Hydrothermal Synthesis of Euhedral Co3O4 Nanocrystals via Nutrient-Assisted Topotactic Transformation of the Layered Co(OH)2 Precursor under Anoxic Conditions: Insights into Intricate Routes Leading to Spinel Phase Development and Shape Perfection
| Autor: | Joanna Gryboś, Angelika Gryczynska, Witold Piskorz, Camillo Hudy, Zbigniew Sojka |
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| Rok vydání: | 2020 |
| Předmět: |
Materials science
Spinel chemistry.chemical_element General Chemistry engineering.material Condensed Matter Physics Anoxic waters chemistry.chemical_compound Nanocrystal Octahedron Chemical engineering chemistry Sodium hydroxide Phase (matter) engineering Hydrothermal synthesis General Materials Science Cobalt |
| Zdroj: | Crystal Growth & Design. 20:7771-7787 |
| ISSN: | 1528-7505 1528-7483 |
| Popis: | Euhedral cobalt spinel cubes, octahedra, and cuboctahedra with narrow size dispersions have been synthesized in a one-pot hydrothermal reaction, using cobalt(II) nitrate and sodium hydroxide at variable concentrations as the only reagents, while their ratio was kept constant at $c_{Co^2+}/c_{OH^–}$ = 2.7. Three main reaction stages, including parent reactive template (PRT) formation, nutrient mediated topotactic nucleation (NTN), and morphogenesis of nanocrystals (MNC), were distinguished. In the NTN step, the primary spinel grains development occurs with the [100] and [111] directions of the $Co_{3}O_{4}$ facets inheriting the [1-11] direction of the elongated PRT plates (formation of cubes) or the [001] direction of the hexagonal PRT plates (formation of octahedra). In an anoxic environment, the excess nitrate anions play a critical role as the $Co^{2+}$ to $Co^{3+}$ oxidants and oxygen donors required to attain the $Co_{3}O_{4}$ stoichiometry. The nucleated $Co_{3}O_{4}$ primary nanocrystals are spontaneously assembled into sub-micrometer spinel mesocrystals via imperfectly oriented attachments and then consolidated into euhedral bulk nanocrystals by a hydrothermal treatment (nanocubes) or via dissolution and reentrant recrystallization processes (octahedra and cuboctahedra). |
| Databáze: | OpenAIRE |
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