Synthesis and characterization of magnetic nanoparticles

Magnetic nanoparticles with average diameter in the range of 6.4-8.3 nni have been synthesized by a chemical co-precipitation of Fe(Ⅱ)and Fe(Ⅲ)salts in 1.5 M NH4OH solution.The size of the magnetic particles is dependent on both temperature and the ionic strength of the iron ion solutions.The magnetic particles formed at higher temperature or lower ionic strength were slightly larger than those formed at lower temperature or higher ionic strength respectively.In spite of the different reaction conditions,all the resultant nanoparticles are nearly spherical and have a similar crystalline structure.At 300 K,such prepared nanoparticles are superparam-agnetic.The saturation magnetizations for 7.8 and 6.4 nm particles are 71 and 63 emu/g respectively,which are only ~ 20-30% less than the saturation magnetization(90 emu/g)of bulk Fe3O4 Our results indicated that a control of the reaction conditions could be used to tailor the size of magnetic nanoparticles in free precipitation.

Synthesis and characterization of magnetic nanoparticles

Magnetic nanoparticles with average diameter in the range of 6.4–8.3 nm have been synthesized by a chemical co‐precipitation of Fe(II) and Fe(III) salts in 1.5 M NH₄OH solution. The size of the magnetic particles is dependent on both temperature and the ionic strength of the iron ion solutions. The magnetic particles formed at higher temperature or lower ionic strength were slightly larger man those formed at lower temperature or higher ionic strength respectively. In spite of the different reaction conditions, all the resultant nanoparticles are nearly spherical and have a similar crystalline structure. At 300 K, such prepared nanoparticles are superparamagnetic. The saturation magnetizations for 7.8 and 6.4 nm particles are 71 and 63 emu/g respectively, which are only ～ 20–30% less than the saturation magnetization (90 emu/ g) of bulk Fe₃O₄. Our results indicated mat a control of the reaction conditions could be used to tailor the size of magnetic nanoparticles in free precipitation.