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Your search keyword '"Trasobares, A."' showing total 22 results
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22 results on '"Trasobares, A."'

3. Monitoring the decomposition of melamine in the solid phase by electron energy loss chronospectroscopy

Author

Trasobares, Susana, Kolczewski, Christine, Raty, Riitta, Borglund, Niclas, Bassan, Arianna, Hug, Gilles, Colliex, Christian, Csillag, Stefan, and Pettersson, Lars G. M.

Subjects
Spectrum analysis -- Usage, Electron beams -- Research, Energy dissipation -- Analysis, Decomposition (Chemistry), Chemicals, plastics and rubber industries
Abstract

Time-resolved electron energy loss spectroscopy is used to investigate the decomposition process of melamine exposed to a high-energy electron beam by monitoring the changes in the energy loss near edge structures (ELNES). Calculations on different CN-containing molecules are performed to simulate the experimental ELNES that is observed at the different decomposition stage and to identify some of the intermediate compounds produced during the degradation process.

Published
2003

6. A bioinspired approach to the synthesis of bimetallic CoNi nanoparticles

Author

Galvez, Natividad, Valero, Elsa, Ceolin, Marcelo, Trasobares, Susana, Lopez-Haro, Miguel, Calvino, Jose J., and Dominguez-Vera, Jose M.

Subjects
Nickel compounds -- Magnetic properties, Nickel compounds -- Electric properties, Nickel compounds -- Structure, Scanning microscopy -- Usage, Superconducting quantum interference devices -- Usage, Chemistry
Abstract

The article presents a new bioinspired approach, which can be used for the synthesis of the various bimetallic CoNi nanoparticles. The characterization and the magnetic and electronic properties of these compounds are also explained.

Published
2010

7. Comparative structural and chemical studies of ferritin cores with gradual removal of their iron contents

Author

Galvez, Natividad, Fernandez, Belen, Sanchez, Purificacion, Cuesta, Rafael, Ceolin, Marcelo, Clemente-Leon, Miguel, Trasobares, Susana, Lopez-Haro, Miguel, Calvino, Jose J., Stephan, Odile, and Dominguez-Vera, Jose M.

Subjects
Oxidation-reduction reaction -- Analysis, Alzheimer's disease -- Research, Ferritin -- Chemical properties, Ferritin -- Structure, Iron -- Chemical properties, Chemistry
Abstract

Several techniques are combined to study the structure, as well as chemistry of the ferritin cores, from which the iron contents are gradually removed. The removal of iron is shown to lead to a drastic change in the polyphasic structure of the ferritins.

Published
2008

11. Experimental evidence of the origin of nanophase separation in low hole-doped colossal magnetoresistant manganites

Author

Cortés-Gil, Raquel, Ruiz-González, M. Luisa, González-Merchante, Daniel, Alonso, José M., Hernando, Antonio, Trasobares, Susana, Vallet-Regí, María, Rojo, J. M., González-Calbet, José M., Cortés-Gil, Raquel, Ruiz-González, M. Luisa, González-Merchante, Daniel, Alonso, José M., Hernando, Antonio, Trasobares, Susana, Vallet-Regí, María, Rojo, J. M., and González-Calbet, José M.

Abstract

While being key to understanding their intriguing physical properties, the origin of nanophase separation in manganites and other strongly correlated materials is still unclear. Here, experimental evidence is offered for the origin of the controverted phase separation mechanism in the representative La1–xCaxMnO3 system. For low hole densities, direct evidence of Mn4+ holes localization around Ca2+ ions is experimentally provided by means of aberration-corrected scanning transmission electron microscopy combined with electron energy loss spectroscopy. These localized holes give rise to the segregated nanoclusters, within which double exchange hopping between Mn3+ and Mn4+ remains restricted, accounting for the insulating character of perovskites with low hole density. This localization is explained in terms of a simple model in which Mn4+ holes are bound to substitutional divalent Ca2+ ions.

