Sage Journals: Discover world-class research

Abstract

The conditions to make nanorods functionalized fabric superhydrophobic have been optimized to obtain three kinds of self-cleaning characteristics such as physical, chemical, and biological. Physical self-cleaning is the lotus effect which is characterized by measuring both water contact and sliding angles. Chemical self-cleaning is the degradation of color stains and solutions due to photocatalytic effect of ZnO when exposed to ultraviolet. Biological self-cleaning refers to the antibacterial activity of functionalized fabric which is characterized by using a Gram-negative bacterium (Escherichia coli) and a Gram-positive bacterium (Staphyloccocus aureus) by both qualitative and quantitative methods using NF ISO 20743:2009 transfer method. The chemical and biological self-cleanings are studied on nanorods functionalized fabric before and after hydrophobization.

Keywords

Self-cleaning functionalization lotus effect antibacterial activity photocatalytic effect

Introduction

Self-cleaning textiles are the ones which clean themselves without any substantial physical assistance. These textiles can be divided into three categories, namely, physical, chemical, and biological self-cleanings. The physical self-cleaning refers to lotus effect that can be defined as the cleaning of lotus leaves due to the rolling of rain droplets on them. The lotus leaves exhibit this characteristic due to the presence of hierarchical roughness structure, i.e., micro-roughness covered with hydrophobic nano-roughness [1 –3]. In various studies [4 –8], textiles have been functionalized with different nanostructures to generate roughness on fibers which on modification with hydrophobic compounds exhibited physical self-cleaning (lotus effect).

The chemical self-cleaning means the degradation of color stains or discoloration of solutions in contact with fabric. For this, the fabric is functionalized with photocatalysts which produce hydroxyl radicals on ultraviolet (UV) light activation. This radical is highly oxidative and non-selective with high-redox potential (E₀ = +3.06 V) [9]. Therefore, it degrades stains and other organic species. Recently, the textiles have been treated with nanoparticles of titanium dioxide (TiO₂) which degraded red wine stains [10 –12] and decolorized methyl orange solution [13].

The biologically self-cleaning textiles have the ability to kill bacteria attached on them and prevent their growth. Several attempts have been made to develop antibacterial fabrics using organic and inorganic species. Nylon fabrics have been functionalized with quaternary ammonium salts to develop antibacterial activity [14,15]. Natural materials like chitosan have also been used to develop antibacterial textiles [16,17]. Inorganic materials, particularly, nanostructures of silver (Ag) and zinc oxide (ZnO) have been used to treat textiles for imparting antibacterial activity. Cotton fabric has been functionalized with ZnO nanoparticles which inhibits the growth of Staphylococcus aureus and Klebsiella pneumonia [18]. In another study, the textile has been functionalized with Ag which prevented growth of bacteria like Escherichia coli K-12 [19]. Cotton fabric deposited with silica particles functionalized with Ag nanoparticle has shown excellent antibacterial activity [20].

It is evident from literature that each type of self-cleaning has been developed individually on different textiles. Recently, some attempts have also been made to integrate more than one self-cleaning characteristics into one fabric. The polyester fabric has been treated with TiO₂ and Ag nanoparticles using polysiloxane. The functionalized fabric shows chemical self-cleaning by degrading dye stains and antibacterial activity [21]. The cotton fabric functionalized with ZnO nanowires exhibits UV protection, chemical, and physical self-cleanings [22]. In another study, ZnO nanoparticles have been attached on the cotton fabric using polystyrene-block-poly(acrylic acid) copolymer for biological self-cleaning against E. coli and S. aureus and chemical self-cleaning by discoloration of methylene blue solution [23]. So far, two self-cleanings have been developed on one fabric.

ZnO appears to be excellent functionalizing material due to its photocatalytic effect [24,25], antibacterial characteristics, [26,27], and the possibility to grow various kinds of nanostructures on different surfaces [28 –31]. These properties of ZnO are yet to be used in textiles. Therefore, the objective of present study is to use ZnO as functionalizing material for polyester fabric to integrate all the three self-cleanings. For this, ZnO nanorods are grown on the fabric to generate nano-roughness which on treatment with octadecyltrimethoxysilane (ODS) exhibits physical self-cleaning. The fabrics with ZnO nanorods have photocatalytic effect and antibacterial properties. However, when ODS is added, these properties are reduced. The challenge of this research was to find the best conditions for ODS hydrophobization to obtain all three properties on the same sample.

