Analysis of chitosan irradiated with high-energy cyclotron ion beams

Analyses of the chitosan disks treated with proton ion beams were performed with Fourier transformed infrared spectrometer spectroscopy (FT-IR), ¹H nuclear magnetic resonance (¹H-NMR), X-ray photoelectron spectroscopy (XPS), color changes and relative viscosity changes. The chitosan disks were irradiated with proton ion beams from a cyclotron ion generator with high energy after calculating in advance the conditions of proton ion beam irradiation such as beam species, time and energies with stopping and range of ions in matter software. Detection of any significant changes in the chemical structures of the beam-treated chitosan samples was not noticed when we compared to those of its corresponding chemical structures of the untreated ones by FT-IR and ¹H-NMR. However, reductions of the molecular weights of the beam-treated samples were verified by the results of both measurement of their relative viscosities and visualization of its color changes. Irradiation of proton ion beams on the chitosan disks led to visual changes of its colors from white to brown. Further analysis of their atomic composition ratios and chemical structures with their survey scans and high resolution C1s XPS spectroscopy demonstrated significantly noticeable differences such as new peak positions in their chemical structures between the untreated and the ion beam-treated chitosans. These results indicated that analyses by XPS and measurement of relative viscosity changes were far more sensitive than those by NMR and FT-IR were in analyzing the changes of the chemical structures of the ion beam-treated chitosan samples in this study. These results indicated that reduction of chitosan molecular weight is possible by irradiation of proton ion beams with high energy.