CHARACTERIZATION OF CHITOSAN AND RARE-EARTH-METAL-ION DOPED CHITOSAN FILMS

A systematic study has been made on the influence of doped rare-earth metal ions (Er3+ and Nd3+) on the molecular interaction present in thi n films fabricated from chitosan-acetic acid solutions (chitosan/HAc). FT-IR spectroscopy (including NIR, MLR and FIR) coupled with X-ray ph otoelectron spectroscopy (XPS) indicate a weak complexation between th e metal ions and amine groups of chitosan. Specifically, the FIR spect ra show broad bands near 550, 480 and 250 cm(-1) for the doped films s uggestive of metal ion-ligand vibrations. XPS indicates multiple chemi cal states of N with an increased percentage of a higher binding energ y state nitrogen caused by a weak interaction with the doped metal ion s. Slight differences in microroughness between the doped and undoped films as observed by X-ray reflectometry may also be related to the do ping. The NIR and Mm spectra do not show any significant changes for a ll the doped and undoped films, implying that the basic molecular conf ormation of chitosan is not changed by the weak complexation.