Nicolet nexus 470

The polysaccharide (2.0 mg) was ground with KBr, pressed into a 1 mm transparent sheet, and then determined on a Nicolet Nexus 470 spectrometer (Thermo Fisher Scientific, Waltham, MA, USA) with a scan range of 400–4000 cm⁻¹.

Protein samples were prepared with potassium bromide (KBr) pellet method [46 (link)]. Infrared spectra were measured with a FT-IR spectrometer (Nicolet Nexus 470, DTGS, Thermo Scientific, Waltham, MS, USA) at 25 °C. For each spectrum 256 interferograms were collected with a resolution of 4 cm⁻¹ with 64 scans and a 2 cm⁻¹ interval from the 4000 to 400 cm⁻¹ region. The system was continuously purged with dry air. Second derivation spectra were obtained with Savitsky–Golay derivative function soft [47 (link)]. The relative amounts of different secondary structure of CPI, 11S and 7S globulins were determined from the infrared second derivative amide spectra by manually computing the areas under the bands assigned to a particular substructure.

The heat of CO₂ adsorption was measured by differential scanning calorimetry (Setaram Instrumentation, Setsys Evolution). Before the measurements, the samples were degassed at 100 °C for 1 h under N₂ flow (50 cm³ min⁻¹). Then, the samples were cooled to 60 °C. Subsequently, the gas was switched to 15% CO₂ (50 cm³ min⁻¹). The heat of adsorption was calculated through the integration of the heat flow curve. Fourier transform infrared (FT-IR) spectra were recorded using an FT-IR spectrometer (Thermo Nicolet NEXUS 470). Prior to the analysis, 3 mg of the adsorbents were grinded with 18 mg of the silica (macroporous silica support) as a diluent. The mixtures were pressed into a self-supporting wafer. Before the FT-IR measurements, each sample was degassed at 100 °C for 3 h under vacuum in an in situ infrared cell equipped with CaF₂ windows. FT-IR spectra were collected at room temperature. Elemental compositions (C, H, and N) of the adsorbents were analysed using a FLASH 2000 (Thermo Scientific) instrument. The contents of transition metal impurities (Fe, Cu, etc.) in PEI and EB-PEI were determined by inductively coupled plasma mass spectroscopy (ICP-MS) using an ICP-MS 7700S instrument (Agilent). In the case of EB-PEI, the metal concentrations were determined after the complete evaporation of the methanol solvent at 60 °C for 12 h under vacuum after its synthesis.

Chemical changes in sorghum samples due to germination were evaluated using a nitrogen-cooled Attenuated Total Reflectance FTIR (Thermo Scientific Nicolet Nexus 470, Waltham, MA, USA) equipped with a mercury/cadmium/telluride detector at a resolution of 4 cm⁻¹ [15 (link)]. The spectra of the samples were scanned in the range 4000–400 cm⁻¹. Data were processed using Omnic software (OMNIC 9.0).

FTIR analysis of the nanofibers was performed to characterize the functional groups in the nanofibers. FTIR data were recorded on a Nicolet Nexus 470 FTIR spectrometer (Thermo Fisher Scientific, Waltham, MA, USA). The FTIR spectrometer was purged continuously with nitrogen. A total of 64 scans were collected with a resolution of 2 cm⁻¹. The infrared spectra were recorded in transmission mode using a PCL/GT nanofiber deposited on a silicon wafer.