Maghemite and hematite nanowires synthesized by nanocasting: precursor effects on structural and magnetic properties

Mesoporous iron oxides with tailored structural and magnetic properties were synthesized using the SBA-15
silica template and two different iron precursors: Fe(NO3)3⋅9H2O and Fe(C5H7O2)3, denoted as FeM-1 and
FeM-2, respectively. The synthesis involved a two-step impregnation-calcination process followed by silica
removal. Comprehensive characterization was performed using techniques such as nitrogen adsorption–
desorption isotherms, TEM, SEM-EDX, XRD, XPS, and M¨ossbauer spectroscopy, as well as magnetic
measurements.
The results revealed significant differences in structural and magnetic properties between the two samples.
FeM-1 exhibited higher structural order, greater homogeneity, and a single-phase α-Fe2O3 composition, whereas
FeM-2 showed a bimodal pore size distribution and a dual-phase composition of α-Fe2O3 and ɣ-Fe2O3. Magnetic
characterization indicated enhanced magnetization in FeM-2 due to the ferrimagnetic nature of ɣ-Fe2O3, while
FeM-1 displayed lower magnetization consistent with the weak ferromagnetic behavior of α-Fe2O3. The combination
of structural and magnetic analyses demonstrated the critical role of precursor selection in tuning the
material properties for potential applications in catalysis and magnetic devices.