3. Characterization
Morphological characterizations of chitin NFs, chitosan NPs, chitosan NFs and water soluble chitosan oligomers were performed using Atomic Force Microscope (AFM) using a Park Systems, XE-100 microscope. Imaging was carried out using non-contact mode cantilever, having a tip radius less than 10 nm operating at a scanning frequency of 0.5 Hz. Chitin NFs was first dispersed in water using ultrasound tip. Then drop of the solution was casted onto a mica piece which is later mounted on the scanning stage of AFM after complete drying.
Transmission electron microscopy (TEM) was used to characterize the morphology of the prepared samples using JEOL JEM-1011 operating at an accelerating voltage of 100 kV. Water dispersions of the nanomaterials were casted on TEM grids and allowed for drying. Dried grids were taken for inspection.
Fourier transform infrared spectroscopy (FTIR) measurements were taken for chitin flakes, chitin NFs and for the mixture of chitosan NFs and chitosan NPs (Bruker FT-IR Vertex 80). Dried samples were placed on top of the ZnSe crystal inside the ATR chamber. The special tightening unit that comes with the instrument was used to ensure the maximum contact between crystal and the sample. FTIR spectra were recorded between 4000 cm−1 and 600 cm−1 with the resolution of 4 cm−1 in the absorbance mode for 128 scans at room temperature.
X-ray diffraction (XRD) measurements were carried out using (Brucker D8 Focus X-ray Diffractometer) Cu-Kα radiation emitted from X-ray tube operated at 30 kV and 25 mA. Samples were dried for 2 h at 60 °C for removal of any excess moisture and diffraction patterns were recorded at room temperature.
Thermogravimetric analysis (TGA) was performed for finely grounded chitin flakes, chitosan flakes, chitin NFs and chitosan NFs and chitosan NPs mixture using Q-600 TGA from TA-Instruments. Approximately 9–10 mg of the sample was placed inside the alumina pan and heated from 30 °C to 700 °C at a heating rate of 20 °C/min under a N2 purge of 100 ml/min.