2,372 research outputs found
Tunable plasmonic resonance of gallium nanoparticles by thermal oxidation at low temperatures
This Accepted Manuscript is available for reuse under a CC BY-NC-ND 3.0 licence after the 12 month embargo period provided that all the terms of the licence are adhered toThe effect of the oxidation of gallium nanoparticles (Ga NPs) on their plasmonic properties is investigated. Discrete dipole approximation has been used to study the wavelength of the out-of-plane localized surface plasmon resonance in hemispherical Ga NPs, deposited on silicon substrates, with oxide shell (Ga2O3) of different thickness. Thermal oxidation treatments, varying temperature and time, were carried out in order to increase experimentally the Ga2O3 shell thickness in the NPs. The optical, structural and chemical properties of the oxidized NPs have been studied by spectroscopic ellipsometry, scanning electron microscopy, grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy. A clear redshift of the peak wavelength is observed, barely affecting the intensity of the plasmon resonance. A controllable increase of the Ga2O3 thickness as a consequence of the thermal annealing is achieved. In addition, simulations together with ellipsometry results have been used to determine the oxidation rate, whose kinetics is governed by a logarithmic dependence. These results support the tunable properties of the plasmon resonance wavelength in Ga NPs by thermal oxidation at low temperatures without significant reduction of the plasmon resonance intensityThis research is supported by the MINECO (CTQ2014-53334-C2-2-R and MAT2016-80394-R) and Comunidad de Madrid (NANOAVANSENS ref. S2013/MIT-3029) projects. ARC acknowledges Ramón y Cajal program (under contract number RYC-2015-18047).
FN acknowledges support from Marie Sklodowska-Curie grant agreement No 641899 from the European Union’s Horizon 2020 research and innovation programm
Plasmonic coupling in closed-packed ordered gallium nanoparticles
Plasmonic gallium (Ga) nanoparticles (NPs) are well known to exhibit good performance in numerous applications such as surface enhanced fluorescence and Raman spectroscopy or biosensing. However, to reach the optimal optical performance, the strength of the localized surface plasmon resonances (LSPRs) must be enhanced particularly by suitable narrowing the NP size distribution among other factors. With this purpose, our last work demonstrated the production of hexagonal ordered arrays of Ga NPs by using templates of aluminium (Al) shallow pit arrays, whose LSPRs were observed in the VIS region. The quantitative analysis of the optical properties by spectroscopic ellipsometry confirmed an outstanding improvement of the LSPR intensity and full width at half maximum (FWHM) due to the imposed ordering. Here, by engineering the template dimensions, and therefore by tuning Ga NPs size, we expand the LSPRs of the Ga NPs to cover a wider range of the electromagnetic spectrum from the UV to the IR regions. More interestingly, the factors that cause this optical performance improvement are studied with the universal plasmon ruler equation, supported with discrete dipole approximation simulations. The results allow us to conclude that the plasmonic coupling between NPs originated in the ordered systems is the main cause for the optimized optical responseThe research is supported by the MINECO (CTQ2014-53334-C2-2-R, CTQ2017-84309-C2-2-R and MAT201676824-C3-1-R) and Comunidad de Madrid (P2018/NMT4349 and S2018/NMT-4321 NANOMAGCOST) projects. ARC acknowledges Ramón y Cajal program (under contract number RYC-2015-18047
Mejora de un suelo degradado por exceso de sal para su uso en cultivos gracias al tratamiento con plantas.