Published
2016

12. Hydrogen interaction with a ceria-zirconia supported gold catalyst. Influence of CO co-adsorption and pre-treatment conditions

Author

and José M. Pintado, Sebastián E. Collins, Susana Trasobares, Eloy del Rio, José J. Calvino, Miguel López-Haro, José M. Cíes, and Serafín Bernal

Subjects
Hydrogen, Analytical chemistry, chemistry.chemical_element, INGENIERÍAS Y TECNOLOGÍAS, Dark field microscopy, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Catalysis, Metal, Ingeniería Química, General Energy, Adsorption, chemistry, Chemisorption, visual_art, visual_art.visual_art_medium, Physical and Theoretical Chemistry, Fourier transform infrared spectroscopy, Powder diffraction
Abstract

This work reports on the hydrogen interaction with a 3 wt % Au/Ce0.62Zr0.38O2 (Au/CZ) catalyst prepared by deposition−precipitation. As deduced from X-ray powder diffraction, electron microscopy (scanning transmission electron microscopy−high-angle angular dark field and high-resolution electron microscopy), and CO volumetric/Fourier transform IR (FTIR) adsorption studies, the investigated catalyst shows a good metal dispersion. By combining FTIR spectroscopy and volumetric chemisorption studies, it is shown that upon treating the Au/CZ catalyst with 40 Torr of H2 at room temperature a fast and very intense spillover effect occurs. As determined from the recorded isotherm, very high values of the apparent H/Au ratio (>8.0) and of the atomic hydrogen surface density (>11.0 H/nm2) are reached. In parallel with this observation, the onset of a characteristic IR band at 2133 cm-1 shows the occurrence of significant support reduction with inherent appearance of Ce3+ species. Moreover, the simultaneous growth of the IR band at 1630 cm-1 due to molecular water strongly suggests that even at room temperature oxygen vacancies are also formed. Additional FTIR spectroscopy studies have shown that the hydrogen spillover is strongly inhibited by either co-adsorption of CO or a reducing pretreatment with flowing 5% H2/Ar at 673 K. These deactivation effects, however, may be reverted by very mild regeneration treatments at room temperature. Fil: Collins, Sebastián Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Cíes, José M.. Universidad de Cádiz; España Fil: del Río, Eloy. Universidad de Cádiz; España Fil: Lopez Haro, Miguel. Universidad de Cádiz; España Fil: Trasobares, Susana. Universidad de Cádiz; España Fil: Calvino, José J.. Universidad de Cádiz; España Fil: Pintado, José M.. Universidad de Cádiz; España Fil: Bernal, Serafín. Universidad de Cádiz; España

Published
2007
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13. Electrochemical Imaging of Dense Molecular Nanoarrays.

Author

Chennit, Khalil, Trasobares, Jorge, Anne, Agnès, Cambril, Edmond, Chovin, Arnaud, Cle'ment, Nicolas, and Demaille, Christophe

Subjects
*ELECTROCHEMICAL sensors, *ATOMIC force microscopy, *GOLD nanoparticles, *FERROCENE, *ELECTROLYTIC reduction
Abstract

The aim of the present work is to explore the combination of atomic force electrochemical microscopy, operated in molecule touching mode (Mt/AFM-SECM), and of dense nanodot arrays, for designing an electrochemically addressable molecular nanoarray platform. A high density nanoarray of single grained gold nanodots (¡«15 nm-diameter nanoparticles, 100 nm pitch) is decorated by a model molecular system, consisting of ferrocene (Fc) labeled polyethylene glycol (PEG) disulfide chains. We show that the high resolution of Mt/AFM-SECM enables the electrochemical interrogation of several hundreds of individual nanodots in a single image acquisition. As a result, the statistical dispersion of the nanodot molecular occupancy by Fc-PEG chains can be reliably quantified, evidencing that as little as a few tens of copies of redox-labeled macromolecules immobilized on individual nanodots can be detected. The electrochemical reactivity of individual nanodots can also be reliably sampled over a large population of nanodots. We evidence that the heterogeneous rate constant characterizing the electron transfer between the nanodots and the Fc heads displays some quantifiable variability but that the electron transfer remains in any case in the quasireversible regime. Overall, we demonstrate that Mt/AFM-SECM enables high throughput reading of dense nanoarrays, with a sensitivity and a read-out speed considerably higher than previously reported for scanning electrochemical microscopy (SECM) imaging of molecular microarrays. [ABSTRACT FROM AUTHOR]

Published
2017
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14. Estimation of π-π Electronic Couplings from Current Measurements.

