Escalab xi spectrometer

For UV–vis spectrum measurement, PEI/glucose (2:1 by weight) solutions were firstly coated on the quartz substrate and then heated to different temperature for 10 min. After that they were placed in the solid-state sample holder, while the reference sample holder was a clean quartz substrate. The transmittance spectra from 300 to 800 nm of the samples were measured using a UV spectrometer (UV 2700, Shimadzu Co., Japan) and the transmittance data measured at 380 nm were reported as a function of heating temperature. X-ray photoelectron (XPS) spectroscopy analysis of the PEI/glucose (2:1 by weight) mixtures coated on the silicon wafer after heating to 30, 80 and 100 °C for 10 min was conducted on the ESCALAB Xi + spectrometer (Thermo Fisher Scientific Ltd., Germany). For Fourier transform infrared (FTIR) characterization, the PEI/glucose (2:1 by weight) solutions were firstly freeze-dried to form a gel-like solid samples and then placed on the sample holder of attenuated total reflectance (ATR) accessory. The sample was immersed for 10 min at 30, 80 and 100 °C in sequence, before the corresponding FTIR spectrum were acquired on an In situ ATR-FTIR spectrometer (IN 10, Thermo Fisher Scientific Ltd., Germany) in a range from 1000 to 4000 cm⁻¹.

Powder X-ray diffraction (XRD) patterns of the samples were recorded on a Bruker D8 (Bruker AXS, Karlsruhe, Germany) advanced diffractometer using a Cu Kalpha radiation (λ = 0.15405 nm). The morphologies of the samples were investigated by scanning electron microscope (SEM, GeminiSEM 500, Carl Zeiss AG, Oberkochen, Germany) and transmission electron microscopy (TEM, Hitachi HT-7700 at 100 kV, Hitachi Limited, Tokyo, Japan). Fourier transform infrared spectroscopy (FT-IR) was acquired using a Nicolet iS10 FT-IR spectrometer (Thermo Fisher Scientific, Waltham, MA, USA). Raman spectroscopies were studied by a single monochromator with a microscope (Renishaw inVia, Renishaw plc, London, UK) equipped with CCD array detector (1024 × 256 pixels) and an edge filter and 633 nm. X-ray photoelectron spectroscopy (XPS) was measured with a Thermo Fisher Scientific ESCALAB Xi⁺ spectrometer (Thermo Fisher Scientific, Waltham, MA, USA) equipped with a monochromatic Al Kα radiation. The binding energies were calibrated using the C 1s peak at 284.4 eV. The relative complex EM parameters in the 2–18 GHz frequency were measured by a microwave vector network analyzer (N5227A, Agilent technologies, Santa Clara, CA, USA).

¹H and ¹³C NMR spectra were recorded on a Bruker DRX-400 (operating at 400 MHz for ¹H and 100 MHz for ¹³C). GC–MS spectra were recorded on an Agilent Technologies 7890B GC-system with an Agilent 5977B MSD and an HP-5MS column (0.25 mm × 30 m × 0.25 μm). High-resolution mass spectra (HRMS) were recorded on the Exactive Mass Spectrometer (Thermo Scientific, USA) equipped with ESI ionization source. X-ray photoelectron spectroscopy (XPS) data were collected with a Thermo Fisher ESCALAB Xi⁺ spectrometer equipped with monochromatic Al Kα radiation. IR spectra were recorded on a PerkinElmer spectrum two spectrometers using the transmittance method. Electron paramagnetic resonance (EPR) spectroscopic measurements were performed on the Bruker A300 spectrometer. Elemental analysis (EA) spectroscopic measurements were recorded on the Elemantar Vario EL cube.