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Open Access journal
ISSN (Print) 1665-3521
Published by SciELO

[672 journals]

Desarrollo de un sustrato flexible y activo para SERS basado en
nanoestructuras de metales nobles (Au y Ag)/poliestireno
- Abstract: Resumen La necesidad de contar con sistemas de detección altamente sensibles de moléculas orgánicas, que sean rápidos y asequibles para su uso en campo, ha empujado el desarrollo de dispositivos basados en el efecto SERS (por sus siglas en inglés: Surface-Enhanced Raman Spectroscopy). En el presente estudio se reporta la síntesis verde de nanopartículas de Au con Cymbopogon citratus y Citrus paradisi, con forma de estrella y triangulares respectivamente; así como la síntesis química de nanopartículas cúbicas de Ag. Las nanoestructuras fueron caracterizadas por medio de espectroscopia UV-Vis y Microscopia Electrónica de Transmisión. Las nanoestructuras de Ag y Au fueron depositadas sobre una superficie de poliestireno acanalado, para evaluar estos sistemas como sustratos activos para SERS utilizando el azul de metileno como molécula objetivo. En todos los casos se consigue una mejora en las señales Raman características del azul de metileno, especialmente cuando se emplean las nanoestructuras con morfología tipo estrella de Au.Abstract The need for fast and affordable portable detection systems, which are highly sensitive to organic molecules, has directed the development of devices based on SERS effect (Surface-Enhanced Raman Spectroscopy). In the present study, the green synthesis of Au nanoparticles assisted with Cymbopogon citratus and Citrus paradisi aqueous extract is reported, which are obtained with star-like and triangular shapes, respectively, as well as the chemical synthesis of cubic Ag nanoparticles. The nanostructures were characterized with UV-Vis spectroscopy and Transmission Electron Microscopy. The Ag and Au nanostructures were deposited on a ribbed polystyrene surface, to evaluate these arrays as active substrates for SERS using methylene blue as target molecule. An improvement in the characteristic Raman signals of methylene blue was observed in all cases, especially when Au nanostructures with star-like morphology are employed.
Pt/Ga-SBA-15 composites synthesis and characterization
- Abstract: Abstract Pt (0.5, 1 and 1.5 wt%) was impregnated by incipient wetness on SBA-15 and corresponding Ga-modified (3, 5, 10 and 20 wt%) composites. Gallium nitrate was incorporated directly during the mesoporous siliceous network synthesis. Materials were characterized by N2 physisorption, X-ray diffraction, Fourier transformed infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. SBA-15 had surface area greater than 800 m²/g that decreased by Ga incorporation in binary materials. It seemed that tetrahedral gallium was well-incorporated into mesoporous silica walls. Pt dispersion slightly diminished (as to that on SBA-15) by augmenting Ga concentration in composites. Corresponding pore size maxima shifted to lower diameters (as to that of non-impregnated supports) after platinum loading suggesting Pt crystals inside pores of SBA-15 and Ga-modified carriers. Large cubic platinum crystals were observed over all prepared materials probably due to sintering (during calcining at 500 °C) of metallic particles weakly interacting with the carriers surface. After materials annealing (500 °C under static air) metallic platinum was evidenced (by XRD) pointing out to noble metal reduction that could be facilitated by decomposition of organic remains from Si alkoxide used during supports synthesis which presence was ascertained by FTIR.

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