Induced shape controllability by tailored precursor design in thermal and microwave-assisted synthesis of \(\mathrm{Fe}_{3}\mathrm{O}_{4}\) nanoparticles

The shape of magnetite nanoparticles (NPs) synthesized by thermal (T) and microwave (MW) approaches was controlled by an optimized methodology, which consists of a prior and easy modification of the \(\upalpha\) terminal position belonging to the iron(III) tris(2,4-pentanedionate) precursor. Round, cuboctahedron, flower-like \(\mathrm{Fe}_{3}\mathrm{O}_{4}\) (<10 nm) and bow-like \(\mathrm{FeF}_{2}\) nanostructures have been synthesized in triethylene glycol media, producing polar dispersible NPs. The \(\upalpha\) terminal group was modified from the initial –\(\mathrm{CH}_{3}\) to –\(\mathrm{Ph},\) –\(^{t}\mathrm{Bu},\) and –\(\mathrm{CF}_{3}\) respectively, inducing defined and characteristic shapes of the obtained NPs: round, cuboctahedron, flower-like \(\mathrm{Fe}_{3}\mathrm{O}_{4},\) and bow-like \(\mathrm{FeF}_{2},\) respectively. The two investigated synthetic methodologies, T and MW, produce similar results, except for the precursor containing the aromatic group (–\(\mathrm{Ph}\)), through which cuboctahedron (T) and elongated polycrystalline microwires (MW) were generated. The ensemble of modified ligands has demonstrated to influence the final shape, structure, and composition of the nanocrystals generated. The resulting NPs were studied by high-resolution transmission electron microscopy, X-ray powder diffraction, and thermogravimetric analysis. Data demonstrated a strong relation between the precursor design and the final morphology of the NPs, which could be explained by different precursor–particle interactions during nucleation and crystal growth. The final composition of all nanostructures was the expected \(\mathrm{Fe}_{3}\mathrm{O}_{4},\) except for the fluorinated precursor where \(\mathrm{FeF}_{2}\) was obtained as the main reaction product.