanol. Then ZnO/SiO2 core/shell nanostruc-ures were removed from the PET fiber by ultrasonic treatmentith a high-power ultrasonic oscillator (2000 W) to form ZnO/SiO2ispersion for TEM investigations. In order to remove ZnO core,

amples were treated with 0.1 M HCl. A small amount of the dis-ersion was deposited onto copper grids, and dried in air at roomemperature before observation.

sicochem. Eng. Aspects 427 (2013) 7– 12 9

2.6.2. XRD patternsAn X-Ray Diffractometer (XRD, D/MAX 2200PC, Rigaku, Japan)

with Cu K� radiation was employed to detect the crystal form of thesamples at a scan speed of 8◦/min in the 2� range between 30◦ and70◦. The tube voltage and the tube current were 40 kV and 40 mA,respectively.

2.6.3. UV-shielding property of textilesThe UV–vis spectra of the sample were recorded using an

ultraviolet–visible spectrophotometer (UV–vis 754PC, ShanghaiSpectrum Instruments Co, China).

2.6.4. UV-durability testAn artificial light source (UV lamp, Osram Ultra Vitalux 300 W)

emitting a gauss shaped spectrum which peaked at 370 nm witha cut off at 290 nm was used for irradiation. Textiles were placedunder the UV lamp for up to 40 h. Water contact angles (WCAs) ofsamples were measured at ambient temperature on a video opti-cal contact angle system (OCA 20, Dataphysics, Germany). All thecontact angles were determined by averaging values measured at5–6 different points on each sample surface with a water dropletof 5 �L. Because the protruding fibers have some elasticity and canthus exhibit forces on the water droplet, it is difficult to yield accu-rate values for advancing and receding water contact angles, so onlystatic WCAs are reported.

3. Results and discussion

3.1. Morphology and structure of samples

The morphologies of the modified PET textiles were shown inFig. 2. It was found that disk-like platelets and pencil-like rods withdifferent diameters of ZnO were formed depending on the zincsalt concentration. When the zinc salt concentration was between0.25 M and 0.15 M, disk-like ZnO platelets were formed, as shownin Fig. 2(a) and (b). When the zinc salt concentration was 0.25 M,the average diameter and thickness of the disk-like ZnO are about10 �m and 1 �m, respectively. While when the zinc salt concen-tration was reduced to 0.10 M, average diameter and thickness ofthe disk-like ZnO are about 6 �m and 0.2 �m, respectively. So wecan infer that both the diameter and the thickness of the disk-likeZnO decreased with decreasing zinc ion concentration. When thezinc salt concentration was reduced to 0.15 M, some ZnO nano-rodswere also formed as transition state.

From Fig. 2(c), (e) and (f), it can be seen that pencil-like ZnOnanorods with different diameters were tidily wrapping the fiberswhen the zinc salt concentration were lower than 0.10 M. The diam-eter of the ZnO nanorods decreased with the declination of thezinc salt concentration. Moreover, the density of the ZnO nanorodson the PET fiber surfaces also decreased correspondingly. Typicalpencil-like ZnO nanorods with dimensions of about 50–300 nm indiameter were obtained on the PET fibers.

XRD patterns of samples A0, A1, A2, A5, and A7 were shown inFig. 3. It can be seen that there are no characteristic peaks in theshown range for sample A0 and sample A1. It indicates that thedisk-like ZnO platelets in samples A1 were amorphous state andthe structure of them was not inerratic. This might be because thatwhen the zinc salt concentration was between 0.10 M and 0.25 M,the zinc ions were enough to meet the need of every direction toform the amorphous phase disk-like ZnO, which is different fromthe crystalline disk-like ZnO [16]. While as for the XRD patterns

wurtzite structure, and the diffraction peaks can be indexed to ahexagonal structure with cell constants of a 3.24 A and b 5.19 A(JCPDS card No. 36-1451) when the zinc salt concentration ranged

10 C.-H. Xue et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 427 (2013) 7– 12

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ig. 2. SEM images of samples A1 (a), A2 (b), A3 (c), B3 (d), A5 (e), B5 (f), A7 (g), and

rom 0.025 M to 0.10 M. No characteristic peaks of other impuri-ies, such as Zn(OH)2, were detected in the patterns, suggestinghat only single-phase ZnO crystals were formed under these con-itions. Moreover, XRD of the ZnO crystals on the PET substrateslso showed strong preferred orientation along the c-axis becausehe [1 0 1] reflection was greatly enhanced relative to the [0 0 2] and1 0 0] maximum reflection. These results indicated that almost allhe ZnO nanorods are hexagonal phase. This is because when theinc salt concentration was lower than 0.10 M, the zinc ions wereot enough to meet the need of every direction of crystal face to

orm the ZnO nano crystals, then it preferred to meet the need of-axis direction to form the ZnO nanorods. In addition, it was notedhat the diffraction peaks of A3 are relatively higher than others,hich indicated that the ZnO nanorods were better grown on thebers when the zinc salt concentration was 0.10 M. All these mightuggest that the orientation along the c-axis was preferred whenhe concentration of zinc salt was not enough, while little prefer-ntial orientation occurred when the concentration of zinc salt wasuch higher. This made it possible to grow ZnO nanorods radially

n the fibers by well control of the hydrothermal conditions.

