FRD - Investigación - Ciencia y Tecnología

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Author: search.filters.author.Gutierrez, Marina

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Now showing 1 - 6 of 6
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    Kinetic and plasmonic properties of gold nanorods adsorbed on glass substrates
    (2019-09-19) Gutierrez, Marina; Scarpettini, Alberto F
    Monodisperse gold nanorods with different sizes were synthesized and adsorbed on chemically modified glass substrates. Influence of surfactant molar concentration on nanorod adsorption was studied and the optimum range was determined. During substrate coverages we monitored the growth of longitudinal localized Surface plasmon resonances at short times due to density increase of isolated nanorods and, at longer times, their subsequent decrease and a concurrent growth of coupling resonances owing to nanoparticle surface mobility andaggregation. Temporal evolution of amplitudes of resonance peaks in extinction spectra and nanorod counting statistics in electron micrographs were used to model both coverage and aggregation processes, as exponential- like functions of time. Their characteristic times and saturation values were analyzed and related to kinetic parameters, nanorod dimensions and extinction coefficients. This work can be used as a predictive tool to prepare plasmonic substrates with desired optical resonances.
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    Optical coherence tomography-based scanning system for shape determination, wall thickness mapping, and inner inspection of glass containers
    (2013-02) Morel, Eneas Nicolás; Gutierrez, Marina; Miranda, Hernán; Sambrano, Edgardo; Torga, Jorge Román
    In this work we present a method that enables simultaneous measurement of shape and wall parameters of glass containers. The system is based on the optical coherence tomography technique, employing the spectral domain configuration. The data were obtained by measuring the spatial coordinates of a sequence of points in a predefined region of a sample that includes points on the surface and in the interior of the material. Dimensional parameters, thickness mapping, and tomography studies of the interior of the sample walls can be obtained from these measurements.
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    Nanorod-based plasmonic substrates with predefined optical resonances
    (2018) Scarpettini, Alberto; Gutierrez, Marina
    To design and fabricate plasmonic substrates to be used in ultrasensitive chemical sensing or surfaceenhanced spectroscopies, it is important to achieve control on the morphology, dimensions and surface density of metallic nanostructures on the substrate, and therefore to achieve control on their optical resonances. In this direction, monodisperse colloidal gold nanorods were synthesized in a seed-mediated growth [1] with a longitudinal surface plasmon resonance tunable in wavelengths from 600 to 1000 nm. These nanorods with well-controlled size and aspect ratio were used as plasmonic building blocks. Glass substrates were chemically modified and the synthesized gold nanorods were adsorbed through a dipping process [2]. The nanostructured coverage dynamics of these substrates was characterized by spectrophotometry and electron microscopy (Fig. 1). A nanoparticle surface aggregation was observed during the coverage process at long times. This aggregation is dominated by the mobility of the isolated nanorods, which first join in dimers and, further in time, in clusters of higher number of nanorods, changing from well-defined longitudinal plasmons to more complex coupling resonances. Evolution of amplitudes of resonance peaks in extinction spectra and nanorod counting statistics were used to model both coverage and aggregation processes [3]. Their characteristic times and saturation values were analyzed and related with kinetic parameters and nanorod extinction coefficients. This work can be used as a predictive tool to prepare plasmonic substrates with desired optical resonances.
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    Fabricación y Caracterización de Sustratos Plasmónicos Basados en Nanobastones de Oro
    (2015) Scarpettini, Alberto; Gutierrez, Marina
    Se fabricaron sustratos plasmónicos mediante el recubrimiento controlado de superficies de vidrio y películas delgadas de oro con nanobastones de oro. Estos sustratos nanoestructurados poseen resonancias ópticas en el rango visible e infrarrojo cercano del espectro electromagnético, y producen grandes intensificaciones de campo, llamados puntos calientes, en regiones muy localizadas de su superficie. El control de estas propiedades ópticas y la posibilidad de sintonizar la respuesta espectral de un sustrato son fundamentales para el diseño y construcción de sensores moleculares ultrasensibles y de sondas de microscopía óptica de altísima resolución. Se sintetizaron nanobastones de oro utilizando métodos de crecimiento mediado por semillas, con un preciso control de sus dimensiones finales. Se obtuvieron suspensiones monodispersas y con alta eficiencia. Se modificaron químicamente superficies de vidrio y películas de oro para adsorber nanobastones de oro. Se controló la densidad de recubrimiento superficial mediante el tiempo de inmersión de los sustratos en la solución coloidal. Se caracterizaron los sustratos fabricados mediante espectros de extinción e imágenes de microscopía electrónica. Se obtuvieron recubrimientos homogéneos con bandas de absorción dadas por el acoplamiento de las resonancias de los nanobastones con el material del sustrato.
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    Monitoring the Photothermal Reshaping of Individual Plasmonic Nanorods with Coherent Mechanical Oscillations
    (2018-12-03) Scarpettini, Alberto; Della Picca, Fabricio; Gutierrez, Marina; Bragas, Andrea
    Light absorption in gold nanoparticles leads to metal heating that induces photothermal reshaping because of atomic surface diffusion at temperatures well below the gold melting point. In this work, we perform time-resolved experiments to measure the frequencies of the extensional coherent mechanical mode in single gold nanorods, as a monitor of the changes in their aspect ratio produced by this photoinduced reshaping. We show that photothermal reshaping always occurs in typical pump–probe experiments conducted in air even at low-excitation light irradiance and usually long measuring times. The reshaping effect can be reduced by a polymer coating, which allows faster heat dissipation from the nanoparticle to the environment.
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    Recubrimiento controlado de sustratos de vidrio con nanobastones metálicos
    (2015-03-12) Gutierrez, Marina; Paredes, María Yanela; Scarpettini, Alberto
    Se realizó la síntesis de nanobastones de oro monodispersos con una eficiencia superior al 80% sobre el total de nanopartículas, caracterizado por una resonancia plasmónica longitudinal cercana a los 800 nm. Se modi- ficaron superficialmente sustratos de vidrio y se los recubrió con los nanobastones sintetizados, con control de la densidad superficial. Se monitoreó la dinámica del recubrimiento a través de espectros de extinción, y se observó una densidad máxima de saturación dada por repulsión electrostática y un tiempo característico del proceso. Luego de alcanzada la saturación de nanobastones por unidad de área se observa un ensancha- miento de las resonancias hacia el infrarrojo, debido a interacciones entre los nanobastones por producirse agregaciones sobre la superficie. Estos resultados tienen aplicación inmediata en el diseño y fabricación de dispositivos plasmónicos, por ejemplo en el sensado molecular.