## 3 Results  
In this study, we have synthesized GrNs via two different methods, namely, CVD and PECVD. The antibacterial effect of CVD Gr nanosheets transferred onto G substrates has been examined according to the number of layers (monolayer/1-2 layers/2-3 layers). The effects of PECVD Gr nanowalls synthesized onto G substrates at 100, 150, and 200 W RF powers have been also analyzed. Furthermore, the antibacterial effect of CVD monolayer graphene nanosheet synthesized onto Ni substrate has been studied. Gram-negative _E. coli_ and Gram-positive _S. aureus_ were used to examine their response to the GrNs synthesized onto G and Ni substrates. Cell viability (inverse to cell death) was monitored to evaluate the antibacterial activity of coated and uncoated samples. The characterization process of graphene nanosheets synthesized using the CVD technique was performed by Raman spectroscopy. Raman analyses of monolayer (a), 1-2 layers (b), 2-3 layers (c) Gr nanosheets transferred onto G substrates using the CVD technique are presented in Figure 2a-c respectively. As a result of Raman analysis, it was determined that the Gr nanosheets transferred onto G substrate by the CVD method had a characteristic 2D peak position at 2693 cm\({}^{-1}\) and a G peak at 1590 cm\({}^{-1}\). The number of layers of graphene nanosheets synthesized using the CVD technique was determined by calculating their \(\rm I_{2D}/I_{G}\) ratio. These ratios were calculated as 3.6, 1.98, 0.78, and 0.59, respectively, and thus, it was determined that the thin films were monolayer, 1-2-layer, and 2-3-layers, respectively. These rates determined for monolayer graphene synthesis in our study are well compatible with the literature and our previous studies [19; 20; 21; 22]. The \(\rm I_{D}\) peak, which is frequently detected in Raman analysis of carbon-based structures and shows its presence at about 1350 cm\({}^{-1}\), was not encountered in these films and confirmed the monolayer graphene structure. TEM analysis was carried out to see the negative effects of the transfer of CVD-grown graphene in Figure 3. TEM image shows that the CVD graph perfectly covered the G used as a substrate, that is, there was no wrinkle, and it was also monolayer. The characterization process of graphene nanowalls synthesized using the CVD technique was also performed by Raman spectroscopy. Raman analysis showed that the Gr nanowalls synthesized on the G substrates with 100, 150, and 200 W RF power by PECVD method had D peaks at approximately 1347 cm\({}^{-1}\), G at 1590 cm\({}^{-1}\), and 2D peaks at 2690 cm\({}^{-1}\)[42; 43]. The D peaks were quite severe compared to the other peaks, and similarly, the intensity of the 2D peak was quite weak compared to the others. Representation of the D peak was interpreted as defective of the structure and these defects were explained by the presence of a plasma [43]. Similarly, the structural properties of Gr nanowalls synthesized on G substrates at various RF power values (100, 150, and 200 W) using the PECVD technique were examined by Raman analysis and are presented in Figure 4a-c, respectively. Digital photographs of the CVD and PECVD grown graphene samples on G and Ni substrates are given in Figure 5. SEM analysis was carried out for the graphene nanowalls. SEM images at different magnifications for the graphene nanowalls produced at 600 \({}^{\circ}\)C were taken and are shown in Figure 6. From SEM images, the homogeneous  
Figure 2: Raman analyses of (**a**) monolayer, (**b**) 1-2 layers, and (**c**) 2-3 layers Gr nanosheets, which were transferred onto G substrates using the CVD technique. Figure 7 exhibits the cell viability (%) of _E. coli_ and Figure 8 shows the cell viability (%) of _S. aureus_. The antibacterial activities of the samples against _E. coli_ and _S. aureus_ are shown in Figures 9 and 10, respectively. It is observed that GrNs on the substrates show different antibacterial activities.