Karine Elihn

Nanoparticle formation by laser-assisted photolysis of ferrocene.

Abstract Laser-assisted formation of iron-containing nanoparticles has been performed by photolytic dissociation of ferrocene vapour by a pulsed ArF excimer laser at 193 nm. The process was carried out at atmospheric pressure, either in an inert atmosphere of argon or in a reactive gas mixture of argon and oxygen. Differential mobility analysers, DMA s, were used for the determination of the particle sizes. By changing laser parameters such as beam size, pulse energy and repetition rate, particle sizes ranging from 3 to 100 nm, were generated. Morphology and size of the nanoparticles were studied via transmission electron microscopy, TEM, and structural information was obtained from electron diffraction. Chemical composition was determined through X-ray photoelectron spectroscopy, XPS, and energy dispersive X-ray spectroscopy, EDX.

Formation and emission spectroscopy of laser-generated nanoparticles

Fe nanoparticles, with both fcc and bcc structures and with a C shell that protects against oxidation, were generated by the laser-assisted photolytic chemical vapor decomposition of ferrocene (FeCp2). Amorphous W and WN0,3 nanoparticles were formed by laser ablation (LA) of solid W in Ar and in N2 ambient, respectively. Laser-assisted chemical vapor deposition of W yielded crystalline W nanoparticles (β phase) from a WF6/H2/Ar gas mixture. ArF excimer laser was used as the radiation source in all the experiments. Measurements and analysis of the emitted blackbody-like radiation from the laser heated particles were performed and dominant cooling processes such as evaporation and heat transfer by the ambient gases were identified. The particles could be heated up to the boiling and melting point of Fe and W, respectively. Lognormal particle size distributions were found for Fe/C and W nanoparticles generated by vapor decomposition or deposition processes respectively, and then modeled at low particle concentration (with no coagulation). The thickness of the C shell was practically independent of the laser fluence, while the size of the Fe core could be varied for the Fe/C particles. The LA yielded no lognormal-type distribution for the amorphous WN0,3 particles.