Light emitting devices based on nanostructured semiconductors

Light emitting devices based on high-efficiency photoluminescence (PL) fluorescent nanocrystals have been investigated in terms of the generation of light from the structure using a variety of deposition methods. An automated modified layer-by-layer (LbL) self-assembly technique has been employed to produce multilayers of thiol-capped red fluorescing CdTe nanocrystals. Indium- tin-oxide (ITO) and aluminium electrodes were used as the electrodes. Morphological characterization was carried out through Schottky field effect (SFEG) SEM and atomic force microscopy (AFM). The structures built presented clear red electroluminescence (EL) to the naked eye. Turn on voltages were found to be in the range of 3-6 volts while the onset current was in the order of tens of microamperes. The role of structure homogeneity, the presence of pinholes and lifetime extension were features addressed during this investigation. Samples with a lifetime of continuous operation in air longer than 60 minutes and highly stable EL spectra were achieved; EL was visible to the unaided eye, although the brightness was still below the commercial standards and has not yet been qualified

Insights into the relationship between inherent materials properties of PZT and photochemistry for the development of nanostructured silver.

Recently there has been great interest in using patterned ferroelectric materials for the photochemical growth of metal nanostructures. Variations in surface and sub-surface structure influence the photochemical processes. Here we show that crystallography, and hence remnant polarization, of the ferroelectric affects photo-deposition. The ratio of metal growth on c– and c+ domains varies from 1 : 2 for [100] to 1 : 100 for [111]. This is shown to be dependent on the variations in the band structu

Cathodic and Anodic Material Diffusion in Polymer/Semiconductor-Nanocrystal Composite Devices

In the present day, the information technologies and telecommunications sector continually increase their demand for low cost, low power consumption, high performance electroluminescent devices for display applications. Furthermore, general lighting applications, such as white light and large array colour displays, would also benefit from an increase in the overall efficiency. Several technologies are being investigated to fulfill these needs, such as organic light emitting diodes (OLED), polymeric light emitting diodes (PLED) and field effect emission devices. A new and promising technology is light emitting devices (LEDs) based on nanostructured materials. With organic LEDs (OLEDs) already making an impact on the market in an increasingly large number of applications, hybrid technologies based on organic/inorganic nano-composites are a potential the next step. The incorporation of highefficiency fluorescent semiconductor nanoparticles has been shown to have a beneficial effect on device performance, [1] modify the colour output from the device 2 and provide a simplified route to generation of LED type devices. [3

Fabrication and characterization of red-emitting electroluminescent devices based on thiol-stabilized semiconductor nanocrystals

Thiol-capped CdTe nanocrystals were used to fabricate light-emitting diodes, consisting of an emissive nanocrystal multilayer deposited via layer-by-layer, sandwiched between indium-tin-oxide and aluminum electrodes. The emissive and electrical properties of devices with different numbers of nanocrystal layers were studied. The improved structural homogeneity of the nanocrystal multilayer allowed for stable and repeatable current- and electroluminescence-voltage characteristics. These indicate that both current and electroluminescence are electric-field dependent. Devices were operated under ambient conditions and a clear red-light was detected. The best-performing device shows a peak external efficiency of 0.51% and was measured at 0.35mA/cm2 and 3.3V

Radiative capture reaction for 17^{17}Ne formation within a full three-body model

Background: The breakout from the hot Carbon-Nitrogen-Oxigen (CNO) cycles can trigger the rp-process in type I x-ray bursts. In this environment, a competition between $^{15}\text{O}(\alpha,\gamma){^{19}\text{Ne}}$ and the two-proton capture reaction $^{15}\text{O}(2p,\gamma){^{17}\text{Ne}}$ is expected. Purpose: Determine the three-body radiative capture reaction rate for ${^{17}\text{Ne}}$ formation including sequential and direct, resonant and non-resonant contributions on an equal footing. Method: Two different discretization methods have been applied to generate $^{17}$Ne states in a full three-body model: the analytical transformed harmonic oscillator method and the hyperspherical adiabatic expansion method. The binary $p$--$^{15}$O interaction has been adjusted to reproduce the known spectrum of the unbound $^{16}$F nucleus. The dominant $E1$ contributions to the $^{15}\text{O}(2p,\gamma){^{17}\text{Ne}}$ reaction rate have been calculated from the inverse photodissociation process. Results: Three-body calculations provide a reliable description of $^{17}$Ne states. The agreement with the available experimental data on $^{17}$Ne is discussed. It is shown that the $^{15}\text{O}(2p,\gamma){^{17}\text{Ne}}$ reaction rates computed within the two methods agree in a broad range of temperatures. The present calculations are compared with a previous theoretical estimation of the reaction rate. Conclusions: It is found that the full three-body model provides a reaction rate several orders of magnitude larger than the only previous estimation. The implications for the rp-process in type I x-ray bursts should be investigated.Comment: 10 pages, 10 figures. Corrected versio

Photochemical growth of silver nanoparticles on c- and c+ domains on PZT thin films

The photochemical growth of silver nanoparticles on the negative domains of lead zirconate titanate thin films is reported. A sample of highly [100] orientated lead zirconate titanate, with a ratio of 30:70, that was 65−70 nm thick grown on Pt-coated MgO was poled by use of piezoresponse force microscopy to produce defined regions of surface positive and negative polarization. A comparison between the growth of silver nanoparticles on the surface of the lead zirconate titanate when illuminated with two sources of super band gap UV is given. In both cases the wavelength of illumination leads to growth on the positive domains but only illumination with a Honle H lamp, with a high photon output over 250−200 nm, caused significant growth of silver nanoparticles on the negative domain. The deposition on the negative domain is explained in terms of changed band bending due to the excitation of electrons into the conduction band, the rate of decay to the ground state, and dimensions of the ferroelectric film. The rate of deposition of silver nanoparticles on the negative domains is approximately half that on the positive domains

