Modelización Ab-Initio de nanosistemas basados en grafeno y heteroestructuras espintrónicas

El grafeno es un alótropo bidimensional del carbono, con propiedades fı́sicas y quı́micas excepcionales, es un material flexible, liviano, transparente, con alta movilidad de carga y gran área superficial, entre otras. Desde su obtención experimental en el 2004 por Andre Geim y Konstantin Novoselov, hasta la fecha,ha sido un material prometedor con múltiples aplicaciones en campos como la electrónica, bioingenierı́a, biomedicina y nanotecnologı́a.Particularmente, en la construcción de biosensores, el grafeno es un material que ofrece muchas ventajas, ya que, es sensible, selectivo, de bajo ruido electrónico intrı́nseco y además, biocompatible. Trabajos experimentales y teóricos dancuenta de la facilidad del grafeno para adsorber bacterias, células e incluso moléculas, hecho que permite estudiar qué propiedades especı́ficas modifica el material luego de la adsorción, información útil para la eventual funcionalización y caracterización de un biosensor basado en grafeno. Trabajos en esta dirección, con nucleobases de ADN han sido explorados por diversos investigadores.Dependiendo del tipo de interacción generada entre el grafeno y las moléculas de interés biológico, los mecanismos o modos de sensado pueden ser: ópticos, magnéticos, mecánicos y electrónicos. De acuerdo a la literatura, en los últimosaños ha ganado gran interés el desarrollo de transistores de efecto de campo basados en grafeno (GFETs), que son dispositivos electrónicos con tres contactos metálicos (fuente ?source?, drenaje ?drain d? y compuerta ?gate?) y un canal degrafeno. Al aplicar voltajes de polarización tanto en el drenaje como en la compuerta, es posible medir la respuesta del dispositivo, obteniendo la conductancia y las curvas de corriente caracterı́sticas, antes y después de la interacción entrela superficie de grafeno con biomoléculas.Fil: Rodríguez Sotelo, Sindy Julieth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; Argentin

Theoretical study of the adsorption of histidine amino acid on graphene

Previous studies have demonstrated how the interactions between biomolecules and graphene play a crucial role in the characterization and functionalization of biosensors. In this paper we present a theoretical study of the adsorption of histidine on graphene using density functional theory (DFT). In order to evaluate the relevance of including the carboxyl (-COOH) and amino (-NH2) groups in the calculations, we considered i) the histidine complete (i.e., with its carboxyl and its amino groups included), and ii) the histidine's imidazole ring alone. We calculated the density of states for the two systems before and after adsorption. Furthermore, we compared the results of three approximations of the exchange and correlation interactions: local density (LDA), the generalized gradients by Perdew, Burke and Ernzerhof (GGA-PBE), and one including van der Waals forces (DFT-D2). We found that the adsorption energy calculated by DFT-D2 is higher than the other two: Eads-DFT-D2 >E ads-LDA >E ads-GGA . We report the existence of charge transfer from graphene to the molecule when the adsorption occurs; this charge transfer turns up to be greater for the complete histidine than for the imidazole ring alone. Our results revealed that including the carboxyl and amino groups generates a shift in the states of imidazole ring towards EF .Fil: Rodríguez Sotelo, Sindy Julieth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Makinistian, Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Albanesi, Eduardo Aldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; Argentin

Propuesta para el aprendizaje de la primera ley de newton con estudiantes de grado décimo de la Escuela Tecnológica Instituto Técnico Central

En éste documento se expone una experiencia de aula implementada en el primer semestre del año 2008 por estudiantes de licenciatura en Física de noveno semestre de la Universidad Distrital. Se presenta una propuesta para el aprendizaje de la Primera ley de Newton (ley de Inercia), por medio de una secuencia de actividades de corte interaccionista y en contraposición al modelo conductista se pretende iniciar en la conceptualización de la Dinámica. Cabe señalar que además, se intentan desarrollar algunas competencias comunicativas, pues el diseño posibilita que se active el pensamiento físico, en tanto promueve el comportamiento social y busca ciertos niveles de equidad en el aula de clases.Fil: Ortiz Sánchez, Domingo. Universidad Pedagógica Nacional; ColombiaFil: Méndez, Rudy. Universidad Distrital Francisco José de Caldas; ColombiaFil: Rodríguez Sotelo, Sindy Julieth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; Argentina. Universidad Nacional del Litoral; ArgentinaFil: Santiesteban, Sandra Nathaly. Universidad Distrital Francisco José de Caldas; Colombi

First principles calculations and experimental study of the optical properties of Ni-doped ZnS

