Physicochemical Properties of Hematite Nanoparticles Obtained via Thermogravimetric Conversion of Biosynthesized Nanomaghemite

Ramos-Guivar J.A.; Marcos-Carrillo M.D.P.; Rueda-Vellasmin R.; Manrique-Castillo E.V.; Checca-Huaman N.-R.; Santos B.L.D.; Macedo W.A.A.; Passamani E.C. · Materials (2025) · DOI: 10.3390/ma18204677

Resumen

Hematite nanoparticles ((Formula presented.)) were synthesized through a thermal conversion of synthetic and biosynthesized nanomaghemite ((Formula presented.)) precursors. X-ray diffraction data confirmed phase-pure hematite with crystallite sizes of 54 and 56 nm for the H1 and H2 samples, respectively. Transmission electron microscopy (TEM) revealed a bimodal-like distribution feature (peaks at 18.5 and 35.5 nm) for the H1 sample, while the histogram plot of the H2 sample displayed a homogeneous particle size distribution with a mean size of 28 nm. X-ray photoelectron spectroscopy confirmed Fe3+ ions as the dominant oxidation state in both samples. In addition, while 57Mössbauer spectroscopy indicated relaxation effects and line broadening for the H1 sample at both 300 K and 16 K, consistent with incomplete (Formula presented.) transformation, the H2 sample exhibited spectra at the same temperatures resembling a bulk-like hematite. Magnetometry supported these findings since the H1 sample showed enhanced coercivity (2.2 kOe) and remanence (0.23 emu/g), features attributed to a residual ferrimagnetic contribution of (Formula presented.), and the H2 sample exhibited weaker ferromagnetism, as typically found in nanoscale hematite. These results highlight the synergistic use of X-ray photoelectron and Mössbauer spectroscopies, and magnetic measurements to reveal subtle multiphase coexistence, demonstrating that precursor chemistry and biosynthetic functionalization decisively govern the structural and magnetic evolution of (Formula presented.).

Instituciones: Universidad Nacional Mayor de San Marcos