key: cord-0993411-74yyg5je authors: Alagarasan, Devarajan; Harikrishnan, A.; Surendiran, M.; Indira, Karuppusamy; Khalifa, Amany Salah; Elesawy, Basem H. title: Synthesis and characterization of CuO nanoparticles and evaluation of their bactericidal and fungicidal activities in cotton fabrics date: 2021-09-12 journal: Appl Nanosci DOI: 10.1007/s13204-021-02054-5 sha: 6ca5462162eb0355488a790985e2921db65469be doc_id: 993411 cord_uid: 74yyg5je Textiles functionalized with copper oxide nanoparticles (CuO NPs) have become a favourable material to inhibit the spread of diseases due to their anti-microbial properties. In the present work, a successful procedure for in situ growth of CuO NPs in textiles was developed. Results showed that the combination of in situ synthesis and pad–dry–cure method promoting a uniform and dense adsorption of nanoparticles on the surface of the fabrics. The CuO NP-coated fabrics was characterized using XRD, SEM, EDX, TEM, and FTIR techniques. The CuO NP-coated cotton fabrics showed better anti-bacterial activity against various bacteria’s namely Staphylococcus aureus, Escherichia coli, Pseudomonas fluorescens and Bacillus subtilis. Besides, it also showed better antifungal activity against Candida albicans. The CuO NPs impregnated cotton fabrics exhibit a bacterial reduction of more than 90%, which is sustainable even after 20 washing cycles. Therefore, the CuO NP-coated fabrics has great potential to be used as coatings for medical, cosmetic or sports fabrics. Infections are a main contributor to the global disease. High mortality rates are associated with the diseases such as lower respiratory infections, diarrhoea, tuberculosis, human immune deficiency virus infection and malaria (Huma et al. 2018) . Infectious diseases are caused by pathogenic microorganisms such as bacteria, viruses, parasites, and fungi (Rao et al. 2020) . Coronavirus disease 2019 (COVID-19) is the transparent example which causes severe acute respiratory syndrome. In addition, other organs also affected and it is transmitted through one person to another directly or indirectly causing high mortality and morbidity rates (Chauhan et al. 2020) . Healthcare-Associated Infections (HAIs) like COVID-19 can be spread through the same ways by hands or contaminated surfaces and are found in hospital surroundings. HAIs are developed by stayed patients in hospital (Mousavi et al. 2021) . Moreover, HAIs are not only severe community health problem but also associated with many issues such as medicinal costs, psychological worries, quality of life decrease, side effects and mortality (Harun et al. 2020) . We can protect human community by taking precautions such as sanitation, hygiene and proper use of personal protective equipment (PPE). The proper use of gloves and masks, hats, isolation clothing, protective clothing, and other PPEs is a significant kit to protect health care workers from HAIs. Consequently, protective clothing, like health-care workers uniforms should functionalized with antimicrobial finishing agents, which could be an alternate to decrease and protect COVID-19 and HAIs (Balasubramaniam et al. 2021) . Nanotechnology techniques can alter textile fabric at the molecular level, thus creating advanced materials that can be several times more effective than the untreated fabric. Nanotechnology covers a good range of efficient tools and techniques to protect desirable fabric characteristics, most of these focusing on modifications of the fabric surface using nanoparticles. Nanoparticles can help to enhance the physical properties of conventional textiles in areas such as antimicrobial properties, water repellence, soil resistance, antistatic, anti-infrared and flame-retardant properties. Nanoparticles have more surface-to-volume ratio, so easily adsorb the microorganisms and dormant them. Besides, nanoparticles, due to their large surface-to-volume ratio offer high number of active sites for antibacterial reactions to take place (Khan et al. 2020) . The size of biological molecules and structures are almost similar to the nanoparticles. This makes them an exciting applicant in both in vivo and in vitro biomedical research (Nienhaus et al. 2020) . When metal nanoparticles are coated on to material surfaces with antimicrobial and antiviral properties, they would be used for huge applications in various areas such as synthetic textiles, water treatment, biomedical and surgical devices, food processing and packaging (Sadique et al. 2021) . In this connection, silver nanoparticle is broadly investigated with excellent antibacterial activity. However, its usage is limited due to the high cost. Whereas, copper oxide nanoparticles (CuO Nps) exhibiting good antibacterial efficiency and also cost-effective material, so it is believed to be a more suitable choice (Sathiyavimal et al. 2020 ). Among various types of materials such as silver, copper, ZnO and TiO 2 