Functionalization of Cotton Fabric by Metal and Metal Oxides Nanoparticles for Antibacterial and UV-Radiation Protection Applications

Abstract

This study aimed to produce wash durable antibacterial, and UV-protective cotton fabrics by first modifying cotton fabric (Cot). The cotton fabrics were modified by covalently linking L- methionine (Am), used as the binder, via esterification and then functionalizing the modified cotton fabrics (AmCot) with silver (Ag), copper oxide (CuO), zinc oxide (ZnO), and titanium dioxide (TiO2) nanoparticles (NPs) and Ag-CuO, Ag-ZnO, Ag-TiO2 and CuO-TiO2 bimetallic nanocomposites (NCPs) to take advantage of their possible synergistic antibacterial and UV- protective properties.. Nitrate salts of Ag, Cu, and ΖnO and titanium isopropoxide (TIP) were reduced by NaBH4 in situ to form the NPs and NCPs onto the surface of AmCot. Fourier transform infrared (FTIR) and micro-Raman spectroscopy confirmed Am's chemical modification of the cotton fabrics. X-ray diffraction (XRD) revealed the crystallographic structure and the average crystalline size of Ag, CuO, TiO2, and ZnO NPs in AmCot+Ag, AmCot+CuO, AmCot+TiO2, and AmCot+ZnO which were 30.10, 18.13, 30.12 and 14.88 nm respectively. The average crystalline size of Ag NPs in AmCot+Ag-CuO, AmCot+Ag-ZnO, and AmCot+Ag-TiO2 were 30.34, 27.24, and 16.85 nm, respectively. The average crystalline size of CuO, ZnO, and TiO2 NPs in AmCot+Ag-CuO, AmCot+Ag-ZnO, and AmCot+Ag-TiO2 were 11.75, 9.16, and 22.50 nm, respectively. The AmCot+CuO-TiO2 yielded CuO and TiO2 NPs with average crystalline sizes of 18.09 and 32.05 nm, respectively. X-ray photoelectron spectroscopy (XPS) further supported the ATR-FTIR and XRD results. Scanning electron microscopy (SEM) showed the distribution of the NPs and NCPs on the fibers of functionalized amine-modified cotton, and energy-dispersive X-ray (EDX) mapping of sulfur (S), oxygen (O), and nitrogen (N) supported the esterification reaction between Am and Cot. The mapping further supported the evidence of Ag, CuO, ZnO, and TiO2 NPs on the respective functionalized AmCot. The ultraviolet protection factor (UPF) examined by UV-vis diffuse reflectance spectroscopy (UV-DRS) was 7.54, 27.76, 58.5, 26.5, and 16.97 for AmCot, AmCot+Ag, AmCot+CuO, AmCot+TiO2 and AmCot+ZnO, respectively. AmCot+Ag-CuO, AmCot+Ag- ZnO, AmCot+Ag-TiO2, and AmCot+CuO-TiO2 had UPF values of 36.21, 48.2, 28.5, and 26.5, respectively. The results showed that the functionalization of AmCot by the NPs and NCPs resulted in good UV protection. The NP and NCP functionalized AMCot antibacterial activity, water absorbability, and vapor permeability were also analyzed. AmCot did not show any antibacterial activity, whereas the NP and the NCP functionalized fabrics showed excellent antibacterial activity against Gram-negativee (E. coli and P. aeruginosa) and Gram-positive (S. aureus and S. pyogenes) bacteria species with excellent wash durability of up to 50 wash cycles. The largest zone of inhibition (ZOI) was reported for AmCot+Ag-ZnO and AmCot+Ag- CuO. For AmCot+Ag-ZnO against E. coli and S. aureus, the ZOI was 22.6± 0.6 and 21.7 ± 0.1 before washing and 21.1 ± 0.2 and 18.5 ± 0.2 after 50 washing cycles respectively. The ZOI of AmCot+Ag-CuO against E. coli and S. aureus was 22.1 ± 0.8 and 19.6 ± 0.8 before washing, and 20.3 ± 0.4 and 18.8 ± 0.7 after 50 washing cycles, respectively. Moreover, the change in water absorption and vapor permeability properties after functionalization was within 10%, which is acceptable regarding important properties and comfort.