Laser-induced self-assembly of iron oxide nanostructures with controllable dimensionality

The nanosecond pulsed laser ablation of fine iron powder submerged under different liquid media (water, methanol, ethanol, and isopropanol) is used to rapidly produce a variety of iron oxide nanostructures from nanoparticles to nanowires and nanosheets. The dimensionality of the nanostructures is shown to be a consequence of two controllable mechanisms. The rapid oxidation, collisional quenching, and coalescence of the ablation products are suggested as the dominant mechanisms for the formation of zero-dimensional nanostructures such as hematite (α-Fe2O3) nanoparticles in water, or iron oxyhydroxide nanoparticles under alcohols. By employing different laser wavelengths (248 and 532 nm) it is demonstrated that the growth of extended iron oxyhydroxide nanostructures (one-dimensional nanowires and two-dimensional nanosheets) under methanol is possible and is a consequence of a second self-assembly mechanism driven by interaction between the UV laser pulses and the ablation products.