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D'Urso C.,CNR Institute of Advanced Energy Technologies Nicola Giordano | Bonesi A.,INIFTA | Triaca W.E.,INIFTA | Luna A.M.C.,INIFTA | And 2 more authors.
International Journal of Electrochemical Science | Year: 2012

Three Pt-based anode catalysts supported on Vulcan XC-72R (VC) were prepared by using a modified polyol process. These materials were characterized and tested by X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF) and Transmission Electron Microscopy (TEM). XRD and TEM analysis indicated that especially the ternary anode catalysts consisted of uniform nanosized particles with sharp distribution. The Pt lattice parameter was smaller, in the ternary PtSnIr catalyst whereas it increased with the addition of Sn and Rh, in the corresponding binary and ternary catalysts. Cyclic voltammetry (CV) measurements showed that Sn, Ir and Rh may act as promoter of Pt enhancing ethanol electro-oxidation activity. It was found that the direct ethanol fuel cell (DEFC) performances were significantly improved with these modified anode catalysts. This effect on the DEFC performance is attributed to the so-called bi-tri-functional mechanism and to the electronic interaction between Pt and additives. The performance increased significantly with the temperature. However, it was also possible to observe some decay with time for all catalysts due to the formation of surface poisons, probably consisting in CO-like species. At 60 °C, the PtSnIr catalyst showed the best performance, as a result of a proper morphologyand promoting effect. © 2012 by ESG (www.electrochemsci.org).

Okulik N.B.,National University of the Chaco Austral | Jubert A.H.,CEQUINOR | Castro E.A.,INIFTA
Journal of Molecular Modeling | Year: 2012

A theoretical study on the series of compounds "PhSeX", where Ph=phenyl, Se=selenium and X=Cl, Br, I, CN or SCN, is reported and compared with previously reported experimental data. The molecular geometry for these PhSeX compounds was studied at the DFT/B3LYP level of calculation by means of the 6-311G(d,p) basis set. The equilibrium structures of the molecules were dependent on the method employed to compare the known solid structures. A topological study of the calculated PhSeX species, based on the AIM theory, was carried out to gain a deeper insight into the bonding nature and to find an explanation for the structural diversity exhibited by these PhSeX compounds. The results reported herein illustrate the subtle differences in the solid-state structures of PhSeX compounds. © Springer-Verlag 2011.

Ruiz D.L.,Laboratorio Of Estudio Of Compuestos Organicos Ladecor | Albesa A.G.,INIFTA | Ponzinibbio A.,Laboratorio Of Estudio Of Compuestos Organicos Ladecor | Allegretti P.E.,Laboratorio Of Estudio Of Compuestos Organicos Ladecor | Schiavoni M.M.,Laboratorio Of Estudio Of Compuestos Organicos Ladecor
Journal of Physical Organic Chemistry | Year: 2010

Solvent effects on tautomeric equilibria in several β-ketonitriles has been investigated using nuclear magnetic resonance (NMR) spectroscopy and theoretical methods. The experimental chemical shifts were compared with theoretical values obtained by using gauge-including atomic orbital (GIAO) calculations, implemented at Density Functional Theory (DFT) level with hybrid functionals, B3LYP calculations. The solvent effect on the calculated structures has been taken into account through the polarized continuum model (PCM) for chloroform, acetone and dimethyl sulfoxide (DMSO). Also, some structural parameters were calculated in gas phase and in three different solvents. Copyright © 2010 John Wiley and Sons, Ltd.