Materials and processes

Growth of nanorods

The plain woven plasma-treated polyester polyethylene terephthalate (PET) fabric was functionalized with ZnO nanorods according to our recently published work [32]. The fabric was seeded with ZnO seeds which were prepared by using 90 mM zinc acetate dihydrate (ACS reagent ≥98% from Sigma Aldrich) and 75 mM sodium hydroxide. This seeded fabric was placed in 100 mM solutions of zinc nitrate hexahydrate (reagent grade 98%, Sigma Aldrich) and hexamethylenetetramine (ACS reagent grade assay ≥99.0%, Sigma Aldrich) at 90℃ for 4 h. Then, the sample was rinsed five times in distilled water and dried at 120℃ for 10 min. The sample obtained is called N.

Hydrophobization

PET fabric functionalized with ZnO nanorods was modified with ODS (Sigma Aldrich, Technical grade 90%). Two methods, solution method (samples S) and vapor deposition method (samples V), were used to apply ODS on the treated PET fabric.

In solution method, ODS solutions with its various concentrations (0.05% to 4% v/v) were prepared in absolute ethanol (Carlo Erba 99.7%). The nanorods functionalized fabric samples were placed in these solutions for 24 h at 40℃ and cured at 150℃ for 5 min. In vapor deposition method, 200 µL of ODS was placed in ceramic dish at the bottom of Teflon bottle in which samples were held vertically, and the bottle was placed in an oven at 150℃ for 1, 2, 3 and 4 h.

Characterization

Nanorods

The morphologies of nanorods were characterized by scanning electron microscope (SEM; HITACHI S-3500N). As samples were not conducting, they were metalized with ultrathin coating of gold in order to avoid accumulation of static charges on surface and to obtain high-resolution images. FEI Tecnai G2 20 transmission electron microscope was also used to study the morphology and size of nanorods. Nanoscope III from Digital Instrument was used for atomic force microscopy (AFM) imaging in the AFM mode. The chemical compositions of samples were characterized by using XPS. SSX 100/206 photoelectron spectrometer from Surface Science Instruments (USA) equipped with a monochromatized micro focused Al X-ray source (powered at 20 mA and 10 kV) was used for this purpose. The angle between the surface normal and the axis of the analyser lens was equal to 55°.

Physical self-cleaning (lotus effect)

The physical self-cleaning was characterized on samples S and V by measuring water contact angle (WCA) and water sliding angle (WSA). The WCA measurements were carried out using sessile drop method using Digidrop from GBX, France. On each sample, six measurements were made with 5 µl of water droplet. The WSA was determined according to procedure described elsewhere [32].

Chemical self-cleaning

The chemical self-cleaning was studied by stain degradation and solution discoloration. The C.I. acid blue 9 was chosen for this because it is extensively used in food stuffs. The staining of fabric functionalized with just nanorods (N) was made by dipping the sample in dye solution in water, whereas the hydrophobic fabrics S and V could only be stained when the color was dissolved in acetone. Then they were dried in an oven. For solution discoloration, the sample N was immersed in aqueous solution of acid blue 9, but it was not possible to dip samples S and V due to hydrophobicity. Therefore, they were first soaked in acetone and then immersed in dye solution.

The UV light exposure was carried out at a distance of 18 cm from UV source (300 nm–400 nm with maximum emission at 368 nm) in the light box (VeriVide CAC60). The stain degradation was characterized by measuring the K/S values of the samples with the help of DATA COLOR spectrophotometer SPECTRA FLASH SF 600 PLUS. According to Kubelka-Munk equation, K/S = (1–R)²/2 R, where K = absorption coefficient, S = scattering coefficient, and R = reflectance. The K/S values are directly proportional to the amount of color present on a surface. To study the solution discoloration, the absorbance of dye solution in contact with fabric sample was measured at λ = 628 nm by using JASCO UV/VIS spectrophotometer V-530.

