Structural Evolution of Chemically-Driven RuO2 Nanowires and 3-Dimensional Design for Photo-Catalytic Applications

Growth mechanism of chemically-driven RuO2 nanowires is explored and used to fabricate three-dimensional RuO2 branched Au-TiO2 nanowire electrodes for the photostable solar water oxidation. For the real time structural evolution during the nanowire growth, the amorphous RuO2 precursors (Ru(OH)(3)center dot H2O) are heated at 180 degrees C, producing the RuO2 nanoparticles with the tetragonal crystallographic structure and Ru enriched amorphous phases, observed through the in-situ synchrotron x-ray diffraction and the high-resolution transmission electron microscope images. Growth then proceeds by Ru diffusion to the nanoparticles, followed by the diffusion to the growing surface of the nanowire in oxygen ambient, supported by the nucleation theory. The RuO2 branched Au-TiO2 nanowire arrays shows a remarkable enhancement in the photocurrent density by approximately 60% and 200%, in the UV-visible and Visible region, respectively, compared with pristine TiO2 nanowires. Furthermore, there is no significant decrease in the device's photoconductance with UV-visible illumination during 1 day, making it possible to produce oxygen gas without the loss of the photoactvity.close1

Microscopic origin of the PTC effect in niobium-doped barium titanate

The influence of bulk conductivity on the PTC effect of Nb-doped barium titanate is investigated. Both macroscopic and microscopic resistance measurements are performed as a function of temperature. The macroscopic measurement refers to the whole sample while the microscopic one, obtained by photolithography techniques, concerns only several grains. The results show that the increase of resistivity occurs in two steps: first, an abrupt variation at the Curie temperature T-c which is ascribed to the phase transition in the bulk; second, a continuous increase above T-c which is usually explained from grain boundary potential barriers only. However, our results suggest that a nonnegligible contribution of the bulk is also involved in this increase above T-c

Luminescence of Germanate Garnets with terbium on dodecahedral and octahedral lattice sites.

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