Raman Spectroscopy and DFT calculations for the Electronic Structure Characterization of Conjugated Polymers

Flash presentationIn the last three decades, there has been a broad academic and industrial interest in conjugated polymers as semiconducting materials for organic electronics. Their applications in polymer light-emitting diodes (PLEDs), polymer solar cells (PSCs), and organic field-effect transistors (OFETs) offer opportunities for the resolution of energy issues as well as the development of display and information technologies1. Conjugated polymers provide several advantages including low cost, light weight, good flexibility, as well as solubility which make them readily processed and easily printed, removing the conventional photolithography for patterning2. A large library of polymer semiconductors have been synthesized and investigated with different building blocks, such as acenes or thiophene and derivatives, which have been employed to design new materials according to individual demands for specific applications. To design ideal conjugated polymers for specific applications, some general principles should be taken into account, including (i) side chains (ii) molecular weights, (iii) band gap and HOMO and LUMO energy levels, and (iv) suited morphology.3-6 The aim of this study is to elucidate the impact that substitution exerts on the molecular and electronic structure of π-conjugated polymers with outstanding performances in organic electronic devices. Different configurations of the π-conjugated backbones are analyzed: (i) donor-acceptor configuration, (ii) 1D lineal or 2D branched conjugated backbones, and (iii) encapsulated polymers (see Figure 1). Our combined vibrational spectroscopy and DFT study shows that small changes in the substitution pattern and in the molecular configuration have a strong impact on the electronic characteristics of these polymers. We hope this study can advance useful structure-property relationships of conjugated polymers and guide the design of new materials for organic electronic applications.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Analysis of the effect of mobile terminal speed on WLAN/3G vertical handovers

Proceedings of IEEE Global Telecommunications Conference, GLOBECOM '06, San Francisco, California, 27 november - 1 december, 2006.WLAN hot-spots are becoming widely spread. This, combined with the availability of new multi-mode terminals integrating heterogeneous technologies, opens new business opportunities for mobile operators. Scenarios in which 3G coverage is complemented by WLAN deployments are becoming available. Thus, true all-IP based networks are ready to offer a new variety of services across heterogeneous access. However, to achieve this, some aspects still need to be analyzed. In particular, the effect of the terminal speed on the detection and selection process of the preferred access network is not yet well understood. In fact, efficiency of vertical handovers depends on the appropriate configuration of mobile devices. In this paper we present a simulation study of handover performance between 3G and WLAN access networks showing the impact of mobile users’ speed. The mobile devices are based on the IEEE 802.21 cross layer architecture and use WLAN signal level thresholds as handover criteria. A novel algorithm to dynamically adjust terminals’ configuration is presented.Publicad

Practical Evaluation of a Network Mobility Solution

IFIP International Workshop on Networked Applications, Colmenarejo, Madrid/Spain, 6–8 July, 2005As the demand of ubiquitous Internet access and the current trend of all-IP communications keep growing, the necessity of a protocol that provides mobility management increases. The IETF has specified protocols to provide mobility support to individual nodes and networks. The Network Mobility (NEMO) Basic Support protocol is designed for providing mobility at IP level to complete networks, allowing a Mobile Network to change its point of attachment to the Internet, while maintaining ongoing sessions of the nodes of the network. All the mobility management is done by the mobile router whilst the nodes of the network are not even aware of the mobility. The main aim of this article is evaluating the performance of the NEMO Basic Support protocol by using our implementation. We also discuss the design of an implementation of the NEMO Basic Support protocol.Publicad

Una aproximación a las concepciones del infinito de estudiantes de grado once desde la teoría APOE

En esta experiencia de aula se reportan algunos resultados del trabajo realizado en el marco del curso de Didáctica de la Matemática de la Licenciatura en Matemáticas de la Universidad Pedagógica Nacional de Bogotá, Colombia, para estos efectos inicialmente se presentan algunos referentes teóricos propios de la teoría APOE que fueron utilizados para analizar los resultados obtenidos con la aplicación de la paradoja de las pelotas de tenis, la cual se desarrolló con la intención de hacer una aproximación a las concepciones que tienen los estudiantes de grado once del Colegio Integrado Eduardo Caballero Calderón sobre el concepto de infinito

Conjugated Polymers for Organic Electronics: Structural and Electronic Characteristics

