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 TiO2 film. The physicochemical properties of the original and oxidized CS solutions were characterized by ultraviolet–visible (UV–Vis) spectroscopy, 13C 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.
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