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Role of water during crystallization of amorphous cobalt phosphate nanoparticles

  • The transformation of amorphous precursors into crystalline solids and the associated mechanisms are still poorly understood. We illuminate the formation and reactivity of an amorphous cobalt phosphate hydrate precursor and the role of water for its crystallization process. Amorphous cobalt phosphate hydrate nanoparticles (ACP) with diameters of ∼20 nm were prepared in the absence of additives from aqueous solutions at low concentrations and with short reaction times. To avoid the kinetically controlled transformation of metastable ACP into crystalline Co₃(PO₄)₂ × 8H₂O (CPO) its separation must be fast. The crystallinity of ACP could be controlled through the temperature during precipitation. A second amorphous phase (HT-ACP) containing less water and anhydrous Co₃(PO₄)₂ was formed at higher temperature by the release of coordinating water. ACP contains approximately five molecules of structural water per formula unit as determined by thermal analysis (TGA) and quantitative IRThe transformation of amorphous precursors into crystalline solids and the associated mechanisms are still poorly understood. We illuminate the formation and reactivity of an amorphous cobalt phosphate hydrate precursor and the role of water for its crystallization process. Amorphous cobalt phosphate hydrate nanoparticles (ACP) with diameters of ∼20 nm were prepared in the absence of additives from aqueous solutions at low concentrations and with short reaction times. To avoid the kinetically controlled transformation of metastable ACP into crystalline Co₃(PO₄)₂ × 8H₂O (CPO) its separation must be fast. The crystallinity of ACP could be controlled through the temperature during precipitation. A second amorphous phase (HT-ACP) containing less water and anhydrous Co₃(PO₄)₂ was formed at higher temperature by the release of coordinating water. ACP contains approximately five molecules of structural water per formula unit as determined by thermal analysis (TGA) and quantitative IR spectroscopy. The Co²+ coordination in ACP is tetrahedral, as shown by XANES/EXAFS spectroscopy, but octahedral in crystalline CPO. ACP is stable in the absence of water even at 500 °C. In the wet state, the transformation of ACP to CPO is triggered by the diffusion and incorporation of water into the structure. Quantitative in situ IR analysis allowed monitoring the crystallization kinetics of ACP in the presence of water.zeige mehrzeige weniger

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Metadaten
Autor*innen:S. Bach, M. Panthöfer, Ralf BienertORCiD, Ana de Oliveira Guilherme BuzanichORCiD, Franziska EmmerlingORCiD, W. Tremel
Dokumenttyp:Zeitschriftenartikel
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):Crystal Growth & Design
Jahr der Erstveröffentlichung:2016
Verlag:ACS Publications
Jahrgang/Band:16
Ausgabe/Heft:8
Erste Seite:4232
Letzte Seite:4239
DDC-Klassifikation:Naturwissenschaften und Mathematik / Chemie / Analytische Chemie
Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Freie Schlagwörter:Calcium-carbonate; Crystal-growth; Fluorapatite-gelatin nanocomposites; Nucleation; Polymorphism; Zinc phosphate
DOI:10.1021/acs.cgd.6b00208
ISSN:1528-7483
ISSN:1528-7505
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:04.10.2016
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:04.10.2016
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