Influence of solvents, reaction temperature, and aging time on the morphology of iron oxide nanoparticles

Abstract

We report a simple approach to generate iron-oxide nanoparticles (IONPs) with controlled shapes, such as tetrahedron, cuboctahedron, cube, octopod, irregular polyhedron, and quasi-spherical by altering the experimental conditions such as reaction solvents, reaction time, and aging time of particles. For this, the iron oleate (precursor) was thermally decomposed in the solvents dibenzyl ether (DBE), 1-octadecene (ODE), tri-n-octylamine (TOA), and oleylamine (OLY) and the reaction temperatures (from 290 to 365 °C) and aging time of particles (from 0 to 60 min) were varied in these solvents. We find that DBE and ODE solvents non-coordinates with the IONP surface and the variation of reaction temperature and aging time lead to different particle morphology in these solvents. On the other hand, TOA and OLY solvents coordinate with the particle surface and the surface diffusional barriers owing to the coordination of these solvents lead to different particle morphology. We also propose IONP shape formation mechanisms in these non-coordinating and coordinating solvents for different experimental conditions by considering the relative rate of iron-oxide monomers deposition onto {111} facets of growing crystals over the surface diffusion of the deposited monomers toward {100} facets.