Betanin dye extracted from ayrampo (Opuntia soehrensii) seeds to develop dye-sensitized solar cells.

Pigments extracted from ayrampo seeds of the Peruvian-native prickly pear (Opuntia soehrensii) were used in dye-sensitized solar cells with promising efficiencies. The performance of the solar cells was then improved via the addition of citric acid to stabilise the photosensitive dye, and an efficiency of 1.41% was achieved with current output remaining stable after 7 days. Upon testing in low-light conditions, the solar conversion efficiency of devices increased to 4%. This paper not only highlights the potential of natural sensitizers in DSSCs but also shows that simple extraction and gentle handling methods can contribute to the device performance.

Extraction of 2'-O-apiosyl-6'-O-crotonic acid-betanin from the ayrampo seed (Opuntia soehrensii) cuticle and its use as an emitting layer in an organic light-emitting diode.

The molecule 2'-O-apiosyl-6'-O-crotonic acid-betanin (called Achkiy) was obtained after an ecofriendly and low-cost purification process of the extract from the ayrampo seed cuticle. Results from EDS give us an idea of the organic elements present in the ayrampo cuticle layer composed of carbon, oxygen and nitrogen. Further characterization analysis of ayrampo extract by Fourier Transform Infrared Spectrophotometry (FTIR) corroborated the presence of characteristic functional groups corresponding to carboxyl, carbonyls, hydroxyls and secondary amines. On the other hand, we have confirmed by absortion peak the glucose, apiosyl, crotonic acid and betanin at 227 nm, 276 nm, 291 nm and 534 nm bands respectively. Mass Spectrometry (MS) characterization was used finally to identify the electroactive Achkiy molecule. This molecule was tested in an Organic Light Emitting Diode (OLED) achieving a luminance of 4.8 Cd m-2 when bias voltage of 16.5 V and a current of 34.1 mA was applied. In addition, the irradiance generated by the Achkiy layer reaches a value of ≈ 113.3 µW m-2 emitting light with a λ ≈ 390.10 nm. These preliminary results report an interesting molecule extracted from a natural pigment wich emits light in the blue region.

Electrical and optical properties of reduced graphene oxide thin film deposited onto polyethylene terephthalate by spin coating technique.

We present the reduction of solution processed graphene oxide films by hydrogen iodide vapor. The films were studied by Raman spectroscopy and Fourier-transform infrared spectroscopy and its optoelectronic properties characterized. We obtained reduced graphene oxide films on polyethylene terephthalate flexible substrates with good electrical properties, 3.74×10-6 Ω·m, and high optical transmittance of 70% in the visible range. The fabricated layers contain graphene sheets with sizes up to ∼10 µm long and ∼6 µm wide. The presented solution, with highly concentrated processed graphene oxide, could be used as printing ink for manufacturing transparent and conductive electrodes on plastic substrates without the requirement of elevated temperatures.

Simple light-emitting electrochemical cell using reduced graphene oxide and a ruthenium (II) complex.

We report the use of conducting substrates from reduced graphene oxide (rGO) applied in light-emitting electrochemical cells (LECs) in which we used an electroluminescent polymer as a light-emitting layer. The emitting layer was composed of an organic metal complex of tris(2, 2'-bipyridine) ruthenium (II) linked to the sodium tetrafluoroborate anion ([Ru(bpy)3]+2)(BF4)-1. The luminance generated from the electroluminescent device was 6.89 Cd/m2 when applying a voltage of 13.48 V and a current of 10.19 mA. The luminance of this device was kept on almost constant for 36.84 min. The prolonged lifetime of the electrochemical device was achieved by depositing an rGO thin layer with a 161.3 nm thickness inside the LEC structure.

El Salvador: 1954-1991: poder de compra de los salarios mínimos, antes y durante la guerra civil / El Salvador: 1954-1991: evolution of the purchasing power of minimum wages affected by the war

Este estudio se realizó a partir de datos oficiales disponibles en El Salvador, sobre salarios, precios al por menor e índices de precios. El análisis incluye: la evolución comparativa de los salarios mínimos urbanos y agropecuarios; la evolucón comparativa del promedio de las horas trabajadas y los salarios de mujeres y hombres obreros en la industria manufacturera del Departamento de San Salvador; el desarrollo del poder de compra, tanto general como alimentario, de un salario de referencia que es el salario mínimo urbano de la zona metropolitana de San Salvador; la variación de los precios al por menor de 47 alimentos y otros productos y derivados básicos (combustibles domésticos y corte de cabello de hombre) en la ciudad de San Salvador...

El Salvador (1954-1991): evolution du pouvoir d'achat des salaires minimums affecte par la guerre / El Salvador 1954-1991: evolution of the purchasing power of minimum wages affected by the war

Este estudio está hecho a partir de datos oficiales disponibles en El Salvador sobre salarios, precios al por menor e índices de precios. Se analizó: la evolución comparativa de los salarios mínimos urbanos y agrícolas. La evolución comparativa del promedio de las horas trabajadas y salarios de mujeres y hombres obreros en la industria manufacturera del Departamento de San Salvador. El desarrollo del poder de compra tanto general como alimentario de un salario de referencia que es el salario mínimo urbano del área metropolitana de San Salvador. La variación de los precios al por menor de 47 alimentos y varios (combustibles domésticos y corte de cabello para hombre) en la Ciudad de San Salvador. Los precios están expresados, primero en colones corrientes; luego en horas de trabajo, pagadas al salario mínimo urbano, necesarias para adquirir ciertas cantidades físicas (kilogramo, litro, unidad, etc.), 1000 kilocalorías y 100 gramos de proteína de alimentos...