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

Abstract 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 NaNO 3 in an N 2 -deaerated aqueous NaOH solution (pH=12–13) at various temperatures below 37 °C. As the synthesis temperature increases from 4 to 37 °C, the MNPs are decreased in size ( d ) from 102±5.6 to 31.7±4.9 nm and widened in size distribution, Δ 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.