Gara P.M.D.,Institute Terapia Radiante S.A. | Garabano N.I.,University of Buenos Aires | Portoles M.J.L.,INIFTA | Moreno M.S.,Bariloche Atomic Center | And 4 more authors.
Journal of Nanoparticle Research | Year: 2012

The capability of silicon nanoparticles to increase the yield of reactive species upon 4 MeV X-ray irradiation of aqueous suspensions and C6 glioma cell cultures was investigated. ROS generation was detected and quantified using several specific probes. The particles were characterized by FTIR, XPS, TEM, DLS, luminescence, and adsorption spectroscopy before and after irradiation to evaluate the effect of high energy radiation on their structure. The total concentration of O 2 ·-/HO 2 ·, HO ·, and H 2O 2 generated upon 4-MeV X-ray irradiation of 6.4 μM silicon nanoparticle aqueous suspensions were on the order of 10 μM per Gy, ten times higher than that obtained in similar experiments but in the absence of particles. Cytotoxic 1O 2 was generated only in irradiation experiments containing the particles. The particle surface became oxidized to SiO 2 and the luminescence yield reduced with the irradiation dose. Changes in the surface morphology did not affect, within the experimental error, the yields ofROSgenerated per Gy. X-ray irradiation of glioma C6 cell cultures with incorporated silicon nanoparticles showed a marked production of ROS proportional to the radiation dose received. In the absence of nanoparticles, the cells showed no irradiation- enhanced ROS generation. The obtained results indicate that silicon nanoparticles of <5 nm size have the potential to be used as radiosensitizers for improving the outcomes of cancer radiotherapy. Their capability of producing 1O 2 upon X-ray irradiation opens novel approaches in the design of therapy strategies. © Springer Science+Business Media B.V. 2012.

Sarabadani J.,Max Planck Institute for Polymer Research | Milchev A.,Max Planck Institute for Polymer Research | Milchev A.,Bulgarian Academy of Science | De Virgiliis A.,INIFTA | Vilgis T.A.,Max Planck Institute for Polymer Research
Soft Materials | Year: 2014

We investigate the dynamic and static properties of a polymer melt near solid surfaces. The melt, composed of linear chains, is confined between two solid walls with one of the walls being repulsive; whereas the opposite, attractive wall, is characterized by different degrees of roughness, caused by an array of short perpendicular pillars with variable grafting density. We demonstrate the remarkable fact that the conformations of chains in the melt at the interfaces are mostly unaffected by the strength of substrate/polymer attraction. Moreover, they practically coincide with the conformations of a single end-grafted chain at the critical point of adsorption, in agreement with Silberbergs hypothesis. This agreement is corroborated by the analysis of the size distributions of trains, loops, and tails of melt chains at the walls that are found to be perfectly described by analytical expressions pertaining to end-grafted single chains at critical adsorption. The adsorbed amount at the attractive bottom surface is found to scale with macromolecule length as regardless of adsorption strength. We also find that the pressure of the melt PN decreases as PN - P∞ α N-1 (where P∞ is the extrapolated pressure for N → ∞) with growing length N of the chains whereas the surface tension γ at both walls is found to decline as γN α N-2/3. Eventually, a study of the polymer dynamics at the rough interface reveals that surface roughness leads to dramatic drop of the coefficient for lateral diffusion whenever the separation between obstacles (neighboring pillars) becomes less than where Rg is the unperturbed radius of gyration of chains in the bulk. © Taylor & Francis Group, LLC.

Bordon A.G.,University del Nordeste | Profeta M.I.,University del Nordeste | Romero J.M.,University del Nordeste | Jorge N.L.,University del Nordeste | Castro E.A.,INIFTA
Current Organic Synthesis | Year: 2014

3,6-diphenyl-1,2,4,5-tetraoxane(DFT) has been prepared in order to study the effect of temperature on the reaction kinetics in methylcellosolve solution. The thermolysis reaction fulfills a kinetic law of the first order up to conversions approximately 60 % of the DFT. The values of ∆H#=20.2±1.0 kcal mol-1 and ∆S#= -25.3±1.4 cal mol-1 K-1 of the rupture of one O-O bond in the diperoxide molecule were obtained by measuring the remanent diperoxide at different reaction times by GC technique. Benzaldehyde and benzoic acid were detected by GC as the major organics products of the reaction. © 2014 Bentham Science Publishers.