Insights into the relationship between inherent materials properties of PZT and photochemistry for the development of nanostructured silver

Recently there has been great interest in using patterned ferroelectric materials for the photochemical growth of metal nanostructures. Variations in surface and sub-surface structure influence the photochemical processes. Here we show that crystallography, and hence remnant polarization, of the ferroelectric affects photo-deposition. The ratio of metal growth on c− and c+ domains varies from 1 : 2 for [100] to 1 : 100 for [111]. This is shown to be dependent on the variations in the band structure

Armadura paramétrica para soluciones integrales en contextos rurales

como finalidad reivindicar a la madera como un material constructivo pertinente para la edificación. Situación que en México se ha visto limitada por diferentes factores como lo son la sobredimensión de los elementos en reglamentos, la casi inexistente regulación del material y el paradigma de su deficiente seguridad y durabilidad comparada con otros materiales como lo son el acero y el concreto. Los beneficios de este material trascienden sus limitantes, siendo un material sustentable, la madera podría reducir en mayor o menor medida el abuso de materiales contaminantes en la construcción, además México cuenta con un gran abasto de maderas de primera calidad y rápido crecimiento. El primer acercamiento consiste en generar un nuevo mecanismo de construcción entre el usuario y su vivienda; se enfocó en darle solución a un elemento estructural que además de estético, funcione adecuadamente como entrepiso y tenga el potencial de ser un producto fácilmente transportable y autoconstruible. Esta investigación plantea las bases para desarrollar un sistema paramétrico en cubiertas y entrepisos de madera, el alcance de nuestras pruebas de laboratorio a la madera y su resistencia, el cálculo efectuado y el diseño conllevan a una relación global para continuar con la misión

1ª Competencia Nacional de Vivienda Sustentable Resistente a Fenómenos Naturales para estudiantes de arquitectura 2019 (proyecto 8|8)

Este proyecto intenta dar una solución efectiva a un problema bastante serio, tomamos como caso de aplicación el 1er Concurso Nacional de Vivienda Social Sustentable y Resiliente a Fenómenos Naturales para generar una hipótesis localizada en Manzanillo, Colima que plantea cuestionarnos sobre un problema a escala nacional, la demanda creciente de vivienda social y la falta de fundamentos críticos alrededor de la oferta actual. El proyecto se diseñó para que fuera una propuesta competente ante los problemas sociales, ambientales y culturales de una región. La ubicación geográfica en que se encuentra la comunidad de Valle de Las Garzas, es propensa al acecho de huracanes y tormentas tropicales, estas tormentas afectan de forma constante y agresiva a la comunidad creando inundaciones, pérdidas materiales y viviendas enteras Por esto mismo es que surge el interés por dar una solución factible para que la vivienda se convierta en un agente de cambio, no solo a la comunidad sino que de soporte a esta devastación natural, en pocas palabras, crear una vivienda consiente a su entorno. Al analizar la problemática nos damos cuenta que aparte de dar solución a la forma en la que se desarrolla la construcción actualmente, también tenemos que respetar y dar mucha importancia a la vida de la comunidad. No nos referimos a esto como una segunda problemática o algo que también se tiene que resolver, es algo que influye de gran manera en la forma en la que se resuelve el proyecto pues es consciente de su impacto social. Estamos considerando a la entidad de Valle de las Garzas como un barrio en desarrollo en uno de los principales puertos del país, esto genera el suficiente interés para desarrollar proyectos de multivivienda social, pretendemos abordar la crisis ecológica aunado a la demanda de vivienda desde una perspectiva contemporánea, generando modelos de ciudad compacta, con una densidad suficiente para el abasto de su población y que a la vez sea una comunidad habitacional bien conectada con el resto de la ciudad y los servicios. Interesados en el espacio público y colectivo y en el desarrollo de tecnologías para la construcción nace el proyecto 8 I 8

Chromosome-Level Genome Assembly of the Blue Mussel Mytilus chilensis Reveals Molecular Signatures Facing the Marine Environment

The blue mussel Mytilus chilensis is an endemic and key socioeconomic species inhabiting the southern coast of Chile. This bivalve species supports a booming aquaculture industry, which entirely relies on artificially collected seeds from natural beds that are translocated to diverse physical–chemical ocean farming conditions. Furthermore, mussel production is threatened by a broad range of microorganisms, pollution, and environmental stressors that eventually impact its survival and growth. Herein, understanding the genomic basis of the local adaption is pivotal to developing sustainable shellfish aquaculture. We present a high-quality reference genome of M. chilensis, which is the first chromosome-level genome for a Mytilidae member in South America. The assembled genome size was 1.93 Gb, with a contig N50 of 134 Mb. Through Hi-C proximity ligation, 11,868 contigs were clustered, ordered, and assembled into 14 chromosomes in congruence with the karyological evidence. The M. chilensis genome comprises 34,530 genes and 4795 non-coding RNAs. A total of 57% of the genome contains repetitive sequences with predominancy of LTR-retrotransposons and unknown elements. Comparative genome analysis of M. chilensis and M. coruscus was conducted, revealing genic rearrangements distributed into the whole genome. Notably, transposable Steamer-like elements associated with horizontal transmissible cancer were explored in reference genomes, suggesting putative relationships at the chromosome level in Bivalvia. Genome expression analysis was also conducted, showing putative genomic differences between two ecologically different mussel populations. The evidence suggests that local genome adaptation and physiological plasticity can be analyzed to develop sustainable mussel production. The genome of M. chilensis provides pivotal molecular knowledge for the Mytilus complex