*2.6. Fourier Transform Infrared (FT-IR)*

FT–IR spectra were collected using a Bruker Vertex 70 spectrometer and measured in the range of 4000−400 cm−<sup>1</sup> with an RT-DLaTGS detector (Ettlingen, Germany). The KBr diffuse-reflectance mode was used (sample concentration: 1 mg in 100 mg of KBr) for recording the IR spectra of these samples. Data were analysed using the OPUS software (San Francisco, CA, USA).
