Method for synthesizing ferrite nanoparticles ∼30 nm in diameter on neutral pH condition for biomedical applications

Nanosized ferrite spherical particles, similar to30 nm in diameter as revealed by scanning electron microscopy, were synthesized from an aqueous Fe(OH)(2) suspension (pH=7.6-8.0) at 25degreesC by oxidizing it with H2O2. The nanoparticles were of a spinel structure of an intermediate between Fe3O4 and gamma-Fe2O3, as revealed by x-ray diffraction. Compared to the nanoparticles synthesized by our previous method in which an aqueous solution of Fe2++Fe3+ was oxidized by air (oxygen), the nanoparticles increased in size, from similar to10 nm (previous method) to 30 nm. Also saturation magnetization increased, though slightly, from 76 emu/g (previous method) to 80 emu/g (present method). Therefore, the ferrite nanoparticles synthesized by this method will improve the efficiency of magnetic separation. Because synthesis is performed at room temperature and neutral conditions (pH=7.1-7.8), which are compatible with most bioactive molecules (e.g., antibodies and proteins), these molecules will be immobilized onto the surface of the nanoparticles during their syntheses. (C) 2003 American Institute of Physics.