Author

Trasobares, J., Rech, J., Jonckheere, T., Martin, T., Aleveque, O., Levillain, E., Diez-Cabanes, V., Olivier, Y., Cornil, J., Nys, J. P., Sivakumarasamy, R., Smaali, K., Leclere, P., Fujiwara, A., Théron, D., Vuillaume, D., and Clément, N.

Subjects
*LIGHT emitting diodes, *MOLECULAR structure, *ELECTRIC current measurement, *OPTICAL properties, *ELECTRIC charge, *ELECTROCHEMICAL analysis
Abstract

The π-π interactions between organic molecules are among the most important parameters for optimizing the transport and optical properties of organic transistors, light-emitting diodes, and (bio-) molecular devices. Despite substantial theoretical progress, direct experimental measurement of the π-π electronic coupling energy parameter t has remained an old challenge due to molecular structural variability and the large number of parameters that affect the charge transport. Here, we propose a study of π-π interactions from electrochemical and current measurements on a large array of ferrocene-thiolated gold nanocrystals. We confirm the theoretical prediction that t can be assessed from a statistical analysis of current histograms. The extracted value of t ≈35 meV is in the expected range based on our density functional theory analysis. Furthermore, the t distribution is not necessarily Gaussian and could be used as an ultrasensitive technique to assess intermolecular distance fluctuation at the subangström level. The present work establishes a direct bridge between quantum chemistry, electrochemistry, organic electronics, and mesoscopic physics, all of which were used to discuss results and perspectives in a quantitative manner. [ABSTRACT FROM AUTHOR]

Published
2017
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15. Kinetics of conradson carbon residue conversion in the catalytic hydroprocessing of a Maya residue

Author

Ludwig Brouwer, M. A. Callejas, Ana M. Benito, Susana Trasobares, Dieter Severin and, and M. I. Martínez

Subjects
Chemistry, General Chemical Engineering, Kinetics, Analytical chemistry, General Chemistry, Carbon-13 NMR, Industrial and Manufacturing Engineering, Catalysis, Residue (chemistry), Reaction rate constant, Proton NMR, Organic chemistry, Atomic ratio, Asphaltene
Abstract

A residue from a Maya crude was hydroprocessed in a continuous hydroprocessing unit provided with a continuous stirred-tank reactor. The kinetic study of Conradson carbon residue (CCR) conversion was carried out, and the data of CCR conversion fit half-order kinetics, with the activation energy being 277.58 kJ/mol. No dependence of the rate constants on hydrogen pressure was observed. The relationship between CCR and different parameters was studied, and it was found that asphaltenes, hydrogen content, H/C atomic ratio, and residue content (350 °C) were linearly related with CCR content. Gas yield was also found to be linearly related with CCR conversion. A structural analysis was carried out by 13C NMR and 1H NMR, and a linear relationship was found between CCR and aromatic carbon contents for the products obtained at 415 °C, when the products obtained at the same temperature are compared. However, a general relationship for all temperatures was not found.

