2.2.2. UV Protective Textiles

Currently, because of the depletion of the ozone-layer in the atmosphere, ultra-violet radiation is entering the surface of the earth, which is noted to have a harmful effect on both clothes and on human skin. The increased exposure to ultraviolet radiation enhances the probabilities of having several toxic diseases such as skin cancer. Consequently, protection against ultraviolet radiation has turned out to be a necessary property for clothing and textiles (Dhineshbabu et al., 2019, [100]). Certain metal oxide nanomaterials like magnetite nanoparticles, titanium dioxide nanoparticles, zinc oxide nanoparticles, and nano-ceria successfully block ultraviolet radiations, guaranteeing a sustainable as well as better performance relative to the organic ultraviolet absorbers (Sedighi et al., 2018, [101]), (Kathirvelu et al., 2009, [102]), (Becheri et al., 2008, [103]), (Fouda et al., 2018, [104]), (Tsuzuki et al., 2010, [105]), (Cakir et al., 2012, [106]), (Farouk et al., 2010, [107]), (Radetic et al., 2013, [108]), (Attia et al., 2017, [109]), (Attia et al., 2017, [110]). In recent times, the aforementioned nano-inorganic-ultraviolet additives are commonly preferred instead of the organic ones due to their exceptional properties such as harmlessness and chemical stability under UV radiation as well as higher temperature exposure. Properties such as particle size, phase composition, surface properties, crystallinity, and crystal structure

are different factors that influence the ultraviolet blocking property of nano-sized ultraviolet additives (Lee, 2009, [111]), (Dhineshbabu et al., 2018, [112]).

In the latest research work by (Noorian et al., 2020, [113]), zinc oxide nanoparticles were in situ prepared on the modified cotton fabric for developing the multifunctional fabrics. This zinc oxide-4-aminobenzoic acid ligand oxidized cotton fabrics demonstrated superior ultraviolet-protection and substantial antibacterial effectiveness subsequent to 100 abrasion cycles and 20 washing cycles, and hence this could be used in innovative protective textiles. (Dhineshbabu et al., 2019 [100]), designed ultraviolet-blocking as well as fire resistant cotton fabric by coating polyurethane-based MnO2-FeTiO3 nanocomposites. The MnO2-FeTiO3 coated cotton fabrics showed a durable ultra-violet blocking capability and presented better fire resistant properties evaluated utilizing the limited oxygen index. Additionally, the coated cotton fabric maintained its properties in spite of 10 water-laundering cycles thus contributing smart, sustainable, and durable fabric for protective clothing utilization.

### 2.2.3. Antibacterial and Antimicrobial Textiles

Textile fabrics, particularly ones made up of cellulose fibers like lyocell, viscose, linen, and cotton have a greater tendency to be harmed by microorganisms, for example, protozoa, algae, fungi, virus, and bacteria, in the course of their service life (Ahmed et al., 2017, [114]), (Bu et al., 2019, [115]), (Hebeish et al., 2011, [116]), (Xue et al., 2012, [117]), (Zhang et al., 2009, [118]), (Budama et al., 2013, [119]), (Liu et al., 2014, [120]), (Perelshtein et al., 2008, [121]), (Zhang et al., 2014, [122]), (Attia et al., 2017, [123]). Recently, because of the enhancement in awareness about hygiene and health, the antimicrobial feature has developed into an essential prerequisite for all clothes, medial textiles, and household products. In recent times, various metal oxide (like copper oxide, zinc oxide, and titanium dioxide) and metal (such as silica, titanium, gold, zinc, copper, and silver) nanoparticles are receiving considerable research attention as prospective antimicrobial agents. Nanomaterials with a higher surface area-to-volume ratio contribute a superior antimicrobial characteristic relative to traditional antimicrobial agents. Figure 5 demonstrates different mechanisms of antimicrobial activity of metal-oxide and metal nanoparticles. Table 2 presents the textiles modified using different nanoparticles for antimicrobial effects. The utilization of nanocomposites of antimicrobial agents in textiles showed a positive synergistic antimicrobial property relative to a single nanomaterial. Economical and ecofriendly antibacterial properties of cotton fibers loaded with silver nanoparticles prepared from natural Chinese Holly plant extracts were studied by (Ullah N et al., 2014 [124]). The generation of silver nanoparticles from Chinese Holly plant extracts were noted by UV–vis spectrophotometer and noted to be less than 100nm in size, as confirmed by electron microscopy analysis. The antimicrobial properties of these cotton fibers incorporated with silver nanoparticles were assessed against gram-negative *Escherichia coli* bacteria. The test results confirmed superior antibacterial properties by incorporating 1.5% to 4.5% of Chinese Holly leave extracts. The cotton fibers also illustrated fine antibacterial efficacy after numerous washings, making it appropriate for medical usages with an ease. The process for the preparation of multifunctional polyester fabric coated by graphene/silver nanoparticles is shown in Figure 6 (Ouadil et al., 2019, [125]).

