Abstract
Chitosan (CS) was oxidized under mild conditions in solution via photocatalysis using a 45-W compact household fluorescent light source in the presence of an immobilized TiO
2
film. The physicochemical properties of the original and oxidized CS solutions were characterized by ultraviolet–visible (UV–Vis) spectroscopy,
13
C nuclear magnetic resonance spectroscopy, differential scanning calorimetry, Fourier-transform infrared spectroscopy, elemental analysis, pH-potentiometric titration, and gel permeation chromatography. The results showed that CS was effectively oxidized within 4 h of irradiation as indicated by colour changes of the product with the appearance of a new UV–Vis absorption band at 337.7 nm. The results support the formation of carbonyl groups along with negligible change in the polymer chain structure of CS and/or chain scissioning effects. The photocatalysis reported herein is a convenient, feasible and environmentally friendly method for oxidation of natural biopolymers such as CS in solution.