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Oliva M.I.,National University of Cordoba | Oliva M.I.,CONICET | Heredia A.,National University of Costa Rica | Zandalazini C.I.,Centro Laser Of Ciencias Moleculares | And 2 more authors.
Physica B: Condensed Matter

Mixed oxides of Mg-Al-Zn-Fe were obtained by calcination of layered double hydroxides (LDH) prepared by coprecipitation reaction with hydrothermal treatment. The structural characterization of precursors and oxides was carried out by X rays diffraction, showing increases of ZnO phase with the increase of the zinc content. Magnetic behavior was studied by vibrating sample magnetometer (VSM) and by a superconducting quantum interference device (SQUID) showing both paramagnetic and super paramagnetic behavior depending on both particles size and composition. © 2012 Elsevier B.V. Source

Garcia-Vela A.,Institute Fisica Fundamental | Cabanillas-Vidosa I.,Centro Laser Of Ciencias Moleculares | Ferrero J.C.,Centro Laser Of Ciencias Moleculares | Pino G.A.,Centro Laser Of Ciencias Moleculares
Physical Chemistry Chemical Physics

The low-energy collisions of I 2(B,v′ = 21) with He involving collision-induced vibrational relaxation of I 2 are investigated both experimentally and by means of wave packet simulations. The theoretical cross sections exhibit a structure of peaks originated by orbiting resonances of the I 2(B,v′ = 21) - He van der Waals complex formed in the I 2 + He collisions. Such a structure has similar characteristics as the structure of peaks found in the experimental cross sections. In fact, four of the five peaks of the measured cross sections appear at positions nearly coincident with those of four of the peaks found in the theoretical cross sections. Thus this result confirms the experimental finding that enhancement of I 2 vibrational relaxation is caused by the population of I 2(B,v′ = 21) - He orbiting resonances populated upon the low-energy collisions. The possibility of using this mechanism in the vibrational cooling of diatomic molecules is discussed. © the Owner Societies 2012. Source

Fraire J.C.,Centro Laser Of Ciencias Moleculares | Sueldo Ocello V.N.,National University of Cordoba | Allende L.G.,Centro Laser Of Ciencias Moleculares | Veglia A.V.,National University of Cordoba | Coronado E.A.,Centro Laser Of Ciencias Moleculares
Journal of Physical Chemistry C

In this work, we report a simple strategy to obtain ultrasensitive SERS nanostructures by self-assembly of Au nanospheres (NSs). This novel protocol allow us to obtain in a reproducible manner Au NS dimers using cucurbit[6]uril (CB[6]) molecules as linkers. The resulting dimers are stable in colloidal dispersion over several days, generating in this way nanostructures with highly reproducible hot spots. This feature is due to the precise subnanometric control of the molecules that generates interparticle distance and, at the same time, of the capability of placing analyte molecules just within these junctions of ultrahigh field enhancement due to the host-guest properties of the CB[6] molecule. The dimer formation is based on the modification of the metal surface with cysteamine molecules (Cys) previous incubation with CB[6] molecules. The cysteamine-functionalized NSs (Cys/NSs) are positive charged due to the protonation of the amine groups of the Cys molecule at the working pH. These positive groups interact through H-bonds with the carbonyls groups at the portal of the CB[6] molecules. The dimer formation is based on the stoichiometric control between Cys/NPs and CB[6] (ratio 2:1), generating a gap of 1.8 nm and giving rise to SERS enhancements of around 108. The host-guest properties of the CB[6] molecule are used to detect the average SERS enhancement produced by adding methyl viologen (MV) as plasmonic probe. It was found that the average analytical enhancement factor (AEF) for MV is as good as that obtained for the CB[6] itself (around 108). © 2015 American Chemical Society. Source

Fraire J.C.,Centro Laser Of Ciencias Moleculares | Masseroni M.L.,National University of Cordoba | Jausoro I.,National University of Cordoba | Perassi E.M.,Centro Laser Of Ciencias Moleculares | And 2 more authors.
ACS Nano

Detecting, imaging, and being able to localize the distribution of several cell membrane receptors on a single neuron are very important topics in neuroscience research. In the present work, the distribution of metabotropic glutamate receptor 1a (mGluR1a) density on neuron cells on subcellular length scales is determined by evaluating the role played by protein kinase D1 (PKD1) in the trafficking of membrane proteins, comparing the distribution of mGluR1a in experiments performed in endogenous PKD1 expression with those in the presence of kinase-inactive protein kinase D1 (PKD1-kd). The localization, distribution, and density of cell surface mGluR1a were evaluated using 90 nm diameter Au nanoparticle (NP) probes specifically functionalized with a high-affinity and multivalent labeling function, which allows not only imaging NPs where this receptor is present but also quantifying by optical means the NP density. This is so because the NP generates a density (F)-dependent SERS response that facilitated a spatial mapping of the mGluR1a density distribution on subcellular length scales (dendrites and axons) in an optical microscope. The measured F values were found to be significantly higher on dendrites than on axons for endogenous PKD1, while an increase of F on axons was observed when PKD1 is altered. The spatial distribution of the NP immunolabels through scanning electron microscopy (SEM) confirmed the results obtained by fluorescence bright-field analysis and dark-field spectroscopy and provided additional structural details. In addition, it is shown using electrodynamic simulations that SERS spectroscopy could be a very sensitive tool for the spatial mapping of cell membrane receptors on subcellular length scales, as SERS signals are almost linearly dependent on NP density and therefore give indirect information on the distribution of cell membrane proteins. This result is important since the calibration of the F-dependent near-field enhancement of the Au immunolabels through correlation of SERS and SEM paves the way toward quantitative immunolabeling studies of cell membrane proteins involved in neuron polarity. From the molecular biology point of view, this study shows that in cultured hippocampal pyramidal cells mGluR1a is predominantly transported to dendrites and excluded from axons. Expression of kinaseinactive protein kinase D1 (PKD1-kd) dramatically and selectively alters the intracellular trafficking and membrane delivery of mGluR1a-containing vesicles. © 2014 American Chemical Society. Source

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