2.3.2. SpectroscopyFourier transform infrared (FT-IR) spectroscopy was performedusing a Perkin–Elmer Spectrum RXI (USA), in order to determinethe changes in functional groups in the materials. The samples forFT-IR were mixed with KBr. The FT-IR analysis was carried out using50 scans with a resolution of 4 cm−1, in transmittance mode withinthe range of 3600–400 cm−1