**Figure 5.** Different mechanisms of antimicrobial activity of metal-oxide and metal nanoparticles. Reproduced from (Dizaj et al., 2014, [126]).

**Table 2.** Textiles modified using different nanoparticles for antimicrobial effects.

**Figure 6.** Process for the preparation of multifunctional polyester fabric coated by graphene/silver nanoparticles. Reproduced from (Ouadil et al., 2019, [125]).

### 2.2.4. Water and Oil-Repellent Textiles

Water and oil repellency has turned out to be a requirement for entire clothes and this has developed into one of the main targets for textile manufacturers and scientists for years (Asif et al., 2018, [132]). Presently, advanced nanocoatings or nanofinishings are satisfying a majority of similar market necessities with oil and water repellent or superhydrophobic textiles. Information on nanotechnology and textile mutually assist to progress an advanced conception of 'self-cleaning textiles', in which the textiles possess an ability to be cleaned with no laundry treatment (Katiyar et al., 2020, [133]), (Montazer et al., 2020, [134]). There exist two diverse methods prevalently utilized for the advancement of self-cleaning textiles, which are: (i) Photocatalytic activity and (ii) the lotus effect.

The lotus effect is produced by the surface modification of the textile fabric by nanocoating or nanofinishing, usually by utilizing surface modified carbon nanotubes, zinc oxide nanorods, nano-zirconia, or nano-silica (Das et al., 2015, [135]), (Joshi et al., 2012, [136]). In the case of the photo-catalytic activity method, zinc oxide or titanium dioxide nanoparticle-based coating or finish formulations are utilized to develop self-cleaning textiles. Titanium dioxide's photocatalytic activity is dependent on the crystal framework, and the anatase grade titanium dioxide demonstrated superior photo-catalytic activity against contaminants and colorants. (Wang et al., 2010 [137]) demonstrated that gold/titanium dioxide/silicon dioxide nanosol is a superior photocatalyst relative to titanium dioxide nanosol, displaying an improved self-cleaning property also in the existence of visible light. There are also several other works that demonstrate the cotton fabric's photocatalytic self-cleaning property by treatment with titanium dioxide nanowire and titanium dioxide nanowire doped Ag-PVP (Hebeish et al., 2013, [138]), graphene/TiO2 nanocomposites (Karimi et al., 2014, [139]), etc. The work by (Landi et al., 2019 [140]) reported the preparation of photocatalytic nanocomposite materials based on nitrogen-doped nano-titanium dioxide, silicon dioxide, and various percentages of HY zeolite. It was noted that the fabrics coated with the photocatalysts, demonstrated similar RhB decolorization (almost 95%) after 5 h. Fluorine-free superhydrophobic cotton fabrics, having the self-cleaning photocatalytic ability, were fabricated by the combination of superhydrophobic SiO2 and photoactive titanium dioxide (Xu et al., 2015, [141]).
