title: Size effects in MgO cube dissolution.
abstract: Stability parameters and dissolution behavior of engineered nanomaterials in aqueous systems are critical to assess their functionality and fate under environmental conditions. Using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, we investigated the stability of cubic MgO particles in water. MgO dissolution proceeding via water dissociation at the oxide surface, disintegration of Mg(2+)-O(2-) surface elements, and their subsequent solvation ultimately leads to precipitation of Mg(OH)2 nanosheets. At a pH ≥ 10, MgO nanocubes with a size distribution below 10 nm quantitatively dissolve within few minutes and convert into Mg(OH)2 nanosheets. This effect is different from MgO cubes originating from magnesium combustion in air. With a size distribution in the range 10 nm ≤ d ≤ 1000 nm they dissolve with a significantly smaller dissolution rate in water. On these particles water induced etching generates (110) faces which, above a certain face area, dissolve at a rate equal to that of (100) planes.1 The delayed solubility of microcrystalline MgO is attributed to surface hydroxide induced self-inhibition effects occurring at the (100) and (110) microplanes. The present work underlines the importance of morphology evolution and surface faceting of engineered nanomaterials particles during their dissolution.
authors: Institute of Particle Technology, Friedrich-Alexander Universität Erlangen-Nürnberg , Cauerstrasse 4, 91058 Erlangen, Germany.
authors: Stefan O
authors: SO
authors: Baumann
authors: Johannes
authors: J
authors: Schneider
authors: Andreas
authors: A
authors: Sternig
authors: Daniel
authors: D
authors: Thomele
authors: Slavica
authors: S
authors: Stankic
authors: Thomas
authors: T
authors: Berger
authors: Henrik
authors: H
authors: Grönbeck
authors: Oliver
authors: O
authors: Diwald