nanoparticles, there was very limited investigation using CuO Nps for antibacterial, antifungal and superhydrophobic textiles is available (Tian et al. 2018; Bezza et al. 2020; Lalabadi et al. 2019) . While offering the antifungal and antiviral properties, CuO Nps will not create any side effects and skin sensitization. In particular, CuO is a part of II-VI group elemental and it has good semiconducting property owing to its direct band gap (~ 1.74 eV at room temperature) and p-type conductivity. Besides, it has a monoclinic crystal structure. At the nanoscale, CuO exhibits remarkable applications in catalysis, high-temperature superconductors, solar cells, chemical and gas sensors, and lithium ion batteries among others (Fathima et al. 2018) . The CuO Nps inhibit pathogenic bacteria's such as Staphylococcus aureus, Klebsiella pneumoniae, etc. which is responsible for delayed wound healing in humans. Copper ions have also been used as antiviral agents to treat herpes simplex, influenza, and hepatitis A viruses. Furthermore, when compared to silver and gold nanoparticles, CuO Nps demonstrate additional advantages of being inexpensive and chemically stable. These copper oxide impregnated fibers possess broad spectrum biocidal properties and they kill dust mites. Some of the works related to CuO antibacterial studies were investigated recently. El-Nahhal et al. (2012) reported CuO Nps coating on fabrics by ultrasonication technique and evaluate its antibacterial properties against Escherichia coli and Staphylococcus aureus bacteria. Similarly, Perelshtein et al. (2009) had synthesized CuO Nps and subsequently deposited on the surface of cotton fabrics using ultrasound irradiation showing the distribution of CuO nanocrystals (around 15 nm in size) on the fabric surface. The antibacterial activities of the CuO fabric composite were tested against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) cultures. The performance of fabrics coated with 1.4 wt% CuO Nps was investigated. Román et al. (2020) reported the growth of CuO Nps onto cotton textiles by exhaust dyeing method. The results showed that the functionalised textiles with CuO Nps had percentages of bacterial reduction against Escherichia coli (ATCC25922) between 89.7 and 99.7% and showed an improvement in the UPF of cotton from approximately 7-32. However, the detailed anti-microbial mechanism of action for these materials is not yet fully understood. So far, many techniques such as Spray pyrolysis, ultrasonic coating, layer-by-layer deposition, sono-chemical coating and dip coating are used to impregnate nanoparticles onto cotton fabrics. The objective of the findings includes developing functional textiles which is simple, inexpensive, eco-friendly, and can enhance the durability of the superhydrophobic antibacterial and antifungal fabrics. This facile synthesis approach overcomes the limitations of the previous findings and displays promising potential for industrial fabrication of textile materials imparting multiple functionalities. To realize this aim, CuO Nps was coated over the cotton fabrics, and characterized; then antibacterial, antifungal and hydrophobic properties were investigated. In a typical synthesis method, 2.56 g of cupric sulphate (from M/s. Sigma Alrich) and 0.2 g of starch (from M/s. Sigma Alrich) were dissolved in 10 ml of distilled water and heated at 70 °C for 10 min to combustion reaction takes place. The resultant product was washed twice with distilled water to remove excess soluble starch and the obtained precipitate was dried in hot air oven at 120 °C for 2 h. Furthermore, the dried samples were calcined at 600 °C for 2 h to obtain very fine black-colored CuO Nps. The CuO Nps were coated on cotton fabrics using "pad-dry-cure" method. A dispersion containing CuO Nps (2%) and sodium alginate binder (1%) in 200 mL of distilled water was prepared. A fine medium 100% cotton woven fabric cut to the size of 30 × 30 cm and immersed in the solution for 30 min in laundero-meter at 50 °C under constant mixing. Then, it was passed through a padding mantle with a pressure of 15 kgf/cm 2 to remove excess solution. The material-to-liquor ratio was 1:20 and 100% wet pick-up was maintained for all the samples. After padding, the fabric was air-dried at 100 °C for 3 min and then cured for 5 min at 140 °C (Coyle et al. 2007 ). The X-ray diffraction analysis were carried out on a X-ray diffract meter (Rigaku Ultima IV) with Cu Kα radiation source (λ = 1.54016 Å) at 60 kV over the range of 2θ from 20° to 80° with 0.02 step size. The surface morphology of all the samples and the elemental analysis of pristine CuO NPs were examined by SEM (Hitachi S-3400 N) with energy dispersive X-ray (EDX) attachment setup (make -Thermo scientific). The surface morphology of CuO Np-coated cotton fabrics were carried out using FE-SEM (ZEISS). The size and morphology of CuO Nps were studied using TEM (H-9500.300 kV). The