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 thin films fabricated from chitosan-acetic acid solutions (chitosan/HAc). FT-IR spectroscopy (including NIR, MLR and FIR) coupled with X-ray photoelectron spectroscopy (XPS) indicate a weak complexation between the metal ions and amine groups of chitosan. Specifically, the FIR spectra show broad bands near 550, 480 and 250 cm(-1) for the doped films suggestive of metal ion-ligand vibrations. XPS indicates multiple chemical states of N with an increased percentage of a higher binding energy state nitrogen caused by a weak interaction with the doped metal ions. Slight differences in microroughness between the doped and undoped films as observed by X-ray reflectometry may also be related to the doping. The NIR and Mm spectra do not show any significant changes for all the doped and undoped films, implying that the basic molecular conformation of chitosan is not changed by the weak complexation.