## 3 Results and Discussion
### Antibacterial Performance  
To observe their effectiveness as antibacterial agents, GO/Zn (OH)\({}_{\rm x}\) nanocomposite with various amounts of Zn (OH)\({}_{\rm x}\) coatings was evaluated against both Gram-positive _B. megaterium_ and Gram-negative _E. coli_ bacteria. The disk diffusion method was used to observe the inhibition zone of the GO/Zn (OH)\({}_{\rm x}\) nanocomposite with different concentrations of Zn(OH)\({}_{\rm x}\). In this method, the samples were placed on agar plates with the bacteria and incubated for 48 h at 37 \({}^{\circ}\)C. The size of the inhibition zone was measured using the ImageJ software (version 1.53t). The resulting inhibition zone growth can be observed in Figure 10A-D and Figure 11A-D, respectively. The results in Figures 10 and 11 show clearly that the GO/Zn (OH)\({}_{\rm x}\) composites inhibited the growth against both _E. coli_ and _B. megaterium_ bacteria. The inhibition zone growth capacity after 48 h of the GO/Zn (OH)\({}_{\rm x}\) nanocomposite samples with 0, 25, 50, and 75 wt. % of Zn (OH)\({}_{\rm x}\) against Gram-positive, _B. megaterium_ bacteria (Figure 10) was 43.67, 47.07, 69.79, and 77.01%, respectively. The antibacterial activity results (Figure 11) of GO/Zn (OH)\({}_{\rm x}\) nanocomposites against Gram-negative _E. coli_ showed inhibition zone efficiency of 19.07, 33.44, 53, and 57.47% for 0, 25, 50, and 75 wt. % Zn (OH)\({}_{\rm x}\) coating concentrations, respectively. Figure 9: Zn 2P\({}_{3/2}\) and Zn2P\({}_{1/2}\) XPS spectra for the GO/Zn (OH)\({}_{\rm x}\) samples with different Zn (OH)\({}_{\rm x}\) concentrations: of (**A**) (25 wt.%), (**B**) (50 wt.%), and (**C**) (75 wt.%). The antibacterial efficiency of GO has been reported previously to show good antibacterial activity against _E. coli_[17]. Our antibacterial activity results shown in Figures 10 and 11 are similar to those reported on Al/GO composite against Gram-negative strain _E. coli_[73] and Ag/CuO/GO nanocomposites against Gram-negative strain _E. coli_ and Gram-positive _S. aureus_[74]. In fact, the results shown in Figures 11 and 12 confirm that the Zn (OH)\({}_{\mathrm{x}}\) coating improved the antibacterial activity of GO against _B. megaterium_ and _E. coli_ bacteria. The relationship between the coating concentration of Zn(OH)\({}_{\mathrm{x}}\) on GO and the growth of inhibition was positive. Also, the zone of inhibition was significantly larger in the Gram-positive bacteria for the GO/Zn (OH)\({}_{\mathrm{x}}\) composite. This could be attributed to the fact that Zn (OH)\({}_{\mathrm{x}}\) performs exceptionally well against Gram-positive bacteria [75; 76; 77; 78; 79; 80]. Table 3 illustrates the inhibition zone diameter with the standard deviation of the GO/Zn (OH)x composite samples with different concentrations of Zn (OH)x NPs. Table 3 clearly shows the substantial positive progression from the initial zone of inhibition of the non-coated GO to GO with 75% Zn (OH)\({}_{\mathrm{x}}\) coating. The initial zone of inhibition for the non-coated GO was 1.93 cm and increased to 4.82 cm against the Gram-positive _B. megaterium_. There was also an increase in the inhibition zone diameter for _E. coli_ from 1.34 cm to 2.41 cm. The results shown in Figures 10-12 confirm that GO/Zn (OH)\({}_{\mathrm{x}}\) composites have good and improved antibacterial properties compared to the pristine GO. In fact, the results reported in this study on the antibacterial properties of GO and GO/Zn(OH)x nanocomposites are  
Figure 10: Inhibition zone against _B. megaterium_ of GO/Zn (OH)x nanocomposites with different coating amounts of Zn (OH)\({}_{\mathrm{x}}\): (**A**) 0%, (**B**) 25%, (**C**) 50%, and (**D**) 75 wt. %. in agreement with those reported on different/similar systems [81; 82]. The addition of zinc dehydrates to GO improved its antibacterial properties (Figure 12).