The use of organic materials to design electronic devices has actually presented a broad interest for because they constitute an ecological and suitable resource for our current "electronic world". These materials provide several advantages (low cost, light weight, good flexibility and solubility to be easily printed) that cannot be afforded with silicium. They can also potentially interact with biological systems, something impossible with inorganic devices. Between these materials we can include small molecules, polymers, fullerenes, nanotubes, graphene, other carbon-based molecular structures and hybrid materials. Actually these materials are being used to build electronic structures into electronic devices, like organic light-emitting diodes (OLEDs), organic solar cells (OSCs), and organic field-effect transistors (OFETs), constituting and already commercial reality. Some of them are used on a widespread basis1, and are the focus of some recent researches in molecules2,3 and polymers4-6 suitable for these purposes. In this study we analyze the electronic and molecular characteristics of some different π-conjugated structures in order to evaluate their potential as semiconducting materials for organic electronics. For this purpose we focus on the study of conjugated polymers with different backbones configurations: (i) donor-acceptor configuration, (ii) 1D lineal or 2D branched conjugated backbones, and (iii) encapsulated polymers. To achieve this goal, we use a combined experimental and theoretical approach that includes electronic spectroscopies (i.e., absorption, emission and microsecond transient absorption), vibrational Raman spectroscopy and DFT calculations. These structural modifications are found to provoke a strong impact on the HOMO and LUMO levels and the molecular morphology, and, consequently, on their suitability as semiconductors in organic electronic applications.References 1. S. R. Forrest, M. E. Thompson. Chem. Rev., 2007, 107, 923 2. R. C. González-Cano, G. Saini, J. Jacob, J. T. López Navarrete, J. Casado and M. C. Ruiz Delgado. Chem. Eur. J. 2013, 19, 17165 3. J. L. Zafra, R. C. González-Cano, M. C. Ruiz Delgado, Z. Sun, Y. Li, J. T. López Navarrete, J. Wu and J. Casado. J. Chem. Phys. , 2014, 140, 054706 4. M. Goll, A. Ruff, E. Muks, F. Goerigk, B. Omiecienski, I. Ruff, R. C. González-Cano, J. T. López Navarrete, M. C. Ruiz Delgado, S. Ludwigs. Beilstein J. Org. Chem., 2015, 11, 335. 5. D. Herrero-Carvajal, A. de la Peña, R. C. González-Cano, C. Seoane, J. T. López Navarrete, J. L. Segura, J. Casado, M. C. Ruiz Delgado, J. Phys. Chem. C, 2014, 118, 9899. 6. M. Scheuble, Y. M. Gross, D. Trefz, M. Brinkmann, J. T. López Navarrete, M. C. Ruiz Delgado, and S. Ludwigs, Macromolecules, 2015, 48, 7049.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Fluage de monocristaux de NiO

NiO single crystals have been subjected to constant-load compressive creep along (100). Stresses between 50 MPa and 120 MPa and temperatures between 950 °C and 1 200 °C were studied. The activation energy observed suggests that oxygen diffusion is the rate-controlling process.Des expériences de compression à charge constante, selon , ont été réalisées sur des monocristaux de NiO. Les contraintes utilisées vont de 50 MPa à 120 MPa et les températures de 950 °C à 1200 °C. L'énergie d'activation du fluage suggère que la diffusion de l'oxygène joue un rôle prédominant sur la cinétique de déformation plastique

The Nature of the Gould Belt from a Fractal Analysis of its Stellar Population

The Gould Belt (GB) is a system of gas and young, bright stars distributed along a plane that is inclined with respect to the main plane of the Milky Way. Observational evidence suggests that the GB is our closest star formation complex, but its true nature and origin remain rather controversial. In this work we analyze the fractal structure of the stellar component of the GB. In order to do this, we tailor and apply an algorithm that estimates the fractal dimension in a precise and accurate way, avoiding both boundary and small data set problems. We find that early OB stars (of spectral types earlier than B4) in the GB have a fractal dimension very similar to that of the gas clouds in our Galaxy. On the contrary, stars in the GB of later spectral types show a larger fractal dimension, similar to that found for OB stars of both age groups in the local Galactic disk (LGD). This result seems to indicate that while the younger OB stars in the GB preserve the memory of the spatial structure of the cloud where they were born, older stars are distributed following a similar morphology as that found for the LGD stars. The possible causes for these differences are discussed.Comment: 20 pages including 7 figures and 1 table. ApJ (in press

Caracterización Electrónica y Molecular de Materiales Orgánicos Conjugados: Estudio Experimental y Teórico