Fig. 2(d), (f) and (h) indicated that SiO2 shells were deposited

n the surface of the ZnO nanorods uniformly. The composition ofhe modified PET samples was further confirmed by EDS analysis

Fig. 3. XRD patterns of samples A0, A1, A2, A5, and A7.

). The insets were the higher-magnification images for the corresponding samples.

(Fig. 4), and the morphology of the nanorods were further con-firmed by TEM (Fig. 5). Fig. 4 shows the EDS analysis coupled to SEMof samples A0, A5, and B5. Fig. 4(a) for sample A0, the hydrolyzedPET textile, showed that four peaks have been clearly observed fromthe spectrum, which are identified as gold caused by the sputtercoating of gold on the samples for SEM, oxygen and carbon in thepolymer of PET. Comparing Fig. 4(b) with Fig. 4(a), a strong peakand a weak peak identified as zinc were clearly observed with theexception of the four peaks which were identical to those of PET tex-tiles. And the weight percentage of element O increased from 2.99%to 4.11% which were resulted from the growth of ZnO nanorods. Itis obvious that the nanorods are composed of zinc and oxygen only.Compared with Fig. 4(b), Fig. 4(c) showed an additional peak iden-tified as silicon indicating the incorporation of SiO2 on the surfaceof the textiles.

Fig. 5 shows the TEM images of ZnO/SiO2 core/shell nanostruc-tures removed from sample B5 and the acid treated B5 with 0.1 MHCl. It can be seen from Fig. 5(a) that the ZnO nanorods with a diam-eter about 50 nm were coated uniformly by a shell with a thicknessof about 20 nm, forming a typical ZnO/SiO2 core/shell structure.After treatment with HCl, the nanostructures left a hollow shelldue to the removing of ZnO core, as shown in Fig. 5(b). The innersurface of the hollow shell is smooth and sharp, indicating a fullcoverage of the nanorod core by SiO2 before acid treatment. Thecoating of ZnO by SiO2 shell might facilitate the suppression of thephotoactivity of ZnO under UV light.

3.2. UV-shielding property

The UV-blocking ability of textiles was characterized by UV-transmittance as a convenient way [23]. From Fig. 6, it can be seenthat the transmittance of the textiles with ZnO nanorods growndecreases obviously both in the visible range and the UV spectrum,especially in the wavelength range of 280–370 nm, compared tothe hydrolyzed PET textiles. The decrease of transmittance in theUV range is much more than that in the visible range. First of all,ZnO is a material with excellent ultraviolet absorption propertydue to its high content of crystallinity, efficient separation of elec-tron and hole pairs, and quantum confinement effect [24]. On theother hand, the light scattering of ZnO nanorods contributes to the

UV shielding property of the ZnO modified PET textiles. Moreover,a slight decrease of transmittance is observed for the PET textilescoated with SiO2 following the growth of ZnO both in the visiblerange and the UV spectrum.

C.-H. Xue et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 427 (2013) 7– 12 11

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coating on the ZnO surface suppressed the photodegradation ofHDTMS by ZnO under long-term UV illumination. Therefore, it ispossible to optimize this technique to fabricate light-durable mul-

Fig. 4. EDS analysis of sample A0 (a), A5 (b), and B5 (c).

.3. Superhydrophobic property and UV durability

WCAs in Table 1 showed that growth of ZnO nanorods onbers further increased the superhydrophobicity due to the sur-

ace roughening effect, as evidenced by SEM in Fig. 2. Coating ofiO2 on the textiles might slightly decrease the roughness of thenO nanorod decorated textiles, thus showing a slight decreasef the corresponding WCAs. Fig. 7 shows the states of the waterroplets on the hydrophobized samples of the as-fabricated tex-iles. From Fig. 7(a)–(d) and (i)–(l) with water droplets on samples,t was found that the WCAs of all the eight samples were greaterhan 150◦ and showed excellent superhydrophobicities.

