Novel mesoporous Gd 3+ doped Cr 2 O 3 nanomaterials: Synthesis, characterization, catalytic and antitumor applications

Insights into the Fe3+ Doping Effects on the Structure and Electron Distribution of Cr2O3 Nanoparticles

Herein, we carefully investigated the Fe3+ doping effects on the structure and electron distribution of Cr2O3 nanoparticles using X-ray diffraction analysis (XRD), maximum entropy method (MEM), and density functional theory (DFT) calculations. We showed that increasing the Fe doping induces an enlargement in the axial ratio of c/a, which is associated with an anisotropic expansion of the unit cell. We found that as Fe3+ replaces Cr in the Cr2O3 lattice, it caused a higher interaction between the metal 3d states and the oxygen 2p states, which led to a slight increase in the Cr/Fe-O1 bond length followed by an opposite effect for the Cr/Fe-O2 bonds. Our results also suggest that the excitations characterize a well-localized bandgap region from occupied Cr d to unoccupied Fe d states. The Cr2O3 and Fe-doped Cr2O3 nanoparticles behave as Mott-Hubbard insulators due to their band gap being in the d-d gap, and Cr 3d orbitals dominate the conduction band. These findings suggest that the magnitude and the character of the electronic density near the O atom bonds in Cr2O3 nanoparticles are modulated by the Cr-Cr distances until its stabilization at the induced quasi-equilibrium of the Cr2O3 lattice when the Fe3+ doping values reaches the saturation level range.

Novel mesoporous MnO2/SnO2 nanomaterials synthesized by ultrasonic-assisted co-precipitation method and their application in the catalytic decomposition of hydrogen peroxide

Novel mesoporous MnO₂/SnO₂ catalysts were successfully synthesized via traditional and ultrasonic co-precipitation methods. Moreover, their catalytic efficiencies were evaluated in decomposition of hydrogen peroxide (H₂O₂). Interestingly, it was found that the mixing of MnO₂ with SnO₂ catalyst led to a significant improvement in their catalytic efficiencies compared with single oxides catalysts. However, the influence of ultrasonic power and irradiation time on MnO₂/SnO₂ nanomaterials were compared to get optimum synthetic condition. Subsequently, the catalysts were characterized by X-ray diffraction (XRD), N₂ adsorption-desorption analysis and high-resolution transmission electron microscopy (HR-TEM). Results represented that the effect of ultrasonic power and irradiation time on MnO₂/SnO₂ catalysts exerted a great influence on the BET surface area and average particle diameter. Furthermore, the results showed that the best catalytic efficiency was obtained for the mesoporous MnO₂/SnO₂ catalyst which is sonicated at power of 60% for 30 min as optimum conditions. Finally, the outcomes appeared that the catalysts synthesized by ultrasonic co-precipitation method were more efficient than those synthesized by traditional co-precipitation in catalyzing H₂O₂ decomposition.