Effect of OH− concentration on Fe3O4 nanoparticle morphologies supported by first principle calculation

It has been known that morphology and size could affect the properties of crystalline magnetite (Fe3O4). However, specific principle for a simple and predictable way to control them was still absent. Alkali concentration has been demonstrated to be an influential factor on the morphology changes in an ethylene glycol/diethylene glycol (EG/DEG) binary solvothermal system. In this work, crystalline Fe3O4 nanoparticles with a variety of morphologies including clusters, solid spheres, octahedron, truncated-octahedrons, tetrakaidecahedrons and truncated-cubes were prepared in a facile way. Furthermore, first principle calculation based on density functional theory was carried out to calculate the adsorption energies of OH− on different crystal planes of Fe3O4. The calculation results interpreted the crystal morphology changes accordingly, despite of the simplicity of the calculation model. The agreement between the theoretical calculation and the experimental data indicates the promising benefit of using first principle calculation to predict and design crystal morphologies in the future. On the other hand, size of the anisotropic octahedral Fe3O4 nanoparticles could be regulated from 30 nm to 115 nm by changing the volume ratio of EG/DEG with a certain OH− concentration.