The effects of IL pretreatment on the chemical compositions were studied using FTIR spectroscopy. The air-dried samples were placed in a Thermo Scientific Nicolet iN10 Fourier transform infrared spectrometer (USA). The IR spectra were recorded in the wave number range of 700 to 4000 cm−1 at 4 cm−1 resolution for 20 scans prior to the Fourier transformation. All peak intensities were recorded and analyzed by FTIR software.
NMR measurements were conducted by a 13C CP-MAS NMR spectrometer (Bruker AVANCE-III AV 400 MHz, Germany) operating at 100.6 MHz. All samples put in a 5-mL centrifuge tube before being sent to NMR measurements. The chemical shifts were determined in CP-MAS (Cross-polarization magic angle spinning) spectra using the cellulose C-1 signal as an internal standard (δ105 ppm).
NMR measurements were conducted by a 13C CP-MAS NMR spectrometer (Bruker AVANCE-III AV 400 MHz, Germany) operating at 100.6 MHz. All samples put in a 5-mL centrifuge tube before being sent to NMR measurements. The chemical shifts were determined in CP-MAS (Cross-polarization magic angle spinning) spectra using the cellulose C-1 signal as an internal standard (δ105 ppm).