Nanoparticules métalliques anisotropes synthétisées par voie chimique : fils, plaquettes et particules hybrides de cobalt-nickel, propriétés structurales et magnétiques ; fils d'argent auto-organisés

Abstract : The present manuscript is focused on syntheses of anisotropic shape metallic particles in nanometric scale by polyol process. Two ways were explored: one consists to induce an anisotropic growth of cobalt-nickel nanoparticles and the other leading to silver nanowires is related to a template effect.
For cobalt-nickel system, the investigation of the effect of different parameters reveals that the added sodium hydroxide concentration and the ratio of cobalt and nickel precursors salts are keys factors for a morphological control of nanoparticles. Many shapes were observed: 8 nm diameter wires, nanoplates, but also unusual morphologies such as dumbbells. The shape evolution is follow by crystallographic modifications of NPs structure and local variations of cobalt and nickel contents. We show that nanowires grow along the c-axis of the hexagonal structure and nickel enrichment at their extremities. The magnetic investigations of nanoparticles revealed a narrow relation between nanoparticles properties and morphology. The analyses of the system before the reduction operates indicate that morphologies result to cobalt and nickel different reactivity in the medium.
Concerning process assisted by template, silver nanowires with 6 nm diameter and length of several micrometers are prepared in biphasic medium polyol/toluene. They certainly come from an organization of silver nanoparticles and an oriented agglomeration along fibers of silver thiolate.
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Theses
Material chemistry. Université Paris-Diderot - Paris VII, 2005. French


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Submitted on : Sunday, January 6, 2008 - 1:10:57 AM
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Diane Ung. Nanoparticules métalliques anisotropes synthétisées par voie chimique : fils, plaquettes et particules hybrides de cobalt-nickel, propriétés structurales et magnétiques ; fils d'argent auto-organisés. Material chemistry. Université Paris-Diderot - Paris VII, 2005. French. <tel-00202393>

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