Motivación: la producción de alimentos es limitada por diversos factores siendo la salinización del suelo uno de los principales debido a que disminuye la capacidad de producción de los campos agrícolas. Diversos estudios han demostrado que casi la mitad de las zonas agrícolas bajo riego, principalmente de zonas áridas y semiáridas, son afectadas por la salinización del suelo. Muchas de estas áreas son zonas rurales de escaso desarrollo económico y dependientes en gran medida de trabajo en el campo. Un nuevo camino para la recuperación de éstas zonas contaminadas es la fitodesalinización, que es la eliminación del exceso de sales de un suelo por medio de plantas, que son capaces de captarla del suelo y retenerla en su interior, permitiendo que la concentración de sal de dicho suelo disminuya recuperándolos. La fitodesalinización es un proceso rentable, sostenible, no invasivo, alternativo o complementario a otros métodos para solucionar el problema de estos suelos degradados. Arthrocnemum macrostachyum es una especie vegetal de marisma que se utiliza en el proceso de fitodesalinización de este trabajo por ser una planta halófita, es decir, que depende de la sal para tener un buen desarrollo.Métodos: Las plántulas de Arthrocnemum crecieron en solución Hoagland hasta alcanzar el tamaño adecaudo (5 cm). Se plantaron en suelos con un problema de salinidad durante un mes. Tras el tratamiento se usó el suelo problema para comprobar que germinaban trigo y centeno. Tanto el material vegetal como suelo fueron analizados cabo mediante la técnica de espectrometría de masas.Resultados: tras el tratamiento durante un mes con A. macrostachyum se obtuvieron resultados muy interesantes en el campo de la restauración de suelos para el uso agrícola. Así el suelo que sufría problemas con el exceso de sal, tras ser tratado con A. macrostachyum se consiguió que se rebajase casi un 50% la cantidad de sales disueltas en el suelo. Hecho que se ratificó al conseguir que dos cultivos de interés agrícola como el trigo y la cebada, que no germinaban en el suelo salinizado volviesen a hacerlo, aproximadamente una media del 40% respecto a un suelo control. Además se comprobó que no sólo germinaban sino que las plantas consiguieron desarrollarse durante un mes sin problemas.Conclusiones: la especie Arthrocnemum macrostachyum puede ser muy útil en la restauración de suelos degradados por la presencia de sales, y por tanto en la recuperación de zonas para su uso agrícola
The role of the oxide shell in the chemical functionalization of plasmonic gallium nanoparticles
S. Catalán-Gómez, M. Briones, A. Redondo-Cubero, F. J. Palomares, F. Nucciarelli, E. Lorenzo, J. L. Pau, "The role of the oxide shell in the chemical functionalization of plasmonic gallium nanoparticles", SPIE Optics + Optoelectronics Proc. SPIE 10231 (16 May 2017); doi: 10.1117/12.2265665; Copyright 2017 Society of Photo‑Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.Plasmonic Ga nanoparticles (NPs) were thermally oxidized at low temperature in order to increase the native Ga 2 O 3 shell thickness and to improve their stability during the chemical functionalization. The optical, structural and chemical properties of the oxidized NPs have been studied by spectroscopic ellipsometry, scanning electron microscopy, grazing incidence X-ray diffraction and X-ray photoelectron spectroscopy. A clear redshift of the peak wavelength is observed with the increasing annealing time due to the Ga 2 O 3 thickness increase, and barely affecting the intensity of the plasmon resonance. This oxide layer enhances the stability of the NPs upon immersion in ethanol or water. The surface sensitivity properties of the as-grown and oxidized NPs were investigated by linking a thiol group from 6-Mercapto-1-hexanol through immersion. Ellipsometric spectra at the reversal polarization handedness (RPH) condition are in agreement with the Langmuir absorption model, indicating the formation of a thiol monolayer on the NPs
La estación de radiación solar e iluminación de alta calidad del IDMP en Madrid y su aplicación a la edificación
En este trabajo se presenta un estudio de la actividad investigadora que se ha realizado hasta el momento en la estación de radiación solar e iluminación de alta calidad del International Daylight Measurement Program (IDMP) en Madrid ubicada en la E. T. S. de Arquitectura de la Universidad Politécnica de Madrid (40º 25’ N, 3º 41’ W). Esta estación ha centrado su investigación fundamental en dos temas: luminancias y eficacias luminosas de la radiación solar (global, difusa y directa) para todo tipo de cielos, todo ello desde un punto de vista físico, cuyos trabajos y resultados se exponen con detalle. La finalidad de este estudio es poder aplicar los resultados obtenidos a la Edificación, tanto en edificios ya existentes como de nueva construcción, para obtener un máximo confort visual a partir de la iluminación natural, con el consiguiente ahorro energétic
