Monolithic diamond atr crystal

FTIR spectra of freeze-dried chitosan gels were obtained with Nicolet™ iS™10 FT-IR apparatus equipped with a monolithic diamond ATR crystal (Thermo Scientific Inc., Waltham, MA, USA). The measurements were carried out in the range 4000–500 cm⁻¹, with a resolution of 4 cm⁻¹.

The crystal size and structure of the NRs were determined via X-ray diffraction (XRD) on a Philips PW 1820 diffractometer with monochromatized Cu Kα radiation (λ = 1.5406 Å) in the range of 2θ from 20 to 90°. The morphology and particle size were analyzed using a JEOL JEM 1200-EX (Tokyo, Japan) transmission electron microscope (TEM). The FT-IR spectra (ranging from 4000 to 450 cm⁻¹) of the NRs were obtained using a Nicolet iS20 spectrometer equipped with a monolithic diamond ATR crystal (Thermo Fisher Scientific, Waltham, MA, USA). The thermal stability and the amount of the organic coating were evaluated via thermogravimetric analysis (TGA) using a SETA−RAM SetSys-1200 (KEP Technologies, Caluire, France) under a N₂ atmosphere with a heating rate of 10 °C min⁻¹. The optical properties of the NRs were investigated using a UV-Vis spectrophotometer (V-750, Jasco, Tokyo, Japan). The hydrodynamic size (nm), polydispersity (PDI), and ζ-potential (mV) of dispersed NRs in an ethanol/water solution (1:3 ratio) were determined via dynamic light scattering (DLS) at 25 °C using a Zetasizer (Nano ZS Malvern apparatus VASCO Flex™ Particle Size Analyzer NanoQ V2.5.4.0, Malvern, UK).

Fourier transform infrared (FTIR) spectra of the lyophilized chitosan hydrogels were characterized using a Nicolet™ iS50 FT-IR apparatus equipped with a monolithic diamond ATR crystal (Thermo Fisher Scientific Inc., Madison, WI, USA). All spectra were recorded with 100 scans at a 4.0 cm⁻¹ resolution in the range of wavenumbers 4000–500 cm⁻¹.