Sancho M.I.,National University of San Luis | Sancho M.I.,CONICET | Gasull E.,National University of San Luis | Blanco S.E.,National University of San Luis | And 2 more authors.
Carbohydrate Research | Year: 2011

A thermodynamic study of the inclusion process between 2-chlorobenzophenone (2ClBP) and cyclomaltoheptaose (β-cyclodextrin, β-CD) was performed using UV-vis spectroscopy, reversed-phase liquid chromatography (RP-HPLC), and molecular modeling (PM6). Spectrophotometric measurements in aqueous solutions were performed at different temperatures. The stoichiometry of the complex is 1:1 and its apparent formation constant (K c) is 3846 M -1 at 30 °C. Temperature dependence of K c values revealed that both enthalpy (δH° = -10.58 kJ/mol) and entropy changes (δS° = 33.76 J/K mol) are favorable for the inclusion process in an aqueous medium. Encapsulation was also investigated using RP-HPLC (C18 column) with different mobile-phase compositions, to which β-CD was added. The apparent formation constants in MeOH-H 2O (K F) were dependent of the proportion of the mobile phase employed (50:50, 55:45, 60:40 and 65:35, v/v). The K F values were 419 M -1 (50% MeOH) and 166 M -1 (65% MeOH) at 30 °C. The thermodynamic parameters of the complex in an aqueous MeOH medium indicated that this process is largely driven by enthalpy change (δH° = -27.25 kJ/mol and δS° = -45.12 J/K mol). The results of the study carried out with the PM6 semiempirical method showed that the energetically most favorable structure for the formation of the complex is the 'head up' orientation. © 2011 Elsevier Ltd. All rights reserved.

Vignoni M.,INIFTA | Salum M.L.,CONICET | Erra-Balsells R.,CONICET | Thomas A.H.,INIFTA | Cabrerizo F.M.,CONICET
Chemical Physics Letters | Year: 2010

Pterins belong to a family of heterocyclic compounds present in a wide range of living systems and participate in relevant biological functions. Under anaerobic conditions, the unstable red intermediate generated by UV-A irradiation of biopterin, neopterin and 6-hydroxymethylpterin was identified by 1H NMR analysis, in alkaline D2O solutions, as 5,8-dihydro-6-formylpterin. © 2009 Elsevier B.V. All rights reserved.

Fernandez F.M.,INIFTA
Physica Scripta | Year: 2014

In this comment we analyze the results derived recently by Bowen et al (2014 Phys. Scr. 89 015301). We first show that the eigenvalues of the family of the anharmonic oscillators studied by those authors already exhibit a branch point but it is irrelevant for perturbation theory. Second, we show that one of the authors' main contributions, namely that the variational method yields the correct dependence of the eigenvalues on the coupling constant, has been known since long ago. Third, the authors' statement that their Bohr-Sommerfeld eigenvalues are exact is proved wrong by comparison with accurate numerical results.

Type: Journal Article | Journal: Journal of molecular modeling | Year: 2010

The equilibrium structures, the planarity of the C(=O)X linkage and the nature of the chemical bond in the Y-C(=O)-XR(1)R(2) [where: Y= -CH-(CH(2)-CH(2)-CH(3))(2), X=N,O and R(1), R(2)= H; alkyl and aryl groups and lone pair electrons (lp)] molecular fragment of derivates of Valproic acid (Vpa) with antiepileptic activity were studied systematically by means of B3LYP calculations and topological analysis of the electron localization function (ELF). The covariance parameter cov[Omega(i), Omega(j)] reveals a dominating delocalization effect between the lone pair V(O(1)), V(X) and the electron density of the H-C and H-X(1) bonds resulting from the existence of not only non-conventional intramolecular hydrogen bonding patterns as C-H...O/N but also a weak closed-shell stabilizing interaction type arising from a dihydrogen bonding as C-H...H-N, where H...H contacts at a significantly shorter distance than twice the hydrogen atom van der Waals radius. The analyzed data derived from ELF domains were found to be in agreement with the known features and properties of the hydrogen bonding interactions discussed in this work.

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