Abstract
AbstractOxidative precipitation is a facile synthesis method to obtain ferromagnetic iron oxide nanoparticles from ferrous salts—with unexplored potential. The concentration of base and oxidant alone strongly affects the particle's structure and thus their magnetic properties despite the same material, magnetite (Fe3O4), is obtained when precipitated with potassium hydroxide (KOH) from ferrous sulfate (FeSO4) and treated with potassium nitrate (KNO3) at appropriate temperature. Depending on the potassium hydroxide and potassium nitrate concentrations, it is possible to obtain a series of different types of either single crystals or mesocrystals. The time‐dependent mesocrystal evolution can be revealed via electron microscopy and provides insights into the process of oriented attachment, yielding faceted particles, showing a facet‐dependent reactivity. It is found that it is the nitrate and hydroxide concentration that influences the ligand exchange process and thus the crystallization pathways. The presence of sulfate ions contributes to the mesocrystal evolution as well, as sulfate apparently hinders further crystal fusion, as revealed via infrared spectroscopy. Finally, it is found that nitrite, as one possible and ecologically highly relevant reduction product occurring in nature in context with iron, only evolves if the reaction is quantitative.
Highlights
IntroductionIt is found that nitrite, as one possible and ecologically highly relevant reduction product occurring in nature in context via a preliminary hydroxide stage (green rust), from which, in the end, more stable iron (hydr)oxides, such as goethite, lepidocrocite, feroxyhyte, ferrihydrite, or hematite, emerge in an initially nanowith iron, only evolves if the reaction is quantitative
Due to the many possible influences, the seemingly simple that takes place under natural conditions and, in this respect, is reaction becomes very complex in detail
Magnetite nanoparticles from iron(II) sulfate were synthesized via oxidative precipitation and the influence of nitrate concentration as a function of hydroxide concentration was investigated
Summary
It is found that nitrite, as one possible and ecologically highly relevant reduction product occurring in nature in context via a preliminary hydroxide stage (green rust), from which, in the end, more stable iron (hydr)oxides, such as goethite, lepidocrocite, feroxyhyte, ferrihydrite, or hematite, emerge in an initially nanowith iron, only evolves if the reaction is quantitative. K. Mandel Fraunhofer Institute for Silicate Research ISC nanoparticulate products, especially with regard to appearance, purity, and periodicity.[17,19] With regard to introduced, depleted, and released reaction components, environmental chemists, on the other hand, investigate the effects of such concentration changes on affected areas.[4,20,21] At this point, coordination.
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