Dr. Valdés-Morales, Héctor

This study reports the synthesis of erbium (Er)-doped bismuth ferrite (BiFeO3/BFO) nanoparticles at varying molar concentrations (5, 10, and 15 %) using a sol-gel method. X-ray diffraction (XRD) analysis reveals a structural transformation from rhombohedral to orthorhombic upon Er3+ doping, confirming the successful incorporation of Er3+ ions into the BFO lattice. High-resolution transmission electron microscopy (HRTEM) images show that Er-doping leads to a reduction in particle size and a modification of the surface morphology. The bandgap of the Er-doped BFO samples decreases from 2.34 to 2.15 eV with increasing Er content, attributed to the formation of new Er 4f energy levels within the band structure. The magnetic properties of the samples also improve with increasing Er concentration. Photoluminescence (PL) spectra show reduced PL intensity for the 10 % Er-doped BFO sample, indicating a decrease in recombination rates, while electrochemical impedance spectroscopy (EIS) reveals a reduction in charge transfer resistance. Among the samples, the 10 % Er-doped BFO photocatalyst exhibits the highest photocatalytic efficiency. This enhanced activity is attributed to two key factors: efficient separation and migration of photogenerated charge carriers, and a reduced recombination rate of electron-hole pairs, both driven by the rare-earth doping in BFO. Radical trapping experiments further identify hydroxyl (OH•) radicals as the primary species responsible for photocatalytic degradation. This study provides valuable insights into the tunability of BFO's bandgap energy and photocatalytic properties through Er doping.

The study investigates the influence of praseodymium (Pr) doping on bismuth ferrite (BiFeO3/BFO) nanofibers and their structural, morphological, magnetic, optical, and photocatalytic properties. A series of bismuth ferrite nanofibers with varying concentration of Pr (Bi1-xPrxFeO3, x = 0.00, 0.05, 0.10, and 0.15 mol%) were successfully synthesized using an electrospinning technique. XRD patterns revealed that structural transformation occurred from rhombohedral to orthorhombic upon effective doping of Pr3+ into BFO nanofibers. The X-ray photoelectron spectroscopy analysis confirmed that Bi, Fe, and O maintained their native oxidation states of +3 and -2, respectively in the bare and doped systems. Furthermore, the optical band gap value was significantly reduced from 2.35 to 2.22 eV as well as the recombination rates of charge carriers in the doped systems, especially in BP0.15O system. The photocatalytic performance of the prepared samples was studied by measuring the decomposition of rhodamine B (RhB) under sunlight irradiation. Outcomes showed that the doped-BFO nanofibers exhibited enhanced photocatalytic performance compared to pure BFO, with the BP0.15O system showing the 98 % degradation in 60 min. This enhancement could be attributed to the presence of Pr-energy levels, which facilitating enhanced separation, and charge transfer to the surface for the effective redox reactions.