formation of CuO Nps was confirmed through Fourier-transform infrared spectroscopy (Thermo Nicolet Model: 6700). Thermo gravimetric characteristics of CuO NPs, uncoated and CuO Np-coated fabrics were investigated to find the crystallinity temperature and thermal stability using a thermal system (TGA instruments, model Q600-SDT). The Fig. 1a -c shows the XRD pattern of uncoated cotton fabrics, CuO Nps, and CuO Nps incorporated fabrics, respectively. The broad and intense peaks at 2θ = 22.83° and 25.82° in the uncoated cotton fabric indicating the presence of cellulose fibers. The XRD pattern of the as prepared CuO Nps (Fig. 1b) exhibiting sharp diffraction peaks indicating that the nanoparticles were crystalline in nature, and the diffraction peaks matched well with the monoclinic phase of CuO. The diffraction pattern and interplanar spacing closely matched those in the standard diffraction pattern of CuO (JCPDS-98-004-8581) (Hatamie et al. 2015) . The peaks at 2θ = 32. 35, 35.53, 38.80, 48.82, 53.92, 58.30, 61.66, 66.31, 68.13, 72 .77 and 75.14 degrees were assigned to the (110), (002), (111), (20-2), (020), (202), (11-3), (310), (22-1), (311) and (004) reflection lines of monoclinic CuO Nps, respectively. No impurities were detected in the XRD pattern suggesting that the quality of the obtained CuO was high. The crystallite size (L) was calculated using the following Eq. 1 (Indira et al. 2017): where L is crystallite size, K is the Scherer constant, λ is the X-ray wavelength, β is the peak full width of half maximum, and θ the Bragg diffraction angle. The average crystallite size of the CuO Nps was found to be 18 nm. The peaks at 2θ = 35.62° and 38.77° indicate the presence of CuO nanocrystals on fabric surface. The diffraction peaks observed at 35.62°, 38.67°, 48.92°, 58.63°, 61.38° and 66.97° in Fig. 1c are correlated with the formation of monoclinic phase of CuO Nps on cotton fabrics. The observed XRD peaks confirm the existence of CuO Nps after coating on the cotton fabrics along with cellulose. Figure 2a -d shows the SEM and EDX of the samples. From Fig. 2a , it is clear that the CuO NPs distributed around 500 nm. The SEM image of the control fabrics (Fig. 2b) shows grooves and fibrilis on the surface of the fabrics. Whereas, in the case of CuO Nps, presence of dense and compact agglomerates (Fig. 2c) are seen on fabric surface. The chemical composition of CuO Nps studied by EDX measurements showing (Fig. 2d ) the presence of Cu and O with the respective atomic weight percentage of 61.14 (1) L = K ∕ cos , and 38.86. The compositional architecture of respective elements was observed using X-ray mapping method. Here, the X-rays emitted from k-shell of the elemental components of synthesized CuO were mapped using EDX-X-ray profile mapping setup. The elemental composition of Copper (grey) and Oxygen (yellow) in the CuO Nps were quantified from the obtained mapping profile and the results are shown in Fig. 3 . The comparative analysis of Cu and O distribution in the region under mapping further confirmed the presence of uniform distribution of copper and oxygen in the synthesized CuO Nps. Figure 4 illustrates the size and morphology and size distribution of CuO Nps measured by TEM analysis. The surface morphology and size of synthesized CuO Nps shows spherical shape morphology with 10-100 nm particle size distribution. Figure 5 shows the FTIR spectrum of CuO Nps. The absorption peaks at 3521 cm −1 mainly ascribed to OH − groups and peak at 1623 cm −1 is attributed to C-O groups. The three infrared absorption peaks at 470, 628 and 784 cm −1 reveal the formation of vibration modes of CuO nanostructures (Seyedin et al. 2015) . Figure 6 shows thermo gravimetric analysis of CuO Nps which was used to understand the crystallization process and to find the crystallization temperature. The first weight loss occurs at 100 °C due to the vaporization of absorbed water. Second weight loss occurs at 400 °C due to removal of organic Moieties. The mass of the CuO Nps at 400-800 °C showed that this residue of CuO Nps without any impurities could remain intact even at high temperatures. Thereafter, no significant weight loss was observed at higher temperatures supporting the formation of monoclinic crystalline CuO at 700 °C (Joshi and Bhattacharyya 2011) . Figure 7 shows the antibacterial activity of uncoated and CuO Np-coated cotton fabrics against S.aureus, E.coli, P.fluorescens and B.subtilis, which showed that the inhibition zone (formed on agar medium) of each specimen is used to determine the antibacterial activity of fabrics before and after washing. It is noted that uncoated fabrics does not show any antibacterial activity against these pathogens due to the high hydrophobicity of cellulose. The inhibition zones are formed on the inoculated surface, which in turn prevent bacterial growth under and around the hydrophobised fabrics (Sawhney et al. 2008; Cai et al. 