Zinc sulphide doped with nickel (Ni:ZnS) has many applications in different fields like materials science, electronics, optics, and other industrial applications. Experimentally, a large variety of methods have been developed for Ni:ZnS synthesizing, where the chemical synthesis with capping agent is most successful, but has disadvantages like purity and the low performance. In addition, since there is not also much theoretical information about its features, the electronic and optical response of Ni:ZnS were studied, both experimentally by x-ray diffractometry (XRD), transmission electron microscopy (HR-TEM), and x-ray photoelectron spectroscopy (XPS) and theoretically by means of the density functional theory (DFT) calculations, giving an unified understanding of the electrooptical performance of this compound. In the same way, the importance of the inclusion of Ni impurities in the structure was studied and analyzed by the inclusion of a Hubbard potential in the calculations.We found that the optimalUvalue for Ni atoms is 4 eVin agreement with experimental results obtained by XPS. The dielectric function (ε2) for pure and doped systems showed that the influence of the Ni atom is mainly given in the range of low energy regions (E<6 eV), where the new peaks are associated to transitions that include the impurity band states.Fil: Rodríguez Sotelo, Sindy Julieth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Zandalazini, Carlos Ivan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Navarro, J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Vadiraj, K T. Department Of Studies In Environmental Science,;Fil: Albanesi, Eduardo Aldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; Argentin

Electronic transport in a graphene single layer: Application in amino acid sensing

We modeled a type of field-effect transistor device based on graphene for the recognition of amino acids with a potential application in the building of a protein sequencer. The theoretical model used was a combination of density functional theory (DFT) with the non-equilibrium Green's function (NEGF) in order to describe the coherent transport in molecular devices. First, we studied the physisorption of each amino acid on a graphene sheet and we reported the adsorption energy, the adsorption distances, the equilibrium configuration and the charge transfer of ten amino acids that can be considered as representative of all of the amino acids: histidine (His), alanine (Ala), aspartic acid (Asp), tyrosine (Tyr), arginine (Arg), glutamic acid (Glu), glycine (Gly), phenylalanine (Phe), proline (Pro) and lysine (Lys). As a result, significant differences were found in the density of states (DOS) after adsorption and there was a change in the semi-metallic character of the graphene due to the lysine and arginine interactions. Furthermore, we noticed changes in the electrical characteristics of the devices, as the amino acids adsorbed onto the surface of the graphene. The curves of current vs. bias voltage (I-Vb) display a distinct response for each amino acid, i.e. the I-Vb curves produce a characteristic footprint for each amino acid. We identified a possible rectification mechanism related to the voltage profile asymmetry, where the amino acids can control the transport characteristics in the device, i.e. Lys and Phe amino acids physisorbed on graphene act as a molecular diode, where electrons can easily flow in one direction and decrease in the other. This may be promising for the prospect of biosensors: graphene could be used as an amino acid detector.Fil: Rodríguez Sotelo, Sindy Julieth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Albanesi, Eduardo Aldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; Argentin

Computational study of transport properties of graphene upon adsorption of an amino acid: importance of including -NH2 and -COOH groups

The effects of histidine and its imidazole ring adsorption on the electronic transport properties of graphene were investigated by first-principles calculations within a combination of density functional theory and non-equilibrium Greens functions. Firstly, we report adsorption energies, adsorption distances, and equilibrium geometrical configurations with no bias voltage applied. Secondly, we model a device for the transport properties study: a central scattering region consisting of a finite graphene sheet with the adsorbed molecule sandwiched between semi-infinite source (left) and drain (right) graphene electrode regions. The electronic density, electrical current, and electronic transmission were calculated as a function of an applied bias voltage. Studying the adsorption of the two systems, i.e., the histidine and its imidazole ring, allowed us to evaluate the importance of including the carboxyl (-COOH) and amine (-NH2 ) groups. We found that the histidine and the imidazole ring affects differently the electronic transport through the graphene sheet, posing the possibility of graphene-based sensors with an interesting sensibility and specificity.Fil: Rodríguez Sotelo, Sindy Julieth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; Argentina. Universidad Nacional de Entre Ríos; ArgentinaFil: Makinistian, Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Eduardo Albanesi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; Argentina. Universidad Nacional de Entre Ríos; Argentin

