  Nanoparticles of iron were prepared in distilled water using very thin iron
wires and sheets, by the electro-exploding wire technique. Transmission
electron microscopy reveals the size of the nanoparticles to be in the range 10
to 50 nm. However, particles of different sizes can be segregated by using
ultrahigh centrifuge. X-ray diffraction studies confirm the presence of the
cubic phase of iron. These iron nanoparticles were found to exhibit
fluorescence in the visible region in contrast to the normal bulk material. The
room temperature hysteresis measurements upto a field of 1.0 tesla were
performed on a suspension of iron particles in the solution as well as in the
powders obtained by filtration. The hysteresis loops indicate that the
particles are superparamagnetic in nature. The saturation magnetizations was ~
60 emu / gm. As these iron particles are very sensitive to oxygen a coating of
non-magnetic iron oxide tends to form around the particles giving it a core -
shell structure. The core particle size is estimated theoretically from the
magnetization measurements. Suspensions of iron nanoparticles in water have
been proposed to be used as an effective decontaminant for ground water.