2013; Giannossa et al. 2013) . The antibacterial activity is observed for the CuO Np-coated fabrics with a zone of inhibition of 19 mm, 16 mm, 15 mm and 17 mm against S. aureus, E. coli, P. fluorescens and B. subtilis, respectively. A large inhibition zone with a diameter of 19 mm is observed against S. aureus when compare to other pathogens. These results show that the CuO Nps incorporated cotton surface leads to enhanced antibacterial activity against various bacteria. Generally, nanoparticles release ions and in turn interact with microbes, which easily oxidize and die immediately. Similarly, the surfaces of the nanoparticle-coated fabric interact with bacterial cell walls, which results in the reduction of bacterial growth (Sathiyavimal et al. 2021) . A quantitative analysis of the bacterial counts of uncoated and CuO Np-coated fabrics after 24 h contact time is shown in Table 1 . The reduction percentage is calculated by AATCC 100 and tabulated for four pathogens after 24 h incubation. The uncoated fabrics does not show any antibacterial activity during the inhibition time, nevertheless CuO Np-coated fabrics shows greater bacterial reduction percentage as compared to uncoated fabrics. Before washing the CuO Np-coated fabric shows 96%, 94%, 92%, and 89% reduction against S. aureus, E. coli, P. fluorescens and B. subtilis, respectively (Padbury et al. 2015; Patra and Gouda 2013) . The reduction in the percentage of CuO Np-coated fabric after 5, 10, 15, and 20 washes were reduced, which is clearly shown in Table 1 . Figure 8 shows graphical representation of CuO Npcoated fabrics zone of inhibition against various pathogens. Before washing, the CuO Np-coated fabric shows 19 mm, 16 mm, 15 mm and 17 mm zone of inhibition against S. aureus, E. coli, P. fluorescens and B. subtilis, respectively. After 5, 10, 15, 20 washes the zone of inhibition against pathogens found to be reduced, because the intensity of CuO Nps gradually decreased on cotton fabric surface. Antifungal activity of uncoated and CuO-coated cotton fabrics were considered against one fungal strain namely Candida albicans by agar diffusion method. Only very few studies were known in the literature on the antifungal activity of CuO Nps. Figure 9 shows antifungal activity of uncoated and CuO-coated fabrics against Candida albicans. Control fabrics did not showing any activity and the CuO-coated fabrics shown better zone of inhibition (Vigneshwaran et al. 2010; Brzezinski et al. 2011) . Before washing, zone of inhibition of CuO-coated fabrics was found to be 14 mm. After 5, 10, 15, and 20 washes, the zone of inhibition was found to be 11 mm, 9 mm, 5 mm, and 2 mm, respectively (shown in Fig. 10 ). After washing, the antifungal activity of the fabric is gradually decreased. Figure 11 shows the optical microscopy analysis of control and CuO Np-coated fabrics after antifungal The variation of the water contact angles (WCA) of the uncoated fabrics and CuO-coated fabrics demonstrated in Fig. 12 . It can be seen that the uncoated fabric is instantly wetted on the fabric surface by the water droplet due to the high hydrophilic nature, which is attributed to the hydroxyl group and frequent holes in its weaves. Figure 13 shows the water contact angle (WCA) values with image. The uncoated fabric surface presents hydrophilicity with the WCA of 60°, which after coated with CuO Nps is converted to hydrophobic surface with WCA of 110°. After washing, the WCA of coated fabric surface has decreased (Onar et al. 2011; Seil and Webster 2012; Yetisen et al. 2016 ). In the present effort, the CuO Nps were prepared by gelcombustion method. The CuO Nps were successfully incorporated onto the cotton fabrics using pad-dry-cure method. The presence of CuO Nps on the cotton fabrics was proved by XRD, SEM, and EDS analysis. The TGA investigation results showed that, the CuO Np-coated cotton fabrics possess improved thermal stability when compared to the uncoated cotton fabrics. Moreover, CuO Np-coated fabrics showed hydrophobic activity. The antibacterial activity of the CuO Np-coated fabrics shows superior toxicity towards Gram-positive and Gram-negative bacteria. The antifungal activity of CuO Np-coated fabrics shows better toxicity against Candida albicans. The results showed that the CuO Np-coated cotton fabrics could be used as multi-functional materials for healthcare, food, military, and medical applications. 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The authors would like to thank UGC, Govt of India for the financial assistance. Analytical instrumentation facility provided by Central Instrumentation Facility, Centre for Nanoscience and Technology, Pondicherry University, India are thankfully acknowledged. This work was supported by Taif University Researchers Supporting Project number (TURSP-2020/127) Taif University, Taif, Saudi Arabia. . The authors declare that there is no conflict of interest in this paper.