Electronic transport upon adsorption of biomolecules on graphene

Currently, the construction of sensors plays an important role in electronics and bioelectronics, due to the wide range of novel applications for biomedical research, food quality control and environmental monitoring. The sensors for biological application demand materials with special properties, such as: sensitivity, selectivity, biocompatibility, high electronic mobility, low electronic noise and chemical functionality. Due to its unique physical and chemical properties, the graphene has emerged as a suitable candidate for making sensors, since it largest known surface-to-volume ratio; highcharge carrier mobility of up to 200.000 cm2 V−1 s−1 at electron densities of ≈ 2 ×1011 cm−2 , which is significantly higher than that of silicon <1,400 cm2 V−1 s−1 ; mechanical stability and high compatibility with flexible technologies, among others. The electronic properties of graphene are extremely sensitive to the environmental perturbations such as electronic doping and molecular adsorption. Several biomolecules interact with graphene through noncovalent bonds, which typically include the π-π stacking. These interactions can modify the electron density and conductivity in the graphene allowing the detection of the molecules. Theoretical and experimental workspropose nanoelectronic biosensors based on graphene for detecting various biomolecules including DNA, glucose, neurotransmitters, amino acids, proteins and bacteria. In the fabrication of electronic omponents like field-effect transistors (FETs) with the adoption of thin layers of graphene, which consist of two terminals, the source and drain, and a gate that controls the resistance of the device, the highly mobile electrons at or near its surface are extremely sensitive to local charge changes. As a result, the molecules acquire charge when adsorbed, and their binding to a graphene-based gate will disrupt the flow of the electrons. Studying and quantifying the electronic effects due to interaction between substrates and adsorbates can provide tools for the construction of nano graphene-based sensing devices. But,what are the phenomena that underlie the charge transfer between graphene and biomolecules? The different effects generated in the adsorption process of biomolecules and the modification and response of the electrical properties of the graphene, are presented in this review. The chapter was developed in four sections: i) introduction, where the generalities and basic notions of the electronic properties for graphene are presented, together with a brief fundamental of electronic transport based on non-equilibrium Green s functions, and the experimental approaches to current-voltage curves in FET devices; ii) computational modeling of adsorption and devices; iii) experimental realization of devices and; iv) conclusions and final remarks.Fil: Rodríguez Sotelo, Sindy Julieth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Makinistian, Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Grupo Vinculado Bionanotecnología y Sistemas Complejos | Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Grupo Vinculado Bionanotecnología y Sistemas Complejos. - Universidad Tecnológica Nacional. Facultad Regional San Rafael. Grupo Vinculado Bionanotecnología y Sistemas Complejos; ArgentinaFil: Albanesi, Eduardo Aldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; Argentin

Ideas previas, un constructo indispensable en el diseño de situaciones de aula: un ejemplo en ciencias

Actualmente se da una creciente importancia a los conocimientos previos de los estudiantes cuando se proponen estrategias de enseñanza que se interesan por el aprendizaje, Carracosa, Pérez y Valdés (2006) señalan que diversas investigaciones han mostrado que las preconcepciones de los educandos conllevan a errores conceptuales en ciencias. Por ello, este trabajo se propone analizar las ideas previas en estudiantes de grado décimo del Colegio Federico García Larca IED (Bogotá, Colombia) en torno a los sistemas no inerciales y las seudo fuerzas

A theoretical study on the intercalation and diffusion of AlF3in graphite: Its application in rechargeable batteries

Using first-principles calculations based on density functional theory (DFT), we study the aluminum fluoride (AlF3) intercalation in graphite as a new possibility to use this molecule in rechargeable batteries, and understand its role when used as a component of the solvent. We discuss the most stable configuration of the AlF3 molecule in graphite for stage-2 and stage-1 and the diffusion study of the molecule, the migration pathways and the energy barriers. Our results show an average voltage of 3.18 V for stage-2 and 3.44 V for stage-1, which is excellent for anion intercalated batteries. Furthermore, low diffusion energy barriers of the AlF3 intercalant molecules were found (the lowest diffusion energy barrier was 0.17 eV with a diffusion constant in the order of 10-5 cm2 s-1), which could lead to fast (dis)charging of a battery based on AlF3. The present study provides important information to understand the intercalation mechanism of AlF3 graphite layer electrodes, thus encouraging more experimental studies of this system.Fil: Rodríguez Sotelo, Sindy Julieth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Candia, Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Passeggi, Mario Cesar Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Albanesi, Eduardo Aldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Ruano Sandoval, Gustavo Daniel. Comisión Nacional de Energí­a Atómica. Gerencia del Area Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Balseiro). División Colisiones Atómicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentin

Effective masses of the tin sulfide influenced by intrinsic defects: A theoretical prediction

We performed a theoretical study within the Density Functional Perturbation Theory framework to analyze the influence of intrinsic defects in the effective mass of the charge carriers of tin sulfide. We modeled the orthorhombic phase Aem2(39) space-group symmetry and evaluated defects such as residual stress and 1.6%,3.1%, and 4.7% tin vacancy concentration. Our results show that the effective masses exhibit remarkable anisotropy for both holes and electrons; they are larger parallel to the longest axis of the unit cell; besides, the effective masses of the holes present a slight increase when the concentration defect is higher. These results demonstrate that the vacancy defect modifies the effective masses and allow us to infer that large values of effective mass contribute to low mobility between parallel planes with Van der Waals forces. Consequently, it would be reasonable to propose this material like a prominent rectifier diode.Fil: Buitrago Toro, Paula Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Zandalazini, Carlos Ivan. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Rodríguez Sotelo, Sindy Julieth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Navarro Sánchez, Jorge Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Albanesi, Eduardo Aldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; Argentin