Effect of surface coating and solvent interactions on magnetization of iron oxide nanoparticles

Magnetic iron oxide nanoparticles (MIONPs) are being widely used in various biological applications, and they are surface modified with surfactants to increase their biocompatibility or to prevent their agglomeration in various solvents. However, the surfactants interact with the surface atoms of the nanoparticles leading to the formation of a magnetically disordered layer, which in turn reduces the effective magnetic phase. The magnetic phase reduction can also be attributed to the interaction between the surfactant and the solvent. In the current study, the interactions between the surfactants and the suspension media were investigated to understand their effect on magnetization of MIONPs. The surfactant--suspension media interactions were altered by gradually changing the quality of the solvent ranging from good to poor. The saturation magnetization was used to determine the effective concentration of magnetic phase as a function of solvent quality. The difference between the VSM and actual iron oxide concentration indicates the reduction of magnetic phase of the magnetic core as a function of solvent quality.