Effect of graphene substrate on the SERS Spectra of Aromatic bifunctional molecules on metal nanoparticles

The design of molecular sensors plays a very important role within nanotechnology and especially in the development of different devices for biomedical applications. Biosensors can be classified according to various criteria such as the type of interaction established between the recognition element and the analyte or the type of signal detection from the analyte (transduction). When Raman spectroscopy is used as an optical transduction technique the variations in the Raman signal due to the physical or chemical interaction between the analyte and the recognition element has to be detected. Therefore any significant improvement in the amplification of the optical sensor signal represents a breakthrough in the design of molecular sensors. In this sense, Surface-Enhanced Raman Spectroscopy (SERS) involves an enormous enhancement of the Raman signal from a molecule in the vicinity of a metal surface. The main objective of this work is to evaluate the effect of a monolayer of graphene oxide (GO) on the distribution of metal nanoparticles (NPs) and on the global SERS enhancement of paminothiophenol (pATP) and 4-mercaptobenzoic acid (4MBA) adsorbed on this substrate. These aromatic bifunctional molecules are able to interact to metal NPs and also they offer the possibility to link with biomolecules. Additionally by decorating Au or Ag NPs on graphene sheets, a coupled EM effect caused by the aggregation of the NPs and strong electronic interactions between Au or Ag NPs and the graphene sheets are considered to be responsible for the significantly enhanced Raman signal of the analytes [1-2]. Since there are increasing needs for methods to conduct reproducible and sensitive Raman measurements, Grapheneenhanced Raman Scattering (GERS) is emerging as an important method [3].Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Degradación fotocatalítica de la fluoresceína

El color ha tenido un gran significado en las diversas sociedades humanas desde que el hombre comenzó a teñir sus ropas y otros objetos; este fenómeno es el resultado de una compleja serie de respuestas fisiológicas a las radiaciones de longitud de onda situadas en el intervalo 400-750nm, cuando estas inciden en la retina del ojo [8]. En la naturaleza se pueden distinguir gran diversidad de colores, entre ellos los del colibrí o las plumas del pavo real, los cuales se originan por la difracción de la luz en ellos, gracias a la estructura única de las plumas, pero la mayor parte de los colores que se ven en la naturaleza se deben a la absorción de ciertas longitudes de onda de luz visible por los compuestos orgánicos, tales como los colorantes los cuales son sustancias coloreadas que se utilizan para dar color a un objeto determinado o a una tela. [8] El vertido incontrolado de residuos industriales y municipales a ríos y lagos, está causando serios problemas a los recursos hídricos de muchas regiones [15]. La composición de las aguas residuales causa graves impactos cuando se enfrenta a las áreas naturales; un alto contenido de materia orgánica origina el agotamiento del oxígeno disuelto, que tiene un efecto inverso sobre el sistema ecológico. El nitrógeno y el fósforo también conducen a un agotamiento del oxígeno disuelto (es decir, eutrofización) [10], por esto la contaminación del agua reviste gran importancia ya que los contaminantes pueden afectar el equilibrio silvestre y por ende la salud humana.[11] La problemática ambiental planteada a escala mundial por la presencia de altas concentraciones de contaminantes de todo tipo en aguas, [15] ha llevado a que el desarrollo industrial de los países requieran de una constante investigación dirigida hacia la implementación de una tecnología actualizada y adecuada a las 8 necesidades que se plantean en cada momento, tanto de carácter económico, como social y ambiental

Aproximación del arte de acción a la Educación Infantil. Otras formas de interrelación en el contexto educativo

This Artistic research project was created in order to test how to put into practice approaches between Contemporary Art and University daily life. In this particular case, between Action Art and the students at the Early Childhood Education University in Alicante. The generalized lack of awareness about changes which took place in Art in the XX century, demonstrates the lack of interest on the part of students about Contemporary Art, and therefore, it is still remarkable, the distance between Art and life. Thus, as artists and teachers, the chance to carry out specific experiments is open within everyday educational life. Therefore, through Action Art a communicative interaction is possible to be achieved as an active learning process and, in such way, change the usual existing relationships in a predetermine context, creating this way, future Contemporary Art consumers and transmitters.Este trabajo de investigación artística, se crea con el propósito de experimentar sobre cómo llevar a la práctica aproximaciones entre el arte contemporáneo y la vida cotidiana universitaria. En este caso, más concretamente, entre el arte de acción y el alumnado de Educación Infantil de la Facultad de Educación de Alicante. El desconocimiento generalizado sobre los cambios acontecidos en el arte durante el siglo XX, evidencia la falta de interés del alumnado sobre el arte contemporáneo, y por consiguiente, sigue estando vigente, la separación entre arte y vida. Por ello, como artistas y docentes, abrimos la posibilidad de realizar experimentos concretos dentro de la vida cotidiana educativa, para que a través del arte de acción, se llegue a una interacción comunicativa como proceso activo de aprendizaje, y así, cambiar las relaciones habituales que se tienen en un contexto determinado, con el otro y consigo mismo, generando futuros consumidores y transmisores de arte contemporáneo

