Iron nanoparticle growth induced by Kr–F excimer laser photolysis of Fe(CO)5

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In this article the process of nanoparticle formation under the condensation of highly supersaturated atomic vapor produced by the photodissociation of metal-bearing compounds was investigated. The iron nanoparticles were synthesized by Kr–F laser pulse photolysis of Fe(CO)5. The measurements of an optical density of condensed phase were performed using a laser light extinction at a wavelength 633 nm. The particle size during their formation process was measured by a two-color time-resolved laser-induced incandescence. The final iron particle sizes and their structure were analyzed by a transmission electron microscopy. It has been shown that the process of iron particle formation in the investigated conditions could be divided onto three stages: the fast nucleation of iron atoms during 1–2 μs, the surface growth of particles up to the sizes of 1–6 nm with increasing volume fraction of condensed phase during 100–250 μs, and the relatively slow particle coagulation up to the final sizes of 5–9 nm. The effective rate constants of iron clusters and particle growth were extracted using laser light extinction measurements. The essential role of the reactions of iron clusters and particles with the parental Fe(CO)5 molecules was established. The kinetic mechanism of iron nanoparticle growth induced by photo-dissociation of Fe(CO)5 at room temperature based on obtained experimental results and known literature data has been suggested. The results obtained could be used for the developments of methods of synthesis of catalysts, magnetic nanopowders, and others nanomaterials at room temperature. Besides that, the presented experimental data could be useful for the validation of kinetic models of gas-phase condensation of supersaturated vapor of solids.