*3.1. Characterization of Metal NPs Fabrics*

#### 3.1.1. SEM and EDX Analysis

The SEM images of both untreated cotton/lycra (95.5/5.5%) fabric of 15 pick/cm, cotton/lycra (90.8/9.2%) fabric of 19 pick/cm, and cotton (100%) fabric of 22 pick/cm and cotton/lycra (95.5/5.5%) fabric of 15 pick/cm, cotton/lycra (90.8/9.2%) fabric of 19 pick/cm, and cotton (100%) fabric of 22 pick/cm treated with SiO2 NPs are shown in Figure 4A–F, respectively. The results indicated that SiO2 NPs are well-distributed on the surface of the fabric, and the presence of SiO2 NPs on the fabric surfaces was confirmed from EDX data. The elemental EDX data collected for the fabrics under study were presented in Figure 5. The peaks were allocated at 1.9 keV with 1.69% weight and 0.85% atomic absorption of the analyzed spot in the cotton (100%) fabric of 22 pick/cm, and at 1.9 keV with 1.08% weight and 0.54% atomic absorption of the analyzed spot in the cotton/lycra (95.5/5.5%) fabric of 15 pick/cm, as well as at 1.9 keV with 1.61% weight and 0.81% atomic absorption of the analyzed spot in the cotton/lycra (90.8/9.2%) fabric of

19 pick/cm fiber surface—characteristic of Si. The presence of these peaks confirmed that the SiO2 NPs were entirely composed of SiO2. The C and O signals originated from the cellulose polymer. Furthermore, the appearance of SiO2 NPs on treated fabrics were also investigated by elemental mapping analysis, as illustrated in Figure 5E–G. It is apparent from the mapping images that silicon was distributed well on the surface confirming the uniform coating on cotton/lycra composites using SiO2 NPs as a sufficient layer.

**Figure 4.** SEM images of (**A**–**C**) untreated samples. SEM images of cotton/lycra (95.5/5.5%) fabric of 15 pick/cm (**D**), cotton/lycra (90.8/9.2%) fabric of 19 pick/cm (**E**), and cotton (100%) fabric of 22 pick/cm (**F**) treated with SiO2 NPs.

3.1.2. Antibacterial Activity of Blank and SiO2-NP/Cotton/Lycra Composite Fabrics

The antibacterial properties of treated and untreated samples are summarized in Table 3. Ciprofloxacin is used as a standard to correlate the lead samples from the series (4A–I). It is an antibiotic, causing the production of oxidative radicals and bacterial cell death [36]. The results indicated that the untreated samples were not affected, and there were no inhibition areas. On the other hand, the SiO2-NP/cotton/lycra composite fabrics exhibited excellent antibacterial activities against *S. aureus*, *Bacillus cereus*, *E. coli*, and *P. aeruginosa* compared with ciprofloxacin. This may be attributed to the fact that the mode of action of nanoparticles (NPs) is a direct interaction with the bacterial cell wall without the need to penetrate the cell. Most antibiotic resistance mechanisms can enhance the immunity of bacteria causing a lesser response to the antibacterial agent [37]. Samples E and G showed excellent activity against both Gram-positive and Gram-negative bacteria among all treated samples as compared to untreated samples. However, Sample (B) showed good activity against the four model bacteria. Samples (D) and (I) revealed good activity against both Gram-positive and Gram-negative bacteria in comparison to sample (A), which exhibited the lowest activity against Gram-negative (*P. aeruginosa*). Samples (F) and (H) showed good activity against the four model bacteria. However, sample (C) exhibited the lowest activity Gram-positive against (*Bacillus cereus*). In general, Samples (E) and (G) exhibited significantly high antibacterial activity compared to the all other samples in the series (4A–I) and with the standard. Additionally, the density of the pile 19 pick/cm is

better than the other densities, as shown in Figure 6. This relies on the fact that there is more trapped air inside this structure (19 pick/cm) than in other densities. This trapped air helps in extending the zone of inhibition around the sample to 19 pick/cm, rendering it more resistant against bacterial attack. SiO2 NPs' extraordinary antibacterial activity is attributed to their large surface area, which allows for better interaction with microbes [29].

**Figure 5.** EDX spectrum of (**A**) SEM image (**B**) cotton/lycra (95.5/5.5%) fabric of 15 pick/cm, (**C**) cotton/lycra (90.8/9.2%) fabric of 19 pick/cm, and (**D**) cotton (100%) fabric of 22 pick/cm treated with SiO2 NPs, and EDX mapping of cotton/lycra (90.8/9.2%) fabric of 19 pick/cm corresponding to (**E**) carbon, (**F**) oxygen, (**G**) silicon, and (**H**) overlap at 20 μm bar scale.

**Table 3.** Antibacterial Activity of the Blank and SiO2NP/Cotton/Lycra Composites. Cotton (100%) 15 pick/cm (**A**), cotton (100%) 19 pick/cm (**B**), Cotton (100%) 22 pick/cm (**C**), cotton/lycra (90.8/9.2%) 15 pick/cm (**D**), cotton/lycra (90.8/9.2%) 19 pick/cm (**E**), cotton/lycra (90.8/9.2%) 22 pick/cm (**F**), cotton/lycra (94.5/5.5%) 19 pick/cm (**G**), cotton/lycra (94.5/5.5%) 22 pick/cm (**H**), cotton/lycra (94.5/5.5%) 15 pick/cm (**I**).


**Figure 6.** Photograph of Antibacterial Activity of the Blank and SiO2 NP/Cotton/Lycra Composites.
