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Chapitre D'ouvrage Année : 2021

Magnetic Self-Assembling of spherical Co nanoparticles used as building blocks: Syntheses, properties and theory

Résumé

In this chapter, we show that thanks to the use of micellar and organometallic approaches, one can favor the growth of uniform spherical Co NPs with controlled surface passivation (dodecanoic acid or oleylamine), tunable size (from around 4 to 9 nm) and tunable nanocrystallinity (from fcc to hcp structure). As a result of the balance between van der Waals attractions between the metallic NPs, magnetic interactions between the magnetic NPs and solvent-mediated interactions between ligands, these uniform colloidal NPs can be used as building units to form a full set of assemblies which morphology depends on the deposition strategy, involving solvent evaporation. In the case of spontaneous self-assembling of magnetic NPs, compact hexagonal 2D arrays and 3D superlattices called supercrystals can form. In the latter case, either face-centered cubic supercrystalline films or single colloidal crystals can be obtained. Mesostructures of hexagonally ordered columns, labyrinths and void structures can result from assisted self-assembling, induced by the application of an external magnetic field. In highly ordered superlattices, individual NPs act as “artificial atoms” and occupy the lattice sites to form repetitive, periodic “artificial planes". From a fundamental point of view, these artificial solids constitute good models for investigating crystallization behavior. Resulting from collective interactions between neighboring NPs, they exhibit novel magnetic properties. The magnitude of these interactions, and then, the magnetic properties, can be tuned by various parameters including (1) the (crystallographic) nature of the magnetic NP, (2) the NP size, (3) the nature of the coating agent, (4) the nature of the solvent, (5) the evaporation rate and (6) if appropriate, the application of an external field during the solvent evaporation. On the one hand, simulations based on a flory-type solvation theory using Hansen solubility colloidal parameters allow to predict the cobalt NP size. On the other hand, Monte Carlo simulations and free energy theories are able to predict the size and type of patterns appearing during the evaporation of a solution of magnetic NPs under a magnetic field

Domaines

Matériaux
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Dates et versions

hal-03436538 , version 1 (02-08-2022)

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Citer

Johannes Richardi, Christophe Petit, Isabelle Lisiecki. Magnetic Self-Assembling of spherical Co nanoparticles used as building blocks: Syntheses, properties and theory. Davide Peddis; Sara Laureti; Dino Fiorani. New Trends in Nanoparticle Magnetism, 308, Springer, pp.181-216, 2021, Springer Series in Materials Science, 978-3-030-60472-1. ⟨10.1007/978-3-030-60473-8_8⟩. ⟨hal-03436538⟩
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