High Temperature Polyol Synthesis of Superparamagnetic CoFe2O4 Nanoparticles for Magnetic Resonance Imaging Contrast Agents

The superparamagnetic CoFe2O4 nanoparticles with core size of 5-10nm were prepared by high temperature polyol process using FeCl3·6H2O,CoCl2·6H2O and HOOC-PEG-COOH as reactants.The samples had good monodispersibility in aqueous solution.Moreover,the influences of reaction conditions such as varieties of modification agents and their amounts,reaction temperature and time on the size,dispersibility and magnetic properties of CoFe2O4 nanoparticles were investigated.The results indicate that choosing the modification agent with strong polar group,increasing the amount of modification agent,elevating reaction temperature and extending reaction time are beneficial to obtain samples with larger particle size,better water-dispersibility and narrower size distribution.The optimum reaction condition is determined as follows,the weight ratio of metal source to HOOC-PEG-COOH is 1∶10,reaction temperature is 210-220℃ and reaction time is 2h.Magnetic analysis shows that all the samples manifest a well-defined superparamagnetic behavior at room temperature.The larger the particle size is,the higher saturation magnetization is.