Through the transmittance spectra obtained by UV-vis spectrophotometry, the refractive index s and thickness of the incorporated films were estimated by the Swanepoel method , used to simulate wave patterns in transmittance spectra (Eq. 1, 2). In Eq. 1, Ts is the substrate maximum transmission value, while, in Eq. 2, n1 are refractive indices obtained from two consecutives maxima or minima, corresponding to wavelengths l1 and l2.