Published
1998

17. Upgrading of a petroleum residue. Kinetics of conradson carbon residue conversion

Author

Dirección General de Investigación Científica y Técnica, DGICT (España), European Commission, Trasobares, Susana, Callejas, María A., Benito, Ana M., Martínez Fernández de Landa, María Teresa, Severin, Dieter, Brouwer, Ludwig, Dirección General de Investigación Científica y Técnica, DGICT (España), European Commission, Trasobares, Susana, Callejas, María A., Benito, Ana M., Martínez Fernández de Landa, María Teresa, Severin, Dieter, and Brouwer, Ludwig

Abstract

A pretreated petroleum residue was hydroprocessed in a continuous hydroprocessing unit provided with a continuous stirred tank reactor. In this paper, the kinetic study of Conradson carbon residue (CCR) conversion is reported. The range of CCR conversion is 5.6−62.4%. The data of CCR conversion fit first-order kinetics, and the activation energy is 36.3 kcal/mol. No pressure dependence of the rate constants as defined by the equation K = K * was observed. The structural analysis of the feed and products indicated that hydroprocessing produces an increase in the saturated fraction and a decrease in the polar fraction. The higher content of saturated fraction in the products obtained at 400 °C than in those obtained at 415 °C together with the increase in aromatic carbon and decrease in molecular weight in the products processed at 415 °C seem to indicate that cyclization reactions plus aromatization of the formed rings are being produced at this temperature. The asphaltene content was linearly related with the CCR content, and the gas yield and 525+ °C fraction conversion were linearly related with the CCR conversion.

Published
1999

18. Kinetics of sulfur removal from a liquid coal residue in thermal, hydrothermal, and hydrocatalytic cracking

Author

Dirección General de Investigación Científica y Técnica, DGICT (España), European Commission, Martínez Fernández de Landa, María Teresa, Benito, Ana M., Callejas, María A., Trasobares, Susana, Dirección General de Investigación Científica y Técnica, DGICT (España), European Commission, Martínez Fernández de Landa, María Teresa, Benito, Ana M., Callejas, María A., and Trasobares, Susana

Abstract

An asphaltenic residue from deasphalting a synthetic crude obtained by direct liquefaction of a subbituminous Spanish coal was submitted to several upgrading routes. In this paper, the kinetics of sulfur-removal reactions in thermal, hydrothermal, and hydrocatalytic cracking are reported. The sulfur-removal reactions fit a 2.7 kinetic order for the thermal process, a 3.8 kinetic order for the hydrothermal process, and a 4.7 kinetic order for the hydrocatalytic process, the activation energy being lowest in the hydrocatalytic process. The activation energy for the thermal processes is higher in the presence of hydrogen. The percentages of sulfur removal range from 3.6 to 56.6 wt % in thermal cracking, from 15.3 to 61.5 wt % in hydrothermal cracking, and from 19.1 to 55.0 wt % in hydrocatalytic cracking. The percentages of sulfur removal at low reaction times for the three processes increase in the order thermal < hydrothermal < hydrocatalytic.

Published
1998

19. Kinetics of conradson carbon residue conversion in the catalytic hydroprocessing of a Maya residue

Author

Trasobares, Susana, Callejas, María A., Benito, Ana M., Martínez Fernández de Landa, María Teresa, Severin, Dieter, Brouwer, Ludwig, Trasobares, Susana, Callejas, María A., Benito, Ana M., Martínez Fernández de Landa, María Teresa, Severin, Dieter, and Brouwer, Ludwig

Abstract

A residue from a Maya crude was hydroprocessed in a continuous hydroprocessing unit provided with a continuous stirred-tank reactor. The kinetic study of Conradson carbon residue (CCR) conversion was carried out, and the data of CCR conversion fit half-order kinetics, with the activation energy being 277.58 kJ/mol. No dependence of the rate constants on hydrogen pressure was observed. The relationship between CCR and different parameters was studied, and it was found that asphaltenes, hydrogen content, H/C atomic ratio, and residue content (350 °C) were linearly related with CCR content. Gas yield was also found to be linearly related with CCR conversion. A structural analysis was carried out by 13C NMR and 1H NMR, and a linear relationship was found between CCR and aromatic carbon contents for the products obtained at 415 °C, when the products obtained at the same temperature are compared. However, a general relationship for all temperatures was not found.

Published
1998

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