Size-selective breaking of the core-shell structure of gallium nanoparticles
This Accepted Manuscript is available for reuse under a CC BY-NC-ND 3.0 licence after the 12 month embargo period provided that all the terms of the licence are adhered toCore-shell gallium nanoparticles (Ga NPs) have recently been proposed as an ultraviolet plasmonic material for different applications but only at room temperature. Here, the thermal stability as a function of the size of the NPs is reported over a wide range of temperatures. We analyze the chemical and structural properties of the oxide shell by x-ray photoelectron spectroscopy and atomic force microscopy. We demonstrate the inverse dependence of the shell breaking temperature with the size of the NPs. Spectroscopic ellipsometry is used for tracking the rupture and its mechanism is systematically investigated by scanning electron microscopy, grazing incidence x-ray diffraction and cathodoluminescence. Taking advantage of the thermal stability of the NPs, we perform complete oxidations that lead to homogenous gallium oxide NPs. Thus, this study set the physical limits of Ga NPs to last at high temperatures, and opens up the possibility to achieve totally oxidized NPs while keeping their sphericityThe research is supported by the MINECO (CTQ2014-53334-C2-2-R, CTQ2017-84309-C2-2-R, MAT2016-80394-R, MAT 2015-65274-R/FEDER and MAT2017-85089-C2-1-R) and Comunidad de Madrid (NANOAVANSENS ref. S2013/MIT-3029) projects. ARC acknowledges Ramón y Cajal program (under contract number RYC-2015-18047). FN
acknowledges support from Marie Sklodowska-Curie grant agreement No. 641899 from the European Union´s Horizon 2020 research and innovation programm
Coal pit lakes in abandoned mining areas in León (NW Spain): characteristics and geoecological significance
1-14 pMining activity introduces severe changes in landscapes and, subsequently, in land uses. One of the most singular changes is the existence of pit lakes, which occur in active and, more frequently, abandoned mines. Pit lakes are produced by water table interception when open-pit mines deepen. Their characteristics are highly variable, depending on the type of mine, the environment or the climate. In León province there is a long tradition of coal mining that dates back to the nineteenth century, and hundreds of open pits from the 1970s to 2018 have been opened, producing permanent landscape changes. This work analyses the main parameters, including morphological measurements, depth and pH values obtained from aerial photos and field work, of 76 coal pit lakes more than 30 m in length. The vast majority of these pit lakes were unknown until now and were not included in inventories or maps. The data obtained provide baseline knowledge that will allow, in the future, potential uses (storage of water for various uses, recreational use, wildlife habitat, and geological heritage sites) for these pit lakes and establish their importance as a new geoecological environment.S
RESULTADOS PRELIMINARES EN LOS ESTUDIOS DE EFICIENCIA ENERGÉTICA DENTRO DEL PROYECTO DE I+D+i OPTIREG: GESTIÓN EFICIENTE DE REGADÍOS
[ES] El grupo de trabajo WP3 “Eficiencia energética” en el marco del proyecto I+D+i
OPTIREG “Gestión Eficiente de Regadíos” del grupo Tragsa, lleva a cabo diversas
actuaciones encaminadas a conocer el estado energético y organizativo de la gestión de las
CC.RR. modernizadas, buscando metodologías que mejoren las herramientas de diagnóstico
de la situación hídrico-energética de una C.RR., como también estrategias operativas que
mejoren la eficiencia energética adaptándose a la idiosincrasia y condición de cada caso
particular. Para alcanzar estos objetivos, los trabajos se están centrando en varios aspectos:
– Recopilación de medidas efectivas de eficiencia energética aplicadas a los diversos
ámbitos de la infraestructura y organización en que se diversifica una C.RR.
– Caracterización de CC.RR. de Castilla y León con indicadores conocidos y nuevas
propuestas de los mismos (benchmarking).
– Evaluación de los rendimientos de la EB mediante el estudio de las curvas globales H-Q,
P-Q y Rto-Q.
– Estudio de curvas de frecuencia de caudales.
– Elaboración y calibración de modelos hidráulicos de EB y red de riego en dos zonas piloto
para análisis de escenarios simulados con fines a valorar nuevas estrategias de gestión
que mejoren la eficiencia energética sin que se vea mermada la calidad del servicio
(presión y caudal en el hidrante), ni aumenten el coste energético anual.
