Stacking and Registry Effects in Layered Materials: The Case of Hexagonal Boron Nitride

The interlayer sliding energy landscape of hexagonal boron nitride (h-BN) is investigated via a van der Waals corrected density functional theory approach. It is found that the main role of the van der Waals forces is to "anchor" the layers at a fixed distance, whereas the electrostatic forces dictate the optimal stacking mode and the interlayer sliding energy. A nearly free-sliding path is identified, along which bandgap modulations of ~0.6 eV are obtained. We propose a simple geometrical model that quantifies the registry matching between the layers and captures the essence of the corrugated h-BN interlayer energy landscape. The simplicity of this phenomenological model opens the way to the modeling of complex layered structures, such as carbon and boron nitride nanotubes.Comment: 4 Pages, 3 Figure

Mechanism of Near-Field Raman Enhancement in One-Dimensional Systems

We develop a theory of near-field Raman enhancement in one-dimensional systems, and report supporting experimental results for carbon nanotubes. The enhancement is established by a laser-irradiated nanoplasmonic structure acting as an optical antenna. The near-field Raman intensity is inversely proportional to the 10th power of the separation between the enhancing structure and the one-dimensional system. Experimental data obtained from single-wall carbon nanotubes indicate that the Raman enhancement process is not significantly influenced by the specific phonon eigenvector, and is mainly defined by the properties of the nanoplasmonic structure

INTIMatic, una obra de net art

INTIMatic es una obra de net art que consiste en un conjunto de aplicaciones para dispositivos móviles, teléfonos celulares y tablets y para computadoras personales y una página web en donde se propone al interactuador sacarse fotos que serán procesadas para tapar su cara con una banda de píxels, generando automáticamente una situación de preservar la intimidad, basado en la obra "Intimidad Romero".Facultad de Arte

Covalently Functionalized Nanotubes as Nanometer-Sized Probes in Chemistry and Biology

Carbon nanotubes combine a range of properties that make them well suited for use as probe tips in applications such as atomic force microscopy (AFM)1, 2, 3. Their high aspect ratio, for example, opens up the possibility of probing the deep crevices4 that occur in microelectronic circuits, and the small effective radius of nanotube tips significantly improves the lateral resolution beyond what can be achieved using commercial silicon tips5. Another characteristic feature of nanotubes is their ability to buckle elastically4, 6, which makes them very robust while limiting the maximum force that is applied to delicate organic and biological samples. Earlier investigations into the performance of nanotubes as scanning probe microscopy tips have focused on topographical imaging, but a potentially more significant issue is the question of whether nanotubes can be modified to create probes that can sense and manipulate matter at the molecular level7. Here we demonstrate that nanotube tips with the capability of chemical and biological discrimination can be created with acidic functionality and by coupling basic or hydrophobic functionalities or biomolecular probes to the carboxyl groups that are present at the open tip ends. We have used these modified nanotubes as AFM tips to titrate the acid and base groups, to image patterned samples based on molecular interactions, and to measure the binding force between single protein ligand pairs. As carboxyl groups are readily derivatized by a variety of reactions8, the preparation of a wide range of functionalized nanotube tips should be possible, thus creating molecular probes with potential applications in many areas of chemistry and biology.Chemistry and Chemical Biolog

Towards ICT integration in the classroom: a sequence to work on Boyle-Mariotte´s law

El advenimiento del Programa Conectar Igualdad, con la entrega de más de cinco millones de computadoras a estudiantes secundarios de la Argentina, trajo consigo un gran aumento en la demanda de nuevos materiales para la integración pedagógica de las TIC. La presencia de las netbooks en las aulas no implica automáticamente la integración de las TIC a la enseñanza. El uso que se haga de las computadoras dependerá –como es el caso también de otras tecnologías- de la opción didáctica puesta en práctica por los docentes. En este contexto presentamos una propuesta para la enseñanza de la Química que incorpora recursos de las TIC como facilitadores del aprendizaje, en línea con un enfoque indagatorio de la enseñanza de las ciencias. Presentamos una secuencia didáctica diseñada y llevada al aula en una serie de jornadas de capacitación a docentes de escuelas secundarias que este equipo de trabajo viene realizando desde el año 2011 en diferentes provincias de nuestro país. Se trata de una secuencia de actividades diseñada para estudiar la ley de Boyle-Mariotte en la cual se utilizan recursos audiovisuales para obtener datos empíricos y planillas de cálculo para construir una interpretación cuantitativa de estos resultados. Los resultados obtenidos permiten discutir sobre la concordancia entre los modelos y los datos experimentales, así como la relación entre las mediciones y las consideraciones teóricas en el planteo de modelos científicos.The implementation of the Programa Conectar Igualdad, which has made possible the distribution of more than five million netbooks for educational purposes, has also raised the demand for educational resources that facilitate ICT integration to teaching. Availability of netbooks does not necessarily mean that ICT have been integrated in teaching. The way netbooks are used in the classroom depends -as is also true for other technological resources- on the teacher´s didactic choice. In this context, we present a teaching sequence referred to gas laws inscribed in inquiry-based teaching. It has been prepared for continuing professional development sessions on science education with ICT. Sessions take place in different Argentinian provinces since 2011. This sequence focuses on gases properties, in particular on the variations of volume due to changes in pressure. Computers are initially used to play a movie showing a real experiment from which students obtain empirical information. Quantitative study follows, using the GeoGebra software, which allows students to fit the collected data with different mathematical functions. The outcomes give rise to discussion on the different models correlation with empirical data and also on how scientific models are constructed.Facultad de Ciencias Exacta

