## 3 Results
### Functional Properties Evaluation  
#### 3.4.1 Electrical Conductivity  
The electrical properties depend on several factors, such as the GNPs concentration, dispersion, homogeneity, agglomeration, and formation of conductive networks [45]. A thorough study of the influence of various aspects on the electrical properties of the developed samples was performed. First, a comparison between the variation of the electrical resistance (\(\Omega\)) and the concentration of GNPs present in the samples was performed, as illustrated in Figure 9.  
It was possible to observe that the electrical resistance continuously decreased in response to the increasing GNPs concentration, as expected. The obtained results were 2.5 M\(\Omega\) for 0.1%GNPs-PCL, 62.5 k\(\Omega\) for 0.2%GNPs-PCL, 23.6 k\(\Omega\) for 0.5%GNPs-PCL, 7.7 k\(\Omega\) for 1%GNPs-PCL, and 7.5 k\(\Omega\) for the 2%GNPs-PCL. Remembering that the electrical conductivity is the inverse of the resistivity, the electrical conductivity had an increase directly proportional to the GNPs concentration (Figure 9a). This behavior can be attributed to the increasing GNPs, which were mass impregnated onto the membranes, and the consequent network increment. The relationship between the duration of the impregnation process and its influence on the uploaded GNPs mass on the samples, and consequently, on the electrical resistance, was also studied. Regarding this, the uploaded GNPs mass also increased with increasing impregnation time, as expected (Figure 9b), which indicates that more GNPs were embedded into the PCL membranes with time. As a result, membranes with better electrical properties were obtained with higher impregnation times. Figure 8: Raman spectra of the GNPs (black) PCL membrane (dark blue), 0.5% (red), and 2%GNPs-PCL membrane (light blue). After studying the influence of the impregnation times on the electrical properties of the samples, the influence of the GNPs quantity, as well as the influence of the treatment of five successive washes and dryings on the electrical conductivity of the developed samples, was evaluated, measuring the electrical resistance on different places of the samples. The electrical conductivity values, calculated as described previously using the two-wire method, are shown in Table 2 after each water treatment cycle and for the different GNPs concentrations. As can be verified in the results shown in Table 2, as the presence of GNPs in the samples increased (higher concentration), the electrical conductivity also increased considerably, corroborating the well-known electrical properties of these particles [6]. The conductivity performance was also studied after each successive washing and drying cycle. In this sense, it can be observed that the electrical conductivity decreased as the number of washes increased. This was expected, since during the treatment, some of the GNPs present on the sample's surface were released. However, these processes were essential in order to get rid of the excess of GNPs after the impregnation. For the sample produced with 0.05% of GNPs, the values of electrical conductivity were very low (\(6.43\times 10^{-9}\) S/m) at the end of the whole process. However, with 2%, the electrical conductivity value reached 0.08 S/m after the same number of cycles. Therefore, with higher quantities of GNPs on the samples, higher values of electrical conductivity were obtained, even after successive water treatment cycles. This phenomenon can be explained