Vacancy Coalescence during Oxidation of Iron Nanoparticles

Abstract

Supporting Information Available: Detailed synthesis and experimental procedures, UV-vis, XRD, and XAS of the iron/iron oxide nanoparticles, SQUID of the final iron oxide shells, histograms of the particle sizes, and analysis of the electron beam influence during TEM imaging and of the high-temperature oxidation of the particles in solution. This material is available free of charge via the Internet at

Cobalt Fischer–Tropsch Catalyst Regeneration: The Crucial Role of the Kirkendall Effect for Cobalt Redispersion

“…The formation of hollow oxide particles upon oxidation has been reported previously, on several metals including Co, Ni, Fe and Cu [15,16,[18][19][20], and the mechanism responsible for this is the Kirkendall effect, where diffusivity differences of the reactants in solid state reactions results in void formation [21][22][23]. In the case of oxidation of metallic nanoparticles the outward diffusion of the metal (cations) through the growing oxide layer is much faster than the inward diffusion of oxygen.…”

Preparation of tunable-sized iron nanoparticles based on magnetic manipulation in inert gas condensation (IGC)

“…Based on the Cabrera-Mott theory, once an oxide layer initially formed surrounding the NP, transport of electrons from the iron core to the adsorbed oxygen through the oxide layer allows the oxidation to continue. 31 This establishes a strong electric field within the NP that is able to drive the ion diffusion. With the influence of the electric field, Fe cations move towards the particle surface and O anions move towards the core.…”

“…This is observed in Figures 1(a) and 1(b), indicating the presence of a void resulting from the Kirkendall effect. 30,31 Figure 2 shows clearly the size evolution with the thickness of the backing plate introduced in the magnetron head. The faceted morphologies observed for particles larger than $15 nm, i.e., truncated cube (TC) and truncated rhombic dodecahedron (TRD), are presented as insets.…”

“…In any case, Figure 1 demonstrates that with increasing backing plate thickness, the particle size shows a clear decrease, and the morphology experiences an evolution from faceted to close-to-spherical polyhedral shapes. On the other hand, the particle structure varies with the change of size and shape: NPs exhibit a core-shell structure for faceted NPs as well as close-to-spherical particles larger than $8 nm; however, a fully oxidized uniform structure is formed with a void in the center due to the Kirkendall effect 30,31 for nearspherical particles smaller than $8 nm.…”

The Reactivity of Colloidal Inorganic Nanoparticles

“…As well, Cabot et al studied the vacancy coalescence during the oxidation process of iron INPs in solution with a controlled oxygen flow and temperature, which leads to the formation of hollow iron oxide INPs. (Cabot et al, 2007). Also has to be considered that the properties of the INPs exposed to transformation processes can be affected.…”