Shaping Magnetite by Hydroxyl Group Numbers of Small Molecules

Abstract

Despite numerous reports on magnetite formation with the assistance of various additives, the role of hydroxyl group (−OH) numbers in small polyol molecules has not yet been understood well. We selected small molecules containing different −OH numbers, such as ethanol, ethylene glycol, propanetriol, butanetetrol, pentitol, hexanehexol, and cyclohexanehexol, as additives in coprecipitation. By increasing the −OH number in these small polyol molecules, the formation of crystallization was slowed, and the size and shape of magnetite were regulated as well possibly due to the changed complexation strength and the stability of the precursor. The increase in temperature and the Fe 2+ /Fe 3+ ratio can reduce the complexation strength. The nucleation and growth of magnetite proceed possibly through the aggregation of polyol-stabilized amorphous complexes and two-line ferrihydrite with low crystallinity based on the −OH numbers, suggesting a nonclassical pathway. The as-prepared magnetite showed a r 2 /r 1 ratio after in vitro MRI measurement as follows: Fe 3

Recent Advances in Magnetite Crystallization: Pathway, Modulation, and Characterization

“…Small polyol molecules containing hydroxyl groups can complex with the intermediates of magnetite. As the number of hydroxyl groups increased, the complexation strength, the steric hindrance, and the resulting stability of the intermediates were enhanced, which in turn control the size and shape of the magnetite .…”

“…As the number of hydroxyl groups increased, the complexation strength, the steric hindrance, and the resulting stability of the intermediates were enhanced, which in turn control the size and shape of the magnetite. 162 N-Methyldiethanolamine (NMDEA) has the potential to stabilize green rust and reduce the nucleation rate of magnetite, facilitating the formation of larger magnetite crystals. 21 Citrate ligand, an intensively applied reducing and capping agent, may inhibit magnetite formation by its electrostatic and steric repulsion effect, pH buffering effect, and oxidation effect.…”

Systematically Designed Surface and Morphology of Magnetite Nanoparticles Using Monocarboxylic Acid with Various Chain Lengths under Hydrothermal Condition

“…Fe 3 O 4 NPs have been synthesized using various methods such as microemulsion, thermal decomposition, and hydrothermal synthesis. ,− Hydrothermal synthesis is an environmentally friendly method due to the use of water as solvent and the absence of toxic solvents, which can minimize the waste generation. , It can also produce a superior crystallinity of Fe 3 O 4 NPs over other methods due to the high-temperature effect. Additionally, the hydrothermal environment above 200 °C yields a lower dielectric constant than that at the ambient temperature, resulting in a higher solubility of the hydrophobic modifier.…”