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Article Dans Une Revue Journal of Applied Physics Année : 2020

Equilibrium shape of core(Fe)–shell(Au) nanoparticles as a function of the metals volume ratio

Anne Ponchet
Ségolène Combettes
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Patrizio Benzo
Nathalie Tarrat
Magali Benoit

Résumé

The equilibrium shape of nanoparticles is investigated to elucidate the various core–shell morphologies observed in a bimetallic system associating two immiscible metals, iron and gold, that crystallize in the bcc and fcc lattices, respectively. Fe–Au core–shell nanoparticles present a crystalline Fe core embedded in a polycrystalline Au shell, with core and shell morphologies both depending on the Au/Fe volume ratio. A model is proposed to calculate the energy of these nanoparticles as a function of the Fe volume, Au/Fe volume ratio, and the core and shell shape, using the density functional theory-computed energy densities of the metal surfaces and of the two possible Au/Fe interfaces. Three driving forces leading to equilibrium shapes were identified: the strong adhesion of Au on Fe, the minimization of the Au/Fe interface energy that promotes one of the two possible interface types, and the Au surface energy minimization that promotes a 2D–3D Stranski–Krastanov-like transition of the shell. For a low Au/Fe volume ratio, the wetting is the dominant driving force and leads to the same polyhedral shape for the core and the shell, with an octagonal section. For a large Au/Fe ratio, the surface and interface energy minimizations can act independently to form an almost cube-shaped Fe core surrounded by six Au pyramids. The experimental nanoparticle shapes are well reproduced by the model, for both low and large Au/Fe volume ratios.
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Dates et versions

hal-02913274 , version 1 (08-08-2020)
hal-02913274 , version 2 (22-07-2022)

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Citer

Anne Ponchet, Ségolène Combettes, Patrizio Benzo, Nathalie Tarrat, Marie-José Casanove, et al.. Equilibrium shape of core(Fe)–shell(Au) nanoparticles as a function of the metals volume ratio. Journal of Applied Physics, 2020, 128 (5), pp.055307. ⟨10.1063/5.0014906⟩. ⟨hal-02913274v1⟩
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