Crystallization of Transition-Metal Oxides in Aqueous Solution beyond Ostwald Ripening
| Autor: | Eun-Suk Jeong, Inhui Hwang, Sang-Wook Han |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Ostwald ripening
Materials science Aqueous solution Extended X-ray absorption fine structure Crystal growth 02 engineering and technology Surfaces and Interfaces 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences 0104 chemical sciences X-ray absorption fine structure law.invention symbols.namesake Transition metal law Electrochemistry symbols Physical chemistry General Materials Science Crystallization 0210 nano-technology Spectroscopy Wurtzite crystal structure |
| Zdroj: | Langmuir. 36:10565-10576 |
| ISSN: | 1520-5827 0743-7463 |
| DOI: | 10.1021/acs.langmuir.0c01903 |
| Popis: | The crystallization mechanism of transition-metal oxides (TMOs) in a solution was examined based on ZnO crystallization using in-situ x-ray absorption fine structure (XAFS) measurements at the Zn K edge and semi-empirical quantum chemistry (SEQC) simulations. The XAFS results quantitatively determine the local structural and chemical properties around a zinc atom at successive stages from Zn(NO3)2 to ZnO in an aqueous solution. The results also show that a zinc atom in Zn(NO3)2 ions dissolves in a solution and bonds with approximately three oxygen atoms at room temperature (RT). When hexamethylenetetramine (C6H12N4) is added to the solution at RT, a stable Zn-O complex consisting of six Zn(OH)2s is formed, which is a seed of ZnO crystals. The Zn-O complexes partially and fully form into a wurtzite ZnO at 60 and 80 °C, respectively. Based on the structural properties of Zn-O complexes determined by extended-XAFS (EXAFS), SEQC simulations clarify that Zn-O complexes consecutively develop from a linear structure to a polyhedral complex structure under the assistance of hydroxyls (OH-s) in an aqueous solution. In a solution with a sufficient concentration of OH-s, ZnO spontaneously grows through the merging of ZnO seeds (6Zn(OH)2s), reducing the total energy by the reactions of OH-s. ZnO crystallization suggests that the crystal growth of TMO can only be ascribed to Ostwald ripening when it exactly corresponds to the size growth of TMO particles. |
| Databáze: | OpenAIRE |
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