Superparamagnetic magnetite nanopar

Superparamagnetic magnetite nanoparticles were obtained starting from a mixture of iron(II) and
iron(III) solutions in a preset total iron concentration from 0.04 to 0.8 mol l-
1 with ammonia at 25 and
70 8C. The regeneration of cellulose from viscose produces micrometrical spherical cellulose beads in
which synthetic magnetite were embedded. The characterization of cellulose–magnetite beads by X-ray
diffraction, Scanning and Transmission Electron Microscopy and magnetic measurement is reported. X-
ray diffraction patterns indicate that the higher is the total iron concentration and temperature the
higher is the crystal size of the magnetite obtained. Transmission Electron Microscopy studies of
cellulose–magnetite beads revealed the distribution of magnetite nanoparticles inside pores of hundred
nanometers. Magnetite as well as the cellulose–magnetite composites exhibit superparamagnetic
characteristics. Field cooling and zero field cooling magnetic susceptibility measurements confirm the
superparamagnetic behaviour and the blocking temperature for the magnetite with a mean size of
12.5 nm, which is 200 K.