The Fourier Transform Infrared (FTIR) spectroscopy. FTIR spectra were registered on a Bruker ALPHA spectrometer equipped with an attenuated total reflection (ATR) accessory. The spectra were recorded in a range of 400 -4000 cm -1 and a resolution of 2 cm -1 . Samples were vacuumdried before measurement and 32 scans were performed for each specimen.