Actualmente, existe una alternativa ecológica plausible al uso de silicio en materiales para dispositivos electrónicos: los materiales orgánicos policonjugados. Éstos presentan una serie de ventajas frente a los materiales inorgánicos: bajo coste de producción, ligereza, flexibilidad, disponibilidad para ser impresos y posibilidad de interaccionar con material biológico. Dichos materiales pueden ser desde moléculas discretas a polímeros, pasando por estructuras más complejas (fullereno, nanotubos, grafeno…). Se utilizan en dispositivos electrónicos como diodos emisores de luz orgánicos (OLEDs), células solares orgánicas (OSCs) y transistores orgánicos de efecto campo (OFETs), formando parte de la actualidad tecnológica comercial. Se presentan en diferentes soportes [1], y han sido objeto de estudio distintas estructuras moleculares [2,3] y poliméricas [4-6]. En el presente trabajo se analizan las estructuras electrónicas y moleculares de diferentes materiales π-conjugados y las modificaciones que en éstos se pueden ejercer, pudiendo así estudiar su capacidad como potencial material semiconductor en este tipo de aplicaciones. Para ello, se han llevado a cabo de forma paralela una serie de experimentos, incluyendo la espectroscopía Raman, en comparación con cálculos químico-cuánticos en DFT, obteniendo de este modo una visión completa del comportamiento electrónico observado en diferentes modelos moleculares y poliméricos. Referencias [1] S. R. Forrest, M. E. Thompson. Chem Rev. 2007, 107, 923. [2] R. C. González-Cano, G. Saini, J. Jacob, J. T. López Navarrete, J. Casado and M. C. Ruiz Delgado. Chem. Eur. J. 2013, 19, 17165. [3] J. L. Zafra, R. C. González-Cano, M. C. Ruiz Delgado, Z. Sun, Y. Li, J. T. López Navarrete, J. Wu and J. Casado, J. Chem. Phys., 2014, 140, 054706. [4] M. Goll, A. Ruff, E. Muks, F. Goerigk, B. Omiecienski, I. Ruff, R. C. González-Cano, J. T. López Navarrete, M. C. Ruiz Delgado, S. Ludwigs, Beilstein J. Org. Chem. 2015, 11, 335. [5] D. Herrero-Carvajal, A. de la Peña, R. C. González-Cano, C. Seoane, J. T. López Navarrete, J. L. Segura, J. Casado, M. C. Ruiz Delgado, J. Phys. Chem. C, 2014, 118, 9899. [6] M. Scheuble, Y. M. Gross, D. Trefz, M. Brinkmann, J. T. López Navarrete, M. C. Ruiz Delgado, and S. Ludwigs, Macromolecules, 2015, 48, 7049.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Análisis del uso de la fiducia mercantil de administración y fuente de pago como herramienta de financiación para pymes en Colombia

El presente trabajo analiza el uso que se ha dado en Colombia a la Fiducia de administración y fuente de pago, especialmente por parte de las Pymes, parte de una descripción del tipo de fiducia y de las Pymes en sí y explora los principales aspectos que rodean este tipo de negocio fiduciario. Se enfoca en los aspectos operativos, contables, tributarios y legales del negocio y muestra las posibles ventajas que puede la Pyme obtener de él. El trabajo pretende ampliar el conocimiento sobre la Fiducia de administración y pagos, busca fortalecer nuestras competencias laborales y llamar la atención, a través de la academia, de los pequeños y medianos empresarios, así como de emprendedores, de las posibilidades que ofrecen este tipo de esquemas fiduciarios. La investigación es de carácter cuantitativo y se apoya en fuentes secundarias de información como fuentes bibliográficas y trabajos de investigación anteriores. El trabajo muestra las ventajas principales que este tipo de negocio tiene para las entidades de crédito y para las Pymes como acreedores de los anteriores y concluye la forma en que este tipo de negocio se está usando actualmente en el país y las posibilidades que ofrece a los Fideicomitentes, en este caso las Pymes, al momento de necesitar este tipo de negocios.This work analyzes how Merchant Administrative Trust has been used as a source of payment especially for Small Business, beginning with a description of this type of trust and the environment of Small Businesses. It focuses in operative aspects, as well as in accounting, tax and legal issues of the Merchant Administrative Trust business and shows the possible advantages Small Business could obtain from it. This work aims to extend the knowledge of the Merchant Administrative Trust business seeks to strengthen job skills and call our attention, through academia, for small and medium entrepreneurs, about the potential of such schemes trust. This research investigation is made in a quantitative way and it gets support from secondary sources of information such as bibliographic and other works of investigation. This work shows the principal advantages that Merchant Administrative Trust business can offer as credit entities and for Small Businesses as creditors. It also concludes how this type of business is being carried out and the possibilities it brings to Small Businesses