Clove and cinnamon: Novel anti–oxidant fuels for preparing magnetic iron oxide particles by the sol–gel auto–ignition method

Magnetic spinel ferrite particles were successfully prepared from only iron (III) nitrate, using clove and cinnamon plant extracts for the first time as eco-fuels for auto–ignition synthesis. Both natural substances were shown to play dual roles in the synthesis of the magnetic particles; i.e. as fuels (agents for biogenic reduction), and as anti–oxidants for preserving the magnetic phases during subsequent heating. In this regard, no special protective environments such as H2/N2 or argon gases were required during the heat stabilisation process, and samples could be stabilised by heating to 550 °C in air. The magnetic crystalline phase is mostly maghemite (γ-Fe2O3) rather than magnetite (Fe3O4), as revealed by Raman, since no Raman active phonon modes were detected for magnetite, and most of the bands were related to maghemite, with traces of hematite. Both fuels produced strongly magnetic soft ferrites, with magnetisation values of 75 A m2 kg−1, around the expected ones for maghemite Moreover, TG curves showed that maghemite degradation only occurs at relatively high temperatures, namely at 550 °C for Clove, and at 744 °C for Cinnamon, confirming the sustainable nature of the as-obtained materials against oxidation.