Characteristics and magnetic properties of chitosan-coated Fe₃O₄ nanoparticles prepared by ex-situ co-precipitation method

Chitosan-coated iron oxide nanoparticles were synthesized by ex-situ co-precipitation method. Ammonia solution was dropped into the solution containing ferrous and ferric salts through a syringe pump to form Fe₃O₄ nanoparticles. Nanoparticles produced were then coated and crosslinked with chitosan and tripolyphosphate/sulfate, respectively. The physical and magnetic properties of chitosan-Fe₃O₄ nanoparticles were characterized using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and Electron Spin Resonance (ESR) respectively. The results showed that the ratio enhancement between chitosan:Fe₃O₄ increased the particle size, while the crystallite size decreased. Morphology and particle size were also influenced by the ratio of crosslinkers. It was found that the higher tripolyphosphate content contributed to the smaller size and more spherical morphology. In addition, the influence of crosslinking time toward crystallite size was determined by tuning stirring time. The result showed that the longer duration of crosslinking time, the larger crystallite size of chitosan-coated Fe₃O₄ was obtained.