Preparation Of Fe₃O₄ And Fe₃O₄ / Chitosan Nanocomposite Induced By Static Magnetic Field

Fe₃O₄ nanoparticles and Fe₃O₄/chitosan nanocomposites of different morphology were prepared for their good biocompatibility to investigate the influence of magnetic field, and their structures, properties were characterized and analyzed. In detail, Fe₃O₄ nanoparticles were prepared with Massart method under various magnetic fields of 0 T, 0.25 T and 0.45 T. According to the analysis results, degree of crystallinity increased after introduction of magnetic field and the morphology of particles changed from ball-like to stick-like, resulting from orientated growth along certain crystal face. Meanwhile, surface area decreased. All products were proved to be superparamagnetic; more, saturation magnetization were increased by 0.28 times, 1.14 times under 0.25 T and 0.45 T respectively; 13.48 times and 14.10 times for remanent magnetization and 1.45 times for coercive force.Fe³⁺ and Fe²⁺ were uniformly mixed with chitosan and Fe₃O₄/chitosan nanocomposites were prepared under various magnetic fields of 0 T, 0.25 T and 0.45 T with one-step method. The analysis results indicated stable core/shell structure formed due to the existence of chemical bond between Fe₃O₄ and chitosan. Fe₃O₄'s orientated growth along certain crystal face among chitosan lead to formation of stick-like or chain-like structure and decrease of surface area. All nanocomposites were proved to be superparamagnetic, however, saturation magnetization, remanent magnetization and coercive force changed little.Fe₃O₄ nanoparticles were prepared beforehand and were then capsuled into chitosan, in which way Fe₃O₄/chitosan nanocomposites were prepared by two-step method under 0 T, 0.25 T and 0.45 T. Since magnetic field was introduced in the process of cross-linking, morphology of Fe₃O₄ nanoparticles changed little, therefore, chain-like or stick-like particles were not observed; however, Fe₃O₄/chitosan particles aligned and formed fasciculus-like structure.Based on crystal growth theory, mechanism of influence of magnetic field on growth of Fe₃O₄ nanocrystals and formation of one dimensional structure was discussed. The experimental phenomena were also accordingly explained.