title: Anhydrous Amorphous Calcium Oxalate Nanoparticles from Ionic Liquids: Stable Crystallization Intermediates in the Formation of Whewellite.
abstract: The mechanisms by which amorphous intermediates transform into crystalline materials are not well understood. To test the viability and the limits of the classical crystallization, new model systems for crystallization are needed. With a view to elucidating the formation of an amorphous precursor and its subsequent crystallization, the crystallization of calcium oxalate, a biomineral widely occurring in plants, is investigated. Amorphous calcium oxalate (ACO) precipitated from an aqueous solution is described as a hydrated metastable phase, as often observed during low-temperature inorganic synthesis and biomineralization. In the presence of water, ACO rapidly transforms into hydrated whewellite (monohydrate, CaC2 O4 ⋅H2 O, COM). The problem of fast crystallization kinetics is circumvented by synthesizing anhydrous ACO from a pure ionic liquid (IL-ACO) for the first time. IL-ACO is stable in the absence of water at ambient temperature. It is obtained as well-defined, non-agglomerated particles with diameters of 15-20 nm. When exposed to water, it crystallizes to give (hydrated) COM through a dissolution/recrystallization mechanism.
authors.affiliation: Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität, Duesbergweg 10-14, 55099 Mainz (Germany).
authors.forename: Aaron
authors.initials: A
authors.lastname: Gehl
authors.affiliation: Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität, Duesbergweg 10-14, 55099 Mainz (Germany).
authors.forename: Michael
authors.initials: M
authors.lastname: Dietzsch
authors.affiliation: Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität, Duesbergweg 10-14, 55099 Mainz (Germany).
authors.forename: Mihail
authors.initials: M
authors.lastname: Mondeshki
authors.affiliation: Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität, Duesbergweg 10-14, 55099 Mainz (Germany).
authors.forename: Sven
authors.initials: S
authors.lastname: Bach
authors.affiliation: Institut für Geowissenschaften, Johannes Gutenberg Universität, J.-J. Becherweg 21, 55099 Mainz (Germany).
authors.forename: Tobias
authors.initials: T
authors.lastname: Häger
authors.affiliation: Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität, Duesbergweg 10-14, 55099 Mainz (Germany).
authors.forename: Martin
authors.initials: M
authors.lastname: Panthöfer
authors.affiliation: Institut für Physikalische Chemie, Johannes Gutenberg Universität, Duesbergweg 10-14, 55099 Mainz (Germany).
authors.forename: Bastian
authors.initials: B
authors.lastname: Barton
authors.affiliation: Institut für Physikalische Chemie, Johannes Gutenberg Universität, Duesbergweg 10-14, 55099 Mainz (Germany).
authors.forename: Ute
authors.initials: U
authors.lastname: Kolb
authors.affiliation: Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität, Duesbergweg 10-14, 55099 Mainz (Germany). tremel@uni-mainz.de.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Tremel
keywords: amorphous materials; anhydrous materials; biomineralization; calcium oxalates; crystallization