Soft solution in situ synthesis of chitosan/iron oxide nanocomposites and their magnetic properties

Abstract

Chitosan/iron oxide nanocomposites (CS/IO) were synthesized by using soft solution in situ synthesis. An aqueous mixture of iron(II), iron(III) and chitosan was added drop by drop to a solution of a sodium tripolyphosphate crosslinker with stirring for 30 min, resulting in in situ ionically crosslinked chitosan, with incorporated Fe²⁺ and Fe³⁺ (CS/Fe²⁺Fe³⁺). The CS/Fe²⁺Fe³⁺ precursors were then treated in alkaline solution by two different methods, i.e. hydrothermal and refluxing, where the Fe²⁺ and Fe³⁺ ions reacted to form quasi-spherical magnetite–maghemite nanocrystals in the constrained space of the crosslinked chitosan CS/IO nanocomposites. The pressurized hydrothermal system promoted the growth of iron oxide nanocrystals, leading to slightly larger crystallites (3.9–4.3 nm), compared to 3.9 nm from the refluxing system. The iron oxide crystallites also became smaller with increased crosslinking density of the chitosan matrix. The resultant CS/IO nanocomposites exhibited superparamagnetism with M_max in the range of 9.6–15 emu g⁻¹ and low coercivity and magnetic remanence. In addition, they showed high cell viability, 82–96%, indicating them as potential candidates for medical applications.