Biological self-cleaning (antibacterial activity)

Biological self-cleaning of the fabric was studied on samples N, V, and S. A Gram-negative (E. coli ATCC 8739) and Gram-positive (S. aureus ATCC 6538) bacteria were used for this purpose. For the experiments, liquid cultures were prepared by inoculating colonies into test tubes containing 5 mL of Muller Hinton (MH) broth (Biocar Diagnostic, Beauvais, France) maintained at 37℃ for 24 h. A subculture was then prepared by injecting 0.1 mL of bacterial suspension into 5 mL of MH broth, and this was grown at the same temperatures as those described above. Cells were harvested after 18 to 24 h growth period. A dilution of the cell culture was then performed by injecting correct volume of the culture described above into 50 mL of MH broth in order to obtain a cell concentration of (1–3) × 10⁶ colony-forming units of bacteria which could be immediately used for experiments. The antibacterial activity was studied by qualitative and quantitative method.

Qualitative evaluation

The MH (Biocar Diagnostic, Beauvais, France) agar plates were inoculated with 1 mL of the dilution described above. Afterward, a swatch of the test sample (1.2 cm in diameter) was placed on the agar surface and incubated at 37℃ for 24 h before observation. For each sample, the test was repeated three times.

Quantitative evaluation

Reduction of bacterial growth on the functionalized samples was estimated for Gram-negative bacterium E. coli (ATCC 8739) and the Gram-positive bacterium S. aureus (ATCC 6538) using NF ISO 20743:2009 Transfer Method.

Agar plates were inoculated with 1 mL of a MH (Biocar Diagnostic, Beauvais, France) nutrient broth culture containing (1–3) × 10⁶ colony-forming units of bacteria. Afterward, a swatch of the test sample (3.8 cm in diameter) was placed on the agar surface and pressed with a 200 g cylindrical weight for 60 ± 5 s. For every sample (N, S, and V), six swatches were used: three of them were removed from the agar surface and immediately analyzed for counting and three remaining were then removed from the agar surface, placed in a container with the transferred surface face up, and incubated at 37℃ for 24 h in a humidity chamber. For each fabric, 20 mL of neutralizing solution was poured on the test sample in a sterile bag and shaken vigorously using a stomacher shaker for 1 min on each side of the bag.

Serial dilutions were made with sterilized peptone water (Biocar Diagnostic, Beauvais, France), and the suspensions were placed on MH nutrient agar and incubated at 37℃ for 24 h.

The antibacterial activity (A) on the functionalized sample in comparison to the unfunctionalized one was calculated as

A = (log C_{t} - log C_{0}) - (log T_{t} - log T_{0})

(1)

where

logC₀ and logC_t are the decimal logarithm average corresponding to the number of bacteria obtained from the three untreated samples immediately after inoculation and after an incubating period of 24 h, respectively.

logT₀ and logT_t are the decimal logarithm average corresponding to the number of bacteria obtained from the three treated samples immediately after inoculation and after an incubating period of 24 h.

Results and discussion

Physical self-cleaning (lotus effect)

Figure 1 shows the micrograph and topograph of nanorods grown on mircofibers. The nanorods grow uniformly all over the fibers. The roughness generated due to growth of these nanorods on microfibers is 23 ± 3.4 nm. Therefore, a hierarchical roughness structure like lotus leaf has been developed. On modification with hydrophobic chemical (ODS), the nanorods functionalized fabric exhibited physical self-cleaning with very high WCA and very low WSA.

Figure 1.

(a) micrograph of nanorods functionalized fabric sample N and (b) topograph of same sample.

Figure 2(a) shows the effect of ODS concentration deposited on nanorods functionalized fabric by solution method. The WCA increases with increase in ODS concentration and reaches its maximum value when the concentration is 2%. On further increase, it starts decreasing. The WSA decreases and gains minimum value at the same ODS concentration at which WCA is the highest. On the contrary, the WCA angle continues to increase, whereas WSA continues to decrease with increase in vapor deposition time and their values stay constant after 3 h of ODS deposition as shown in Figure 2(b).

Figure 2.

(a) effect of ODS concentration in solution on water contact and water sliding angles and (b) effect of ODS vapor deposition time on water contact and water sliding angles.

In solution deposition method, the more and more molecules of ODS deposited on nanorods with the increase in its concentration in ethanol and all the nanorods were completely covered when the concentration was 2%. Therefore, the WCA and WSA were highest and lowest, respectively, at this concentration. On further increase, the deposition of ODS molecules was so high that they masked the nano-roughness due to which the WCA decreased and WSA increased. After 3% ODS, the WCA and WSA become almost stable. It is so because all the roughness has been masked with ODS and on further increase in its concentration, it did not have any significant effect. However, only a thin layer of ODS was formed in vapor deposition method. Therefore, after gaining the best self-cleaning characteristics at 3 h of deposition, the WCA and WSA remained constant on further increasing deposition time.