Fundamentals and Applications of Surface-Enhanced Raman Spectroscopy (SERS)

When a molecule is adsorbed on some metallic nanostructured surfaces such as silver, copper or gold, it can undergo an enormous enhancement of the Raman signal giving rise to the so called Surface-Enhanced Raman Scattering (SERS). The high sensitivity of this effect allows an accurate structural study of adsorbates at very low concentrations. The SERS effect has historically been associated with the substrate roughness on two characteristic length scales. Surface roughness on the 10 to 100 nm length scale supports localized plasmon resonances which are considered as the dominant enhancement mechanism of SERS (Electromagnetic Enhancement Mechanism: SERS-EM). It is usually accepted that these electromagnetic resonances can increase the scattered intensity by an average factor of ca. 104 to 107. A secondary mechanism often thought to require atomic scale roughness is referred to as Charge Transfer (CT) Enhancement Mechanism (SERS-CT). This mechanism involves the photoinduced transfer of an electron from the metal to the adsorbate or vice versa and involves new electronic excited CT states which result from adsorbate–substrate chemical interactions. It is also estimated that such SERS-CT mechanism can enhance the scattering cross-section by a factor of ca. 10 to 102. These two mechanisms can operate simultaneously, depending on the particular systems and experimental conditions, making difficult to recognize each one and to estimate their relative magnitude in a particular spectrum.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

An MS-CASPT2 Study of the Photodecomposition of 4- Methoxyphenyl Azide. Role of Internal Conversion and Intersystem Crossing

Aryl azides photochemistry is strongly dependent on the substituent relative position, as has been studied by time resolved resonant Raman (TR3) spectroscopy for 4-methoxyphenyl azide and its isomer 3-methoxyphenyl azide. When irradiated at 266 nm, the former results in 4,4’-dimethoxyazobenzene whereas the latter forms 1,2-didehydroazepine. It is proposed that the key step of the reactions is the formation of a nitrene derivative. Recently, it has been proposed by us that nitrenes might have a relevant role in the Surface-Enhanced Raman Scattering (SERS) of p-aminothiophenol, however, the molecular mechanism is not well known in neither of these cases. Therefore, we studied the photodecomposition of 4-methoxyphenyl azide using multiconfigurational self-consistent field methods (MC-SCF) with the CAS-SCF and MS-CASPT2 approximations and calculated the resonant Raman spectra of the relevant species using a multi-state version of Albrecht’s vibronic theory. The results propose that the reaction follows a two steps sequence after irradiation at 266 nm: an intersystem crossing 21A’/23A’’ which decays through a 21A’/21A’’ conical intersection producing molecular nitrogen and triplet 4-methoxyphenyl nitrene in its ground state.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Children´s Participation: The Key to Creative Environments at School

Las investigaciones sobre la construcción de los ambientes creativos en la escuela destacan dos elementos imperativos: la libertad de creación y la expresión de los niños. La presente investigación profundiza los significados de esas categorías en cada campo del conocimiento, con la finalidad de llegar a entendimientos que permitan mejorar las prácticas educativas. A partir del método de la investigación-acción, se diseñó e instrumentó la intervención docente que promovió ambientes participativos y con ello, develar su relación en la generación de acciones creativas por la infancia, lo anterior, evidenció la complementariedad entre ambos ambientes. Cuando se abrieron los espacios de libertad para construir soluciones para mejorar la escuela, los niños generaron acciones que incidieron de forma positiva. Estas acciones fueron avaladas por sus compañeros, profesores y familiares como creativas. Ante ello, Los niños recibieron reconocimiento reciproco por sus contribuciones, en consecuencia, realizaron acciones, por su propia iniciativa, fuera del entorno educativo, por lo que los espacios para la creación aumentaronResearch about the construction of creative environments at school emphasizes two imperatives: the freedom of creation and the children´s expression. The current research deepened the meanings of the categories in each field of knowledge, in order to reach understandings that allow improving educational practices. Based on the action-research method, teaching intervention was designed and implemented that promoted participative environments and with it, unveil their relationship in the generation of creative actions by childhood, the above, evidence the complementarity between both environments. When spaces of freedom were opened to build solutions to improve the school, children generated actions that had a positive impact. These actions were endorsed by their peers, teachers and relatives as creative. Faced with this, the children received reciprocal recognition for their contributions, consequently they carried out actions, on their own initiative, outside of the educational environment, so that spaces for creation increase

Datación magnetostratigráfica de la molasa Surpirenaica (Fm Uncastillo, Oligoceno-Mioceno)

