CS-Fe(II,III) complex as precursor for magnetite nanocrystal

Chitosan-iron ions complex (CS-Fe(II,III) complex) was used as precursor to synthesize magnetite nanocrystals and the mechanism was discussed. The magnetite nanocrystals have diameters of about 10nm and clusters were formed due to slight aggregation of several magnetite nanocrystals. FT-IR and X-ray photoelectron spectrometer (XPS) investigations indicated that the Fe(II) and Fe(III) were chelated by -NH₂ and -OH groups of chitosan in CS-Fe(II,III) complex, and the molar ratio of -NH₂/Fe(II,III) was approximately 2. This chelation effect destroyed the hydrogen bonds of chitosan. In the following alkali treatment process, the chelated Fe(II) and Fe(III) provided nucleation site and formed the magnetite nanocrystals. After alkali treatment, the chelation effect between iron ions and -NH₂ groups disappeared and some kind of weak interaction formed between magnetite and -NH₂ groups. Moreover, the -OH groups of chitosan have an interaction with the synthesized magnetite nanocrystals.