Fulvic acid coated Fe 3 O 4 superparamagnetic nanoparticles were synthesized by a coprecipitation technique with iron salts and a small molecule stabilizer-fulvic acid. The prepared nanoparticles were well dispersed in water with about 10 nm in size according to transmission electron microscopy (TEM) observations. Fourier transform infrared spectroscopy (FTIR) revealed that fulvic acid were successfully covalently bonded to Fe 3 O 4 through the two adjacent phenolic hydroxyl groups and the carboxyl (- COOH ) groups were functionalized to the surface. The vibrating sample magnetometer (VSM) result showed that the nanoparticles were superparamagnetic and the saturation magnetizations were 60 emu/g. Moreover, their efficacy of liver magnetic resonance imaging (MRI) contrast agent was investigated by using live rat and tumor-bearing rabbit models through conventional clinical 1.5T MRI.
