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Experimental and theoretical evidence for oriented aggregate crystal growth of CoO in a polyol

Abstract : Monodispersed about 5 nm sized CoO crystals were prepared by forced hydrolysis of cobalt(II) acetate in diethyleneglycol (DEG) solvent. The adsorption of the solvent molecules on these primary nanocrystals caused their in-situ oriented aggregation resulting in the precipitation of textured submicrometer-sized polycrystals. X-ray diffraction, Infrared spectroscopy, Transmission Electron Microscopy and Thermogravimetry analyses coupled to ab-initio modeling were applied to understand the adsorption mechanism of the alcohol moieties and the role of the molecule-to-surface and molecule-to-molecule interactions in the crystal growth mechanism of these polycrystals. We showed that DEG moieties are mainly adsorbed at the top of the cobalt (100) surface atoms and the process does not involve the whole molecule but only one of its extreme oxygen atoms. As a consequence, adsorbed DEG molecules exhibit an extended configuration which is favorable to intermolecule hydrogen bonding from one covered nanocrystal to another. Interestingly, at high surface coverage, the energy required for DEG attachment to the crystal surface is found to be 18.6 kJ/mol per molecule, while that required for hydrogen bonding between a bearing molecule and a neighbor one is found to be 36,4 kJ/mol per molecule, meaning that the collective departure of an assembly of DEG from the surface of CoO nanocrystals is therodynamically easier, leading thus to the observed final morphology.
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https://hal-univ-lemans.archives-ouvertes.fr/hal-03233876
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Soumis le : mardi 25 mai 2021 - 10:18:33
Dernière modification le : lundi 14 juin 2021 - 16:00:03
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Thomas Gaudisson, Surender Sharma, Rahamane Mohamed, B. Sitamtze Youmbi, Nicolas Menguy, et al.. Experimental and theoretical evidence for oriented aggregate crystal growth of CoO in a polyol. CrystEngComm, Royal Society of Chemistry, 2021, 23 (8), pp.1756 - 1764. ⟨10.1039/d0ce01525c⟩. ⟨hal-03233876⟩

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