One-step preparation of amorphous iron nanoparticles by laser ablation

Amorphous Fe nanoparticles are always difficult to prepare by physical gas-phase methods though rapid cooling rates are applied. Here we report a physical preparation of pure amorphous Fe nanoparticles by laser ablation of a 0.5-mm-diameter Fe wire and the investigation of their formation mechanism. Amorphous Fe nanoparticles with a shell of γ-Fe2O3 and the sizes of 1–3 nm are obtained at the laser power densities above the ablation threshold. Finally, the as-prepared nanoparticles are characterized by XRD, TEM, XPS and VSM to discover the structure, morphology, surface composition, crystallization and magnetic property in detail. We find that the holistic explosive evaporation induced by the small-size target not by the processing parameters determines the nature of the amorphous Fe nanoparticles. The as-prepared amorphous Fe nanoparticles are crystallized at 400 °C with an increase of particle size to about 10 nm.

Graphical abstractAmorphous Fe nanoparticles with a shell of γ-Fe2O3 are obtained by laser ablation of an iron wire. The holistic explosive evaporation induced by the small-size target not by the processing parameters determines the nature of the amorphous Fe nanoparticles. The as-prepared amorphous Fe nanoparticles are crystallized at 400 °C.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We report a novel approach to prepare amorphous Fe nanoparticles by laser ablation. ► Amorphous Fe nanoparticles with a shell of γ-Fe2O3 were obtained. ► Ablation mechanism changed by target size determines the nature of nanoparticles. ► The as-prepared amorphous Fe nanoparticles are crystallized at 400 °C.