Disclosed herein is an iron oxide nanoparticle comprising? 950% magnetite(fe?304) and having a particle diameter size of from 7 to 27 nm when measured using transmission electron microscopy and a magnetisation strength(MS) from 60 to 80 emu/g also disclosed herein are coated iron oxide nanoparticles, methods to make said iron oxide nanoparticles and articles containing the same.