Uniform Magnetite Nanoparticles Larger Than 20 nm Synthesized by an Aqueous Route

Here we present an aqueous route for the synthesis of uniform magnetite nanoparticles with sizes around the monodomain diameter (20-100 nm). The method is based on the precipitation of an Fe(II) salt in a mild oxidant in hydroalcoholic solutions, and leads to highly uniform and crystalline magnetic nanoparticles in a single step. Colloidal suspensions of these particles were directly obtained by simple ultrasonic treatment of the powders thanks to the presence of sulphate anions at the particle surface. All magnetisation curves saturate at much lower magnetic fields and show larger saturation magnetization than samples prepared by coprecipitation. Saturation magnetisation values vary between 83 and 92 emu g-1, close to the theoretical values reported for bulk magnetite at room temperature. Those magnetic particles have shown the maximum heat efficiency for magnetic hyperthermia and they could show great potential in MPI imaging.