## 3 Results and Discussion
### Characterization of the Developed Electrospun Membranes
#### 3.1.2 EDS, ATR-FTIR, GSDR and TGA Analyses  
To further confirm the synthesis of Ag NPs as well as the impregnation of Ag, TiO\({}_{2}\) and MgO NPs onto PCL electrospun membranes, other techniques, such as EDS, ATR-FTIR and GSDR were performed. Moreover, TGA was also used to quantify the amount of NPs present in each sample. The results are shown in Figure 4.  
Figure 3: FESEM images of (**a**) PCL; (**b**) PCL/Ag NPs; (**c**) PCL/TiO\({}_{2}\) NPs and (**d**) PCL/MgO NPs electrospun fibers and their respective diameter distribution histograms. FESEM images were obtained using different magnifications: 100, 20, 10 and 2 \(\upmu\)m.  
The successful impregnation of the NPs onto the surface of PCL membranes was further confirmed by EDS analysis. Figure 4e shows the presence of peaks related to carbon and oxygen, which are the constituent elements of PCL polymer. An additional strong peak appeared at 2.98 keV, which corresponds to silver, confirming the successfully synthesis and impregnation of Ag NPs on PCL fibers' surface [26; 28]. The EDS spectrum from Figure 4b demonstrates the characteristic peaks of titanium element at 4.51 and 4.94 keV, which together with the presence of oxygen element confirms the presence of TiO\({}_{2}\) NPs [29; 30]. Finally, the presence of oxygen and magnesium was detected in EDS profile of PCL/MgO NPs membranes at 0.52 and 1.27 keV, respectively, indicating the presence of MgO NPs [31; 32]. Regarding the ATR-FTIR analysis, PCL spectrum shows the typical bands of this polymer, with the main ones described as follows. The bands at 2941 and 2866 cm\({}^{-1}\) correspond to the asymmetric and symmetric CH\({}_{2}\) stretching, respectively. A strong band at 1724 cm\({}^{-1}\) is related with carbonyl (C = O) stretching. Finally, the bands at 1470, 1240 and 1169 cm\({}^{-1}\) are attributed to C-C bending, asymmetric C-O-C stretching and symmetric C-O-C stretching, respectively. The band at 1294 cm\({}^{-1}\) is from C-O and C-C stretching in the crystalline phase, while the one at 1105 cm\({}^{-1}\) corresponds to C-O and C-C stretching in the amorphous phase [33; 34]. Considering the spectrum of PCL membranes functionalized with PEG-coated Ag NPs, besides the characteristic bands of PCL, the appearance of a new one at 887 cm\({}^{-1}\) is observed, which is attributed to PEG polymer [26; 28]. Other typical bands of PEG coincide with the region of characteristic bands of PCL, and only detect an increase in bands' intensity (1240 and 961 cm\({}^{-1}\)). Moreover, in the spectrum of PCL membranes with Ag-PEG NPs, a broad peak appeared at 3435 cm\({}^{-1}\), which is attributed to stretching vibrations of O-H. This could be due to hydroxyl groups of PEG [35], or could indicate intermolecular hydrogen bonding formed between the groups from PCL and the hydroxyl groups from PEG [26]. Figure 4: EDS analysis of (**a**) PCL/Ag NPs; (**b**) PCL/TiO\({}_{2}\) NPs; (**c**) PCL/MgO NPs electrospun membranes; (**d**) ATR-FTIR; (**e**) GSDR of PCL and PCL/NPs electrospun membranes; (**f**) estimated amount of NPs presented in PCL membranes. The spectrum of TiO\({}_{2}\) powder shows a characteristic band in the region of 900-400 cm\({}^{-1}\), which is attributed to Ti-O stretching vibration. Besides presenting the typical bands of PCL, the PCL/TiO\({}_{2}\) NPs spectrum also demonstrates the presence of a new band in this region, confirming successful incorporation of TiO\({}_{2}\) NPs onto PCL membranes [36; 37]. The spectrum of commercial MgO NPs shows a band around 800-400 cm\({}^{-1}\), which corresponds to Mg-O stretching vibrations [38; 39; 40; 31]. The appearance of the band in the region of 800-400 cm\({}^{-1}\) in the spectrum of PCL/MgO NPs fibers is observed, confirming the presence of these NPs into the PCL membranes' surface. Figure 4e shows the GSDR spectra of PCL/NPs electrospun membranes.