**1. Introduction**

High-performance textiles have significant potential in marketing nano-based functional commodities, such as antibacterial and self-cleaning textiles [1–5]. These nano-based functional textiles can be accomplished by the immobilization of metal and/or metal oxide nanoparticles onto the fabric surface during the finishing process. The great prospects of metal nanoparticles can be effectively employed to provide multifunctional stimulation without deteriorating the exterior properties or negatively affecting the native features of the fibers [6]. Various studies were explored for the usage of Ag0, TiO2, and ZnO nanoparticles as agents for textile surface modification to provide smart fibers with a variety of distinctive properties, like ultraviolet blocking, self-cleaning, and antibacterial activity [7–9]. Different techniques were described recently to tie TiO2 nanoparticles into the fiber surface to present self-cleanable products [10]. The photocatalytic performance of TiO2 nanoparticles upon irradiation with a UN supply was described. The exposure of TiO2 nanoparticles to UV (λ < 388 nm) results in stimulating the electrons of the valence band into the other conduction one to generate holes (h+) and electrons (e<sup>−</sup>). Those reactive entities showed a major role in the commencement of a reduction-oxidation course [11]. TiO2 nanoparticles have been reported as a high-quality substance in photocatalysis under irradiation with an ultraviolet supply owing to its satisfactory optical properties, chemical/physical stability, non-toxicity, and cheapness [12,13]. Nonetheless, some weakness was linked to the use of TiO2 nanoparticles, such as an elevated band-gap (Eg = 3.2 eV). In addition, TiO2 nanoparticles can be excited only under irradiation with an ultraviolet

**Citation:** El-Hamshary, H.; El-Naggar, M.E.; Khattab, T.A.; El-Faham, A. Preparation of Multifunctional Plasma Cured Cellulose Fibers Coated with Photo-Induced Nanocomposite toward Self-Cleaning and Antibacterial Textiles. *Polymers* **2021**, *13*, 3664. https://doi.org/10.3390/ polym13213664

Academic Editors: Antonio Pizzi, Tarek M. Abou Elmaaty and Maria Rosaria Plutino

Received: 16 September 2021 Accepted: 19 October 2021 Published: 24 October 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

supply (λ < 388 nm) to release electrons to conduction band departing holes to the other valence one, limiting their photocatalytic activity under visible or sunlight. Furthermore, the high recombination rate between holes and electrons on TiO2 nanoparticles results in less effective photocatalysis [2–5].

Silver nanoparticles (AgNPs) have been applied as an antimicrobial agent onto a variety of textile substrates in the absence of UV light [14,15]. However, silver nanoparticles can simply influence the colorimetric properties of the treated textile surface by oxidation into the brownish AgO or by aggregation into bigger black microparticles. In addition, silver is a costly metal, and small amounts are ineffective for a variety of realistic products. In order to accomplish the advantageous effects from both Ag0 and TiO2 nanoparticles and reduce their weaknesses, Ag/TiO2 composites were developed by producing AgNPs onto TiO2 nanoparticles, employing a variety of methods to enhance the photocatalytic and antimicrobial properties. The deposition of AgNPs can significantly improve the light-induced catalytic activity of TiO2 nanoparticles. This could be ascribed to the ability of AgNPs to trap electrons at Schottky bar at each contact area of Ag/TiO2 [16–19]. This results in a decrease in the recombination effect between electrons and holes on the surface of TiO2 nanoparticles. Thus, separating the charge was stimulated and the transfer of electrons took place to result in a higher life-time of hole/electron pairs [20–22].

Viscose is a significant material for textiles owing to its high resistance to radiation and high stability to body fluids. The improvement of the antimicrobial properties of viscose has been critical for a variety of healthcare purposes. Therefore, various techniques have been reported to improve the antimicrobial properties of viscose fibers [23]. The weak binding of the colloidal nanoparticles to viscose fibers has been a substantial problem that can be overwhelmed by plasma treatment [24]. Plasma curing by etching was employed to activate the fibrous surfaces to induce the creation of polar groups, such as carbonyl, alcohol, carboxyl, and ether, facilitating better binding to nano-scaled particles [5,25]. Herein, we report the synthesis of TiO2 NPs and Ag/TiO2 nanocomposites as antibacterial and photocatalytic agents and their immobilization onto the surface of viscose fibers via a pad–dry–cure procedure to introduce multifunctional textiles. The morphologies and elemental compositions were evaluated by different analytical techniques. The performance of the Ag/TiO2-coated viscose fibers showed an improved efficiency compared with TiO2 coated viscose fibers.

#### **2. Experimental details**

#### *2.1. Materials*

Viscose fabrics were supplied from Spin and Weaving Misr El-Mahalla Co. (El-Mahalla City, Egypt) Silver(I) nitrate, titanium isopropoxide (TTIP; 97%), acetic acid (65%), silver nitrate (≥99.0%), acetic acid (CH3COOH; 96%), nitric acid (HNO3; 65%), sodium carbonate (Na2CO3), and oxalic acid were obtained from Aldrich (Cairo, Egypt). TiO2 nanoparticles were synthesized according to the previously reported low temperature sol-gel method [18].
