title: Synthesis of ordered mesoporous Fe3O4 and gamma-Fe2O3 with crystalline walls using post-template reduction/oxidation.
abstract: Ordered mesoporous Fe(3)O(4) with crystalline walls (inverse spinel structure) has been synthesized for the first time, representing to the best of our knowledge, the first synthesis of a reduced mesoporous iron oxide. Synthesis was achieved by reducing ordered mesoporous alpha-Fe(2)O(3) (corundum structure) to Fe(3)O(4) spinel then to gamma-Fe(2)O(3) by oxidation, while preserving the ordered mesostructure and crystalline walls throughout. Such solid/solid transformations demonstrate the stability of the mesostructure to structural phase transitions from the hexagonal close packed oxide subarray of alpha-Fe(2)O(3) (corundum structure) to the cubic close packed subarray of Fe(3)O(4) spinel and gamma-Fe(2)O(3). Preliminary magnetic measurements reveal that the spins in both Fe(3)O(4) and gamma-Fe(2)O(3) are frozen at 295 K, despite the wall thickness (7 nm) being less than the lower limit for such freezing in corresponding nanoparticles (>8 nm).
authors.affiliation: School of Chemistry and EaStChem, University of St. Andrews, St. Andrews, Fife KY16 9ST, UK.
authors.forename: Feng
authors.initials: F
authors.lastname: Jiao
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Jumas
authors.forename: Manfred
authors.initials: M
authors.lastname: Womes
authors.forename: Alan V
authors.initials: AV
authors.lastname: Chadwick
authors.forename: Andrew
authors.initials: A
authors.lastname: Harrison
authors.forename: Peter G
authors.initials: PG
authors.lastname: Bruce