Superparamagnetic iron oxide nanoparticles prepared by using an improved polyol method

► Superparamagnetic iron oxide nanoparticles were synthesized by thermal decomposition of Fe(acac)3 in PEG containing PVP or PEI. ► The nanoparticles are jointly coated by PEG/PVP or PEG/PEI. ► The nanoparticles showed high dispersion stability in water and in PBS. ► The properties of nanoparticles were tuned by PVP or PEI.