In order to test the UV durability of the superhydrophobicity ofhe textiles, the textile samples were exposed to UV light for cer-ain time, and the WCAs of the samples were measured. After UVllumination for 40 h, it was found that the WCA of the PET textile

odified only by HDTMS changed little, as shown in Table 1. Whilehe WCA of samples with ZnO nanorods decreased obviously frombove 150◦ to less than 90◦, losing the superhydrophobic property

nd turning to be hydrophilic, as shown in Fig. 7(f)–(h). However,he WCA declination of sample A1 was much less than A3-A8, ashown in Fig. 7(a), (e) with the WCA value decrease from 156◦ to15◦ listed in Table 1. This is because the HDTMS on the surface

Fig. 5. TEM images of nanorods removed from sample B5 (a), and the acid treatedB5 with 0.1 M HCl (b).

of ZnO was decomposed by the photocatalytic degradation of ZnOnano-rods [25,26]. And, the photocatalytic ability of amorphousstate ZnO is lower than that of the crystallographic one.

While samples B1, B3, B5, and B7, which were coated with sil-ica after growth of ZnO and modification with HDTMS, maintainedhighly hydrophobic with WCA almost above 145◦ after UV expo-sure for 40 h, as shown in Fig. 7(m)–(p). This indicates that the silica

Fig. 6. The UV-transmittance of sample A0, A3, and B3.

12 C.-H. Xue et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 427 (2013) 7– 12

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ig. 7. Water droplets on the surfaces of PET textiles (a) A1, (b) A3, (c) A5, (d) A7, (i) Bo UV light for 40 h; (m)–(p) are the corresponding sample of (i)–(l) after exposure

ifunctional outdoor superhydrophobic textiles with UV-shieldingroperty.

It should be noted that growth of ZnO nanostructures changedittle the softness of the textiles as well as the colour, excepthat some white dust like substance appeared on the fibersf sample A1. This might be caused by the amorphous disk-ike ZnO platelets mentioned above. After coating of SiO2, theextiles became a little stiffer and whiter. Further work is ongo-ng for transforming the textiles as coated fabrics for outdoorpplications.

. Conclusions

In summery, ZnO nanostructures with different topographiesere grown on the PET textiles by a hydrothermal method at a low

emperature of 93 ◦C. It is found that when the concentrations ofn(NO3)2 and C6H12N4 ranged from 0.025 M to 0.10 M, pencil-likenO nanorod crystallites can be formed uniformly around the fibers,mparting excellent UV-shielding property to the textiles. And thenO nanorod covering on the fibers roughened dramatically theextile surfaces, favouring the formation of superhydrophobicityn the textiles. By coating the ZnO nanorods with a silica shell, thehotoactivity of ZnO was suppressed, inhibiting the photodegrada-ion as well as the hydrophilic transformation of the textile surface.his process is useful for large-scale fabrication of multifunctionalutdoor superhydrophobic textiles.

cknowledgments

This work was supported by Program for New Century Excel-ent Talents in University (NCET-12-1042), Major State Basicesearch Development Program of China (973 Program) (Granto. 2011CB612309), National Natural Science Foundation of China

Grant No. 51073091), the Research Fund for the Doctoral Programf Higher Education of China (Grant No. 20116125110002), theey Project of Chinese Ministry of Education (Grant No. 212171),rogram for Transformation of Important Scientific and Techno-ogical Achievements of Shaanxi Province (2012KTCG04-07), the

ajor Program of Science Foundation of Shaanxi Province (Granto. 2011ZKC05-7), the Ministry of Education Foundation of Shaanxirovince (Grant No. 11JK0971), and supported by the Academicackbone Cultivation Program of Shaanxi University of Science andechnology (Grant No. XSG2010006).

eferences

[1] C.-H. Xue, W. Yin, S.-T. Jia, J.-Z. Ma, UV-durable superhydrophobic textiles withUV-shielding properties by coating fibers with ZnO/SiO2 core/shell particles,Nanotechnology 22 (2011) 415603.

[

[

B3, (k) B5, and (l) B7; (e)–(h) are the corresponding sample of (a)–(d) after exposurelight for 40 h.

[2] L. Wang, X. Zhang, B. Li, P. Sun, J. Yang, H. Xu, Y. Liu, Superhydrophobicand ultraviolet-blocking cotton textiles, ACS Appl. Mater. Interfaces 3 (2011)1277–1281.

[3] G. Kwak, M. Seol, Y. Tak, K. Yong, Superhydrophobic ZnO nanowire surface:chemical modification and effects of UV irradiation, J. Phys. Chem. C 113 (2009)12085–12089.

[4] C.-H. Xue, J.-Z. Ma, Long-lived superhydrophobic surfaces, J. Mater. Chem. A 1(2013) 4146–4161.

[5] S. Shibuichi, T. Yamamoto, K.T.T. Onda, Super water- and oil-repellent surfacesresulting from fractal structure, J. Colloid Interface Sci. 208 (1998) 287–294.

