A facile approach for the synthesis of porous hematite and magnetite nanoparticles through sol-gel self-combustion

Authors: IMENE GRITLI, AFRAH BARDAOUI, JAMILA BEN NACEUR, SALAH AMMAR, MOHAMMAD ABU HAIJA, SHERIF MOHAMED ABDEL SALAM KESHK, RADHOUANE CHTOUROU

Abstract: Porous magnetite (Fe₃O₄) and hematite (α-Fe₂O₃) nanoparticles were prepared via the sol-gel auto-combustion method. The gels were prepared by reacting ferric nitrates (as oxidants) with starch (as fuel) at an elevated temperature of 200 °C. Different ratios (Φ) of ferric nitrates to starch were used for the synthesis (Φ = fuel/oxidant). The synthesized iron oxides were characterized by Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmet-Teller (BET) and vibrating sample magnetometer (VSM) analysis techniques. The crystal structure, morphology, and specific surface area of the iron oxide nanoparticles (Fe₃O₄ and α-Fe₂O₃) were found to be dependent on the starch content. The FT-IR, XRD and VSM analysis of the iron oxides for Φ = 0.3 and 0.7 confirmed the formation of the α-Fe₂O₃ core, whereas at Φ = 1, 1.7, and 2 showed that Fe₃O₄ cores were formed with the highest saturation magnetization of 60.36 emu/g at Φ = 1. The morphology of the Fe₃O₄ nanoparticles exhibited a quasi-spherical shape, while α-Fe₂O₃ nanoparticles appeared polygonal and formed clusters. The highest specific surface area was found to be 48 m² g^-1 for Φ = 1.7 owing to the rapid thermal decomposition process. Type II and type III isotherms indicated mesoporous structures.

Keywords: Fe₃O₄ nanoparticles, hematite, starch, sol-gel auto combustion

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