To realize molecular spintronic devices, it is important to externally control the magnetization of a molecular magnet. One class of materials particularly promising as building blocks for molecular electronic devices is the paramagnetic porphyrin molecule in contact with a metallic substrate. Here, we study the structural orientation and the magnetic coupling of in-situ-sublimated Fe porphyrin molecules on ferromagnetic Ni and Co films on Cu(100). Our studies involve X-ray absorption spectroscopy and X-ray magnetic circular dichroism experiments. In a combined experimental and computational study we demonstrate that owing to an indirect, superexchange interaction between Fe atoms in the molecules and atoms in the substrate (Co or Ni) the paramagnetic molecules can be made to order ferromagnetically. The Fe magnetic moment can be rotated along directions in plane as well as out of plane by a magnetization reversal of the substrate, thereby opening up an avenue for spin-dependent molecular electronics.
A series of photocatalysts was synthesized by codoping TiO 2 with lanthanum and iodine (La-I-TiO 2 ). The structure and properties of the catalysts were studied by X-ray diffraction (XRD), the Brunauer-Emmett-Teller (BET) method, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectra. The prepared anatase-phase La-I-TiO 2 (molar ratio 20:20:100) calcined at 400 °C had a BET surface area of 92.9 m 2 g -1 , and the crystallite size calculated from XRD data was ∼3.57 nm, and it had a remarkable absorption in the visible light range of 400-550 nm. The catalytic efficiency was tested by monitoring the photocatalytic degradation of oxalic acid under visible light irradiation. An optimum molar ratio of 20:100 La/TiO 2 was determined for the most efficient inhibition of the recombination of electron-hole pairs and the photocatalytic activity of La-I-TiO 2 calcined at 400 °C was significantly higher than that calcined at 500 or 600 °C in aqueous oxalic acid solution. The probable process of oxalic acid degradation was that it was first adsorbed onto the surface of the catalysts, where it reacted with valence band holes (h vb + ) and the surface-bound or adsorbed • OH radicals ( • OH ads ) as well as reactive oxygen species (ROS) derived from oxygen reduction by photogenerated electrons, and finally converted into CO 2 and H 2 O without any stable intermediate.
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