Web Release Date: August 3,
Vacancy Coalescence during Oxidation of Iron Nanoparticles
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Materials Sciences Division, Molecular Foundry, and Advanced Light Source, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, Institut Català d' Estudis i Recerca Avançat and Institut Catal
de
Nanotecnologia, Bellaterra 08193, Barcelona, Spain, Institut de Ciència de Materials de Barcelona, (ICMAB-CSIC),
Campus UAB, Bellaterra 08193, Spain, and Department of Chemistry, University of California at Berkeley,
Berkeley, California 94720
Received April 12, 2007
Abstract:
In the present work, we analyze the geometry and composition of the nanostructures obtained from the oxidation of iron nanoparticles. The initial oxidation of iron takes place by outward diffusion of cations through the growing oxide shell. This net material flow is balanced by an opposite flow of vacancies, which coalesce at the metal/oxide interface. Thus, the partial oxidation of colloidal iron nanoparticles leads to the formation of core-void-shell nanostructures. Furthermore, the complete oxidation of iron nanoparticles in the 3-8 nm size range leads to the formation of hollow iron oxide nanoparticles. We analyze the size and temperature range in which vacancy coalescence during oxidation of amine-stabilized iron nanoparticles takes place. Maghemite is the crystallographic structure obtained from the complete oxidation of iron nanoparticles under our synthetic conditions.
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