Trapping cold atoms using surface-grown carbon nanotubes

We present a feasibility study for loading cold atomic clouds into magnetic traps created by single-wall carbon nanotubes grown directly onto dielectric surfaces. We show that atoms may be captured for experimentally sustainable nanotube currents, generating trapped clouds whose densities and lifetimes are sufficient to enable detection by simple imaging methods. This opens the way for a novel type of conductor to be used in atomchips, enabling atom trapping at sub-micron distances, with implications for both fundamental studies and for technological applications

Towards ICT integration in the classroom: a sequence to work on Boyle-Mariotte´s law

El advenimiento del Programa Conectar Igualdad, con la entrega de más de cinco millones de computadoras a estudiantes secundarios de la Argentina, trajo consigo un gran aumento en la demanda de nuevos materiales para la integración pedagógica de las TIC. La presencia de las netbooks en las aulas no implica automáticamente la integración de las TIC a la enseñanza. El uso que se haga de las computadoras dependerá –como es el caso también de otras tecnologías- de la opción didáctica puesta en práctica por los docentes. En este contexto presentamos una propuesta para la enseñanza de la Química que incorpora recursos de las TIC como facilitadores del aprendizaje, en línea con un enfoque indagatorio de la enseñanza de las ciencias. Presentamos una secuencia didáctica diseñada y llevada al aula en una serie de jornadas de capacitación a docentes de escuelas secundarias que este equipo de trabajo viene realizando desde el año 2011 en diferentes provincias de nuestro país. Se trata de una secuencia de actividades diseñada para estudiar la ley de Boyle-Mariotte en la cual se utilizan recursos audiovisuales para obtener datos empíricos y planillas de cálculo para construir una interpretación cuantitativa de estos resultados. Los resultados obtenidos permiten discutir sobre la concordancia entre los modelos y los datos experimentales, así como la relación entre las mediciones y las consideraciones teóricas en el planteo de modelos científicos.The implementation of the Programa Conectar Igualdad, which has made possible the distribution of more than five million netbooks for educational purposes, has also raised the demand for educational resources that facilitate ICT integration to teaching. Availability of netbooks does not necessarily mean that ICT have been integrated in teaching. The way netbooks are used in the classroom depends -as is also true for other technological resources- on the teacher´s didactic choice. In this context, we present a teaching sequence referred to gas laws inscribed in inquiry-based teaching. It has been prepared for continuing professional development sessions on science education with ICT. Sessions take place in different Argentinian provinces since 2011. This sequence focuses on gases properties, in particular on the variations of volume due to changes in pressure. Computers are initially used to play a movie showing a real experiment from which students obtain empirical information. Quantitative study follows, using the GeoGebra software, which allows students to fit the collected data with different mathematical functions. The outcomes give rise to discussion on the different models correlation with empirical data and also on how scientific models are constructed.Facultad de Ciencias Exacta

Pyrolysis-catalysis of waste plastic using a nickel-stainless steel mesh catalyst for high value carbon products.