Table 1 represents the highest WCAs and lowest WSAs measured on samples S and V and resistance to sliding of droplet. The WCA and WSA measured on untreated polyester fabric which had just micro-roughness when modified with ODS by both methods were 125° and 15°, respectively. This means that the generation of hierarchical roughness structure substantially increases WCA and decreases the WSA. However, the sample functionalized with only nanorods (N) showed very high absorbency. The water droplet placed on fabric was absorbed immediately which could be attributed to capillaries between nanorods. The resistance force to sliding of water droplet offered by the fabric was calculated using WSA and droplet weight (Table 1).

Table 1.

The highest WCA, WSA, and resistance offered by fabric to sliding of droplet.

Sample	Water contact angle	Water sliding angle	Resistance to sliding for 5 µl water droplet (µN)
S fabric	154° ± 2°	3° ± 1.2°	3.43
V fabric	158° ± 2°	1.6° ± 0.4°	1.36
PET fabric (without nanorods +ODS)	125° ± 3°	15° ± 1.5°	13.12

PET: polyethylene terephthalate; ODS: octadecyltrimethoxysilane.

The comparison of the best self-cleaning characteristic by both hydrophobization methods shows that the sample V is better than sample S. The SEM micrographs of samples V and S shown in Figure 3 reveal the reason of this difference. It shows that the nanorods are completely masked with ODS layer in solution deposition method, whereas the individual nanorods can be seen in vapor deposition. The ODS layer deposited on sample S impairs the roughness due to which it has less WCA and high WSA as compared to sample V.

Figure 3.

SEM micrographs of nanorods functionalized samples modified with ODS. (a) sample V and (b) sample S.

To further substantiate this argument that sample S has higher quantity of ODS as compared to sample V, XPS analysis was carried out. XPS C1s spectra of all samples (untreated, N, S, and V) are presented in Figure 4. The peaks at 288.8 eV, 286.3 eV, and 284.8 eV correspond to–COOC–, –C–(O, N), and –C–(C, H), respectively. The heights of these peaks on nanorods functionalized sample are smaller than that of untreated. The nanorods cover the fibers due to which the heights of peak are reduced. The peaks at 288.8 eV and 286.3 eV disappear completely after modification with ODS because it covers PET fiber. However, the peak at 284.8 eV increases significantly for sample S, but the increase is not that significant for sample V. Table 2 also represents the composition of nanorods functionalized fabric modified with ODS by both methods. The sample S has higher percentage of –C–(CH)– as compared to that of V. This means that the deposition of ODS in solution is higher than vapor deposition method which impairs the roughness generated due to nanorods.

Figure 4.

XPS C 1s spectra of samples: (a) untreated polyester fabric, (b) nanorods functionalized polyester fabric, (c) nanorods functionalized polyester fabric modified with ODS by solution method (S), and (d) nanorods functionalized polyester fabric modified with ODS by vapor deposition (V).

Table 2.

XPS analysis data.

Sample	Binding energy
Sample	Na	Zn	–O–	–C–(CH)–	–Si–
	1071 eV	1021 eV	531 eV	288 eV	101 eV
PET + nanorods (N)	0.89	30.64	40.22	28.25	0
PET + nanorods + ODS by vapor method (V)	1.67	27.31	32.99	36.41	1.62
PET + nanorods + ODS by solution method(S)	0.66	17.37	29.18	51.28	1.51

PET: polyethylene terephthalate; ODS: octadecyltrimethoxysilane.

Chemical self-cleaning

The chemical self-cleaning was studied by degradation of dye stains and discoloration of solutions. Figure 5 represents the K/S values measured on samples N, V, and S as function of time. Here, it is worth mentioning that the samples V and S are the ones with best physical self-cleaning characteristics, and sample N is nanorods functionalized fabric without hydrophobization. There is no significant reduction in K/S values measured on sample S even after 24 h. This means that there is no degradation of color stain. Despite the fact that initial concentration of stain on sample N was much higher, about 50% K/S value was reduced in first 20 min, whereas on V, it took 240 min for 50% reduction. In 300 min, about 90% stain was degraded on N. The inset photo (Figure 3) shows the color stain on sample N at the beginning, after 300 min and after 24 h of UV exposure. The fabric became almost white after 300 min.

