A chemical synthesis of FeO (magnetite) nanoparticles (NPs) in the mixture of oleylamine and oleic acid was performed. δ10 nm Fe 3O 4 NPs, Fe(acac) 3 (3mmol) was dissolved in 15 mL of benzyl ether and 15 mL of oleylamine. The solution was dehydrated at 110°C for 1 h under N 2 atmosphere, then quickly heated to 300°C at a heating rate of 20°C/min, and aged at this temperature for 1 h. After the reaction, the solution was allowed to cool down to room temperature. The Fe 3O 4 NPs were extracted upon the addition of 50 mL of ethanol, followed by centrifuging. The magnetic properties of the Fe 3O 4 NPs were studied using a vibrating sample magnetometer (VSM) at room temperature. The corresponding selected area electron diffraction (SAED) pattern showed weak but clear iron oxide spinel structure rings, indicating the formation of spinel structured iron oxide crystal clusters at relatively low temperature.