Sanchez-Lievanos Karla R, Knowles Kathryn E
Department of Chemistry, University of Rochester, Rochester, New York 14627, United States.
Chem Mater. 2022 Aug 23;34(16):7446-7459. doi: 10.1021/acs.chemmater.2c01568. Epub 2022 Aug 1.
This paper describes the first synthetic method to achieve independent control over both the cation distribution (quantified by the inversion parameter ) and size of colloidal ZnFeO nanocrystals. Use of a heterobimetallic triangular complex of formula ZnFe(μ-O)(μ-OCCF)(HO) as a single-source precursor, solvothermal reaction conditions, absence of hydroxyl groups from the reaction solvent, and the presence of oleylamine are required to achieve well-defined, crystalline, and monodisperse ZnFeO nanoparticles. The size of the ZnFeO nanocrystals increases as the ratio of oleic acid and oleylamine ligands to precursor increases. The inversion parameter increases with increasing solubility of the precursor in the reaction solvent, with the presence of oleic acid in the reaction mixture, and with decreasing reaction temperature. These results are consistent with a mechanism in which ligand exchange between oleic acid and carboxylate ligands bound to the precursor complex influences the degree to which the reaction produces a kinetically trapped or thermodynamically stable cation distribution. Importantly, these results indicate that preservation of the triangular Zn-O-Fe core structure of the precursor in the reactive monomer species is crucial to the production of a phase-pure ZnFeO product and to the ability to tune the cation distribution. Overall, these results demonstrate the advantages of using a single-source precursor and solvothermal reaction conditions to achieve synthetic control over the structure of ternary spinel ferrite nanocrystals.
本文描述了第一种能够独立控制胶体ZnFeO纳米晶体的阳离子分布（由反转参数量化）和尺寸的合成方法。要获得结构明确、结晶且单分散的ZnFeO纳米颗粒，需要使用式为ZnFe(μ-O)(μ-OCCF)(HO)的异双金属三角形配合物作为单源前驱体、溶剂热反应条件、反应溶剂中不存在羟基以及存在油胺。随着油酸和油胺配体与前驱体的比例增加，ZnFeO纳米晶体的尺寸增大。反转参数随着前驱体在反应溶剂中的溶解度增加、反应混合物中油酸的存在以及反应温度的降低而增大。这些结果与一种机制相符，即油酸与结合在前驱体配合物上的羧酸根配体之间的配体交换影响反应产生动力学捕获或热力学稳定阳离子分布的程度。重要的是，这些结果表明前驱体的三角形Zn-O-Fe核心结构在反应性单体物种中的保留对于获得相纯的ZnFeO产物以及调节阳离子分布的能力至关重要。总体而言，这些结果证明了使用单源前驱体和溶剂热反应条件来实现对三元尖晶石铁氧体纳米晶体结构的合成控制的优势。