Figure 5.

Stain degradation on samples N, V and S; K/S values were measured as function of time. Inset picture represents the stain color on sample N at the beginning, after 300 min and after 24 h.

The absorbance evolution of dye solutions in contact with samples N, S, and V as function of time is presented in Figure 6. The sample N decolorizes the solution in 240 min, whereas V takes 360 min for discoloration of the same solution. The solution in contact with sample S remained unchanged.

Figure 6.

Evolution of absorbance curves of solutions in contact with samples N, V, and S.

Due to superhydrophobicity, the samples V and S shed the droplets and did not get stained by the dye solution in water, ethanol, and methanol. The solution droplets slipped over the fabric when they were pressed to penetrate into samples for staining. Only very low-energy liquids like acetone could wet the samples. Therefore, the dye solution in acetone was used for staining of samples S and V. Even then, the depth of stain on sample S was very low. The stain and solution degradation by sample N was very quick. Because all the active sites of photocatalyst (ZnO) were available, a thin layer of ODS is formed on top of nanorods in vapor deposition method (sample V) as discussed in physical self-cleaning section. Therefore, the number of active sites was less than N which caused slow degradation. In case of solution deposition of ODS, the nanorods were completely masked and there was no active site available (Figure 7).

Figure 7.

Graphical representation of nanorods functionalized fabric N, functionalized fabric modified with ODS by solution method S and functionalized fabric modified with ODS by vapor deposition method V. ODS: octadecyltrimethoxysilane.

Biological self-cleaning (antibacterial activity)

The antibacterial activities (A) of samples N, V, and S were evaluated by both qualitative and quantitative methods.

Qualitative evaluation

The qualitative evaluation of A of treated fabric was carried out with Gram-negative (E.coli) and Gram-positive (S. aureus) bacteria. The untreated (without nanorods) (C) and functionalized samples N, V, and S were placed on agar plates containing bacterial cultures. After 24 h of incubation in dark, it was observed that the bacteria grew below, above, and in the immediate proximities of sample C. The sample S inhibited the growth above and below but bacteria were observed in their vicinities. The samples V and N caused complete inhibition of bacterial growth on, below as well as in the immediate proximities. The zone of inhibition was bigger in case of sample N than sample V. The antibacterial activity was relatively higher against S. aureus than E. coli.

The functionalized fabric can inhibit the growth of bacteria possibly by two mechanisms. First, the nanorods whose tip diameter is around 50 nm (Figure 8) can penetrate into membranes of bacteria and mechanically damage it. This causes the disintegration, malfunctioning of the permeability barrier, and ultimately death of bacteria [33]. The second important reason is the production and penetration of reactive oxygen species (ROS). The ROS includes ^·OH, H₂O_2, and O₂²⁻. As the bacteria carry negative charge on their surfaces, the penetration of O₂²⁻ seems impossible but the hydroxyl radical and hydrogen peroxide can penetrate into the cell membranes which lead to the death of bacteria.

Figure 8.

TEM image of ZnO nanorods scraped from fabric.

Another possible reason for the zones of inhibition is due to the presence of Zn⁺⁺ ions in the bacterial culture [34]. To determine it, the atomic absorption spectroscopy (AAS) was carried out on the bacterial cultures which were dissolved in 1 mol·L⁻¹ hydrochloric acid after the removal of samples. Table 3 presents the amount of Zn measured by AAS. It shows that the amount of Zn measured in bacterial culture of sample N is higher than that of sample V and the zone of inhibition is also higher. Zn is not detected in the bacterial culture of sample S and also it has no zone of inhibition.

Table 3.

Zone of inhibition and amount of Zn detected in bacterial culture.

Sample	Zone of inhibition	Average [Zn] (g/L)
N	++	0.0473 ± 0.0042
V	+	0.0357 ± 0.0006
S	−−	Non-detected

Note: ++ = big zone of inhibition, + = small zone of inhibition, −−= no zone of inhibition.

It can be said that the presence of Zn⁺⁺ ions was responsible for zone of inhibition because ZnO dissolved in bacterial culture and released Zn⁺⁺ [35]. These ions were attached on the surfaces of bacteria due to electrostatic attraction and prevented their growth.

