Synthesis of magnetic nanostructures: Shape tuning by the addition of a polymer at low temperature

We report a simple method for shape-controlled synthesis of iron oxide spinels such as magnetite (Fe₃O₄) and maghemite (γ-Fe₂O₃) nanostructures using a thermoresponsive polymer poly(vinyl methyl ether) (PVME) by the alkaline hydrolysis of iron salt at low temperature (20 °C). Microscopic analysis confirmed the formation of needle- and flower-shaped iron oxide nanostructures depending on reaction conditions. High-resolution transmission electron microscopic analysis of the needle- and flower-shaped nanostructures as well as their corresponding selected area electron diffraction patterns revealed that the formed nanostructures are crystalline in nature. X-ray diffraction study reveals the formation of well-crystalline pure Fe₃O₄ and γ-Fe₂O₃ nanostructures under different reaction conditions. Fourier transform Infra-red spectroscopic analysis confirms the adsorption of PVME on the surface of iron oxide nanostructures. Finally, the magnetic properties of γ-Fe₂O₃ and Fe₃O₄ nanostructures is studied that shows the superparamagnetic behavior of the formed iron oxide nanostructures. - Graphical abstract: A simple method for shape-controlled synthesis of iron oxide spinels such as magnetite (Fe₃O₄) and maghemite (γ-Fe₂O₃) nanostructures using a thermoresponsive polymer poly(vinyl methyl ether) (PVME) by the alkaline hydrolysis of iron salt at low temperature (20 °C) is described. Display Omitted - Highlights: • Low-temperature method for iron oxide (Fe₃O₄ and γ-Fe₂O₃) nanostructures is described. • Shape of iron oxide nanostructures can be tuned by varying the reaction parameter. • Needle- and flower-shaped iron oxide nanostructures are obtained with polymer. • HRTEM analysis shows iron oxide nanostructures are crystalline in nature. • Both γ-Fe₂O₃ and Fe₃O₄ nanostructures shows superparamagnetic behavior