In Situ Synthesis and Characterization of Water-soluble, Ultrasmall and Superparamagnetic Iron Oxide Nanoparticles Using Poly (Amidoamine) Dendrimer Templates

摘要

Water-soluble, ultrasmall, and superparamagnetic Fe_3O_4 nanoparticles were in-situ prepared using one-step coprecipitation method by using poly (amidoamine) (PAMAM) dendrimer templates. Photographs show that Fe_3O_4 nanoparticles prepared at the Fe~(3+)/Fe~(2+)/PAMAM molar ratio no higher than 40/30/1 disperse stably in water, forming clear colloidal solutions. TEM images show Fe_3O_4 nanoparticles have uniform size and good dispersity. The average diameter of particles is less than 8 nm. The HRTEM image indicates these Fe_3O_4 nanoparticles are of high crystallinity, and their crystal structure belongs to cubic system. XRD patterns show these nanoparticles as prepared are Fe_3O_4 of reverse spinel phase. The hysteresis loops confirm the superparamagnetism of Fe_3O_4 nanoparticles, and the saturation magnetization reaches 48.6 emu/g. FTIR spectra show the strong interactions between Fe_3O_4 nanoparticle surfaces and PAMAM dendrimers. Fe_3O_4 nanoparticles colloidal solutions prepared at the Fe~(3+)/Fe~(2+)/PAMAM molar ratio no higher than 20/15/1 keep on clarify and transparent after 6 months.