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Sauthier G.,Catalan Institute of Nanoscience and Nanotechnology | Figueras A.,Catalan Institute of Nanoscience and Nanotechnology | Gyorgy E.,Catalan Institute of Nanoscience and Nanotechnology | Gyorgy E.,National Institute for Lasers
Journal of the American Ceramic Society | Year: 2012

Hemispherical and columnar TiO 2 array were produced by reactive pulsed laser deposition (PLD) using self-assembled polystyrene (PS) monolayers as templates. The integration of PS microspheres self-assembly processes and PLD permits the creation of periodic arrays in hexagonal arrangement. The micro/nano array architecture demonstrates outstanding catalytic performance in the degradation of methylene blue dye in aqueous solution. The obtained results suggest that besides other structural characteristics the large specific surface area plays an essential role in the improvement of photoactivity of oxide semiconductor catalyst. © 2012 The American Ceramic Society. Source


Baldea I.,University of Heidelberg | Baldea I.,National Institute for Lasers | Koppel H.,University of Heidelberg | Wenzel W.,Karlsruhe Institute of Technology
Physical Chemistry Chemical Physics | Year: 2013

We report results of quantum chemical calculations for the neutral and anionic species of (4,4′)-bipyridine (44BPY), a prototypical molecule with a floppy degree of freedom, placed in vacuo and in solvents. In addition to equilibrium geometries and vibrational frequencies and spectra, we present adiabatic energy curves for the vibrational modes with significant intramolecular reorganization upon charge transfer. Special attention is paid to the floppy strongly anharmonic degree of freedom of 44BPY, which is related to the most salient structural feature, namely the twist angle θ between the two pyridine rings. The relevance of the present results for molecular transport will be emphasized. We show that the solvent acts as a selective gate electrode and propose a scissor operator to account for solvent effects on molecular transport. Our result on the conductance G vs. cos2θ is consistent with a significant transmission in perpendicular conformation indicated by previous microscopic analysis. © 2013 The Owner Societies. Source


Sauthier G.,Catalan Institute of Nanoscience and Nanotechnology | Gyorgy E.,Catalan Institute of Nanoscience and Nanotechnology | Gyorgy E.,National Institute for Lasers | Figueras A.,Catalan Institute of Nanoscience and Nanotechnology | And 2 more authors.
Journal of Physical Chemistry C | Year: 2012

Nitrogen-doped TiO 2 vertically aligned columnar arrays were grown by reactive pulsed laser deposition using self-assembled polystyrene (PS) microsphere monolayers as templates and TiO 2 hemispherical arrays as buffers. The created columnar arrays showed significantly enhanced photocatalytic activity as compared with the reference thin films grown under identical experimental conditions but in the absence of the PS templates, both under visible- as well as UV-light irradiation. The photocatalytic activity decreased with the increase in the nitrogen doping level, suggesting the existence of a threshold value for the nitrogen incorporation in the TiO 2 crystal lattice. © 2012 American Chemical Society. Source


Sauthier G.,Catalan Institute of Nanoscience and Nanotechnology | Perez Del Pino A.,CSIC - Institute of Materials Science | Figueras A.,Catalan Institute of Nanoscience and Nanotechnology | Gyorgy E.,Catalan Institute of Nanoscience and Nanotechnology | Gyorgy E.,National Institute for Lasers
Journal of the American Ceramic Society | Year: 2011

Ag nanoparticles and Ag-TiO2 nanostructures were grown on (001) SiO2 quartz substrates by pulsed laser deposition using a KrF* excimer laser source (λ = 248 nm, τFWHM∼10 ns, I = 10 Hz) for the irradiation of Ag and TiO2 targets. The obtained structures were characterized by atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and UV-visible absorption spectroscopy. Photocatalytic activity was evaluated under near-UV light illumination by decomposition of methylene blue. The relationship between the laser synthesis process parameters and nanoparticles' chemical composition, crystal structure, morphology, shape and size distribution on the substrate surface were investigated and correlated with their optical properties. The established experimental parameters were used for the synthesis of nanostructures consisting of anatase phase TiO2 thin films covered by Ag nanoparticles for photocatalytic applications. The optimum experimental conditions were determined which ensure significantly improved photoactivity in the presence of Ag nanoparticles as compared to the bare oxide surface. © 2011 The American Ceramic Society. Source


Baldea I.,University of Heidelberg | Baldea I.,National Institute for Lasers
Journal of Physics and Chemistry of Solids | Year: 2012

The initial interpretation of the transition voltage (V t) spectroscopy within a tunneling barrier picture has been later challenged within calculations based on the Simmons model. In this communication, it will be shown that the predictions of the Simmons model for V t represent artefacts of an inadequate WKB-type constant barrier approximation, which are exacerbated by those calculations by an incorrect expression of the image potential. © 2012 Elsevier Ltd. All rights reserved. Source

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