– Pasarela de comunicación entre el programa de gestión de riegos Progar y Telegestar.Naranjo Hernández, D.; Colom Delgado, S.; Blanco Redondo, J.; González Muñoz, L.; Iglesias Gómez, S. (2015). RESULTADOS PRELIMINARES EN LOS ESTUDIOS DE EFICIENCIA ENERGÉTICA DENTRO DEL PROYECTO DE I+D+i OPTIREG: GESTIÓN EFICIENTE DE REGADÍOS. En XXXIII CONGRESO NACIONAL DE RIEGOS. Valencia 16-18 junio de 2015. Editorial Universitat Politècnica de València. https://doi.org/10.4995/CNRiegos.2015.1463OC
Biorefinery of biomass of agro-Industrial banana waste to obtain high-value biopolymers
On a worldwide scale, food demand is increasing as a consequence of global population growth. This makes companies push their food supply chains’ limits with a consequent increase in generation of large amounts of untreated waste that are considered of no value to them. Biorefinery technologies offer a suitable alternative for obtaining high-value products by using unconventional raw materials, such as agro-industrial waste. Currently, most biorefineries aim to take advantage of specific residues (by either chemical, biotechnological, or physical treatments) provided by agro-industry in order to develop high-value products for either in-house use or for sale purposes. This article reviews the currently explored possibilities to apply biorefinery-known processes to banana agro-industrial waste in order to generate high-value products out of this residual biomass source. Firstly, the Central and Latin American context regarding biomass and banana residues is presented, followed by advantages of using banana residues as raw materials for the production of distinct biofuels, nanocellulose fibers, different bioplastics, and other high-value products Lastly, additional uses of banana biomass residues are presented, including energy generation and water treatmen
Análisis de Invarianza y Diferencias de Medias Latentes Entre Adolescentes Americanos, Españoles y Chinos Usando la Escala de Ansiedad Social para Adolescentes (SAS-A)
Background: Social anxiety is one of the most prevalent disorders among adolescents (Stein et al., 2017). The main aim of this study was to analyze the equivalence of scores on the Social Anxiety Scale for Adolescents (SAS-A) using structural equation modeling and identify differences in latent means of social anxiety in China, Spain, and the USA. Method: Random sampling was used to recruit participants, which included 536 Chinese (46% girls), 1,178 Spanish (55.3% girls) and 866 North American (55.1% girls) adolescents. The participants’ ages ranged between 14 and 17 years old. Results: The SAS-A three-factor correlated model of social anxiety remained invariant between the Spanish and North American adolescents, but results could not be replicated in the Chinese adolescents [M2 = ΔS-Bχ2 (Δdf, p) = 4732.56 (36, < .01)]. Analyses of latent differences between Spain and the USA showed that Spanish adolescents had higher scores than North Americans for Fear of Negative Evaluation (TS = -9.630; d = .44) and for Social Avoidance and General Anxiety towards people (TS = -2.717; d = .12). Conclusions: The results are interpreted according to the cultural traits of individualism-collectivism and self-construal, and practical implications are discussed.Antecedentes: la ansiedad social es uno de los trastornos con mayor prevalencia en adolescentes (Stein et al., 2017). Así, el propósito principal de este estudio fue analizar la invarianza de la Escala de Ansiedad Social para Adolescentes (SAS-A) mediante un modelo de ecuaciones estructurales y examinar las diferencias de medias latentes en ansiedad social en adolescentes de China, España y EE.UU. Método: los participantes se seleccionaron a través de muestreo aleatorio: 534 chinos (46% chicas), 1.178 españoles (55,3% chicas) y 866 norteamericanos (55,1% chicas), con edades comprendidas entre los 14 y 17 años. Resultados: las puntuaciones del modelo de tres factores correlacionados de ansiedad social de la SAS-A resultaron invariantes entre adolescentes españoles y norteamericanos, pero estos resultados no fueron replicados en adolescentes chinos [M2 = ΔS-Bχ2 (Δdf, p) = 4732.56 (36, < .01)]. El análisis de medias latentes entre España y EE.UU. mostró que los adolescentes españoles manifestaban niveles más altos de Miedo ante las evaluaciones negativas (TS = -9.630; d = .44) y Evitación social y ansiedad general hacia las personas (TS = -2.717; d = .12). Conclusiones: estos hallazgos fueron interpretados atendiendo al de individualismo-colectivismo y las concepciones culturales de la propia persona, analizando sus implicaciones prácticas
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