[6] C.-H. Xue, S.-T. Jia, J. Zhang, L.-Q. Tian, Superhydrophobic surfaces on cottontextiles by complex coating of silica nanoparticles and hydrophobization, ThinSolid Films 517 (2009) 4593–4598.

[7] W. Duan, A. Xie, Y. Shen, X. Wang, F. Wang, Y. Zhang, J. Li, Fabrication of super-hydrophobic cotton fabrics with UV protection based on CeO2 particles, Ind.Eng. Chem. Res. 50 (2011) 4441–4445.

[8] C.-H. Xue, S.-T. Jia, H.-Z. Chen, M. Wang, Superhydrophobic cotton fabrics pre-pared by sol–gel coating of TiO2 and surface hydrophobization, Sci. Technol.Adv. Mater. 9 (2008) 035001.

[9] T. Sun, L. Feng, X. Gao, L. Jiang, Bioinspired surfaces with special wettability,Acc. Chem. Res. 38 (2005) 644–652.

10] M. Callies, D. Quéré, On water repellency, Soft Matter 1 (2005) 55–61.11] A. Steele, I. Bayer, E. Loth, Inherently superoleophobic nanocomposite coatings

by spray atomization, Nano Lett. 9 (2009) 501–505.12] B. Xu, Z. Cai, W. Wang, F. Ge, Preparation of superhydrophobic cotton fab-

rics based on SiO2 nanoparticles and ZnO nanorod arrays with subsequenthydrophobic modification, Surf. Coat. Technol. 204 (2010) 1556–1561.

13] M.H. Huang, S. Mao, H. Feick, H. Yan, Y. Wu, H. Kind, E. Weber, R. Russo, P.Yang, Room-temperature ultraviolet nanowire nanolasers, Science 292 (2001)1897–1899.

14] H. Yan, R. He, J. Johnson, M. Law, R.J. Saykally, P. Yang, Dendritic nanowireultraviolet laser array, J. Am. Chem. Soc. 125 (2003) 4728–4729.

15] J.C. Johnson, H. Yan, P. Yang, R.J. Saykally, Optical cavity effects in ZnO nanowirelasers and waveguides, J. Phys. Chem. B 107 (2003) 8816–8828.

16] R.H. Wang, J.H. Xin, X.M. Tao, UV-blocking property of dumbbell-shaped ZnOcrystallites on cotton fabrics, Inorg. Chem. 44 (2005) 3927–3930.

17] Z. Zhou, Y. Zhao, Z. Cai, Low-temperature growth of ZnO nanorods on PET fab-rics with two-step hydrothermal method, Appl. Surf. Sci. 256 (2010) 4724–4728.

18] Y. Li, Y. Zou, Y. Hou, Fabrication and UV-blocking property of nano-ZnO assem-bled cotton fibers via a two-step hydrothermal method, Cellulose 18 (2011)1643–1649.

19] A. Mills, J. Wang, Simultaneous monitoring of the destruction of stearic acid andgeneration of carbon dioxide by self-cleaning semiconductor photocatalyticfilms, J. Photochem. Photobiol. A 182 (2006) 181–186.

20] D.W. Bahnemann, C. Kormann, M.R. Hoffmann, Preparation and characteriza-tion of quantum size zinc oxide: a detailed spectroscopic study, J. Phys. Chem.91 (1987) 3789–3798.

21] S. Baruah, C. Thanachayanont, J. Dutta, Growth of ZnO nanowires on nonwovenpolyethylene fibers, Sci. Technol. Adv. Mater. 9 (2008) 025009.

22] N. Laugel, J. Hemmerle, C. Porcel, J.-C. Voegel, P. Schaaf, V. Ball, Nanocom-posite silica/polyamine films prepared by a reactive layer-by-layer deposition,Langmuir 23 (2007) 3706–3711.

23] H. Cui, M. Zayat, P.G. Parejo, D. Levy, Highly efficient inorganic transpar-ent UV-protective thin-film coating by low temperature sol–gel procedurefor application on heat-sensitive substrates, Adv. Mater. 20 (2008) 65–68.

24] W.A. Daoud, J.H. Xin, Nucleation and growth of anatase crystallites on cottonfabrics at low temperatures, J. Am. Ceram. Soc. 87 (2004) 953–955.

25] X.-T. Zhang, O. Sato, A. Fujishima, Water ultrarepellency induced bynanocolumnar ZnO surface, Langmuir 20 (2004) 6065–6067.

26] R.-D. Sun, A. Nakajima, A. Fujishima, T. Watanabe, K. Hashimoto, Photoinducedsurface wettability conversion of ZnO and TiO2 thin films, J. Phys. Chem. B 105(2001) 1984–1990.