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Morante J.R.,Catalonia Institute for Energy Research IREC | Morante J.R.,University of Barcelona
Nanotechnology | Year: 2013

Insight into chemical to electrical transduction mechanisms taking place at the surface of a single metal oxide nanowire is reported due to its outstanding importance for determining the characteristics of resistive solid state gas sensors. The surface chemical reaction kinetics is discussed considering competitiveness phenomena among different active sites and gas species on the nanowire taken as a metal oxide monocrystal at the nanoscale level. Experimental results for different representative gas molecules are shown to determine and understand sensor selectivity. The reported gas species are carbon monoxide and water vapour as general reference molecules, and ethanol and ammonia species as special references for gas-solid interactions, respectively, on acid and basic sites. Kinetic properties are proposed as particular signatures for each of the possible surface chemical reactions, allowing their identification and distinction. Likewise, features such as thermal inertia limitation and effects of the molecular and monoatomic absorbed oxygen are also estimated considering operation working modes based on nanowire self-heating. Furthermore, the applicability of a surface electrical field on a one-dimensional metal oxide nanostructure to enhance the surface ionization of the absorbed molecules is also reviewed as a new type of metal oxide based nanosensor for achieving improved selectivity. © 2013 IOP Publishing Ltd.

Bianchi F.D.,Catalonia Institute for Energy Research IREC | Sanchez Pena R.S.,Buenos Aires Institute of Technology
Automatica | Year: 2011

Here, a methodology is presented which considers the interpolation of linear time-invariant (LTI) controllers designed for different operating points of a nonlinear system in order to produce a gain-scheduled controller. Guarantees of closed-loop quadratic stability and performance at intermediate interpolation points are presented in terms of a set of linear matrix inequalities (LMIs). The proposed interpolation scheme can be applied in cases where the system must remain at the operating points most of the time and the transitions from one point to another rarely occur, e.g., chemical processes, satellites. © 2010 Elsevier Ltd. All rights reserved.

Shavel A.,University of Barcelona | Arbiol J.,Catalan Institution for Research and Advanced Studies | Cabot A.,University of Barcelona | Cabot A.,Catalonia Institute for Energy Research IREC
Journal of the American Chemical Society | Year: 2010

A successful synthesis of Cu2ZnxSnySe 1+ x +2 y (CZTSe) nanoparticles is presented. Nearly monodisperse and highly faceted CZTSe nanoparticles were prepared through reaction of metal amino complexes with saturated solutions of selenium in trioctylphosphine at high temperature. High-resolution transmission electron microscopy and X-ray diffraction analysis showed the prepared nanocrystals to have the tetragonal Cu2ZnSnSe4 crystallographic structure. Nanoscale-resolved electron energy loss spectroscopy images showed the presence of the four elements in each individual nanocrystal. Further analyses of the particles chemical composition showed the nanocrystals to be consistently Zn- and Sn-poor. © 2010 American Chemical Society.

Barth S.,Tyndall National Institute | Barth S.,Trinity College Dublin | Hernandez-Ramirez F.,Catalonia Institute for Energy Research IREC | Holmes J.D.,Tyndall National Institute | And 2 more authors.
Progress in Materials Science | Year: 2010

Nanoscale inorganic materials such as quantum dots (0-dimensional) and one-dimensional (1D) structures, such as nanowires, nanobelts and nanotubes, have gained tremendous attention within the last decade. Among the huge variety of 1D nanostructures, semiconducting nanowires have gained particular interest due to their potential applications in optoelectronic and electronic devices. Despite the huge efforts to control and understand the growth mechanisms underlying the formation of these highly anisotropic structures, some fundamental phenomena are still not well understood. For example, high aspect-ratio semiconductors exhibit unexpected growth phenomena, e.g. diameter-dependent and temperature-dependent growth directions, and unusual high doping levels or compositions, which are not known for their macroscopic crystals or thin-film counterparts. This article reviews viable synthetic approaches for growing high aspect-ratio semiconductors from bottom-up techniques, such as crystal structure governed nucleation, metal-promoted vapour phase and solution growth, formation in non-metal seeded gas-phase processes, structure directing templates and electrospinning. In particular new experimental findings and theoretical models relating to the frequently applied vapour-liquid-solid (VLS) growth are highlighted. In addition, the top-down application of controlled chemical etching, using novel masking techniques, is described as a viable approach for generating certain 1D structures. The review highlights the controlled synthesis of semiconducting nanostructures and heterostructures of silicon, germanium, gallium nitride, gallium arsenide, cadmium sulphide, zinc oxide and tin oxide. The alignment of 1D nanostructures will be reviewed briefly. Whilst specific and reliable contact procedures are still a major challenge for the integration of 1D nanostructures as active building blocks, this issue will not be the focus of this paper. However, the promising applications of 1D semiconductors will be highlighted, particularly with reference to surface dependent electronic transduction (gas and biological sensors), energy generation (nanomechanical and photovoltaic) devices, energy storage (lithium storage in battery anodes) as well as nanowire photonics. © 2010 Elsevier Ltd. All rights reserved.

Abello S.,Catalonia Institute for Energy Research IREC | Montane D.,Catalonia Institute for Energy Research IREC | Montane D.,Rovira i Virgili University
ChemSusChem | Year: 2011

The continuous increase in oil prices together with an increase in carbon dioxide concentration in the atmosphere has prompted an increased interest in the production of liquid fuels from non-petroleum sources to ensure the continuation of our worldwide demands while maximizing CO 2 utilization. In this sense, the Fischer-Tropsch (FT) technology provides a feasible option to render high value-added hydrocarbons. Alternative sources, such as biomass or coal, offer a real possibility to realize these purposes by making use of H 2-deficient or CO 2-rich syngas feeds. The management of such feeds ideally relies on the use of iron catalysts, which exhibit the unique ability to adjust the H 2/CO molar ratio to an optimum value for hydrocarbon synthesis through the water-gas-shift reaction. Taking advantage of the emerging attention to hybrid FT-synthesis catalysts based on cobalt and their associated benefits, an overview of the current state of literature in the field of iron-based multifunctional catalysts is presented. Of particular interest is the use of zeolites in combination with a FT catalyst in a one-stage operation, herein named multifunctional, which offer key opportunities in the modification of desired product distributions and selectivity, to eventually overcome the quality limitations of the fuels prepared under intrinsic FT conditions. This review focuses on promising research activities addressing the conversion of syngas to liquid fuels mediated by iron-based multifunctional materials, highlights their preparation and properties, and discusses their implication and challenges in the area of carbon utilization through H 2/CO(+CO 2) mixtures. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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