Search

Abstract: A magnetically separable single-phase MgFe2O4 photocatalyst with a spinel crystal structure was synthesized by using the solid-state reaction method. The formation of spinel structure is confirmed by X-ray diffraction and Fourier transform infrared spectroscopy. The magnetic measurements showed that the photocatalyst material can be separated from water when an external magnetic field is added and redispersed into water solution after the external magnetic field is eliminated. It is one of the promising photocatalysts for waste water treatment. The photocatalytic activity of MgFe2O4 was investigated by using the photo-decomposition of methylene blue dye under visible light. The photoelectrochemical property of the MgFe2O4 was studied by measuring their photocurrent–potential behavior in 1 M NaOH electrolyte under AM 1.5100 mW cm−2 illumination. [Copyright &y& Elsevier]

Structural, magnetic, optical and electronic properties of GeGa 2 O 4 , CoGa 2 O 4 , GeCo 2 O 4 and CoCo 2 O 4 spinel oxides have been studied. Spinel oxides are studied by performing theoretical calculations based on density functional theory. In non-magnetic host GeGa 2 O 4 spinel oxide, significant effects of Co occupancy (at A, B and/or both sites) on the electronic, magnetic and optical behavior have been observed. Among the spinel oxides, the CoGa 2 O 4 , GeCo 2 O 4 and CoCo 2 O 4 spinel oxides show 100% spin-polarization and exhibit stable cubic structure in ferromagnetic phase. The calculated structural and magnetic parameters predict the cation distribution at A and B sites as follows: (G e 2 + ) [ G a 2 3 + ] O 4 − 2 , (C o 2 + ) [ G a 2 3 + ] O 4 − 2 , (G e 4 + ) [ C o 2 2 + ] O 4 − 2 and (C o + 2 ) [ C o 2 3 + ] O 4 − 2 for GeGa 2 O 4 , CoGa 2 O 4 , GeCo 2 O 4 and CoCo 2 O 4 spinel oxides, respectively. The electronic band gap is found to be decreased from 1.605 eV to 0.762 eV for spin↑ state while it is decreased from 1.578 eV to 0.000 eV for spin↓ state with Co occupancy in host GeGa 2 O 4 lattice. Lattice constant decreases (8.7877 Å to 8.1390 Å) as Co occupies B site and/or both (A and B) sites. For GeCo 2 O 4 spinel oxide, the calculated value of total magnetic moment (m tot = 6.12 μ B / f.u) and saturation magnetization (M S = 134.22 emu/g) is found to maximum. Optical properties reveal that the CoGa 2 O 4 , GeCo 2 O 4 and CoCo 2 O 4 spinel oxides have less threshold electronic transition energy relative to host GeGa 2 O 4 spinel oxide. Electronic, magnetic and optical characteristics show potential integration of these spinel oxides in magnetic-semiconducting devices. Image 1 • Effects of Co occupancy on different atomic sites in GeGa 2 O 4 spinel are studied. • Cubic CoGa 2 O 4 , GeCo 2 O 4 and CoCo 2 O 4 spinel oxides show 100% spin-polarization. • Co occupying A, B or both sites decreases the electronic and optical band gap. • GeCo 2 O 4 spinel oxide shows half metallic behavior with m t o t = 6.12 μ B / f.u and M S = 134.22 emu/g. • All spinel oxides show maximum absorption and optical conductivity in UV region. [ABSTRACT FROM AUTHOR]