Bio-inspired synthesis of hematite α-Fe2O3 nanoparticles via rosemary leaf extract: Investigation of structural, magnetic, and electrical properties

Green synthesis is an eco-friendly, low-toxicity, and cost-effective method for the synthesizing nanoparticles. This study investigates the biosynthesis of hematite α-Fe₂O₃ nanoparticles using rosemary leaf extract as a natural reducing and stabilizing agent, focusing on the impact of pH (3, 7, and 11) on their structural, morphological, magnetic, and electrical properties. X-ray diffraction was used to confirm the phase and crystallinity of the nanoparticles, revealing that all samples exhibited the hexagonal structure of hematite. Crystallite size calculations, based on Scherrer’s equation showed that size decreased with increasing pH. The largest crystallites were observed at pH 3, indicating faster growth under acidic conditions. Smaller crystallites had higher surface area and porosity. The Fourier-transform infrared spectroscopy confirms the presence of hematite nanoparticles by showing strong peaks below 600 cm⁻¹ representing the stretching vibrations of Fe-O bonds. Field Emission Scanning Electron Microscopy analysis revealed that the morphology and size of the hematite nanoparticles varied with pH. The nanoparticles synthesized at pH 3 exhibited an aggregated nanoplate shape, while those at higher pH values (7 and 11) produced more semi-spherical morphology. The magnetic characteristics were analyzed using Vibrating Samples Magnetometer, which revealed weak ferromagnetic behavior for all pH values. Additionally, the variations in dielectric constant, dielectric loss factor, and conductivity with frequency were studied using an LCR meter.