Preparation of size-controlled (30-100 nm) magnetite nanoparticles for biomedical applications

Size-controlled magnetite nanoparticles (MNPs) with several dozen nanometers ( nm) were synthesized for biomedical applications. Nanoparticles of single-phase magnetite, as revealed by X-ray analyses and magnetic measurements, were prepared by oxidizing ferrous hydroxide (Fe(OH)(2)) with a weak oxidant NaNO3 in an N-2-deaerated aqueous NaOH solution ( pH = 12-13) at various temperatures below 37 degrees C. As the synthesis temperature increases from 4 to 37 degrees C, the MNPs are decreased in size (d) from 102 +/- 5.6 to 31.7 +/- 4.9 nm and widened in size distribution, Delta d/d increases from 5.5% to 15%. Prepared without using any surfactant, the MNPs are advantageous for immobilizing functional molecules stably on the surfaces for biomedical applications. (c) 2006 Elsevier B.V. All rights reserved.