Investigando a relação óptico-estrutural de nanocompósitos binários α-Fe₂O₃/Fe₃O₄ sintetizados por uma rota sol-gel verde

Abstract

This study investigates the green synthesis of binary a-Fe2O3/Fe3O4 nanocomposites using hydroethanolic extract of Maytenus rigida as a chelating agent. The nanoparticles were synthesized via a sol-gel route, followed by calcination at 400 °C, 500 °C, and 600 °C, and their optical and structural properties were evaluated. X-ray diffraction revealed the presence of 36% Fe3O4 and 64% a-Fe2O3 at 400 °C, varying to 21% Fe3O4 and 79% a-Fe2O3 at 600 °C. The crystallite size of Fe3O4 increased from 58 nm to 251 nm, while that of a-Fe2O3 grew from 227 nm to 659 nm with increasing temperature. Photoluminescence (PL) analyses showed that the nanocomposites exhibit emissions attributed to oxygen (Vo) and iron (VF) vacancies, with PL peaks observed at 286 nm, 332 nm, and 588 nm. The optical bandgap, determined by DRUV, ranged from 3.4 eV to 4.0 eV, depending on the calcination temperature, indicating quantum confinement effects. These results highlight that the increase in temperature promotes anisotropic growth of nanocrystals and defect formation, directly impacting the optical and luminescent properties, with promising applications in sensors and photocatalytic devices.