Nucleation and growth model is generally introduced to understand the formation of inorganic nanoparticles. However, it may not be applied to the entire nanoparticle systems because different precursors and surface ligands are used in the synthesis. Their intrinsic chemical reactivity can lead to a formation pathway to be deviated from classical nucleation and growth model. The formation of metal oxide nanoparticles is one such case, because of several distinct chemical aspects during their synthesis. Typical carboxylate surface ligands, which are often employed in the synthesis of oxide nanoparticles, tend to continuously remain on the surface of the nanoparticles throughout the growth process. They can also act as an oxygen source during the growth of metal oxide nanoparticles. Carboxylates are prone to chemical reactions with different chemical species in the synthesis such as alcohol or amine in that such reactions can frequently leave reactive hydroxyl groups on the surface. Herein, we track the entire growth process of iron oxide nanoparticles synthesized from conventional iron precursors, iron-oleate complex. Mass spectrometry studies show that the iron-oleate has a cluster structure composed of a tri-iron-oxo core and carboxylate ligands, rather than a mononuclear complex. A combinatorial analysis presents that the entire growth, regulated by esterification of chelating ligands and alcohol, is continuous without a discrete nucleation step. As metal-oleate complexes are commonly used for the synthesis of various metal oxide nanoparticles, the continuous growth process may reveal unknown aspects of the metal oxide nanoparticle formation.

Continuous growth of iron-oxo clusters to iron oxide nanoparticles: Insights on iron oxide nanoparticle formation at the early stage

2019 Fall National Meeting

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