The Uncastillo Fm crops out along the southern boundary of the External Sierras, which represents the southernmost limit of the Pyrenean Range. Three tectosedimentary units related to tectonic pulses have been previously differentiated in this formation. The sedimentary evolution of the Uncastillo Fm is mainly related to the tightening of the WNW-ESE Santo Domingo anticline in the External Sierras during Chattian-Aquitanian times and records the younger tectonic movement of the south Pyrenean sole thrust. The Uncastillo Fm represents the change to overall southwardflowing alluvial and fluvial systems from overall west-northwest-flowing fluvial systems (Campodarbe Fm). Recent magnetostratigraphic results from the underlying Campodarbe Fm shift to younger ages (from chron 10r to 7r) the top of the Campodarbe Fm in the proximal area of the fluvial system (Luesia fan). In order to check that reassignment and refine the age of the Uncastillo Fm, a new magnetostratigraphic study has been conducted in laterally equivalent deposits that represent middle-distal areas located to the east of the Luesia fan. These deposits consist of mudstones with interbedded sandstones. These finer grain size sediments allow for a magnetostratigraphic sampling in the Fuencalderas section of ~1300 m, which complete the chronostratigraphic frame of the last tectonic pulses of the Pyrenean Range.Trabajo financiado por los proyectos SEROS (CGL 2014-55900-PL), DR3AM (CGL2015- CGL2014-55118) y Grupos Geotransfer y Análisis de Cuencas de la Universidad de Zaragoza. Es una contribución del Institut de Recerca Geomodels y del Grup de Geodinàmica i Anàlisi de Conques (2014SGR467).Peer Reviewe

Modeling the effect of the electrode potential in SERS by electronic structure calculations.

Surface Enhanced Raman Spectroscopy (SERS), due to the ability of greatly intensify the weak Raman signal of molecules adsorbed to metal surfaces, has proven to be a very useful tool to investigate changes in the electronic structure of metal-molecule surface complex. A deep knowledge of the electronic structure of these metal-molecule hybrid systems is key in electrochemistry, catalysis, plasmonics, molecular electronics, and in the development of selective and ultra-sensitive analytical sensors. The origin of this huge enhancement in SERS is due to two contributions: the electromagnetic (EM), related to surface plasmons, and the chemical mechanism, due to resonant charge transfer (CT) process between the adsorbate and the metal (CTSERS). Unfortunately, the SERS implies very complex phenomena where the molecule and the metal nanoparticle are involved. This fact makes challenging to build realistic theoretical models that take into account both the metal and the molecule at quantum level. We propose a methodology, based on DFT and ab initio electronic calculations, to simulate the effect of the electrode potential on the absorption, on the charge transfer states energies, and on the electronic excitations in metal-molecule hybrid systems from a microscopic point of view. This methodology consists on the prediction of Raman intensities from ab initio calculations of the geometries or the energy gradients at the excited states Franck-Condon point, bringing the possibility to predict the intensities in CTSERS as well as in resonance Raman without the need to know the excited state geometries, not always feasible to compute. The microscopic model adopted to mimic the effect of the interphase electric potential consist in a molecule adsorbed to a linear silver cluster [Agn-Adsorbate]q, were n is the number of silver atoms, and the total charge of the system (q) is zero for n=2 and q=±1 for n=1, 3 and 7.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

La caída del imperio automotriz estadounidense

El propósito del ensayo es conocer cómo la crisis económica actual afecta la otrora poderosa industria automotriz norteamericana, para lo cual analizamos las raíces de la crisis automotriz estadounidense. También delineamos las acciones emprendidas por las tres principales empresas automotrices: General Motors, Chrysler y Ford. Finalmente, ofrecemos las conclusiones que la investigación vertió.El propósito del ensayo es conocer cómo la crisis económica actual afecta la otrora poderosa industria automotriz norteamericana, para lo cual analizamos las raíces de la crisis automotriz estadounidense. También delineamos las acciones emprendidas por las tres principales empresas automotrices: General Motors, Chrysler y Ford. Finalmente, ofrecemos las conclusiones que la investigación vertió

Multiconfigurational second-order perturbation study of the decomposition of the radical anion of nitromethane

The doublet potential energy surfaces involved in the decomposition of the nitromethane radical anion (CH3NO2−) have been studied by using the multistate extension of the multiconfigurational second-order perturbation method (MS-CASPT2) in conjunction with large atomic natural orbital-type basis sets. A very low energy barrier is found for the decomposition reaction: CH3NO2−→[CH3NO2]−→CH3+NO2−. No evidence has been obtained on the existence of an isomerization channel leading to the initial formation of the methylnitrite anion (CH3ONO−) which, in a subsequent reaction, would yield nitric oxide (NO). In contrast, it is suggested that NO is formed through the bimolecular reaction: CH3+NO2−→[CH3O-N-O]−→CH3O−+NO. In particular, the CASSCF/MS-CASPT2 results indicate that the methylnitrite radical anion CH3ONO− does not represent a minimum energy structure, as concluded by using density functional theory (DFT) methodologies. The inverse symmetry breaking effect present in DFT is demonstrated to be responsible for such erroneous [email protected]