Structural characterization of green synthesized magnetic mesoporous Fe₃O₄NPs@ME

Mesoporous magnetite nanoparticles (Fe₃O₄NPs) were synthesized by using the leaf extract of Mussaenda erythrophylla (ME) by a cheap and simple method – green synthesis. The synthesized Fe₃O₄NPs@ME were characterized by various techniques. A strong absorption spectrum without any specific peak in the UV–vis image designated the formation of iron-containing nanoparticles. XRD image confirmed the presence of only magnetite and the purity was ascertained by the absence of other forms of iron-containing nanoparticles. The average crystallite size was calculated as 18.58 nm and the lattice parameter was 8.38 Å which was close to the magnetite standards. FE-SEM image portrayed spherical aggregates and EDS showed signature peaks for Fe and O elements. XPS image showed the presence of peaks for oxygen, ferrous, and ferric ions which are consistent with magnetite along with carbon on the surface. Mesoporous structure (5.78 nm) was affirmed by BET results which showed a higher surface area (174.15 m²/g) than the commercial one. The FTIR bands obtained at 454.25 and 667.39 cm⁻¹ corresponded to the distinctive Fe–O linkage, substantiating the formation of magnetite. The stability of the magnetite at very high temperature was validated by TGA results which showed a 15% total reduction in weight. The magnetite showed superparamagnetism with a low saturation magnetization value (5.14 emu/g) which confirmed the existence of non-magnetic surface layers arising from the phytomolecules residing in the leaf extract of M. erythrophylla. Hence, the pure, crystalline, and mesoporous Fe₃O₄NPs@ME with large surface area obtained by the above-mentioned facile procedure will surely make an impact in many areas such as catalysis, adsorption, and biomedical engineering.