A stainless steel mesh loaded with nickel catalyst was produced and used for the pyrolysis-catalysis of waste high density polyethylene with the aim of producing high value carbon products, including carbon nanotubes. The catalysis temperature and plastic to catalyst ratio were investigated to determine the influence on the formation of different types of carbon deposited on the nickel-stainless steel mesh catalyst. Increasing temperature from 700 to 900 °C resulted in an increase in the carbon deposited on the nickel loaded stainless steel mesh catalyst from 32.5 wt.% to 38.0 wt.%. The increase of sample to catalyst ratio reduced the amount of carbon deposited on the mesh catalyst in terms of g carbon g(-1) plastic. The carbons were found to be largely composed of filamentous carbons, with negligible disordered (amorphous) carbons. Transmission electron microscopy analysis of the filamentous carbons revealed them to be composed of a large proportion (estimated at ∼40%) multi-walled carbon nanotubes. The optimum process conditions for carbon nanotube production, in terms of yield and graphitic nature, determined by Raman spectroscopy, was catalysis temperature of 800 °C and plastic to catalyst ratio of 1:2 where a mass of 334 mg of filamentous/multi-walled carbon nanotubes g(-1) plastic was produced

Towards ICT integration in the classroom: a sequence to work on Boyle-Mariotte´s law

El advenimiento del Programa Conectar Igualdad, con la entrega de más de cinco millones de computadoras a estudiantes secundarios de la Argentina, trajo consigo un gran aumento en la demanda de nuevos materiales para la integración pedagógica de las TIC. La presencia de las netbooks en las aulas no implica automáticamente la integración de las TIC a la enseñanza. El uso que se haga de las computadoras dependerá –como es el caso también de otras tecnologías- de la opción didáctica puesta en práctica por los docentes. En este contexto presentamos una propuesta para la enseñanza de la Química que incorpora recursos de las TIC como facilitadores del aprendizaje, en línea con un enfoque indagatorio de la enseñanza de las ciencias. Presentamos una secuencia didáctica diseñada y llevada al aula en una serie de jornadas de capacitación a docentes de escuelas secundarias que este equipo de trabajo viene realizando desde el año 2011 en diferentes provincias de nuestro país. Se trata de una secuencia de actividades diseñada para estudiar la ley de Boyle-Mariotte en la cual se utilizan recursos audiovisuales para obtener datos empíricos y planillas de cálculo para construir una interpretación cuantitativa de estos resultados. Los resultados obtenidos permiten discutir sobre la concordancia entre los modelos y los datos experimentales, así como la relación entre las mediciones y las consideraciones teóricas en el planteo de modelos científicos.The implementation of the Programa Conectar Igualdad, which has made possible the distribution of more than five million netbooks for educational purposes, has also raised the demand for educational resources that facilitate ICT integration to teaching. Availability of netbooks does not necessarily mean that ICT have been integrated in teaching. The way netbooks are used in the classroom depends -as is also true for other technological resources- on the teacher´s didactic choice. In this context, we present a teaching sequence referred to gas laws inscribed in inquiry-based teaching. It has been prepared for continuing professional development sessions on science education with ICT. Sessions take place in different Argentinian provinces since 2011. This sequence focuses on gases properties, in particular on the variations of volume due to changes in pressure. Computers are initially used to play a movie showing a real experiment from which students obtain empirical information. Quantitative study follows, using the GeoGebra software, which allows students to fit the collected data with different mathematical functions. The outcomes give rise to discussion on the different models correlation with empirical data and also on how scientific models are constructed.Facultad de Ciencias Exacta

Covalently Functionalized Nanotubes as Nanometer-Sized Probes in Chemistry and Biology

Carbon nanotubes combine a range of properties that make them well suited for use as probe tips in applications such as atomic force microscopy (AFM)1, 2, 3. Their high aspect ratio, for example, opens up the possibility of probing the deep crevices4 that occur in microelectronic circuits, and the small effective radius of nanotube tips significantly improves the lateral resolution beyond what can be achieved using commercial silicon tips5. Another characteristic feature of nanotubes is their ability to buckle elastically4, 6, which makes them very robust while limiting the maximum force that is applied to delicate organic and biological samples. Earlier investigations into the performance of nanotubes as scanning probe microscopy tips have focused on topographical imaging, but a potentially more significant issue is the question of whether nanotubes can be modified to create probes that can sense and manipulate matter at the molecular level7. Here we demonstrate that nanotube tips with the capability of chemical and biological discrimination can be created with acidic functionality and by coupling basic or hydrophobic functionalities or biomolecular probes to the carboxyl groups that are present at the open tip ends. We have used these modified nanotubes as AFM tips to titrate the acid and base groups, to image patterned samples based on molecular interactions, and to measure the binding force between single protein–ligand pairs. As carboxyl groups are readily derivatized by a variety of reactions8, the preparation of a wide range of functionalized nanotube tips should be possible, thus creating molecular probes with potential applications in many areas of chemistry and biology