Quantitative evaluation

Figure 9 shows the counting of S. aureus and E. coli population (in decimal logarithm average per milliliter) directly on the samples after inoculation (t = 0) and after an incubation period of 24 h (t = 24 h). The A for S. aureus with treated samples of N, V, and S are 4.47, 4.75, and 4.42, whereas for E. coli, are 2.99, 4.10, and 2.85, respectively. The percentage mortality of the bacteria was calculated by equation (2) and presented in Table 4:

Percentage mortality = (log T_{t} - log C_{t}) \times 100 / {logT}_{t}

(2)

Figure 9.

Antibacterial activity of samples, i.e., untreated (C), nanorods functionalized (N), nanorods functionalized modified with ODS by solution method (S) and modified by vapor deposition method (V) against S. aureus and E. coli.

Table 4.

Percentage mortality of bacteria for samples N, V, and S.

Bacteria	N (%)	S (%)	V (%)
S. aureus	99	96	99
E. coli	53	58	95

It is quite clear that the functionalized samples are more effective against S. aureus than E. coli. This difference in antibacterial activity is due to the difference in cell membranes of both the bacteria. The killing and growth inhibition of bacteria takes place due to both physical and chemical mechanisms. The Gram-negative bacteria membranes have some additional components. For instance, Gram-negative bacteria contain the extra outer membranes and the pathogen-associated molecular patterns which include lipopolysaccharide (consisting of lipid A, core polysaccharide, and O antigen), porins, and particular fragments of peptidoglycan. This structure prevents attachment of ZnO on the surface [36]. The complex structure of Gram-negative bacteria mentioned above also acts as permeability barrier to ROS and prevents their penetration into the membrane [37]. S. aureus is charged less negatively as compared to E. coli [38]. This will lead to penetration of negatively charged reactive oxygen species like peroxide and superoxide ions in addition to hydroxyl radicals into S. aureus membrane which cannot penetrate into E. coli that has higher negative charge. This penetration causes the death of S. aureus.

Another important point is the higher antibacterial activity of samples V as compared to N and S against E. coli. To understand this difference, it is important to recall the formation of biofilm on a surface which takes place in five steps [39]: (i) reversible attachment of bacteria on surface, (ii) transition from reversible to irreversible attachment by production of extracellular polymers by the bacteria, (iii) early development of biofilm architecture, (iv) development of microcolonies into a mature biofilm, and (v) dispersion of cells from the biofilm into surrounding environment. It shows that bacteria will grow only when the transition between their reversible and irreversible attachment takes place. The nanostructured superhydrophobic surfaces prevent the attachment of bacteria and they take longer time to attach and make colonies [40]. The rod-like bacteria cannot attach themselves properly on these surfaces [41]. E. coli whose morphology is also rod-like finds it difficult to attach on superhydrophobic nanorods functionalized fabric; therefore, the samples V and S prevent the attachment of bacteria. The sample V has higher antibacterial activity than S. As shown in Figure 3, the sample S is completely masked with ODS, and the production of ROS seems impossible which is also confirmed by the degradation of dye stain and solution (Figures 5 and 6). It can be said that the sample S only prevents the transition of bacterial attachment from reversible to irreversible. Therefore, some of bacteria adhered at t = 0 could not attach themselves irreversibly and were removed from the surface. The sample V could degrade both stains and solutions; therefore, it has double characteristics; prevention to attachment due to superhydrophobicity and production of ROS. This synergistic effect enhances the antibacterial bacterial activity of V which is much higher than sample N against E. coli, because it inhibits the growth only by production of ROS.

Conclusion

The conditions for hydrophobization of nanorods functionalized fabric have been optimized to obtain all three types of self-cleanings on single fabric. The samples modified by vapor deposition method showed better physical self-cleaning characteristics than the ones modified by solution method. Sample V showed chemical self-cleaning as well but the sample S could not degrade the color stains and decolorize solutions due to deposition of thick layer of ODS.

All three samples prevented the growth of bacteria, but they had different zones of inhibition. The zone of inhibition was bigger for sample N as compared to sample V, whereas the sample S did not have any zone. The antibacterial activity was higher against S. aureus as compared to E. coli. The sample V was more effective against E. coli as compared to other two samples (N and S).

