2.6. Fourier transform infrared (FTIR) spectroscopy
The FTIR spectra were recorded on a Fourier transform infrared
(FTIR) instrument (Magna 560, Nicolet, Thermo Electron Corp.,
USA) in the range of 400–4000cm−1 with a resolution of 4 cm−1.
The dried samples were ground into powder by a fiber microtome
and then blended with KBr before pressing the mixture into ultrathin
pellets.