Publications by authors named "Gustavo Torchia"

5 Publications

  • Page 1 of 1

A study of polymer chain diffusion by surface enhanced Raman: effects of plasmonic substrate topology.

Soft Matter 2018 May;14(17):3315-3323

Institute of Materials Science and Technology (INTEMA), National Research Council (CONICET), University of Mar del Plata, Mar del Plata, Argentina.

We report on a new methodology to track chain interdiffusion between polymer slabs based on Raman enhanced by plasmonic substrates. Diffusion is studied in a deuterated-polystyrene/polystyrene (dPS/PS) polymer pair, designed to provide a well-characterized diffusion behavior. The bilayer, 160 nm thick in total, is supported on a plasmonic substrate that provides local amplification of Raman signals in sample regions of close proximity to it. Gold-based substrates with structures of inverted pyramids, spherical nanoparticles and tipped pillars were investigated. Interdiffusion between dPS and PS is promoted upon annealing and followed in situ by dynamic spectral acquisition. A simple model that describes the coupling between the sampled region arising from the plasmonic effect and the diffusion process is employed to interpret spectral evolution data. It is shown that a highly regular topology and surface continuity are key features of the plasmonic substrate in order to provide reliable results. With pyramidal substrates, the most suitable substrates for this application, data are consistent with diffusion coefficients in the range 10-13-10-15 cm2 s-1 and dimensions of sampled regions below 40 nm. The strategy provides a reliable labeling-free technique to investigate polymer interdiffusion on the nanoscale.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c8sm00017dDOI Listing
May 2018

A new method for relative Sr determination in human teeth enamel.

J Anthropol Sci 2011 1;89:153-60. Epub 2011 Jul 1.

Centro de Investigaciones Opticas, (CONICET La Plata, CIC), CC 124, 1900, La Plata, Argentina.

We present a new method to determine Sr/Ca changes in hard dental tissues based on laser ablation and spectroscopic detection. By using femtosecond Laser Induced Breakdown Spectroscopy (fs-LIBS), we micro mapped the relative amount of strontium in the enamel of three human lower third molar. We also analyzed the Sr/Ca ratio along the striae of Retzius. Results show that microlibs allows detection of variation in relative Sr/Ca ratio through enamel. The same values of Sr/Ca ratio were found along a single stria. The method has a precision better than 95% and is sensitive enough to detect Sr/Ca ratio variations among striae and within stria. Fs-LIBS generates information in a fast and simple way that can be used by non-specialists to make inferences about diet or mobility in human populations and fossil hominids.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4436/jass.89012DOI Listing
April 2012

Alternative configuration for an optical ring resonator angular rate sensor by using a standard laser diode.

Appl Opt 2011 Jul;50(20):3449-54

Centro de Investigaciones Ópticas Comisión Nacional de Investigaciones Científicas y Técnicas La Plata—Comisión de Investigaciones Científicas de la Provincia de Buenos Aires, Camino Centenario y 506 s/n Casilla de Correo no. 3, 1897 Gonnet, Pcia Buenos Aires, Argentina.

In this work, we present an alternative approach to angular velocity optical sensing based on two-ring resonators. This configuration admits the use of a standard laser diode source (0.1 nm, 10,000 MHz, FWHM) reaching higher sensitivities when narrow spectral laser sources (1 MHz, FWHM) are used. We compare this configuration with the standard single-ring resonator angular rate sensor (SRARS), which must use a narrow laser at input. Finally, we conclude that the sensitivity of this new approach can also be enhanced by coupling high-power broadband laser sources in a large range (from 1°/h to 10,000°/h), reaching performance similar to that of a standard SRARS configuration.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/AO.50.003449DOI Listing
July 2011

Femtosecond laser written surface waveguides fabricated in Nd:YAG ceramics.

Opt Express 2007 Oct;15(20):13266-71

Near surface channel waveguides have been fabricated in Neodymium doped YAG ceramics by using IR femtosecond laser irradiation at the low frequency regime. Single mode guidance has been demonstrated with propagation losses of ~1 dB/cm. Time resolved confocal micro-luminescence experiments have been used to determine the spectroscopic properties of the Nd(3+) laser ions in the channel waveguide as well as to elucidate the waveguide formation processes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/oe.15.013266DOI Listing
October 2007

Synthesis of ceramic nanoparticles by ultrafast laser ablation of solid targets in water.

J Nanosci Nanotechnol 2006 Jul;6(7):1961-7

Servicio Láser, Universidad de Salamanca, Spain.

We report production of nanoparticles of several advanced ceramics (Si3N4, SiC, AlN, and Al2O3) by ablation with femtosecond laser pulses of solid targets submerged in deionized water. The products withstand comparison with commercial nanoparticle suspensions obtained by other techniques as they are analyzed by means of transmission electron microscopy. As compared with metal nanoparticles produced with the same technique, we have found that the overall dependence of mean sizes and distribution widths on the laser fluence is similar. We explain why it is difficult to synthetize very small (<5 nm) and monodisperse particles in terms of ablation mechanism and discuss the aplicability of the technique for industrial production.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1166/jnn.2006.365DOI Listing
July 2006