On the basis of preceding conclusion, it can be concluded that chemical and biological self-cleanings have been demonstrated by sample N. The sample S has physical and biological self-cleanings. All three self-cleanings, i.e., physical, chemical, and biological have been integrated into sample V.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

References

Guo

Liu

. Biomimic from the superhydrophobic plant leaves in nature: Binary structure and unitary structure. Plant Sci 2007; 172: 1103–1112.

Bhushan

Jung

Biomimetics inspired surfaces for superhydrophobicity, self-cleaning, low adhesion, and drag reduction. In: Bhushan

(ed.). Nanotribology and nanomechanics II, Berlin, Heidelberg: Springer, 2011, pp. 533–699.

Bhushan

. Biomimetics: Lessons from nature-an overview. Phil Trans R Soc A 2009; 367: 1445–1486.

Leng

Shao

de With

. Superoleophobic cotton textiles. Langmuir 2009; 25: 2456–2460.

Xue

C-H

Jia

S-T

Zhang

. Superhydrophobic surfaces on cotton textiles by complex coating of silica nanoparticles and hydrophobization. Thin Solid Films 2009; 517: 4593–4598.

Bae

Min

Jeong

. Superhydrophobicity of cotton fabrics treated with silica nanoparticles and water-repellent agent. J Colloid Interface Sci 2009; 337: 170–175.

. The friction property of super-hydrophobic cotton textiles. Appl Surf Sci 2010; 256: 4220–4225.

Zhuang

. Fabrication of superhydrophobic cotton fabrics by silica hydrosol and hydrophobization. Appl Surf Sci 2011; 257: 5491–5498.

Daneshvar

Salari

Khataee

. Photocatalytic degradation of azo dye acid red 14 in water on ZnO as an alternative catalyst to TiO₂. J Photochem Photobiol A 2004; 162: 317–322.

10.

Bozzi

Yuranova

Guasaquillo

. Self-cleaning of modified cotton textiles by TiO₂ at low temperatures under daylight irradiation. J Photochem Photobiol A 2005; 174: 156–164.

11.

Meilert

Laub

Kiwi

. Photocatalytic self-cleaning of modified cotton textiles by TiO₂ clusters attached by chemical spacers. J Mol Catal A: Chem 2005; 237: 101–108.

12.

Yuranova

Mosteo

Bandara

. Self-cleaning cotton textiles surfaces modified by photoactive SiO₂/TiO₂ coating. J Mol Catal A: Chem 2006; 244: 160–167.

13.

Long

Zhou

. Synthesis and characterization of self-cleaning cotton fabrics modified by TiO₂ through a facile approach. Surf Coat Technol 2009; 203: 3728–3733.

14.

Kim

Sun

. Durable antimicrobial finishing of nylon fabrics with acid dyes and a quaternary ammonium salt. Text Res J 2001; 71: 318–323.

15.

Son

Y-A

Sun

. Durable antimicrobial nylon 66 fabrics: Ionic interactions with quaternary ammonium salts. J Appl Polym Sci 2003; 90: 2194–2199.

16.

Tavaria

Soares

Reis

. Chitosan: Antimicrobial action upon staphylococci after impregnation onto cotton fabric. J Appl Microbiol 2012; 112: 1034–1041.

17.

Ferrero

Periolatto

. Antimicrobial finish of textiles by chitosan UV-curing. J Nanosci Nanotechnol 2012; 12: 4803–4810.

18.

Nadanathangam

Sampath

Kathe

. Functional finishing of cotton fabrics using zinc oxide–soluble starch nanocomposites. Nanotechnology 2006; 17: 5087–5087.

19.

Yuranova

Rincon

Bozzi

. Antibacterial textiles prepared by RF-plasma and vacuum-UV mediated deposition of silver. J Photochem Photobiol A 2003; 161: 27–34.

20.

Nischala

Rao

Hebalkar

. Silica–silver core–shell particles for antibacterial textile application. Colloids Surf B 2011; 82: 203–208.

21.

Dastjerdi

Montazer

. Nano-colloidal functionalization of textiles based on polysiloxane as a novel photo-catalyst assistant: Processing design. Colloids Surf B 2011; 88: 381–388.

22.

Ates

Unalan

. Zinc oxide nanowire enhanced multifunctional coatings for cotton fabrics. Thin Solid Films 2012; 520: 4658–4661.

23.

Çakır

Budama

Topel

. Synthesis of ZnO nanoparticles using PS-b-PAA reverse micelle cores for UV protective, self-cleaning and antibacterial textile applications. Colloids Surf A 2012; 414: 132–139.

