## 3 Results and Discussion  
### Chemical Surface Characterization of the RC/IL Films  
Chemical surface characterization of the RC/IL films was performed via the XPS technique, which gives information of the elements present on the surface of a given sample by analyzing the high-resolution spectra. XPS survey spectra at a take-off angle of 45\({}^{\circ}\) for both RC/IL samples are given as Supplementary Information (Figure S2), where the photoemission lines corresponding to the characteristic ILs elements are indicated (C, N, F, P for the RC/BMIMPF\({}_{6}\) film or C, N, Cl for the RC/Aliquat film), but the presence of two other non-characteristic elements, oxygen and silicon, associated with the cellulosic support (characteristic or impurities elements) are also indicated, and this point will be discussed later. The atomic concentration percentage (A.C. %) of the ILs characteristic elements detected on the surface of the RC/IL films were obtained by the corresponding curve area, as shown in Figure 1 for the core level spectra of the different elements. As can be seen in Figure 1a, the C 1s signals obtained for the RC/BMIMPF\({}_{6}\) film shows: (i) a clear peak at a binding energy (B.E.) of 285.0 eV (C\({}_{1}\)), which corresponds to aliphatic carbon, additives or pollution (-CH-, -C-, \(\beta\)-C) [47] and represents 55.9% of the total carbon contribution, (ii) a certain plateau (C\({}_{2}\), from 286.1 eV to 286.6 eV) associated with the imidazolium group, C=N and C-N bonds (33.2% of the total area) [41] although it might also include C-O bonds from the support, (iii) a small shoulder (C\({}_{3}\), at around 289.0 eV and 10.9% of area) associated with the O=C-O, CO\({}_{3}\) bonds from the support [47], as can be observed in Figure 1b, where a comparison of the normalized C 1s spectra obtained for the BMIMPF\({}_{6}\) IL, the RC/BMIMPF\({}_{6}\) film and the RC-support is shown. The C 1s spectra corresponding to the RC/AliquatCl film also showed a significant peak at the B.E. of 285.0 eV (72.6% of the total area), higher than that exhibited by the RC/BMIMPF\({}_{6}\) film in agreement with its higher aliphatic chain, plus two small shoulders, at 286.2 eV (21.7% of area) and at 287.8 eV (5.6% of carbon area), associated with C-O and O-C-O bonds, respectively, both from the RC-support. Figure 1: Core level spectra signals for: (**a**) C 1s for RC/AliquatCl film (blue solid line) and RC/BMIMPF\({}_{6}\) film (red solid line); (**b**) comparison of normalized C 1s signal for the RC/BMIMPF\({}_{6}\) film (red solid line), RC-support (black dashed line) and BMIMPF\({}_{6}\) IL (red dashed–dot line); (**c**) N 1s (blue solid line) for RC/AliquatCl film and red solid line for RC/BMIMPF\({}_{6}\) film; (**d**) comparison of N 1s signal for the IL AliquatCl (blue dashed–dot line) and the RC/Aliquat (blue solid line). The N 1\(s\) core level spectra obtained for both RC/IL films is shown in Figure 1c, where two peaks, N\({}_{1}\) and N\({}_{2}\), at around 402.2 eV and 399.4 eV can be observed; the comparison of the N 1\(s\) signal obtained for the RC/AliquatCl film and the AliquatCl IL presented in Figure 1d clearly shows the correspondence of the peak at 402.2 eV (N\({}_{1}\)) with that exhibited by the IL, while the N\({}_{2}\) peak is associated with support impurities that could depend on the sample water content, as it was obtained for polymeric inclusion membranes fabricated with 60% of AliquatCl and 40% of cellulose triacetate [14], and it is provided as Supplementary Information (Figure S3a). In the case of the RC/BMIMPF\({}_{6}\) film, the peaks are related to the C-N link and protonated nitrogen, respectively; a comparison of nitrogen normalized spectra for the RC/BMIMPF\({}_{6}\) and the BMIMPF\({}_{6}\) IL is also given as Supplementary Information (Figure S3b).