24.

Pare

Jonnalagadda

Tomar

. ZnO assisted photocatalytic degradation of acridine orange in aqueous solution using visible irradiation. Desalination 2008; 232: 80–90.

25.

Gouvêa

CAK

Wypych

Moraes

. Semiconductor-assisted photocatalytic degradation of reactive dyes in aqueous solution. Chemosphere 2000; 40: 433–440.

26.

Tam

Djurisic

Chan

CMN

. Antibacterial activity of ZnO nanorods prepared by a hydrothermal method. Thin Solid Films 2008; 516: 6167–6174.

27.

Sivakumar

Balaji

Prabhawathi

. Effective antibacterial adhesive coating on cotton fabric using ZnO nanorods and chalcone. Carbohydr Polym 2010; 79: 717–723.

28.

Han

. Hydrothermal synthesis of ZnO nanobelts and gas sensitivity property. Solid State Commun 2007; 141: 506–509.

29.

Khan

Faisal

Rahman

. Low-temperature growth of ZnO nanoparticles: Photocatalyst and acetone sensor. Talanta 2011; 85: 943–949.

30.

Zhou

. Hydrothermal synthesis of ZnO nanorod arrays with the addition of polyethyleneimine. Mater Res Bull 2008; 43: 2113–2118.

31.

Kansal

Ali

Kapoor

. Synthesis of flower like zinc oxide nanostructure and its application as a photocatalyst. Sep Purif Technol 2011; 80: 125–130.

32.

Ashraf

Champagne

Perwuelz

. Photocatalytic solution discoloration and self-cleaning by polyester fabric functionalized with ZnO nanorods. J Ind Text. Epub ahead of print 13 January 2014. DOI: 10.1177/1528083713519662.

33.

Applerot

Lipovsky

Dror

. Enhanced antibacterial activity of nanocrystalline ZnO due to increased ROS-mediated cell injury. Adv Funct Mater 2009; 19: 842–852.

34.

Zhang

Jiang

Ding

. Mechanistic investigation into antibacterial behaviour of suspensions of ZnO nanoparticles against E. coli. J Nanopart Res 2010; 12: 1625–1636.

35.

Perelshtein

Applerot

Perkas

. Antibacterial properties of an in situ generated and simultaneously deposited nanocrystalline ZnO on fabrics. ACS Appl Mater Interfaces 2008; 1: 361–366.

36.

Tayel

El-Tras

Moussa

. Antibacterial action of zinc oxide nanoparticles against foodborne pathogens. J Food Saf 2011; 31: 211–218.

37.

Espitia

Soares

NDT

Coimbra

JID

. Zinc oxide nanoparticles: Synthesis, antimicrobial activity and food packaging applications. Food Bioprocess Technol 2012; 5: 1447–1464.

38.

Sonohara

Muramatsu

Ohshima

. Difference in surface properties between Escherichia coli and Staphylococcus aureus as revealed by electrophoretic mobility measurements. Biophys Chem 1995; 55: 273–277.

39.

Houdt

Michiels

. Role of bacterial cell surface structures in Escherichia coli biofilm formation. Res Microbiol 2005; 156: 626–633.

40.

Loo

C-Y

Young

Lee

W-H

. Superhydrophobic, nanotextured polyvinyl chloride films for delaying Pseudomonas aeruginosa attachment to intubation tubes and medical plastics. Acta Biomater 2012; 8: 1881–1890.

41.

Fadeeva

Truong

Stiesch

. Bacterial retention on superhydrophobic titanium surfaces fabricated by femtosecond laser ablation. Langmuir 2011; 27: 3012–3019.

Study the multi self-cleaning characteristics of ZnO nanorods functionalized polyester fabric

Abstract

Keywords

Introduction

Materials and processes

Growth of nanorods

Hydrophobization

Characterization

Nanorods

Physical self-cleaning (lotus effect)

Chemical self-cleaning

Biological self-cleaning (antibacterial activity)

Qualitative evaluation

Quantitative evaluation

Results and discussion

Physical self-cleaning (lotus effect)

Chemical self-cleaning

Biological self-cleaning (antibacterial activity)

Qualitative evaluation

Quantitative evaluation

Conclusion

Footnotes

Declaration of Conflicting Interests

Funding

References