Domestic and mineralogical waste, as well as the one produced from various industries is thrown mostly in rivers, generating high amounts of heavy metals, becoming a threat for the health for residents in the areas near the river. Established techniques of polluted water can be used in order to determine the heavy metal concentration, however, some of them require high energy consumption and sophisticated equipment. An alternative method is an indirect analysis that consists in the measurement of cadmium levels with the application of the optical study of the flora of the region near the river using UV-VIS basic spectroscopy. This analysis allow us to measure the amount of cadmium (a metal that directly affects health) found in the grown plant. Therefore, the specie Raphanus sativus was used due to its fast growth, and the fact that it requires high amounts of water for its growth. The optical study was performed applying different concentrations of the metal. Such concentrations were kept within then maximum of heavy metals allowed in river water. UV-VIS spectroscopy was performed with light sources of unpolarized light and polarized light, allowing performing the purposed research, determining a trend line between the concentration of cadmium and the intensity of light around 675nm of the spectrum.
The teaching of science is a global problem, general studies have been carried out which take into account the effects of color in the educational environment and have had revealing results, however a study has not been made to measure the effects of color in the learning of the sciences, in this specific case of Physics and mathematics. A study of the effects of color on science teaching was conducted, controlling color of various materials such as slides used in class, markers on blackboard, pens, paper sheets, laboratory materials and teacher's clothing color. In this paper we present results of student academic performance, opinion about the subject, development of logical abilities and a comparison with the teaching of science in a free way, that is to say, without control of color. There is also a study of color effects in science education distinguishing between genders and finally comparing the general results in the educational field with those obtained in this work.
The present work shows the teaching and motivation of University students to think about optics and color effects. The methodology consists of studying the different optical phenomena that occur through the sunsets and then do a correlation of this information with the phenomena and optical effects of the color of class presentations; to determine the motivation and attention of students.
In this work we present the results of a study of twenty natural pigments obtained from plants and insects from southern Ecuador. Many of them will be considered as a potential natural sensitizer for the construction of DSSCs. The results indicate that these pigments have a good performance in the absorbance and wavelength spectra. Were selected four best pigments for the construction of DSSCs, Rumex tolimensis Wedd, Raphanus sativus, Hibiscus sabdariffa, and Prunus serótina, however the conversion efficiency is lower than 1%.
The scientific community and some sectors of industry have been working with organic dyes for successful applications in OLED´s, OSC´s, however, most of the used dyes and pigments are synthetic. In this work is investigated the use of natural dyes for its application in organic light emitting diodes, some of the studied species are chili, blackberry, guayacan flower, cochinilla, tree tomato, capuli, etc. In this study the dyes are deposited by direct deposition and SOL-GEL process doped with the natural organic dye, both methods show good performance and lower fabrication costs for dye extraction, this represents a new alternative for the fabrication of OLED devices with low requirements in technology. Most representative results are presented for Dactylopius Coccus Costa (cochinilla) and raphanus sativus´ skin.
The results on characterization of the main photoelectric properties of the polymer:fulleren based composite
material by using the non-steady-state photo-electromotive force (p-EMF) and modulated photocurrent technique are
presented. By measuring this current under different experimental conditions, important material photoelectric
parameters such as drift L0 and diffusion length LD, photocarrier's lifetime τ ; quantum efficiency of charge
generation φ can be determined. The 50% of the composite weight consists of a mixture of the hole-conducting
polymer PF6:TPD (poly-hexyle-triophene:N,N'-bis(4-methylphenyl)-N,N'-bis-(phenyl)-benzidine) sensitized with the
highly soluble C60 derivative PCBM (phenyl-C61-butyric acid methyl ester) . Seven samples with varied
polymer:sensitizer weight ratio (49:1wt.-%, 45:5wt.-%, 40:10wt.-%, 15:35wt.-%, 25:25wt.-%, 10:40wt.-%, 5:45wt.-%)
where prepared. The remaining 50% were two azo-dyes 2,5-dimethyl-(4-p-nitrophenylazo)-anisole (DMNPAA) and 3-
methoxy-(4-p-nitrophenylazo)-anisole (MNPAA) (25wt.-% each). Photoconductive composite film was sandwiched
between two glass plates covered by transparent ITO electrodes. Two counter-propagating beams derived from a cw
HeNe laser (λ = 633nm) intersected inside the detector creating an interference pattern. The output photo-EMF
current (SEE MANUSCRIPT FOR EQUATION) was detected as a voltage drop by a lock-in amplifier.
At polymer sensitizer ratio 25:25wt.-% the signal sign changes to the opposite revealing that the majority
carriers at this and higher concentration of sensitizer are electrons. Our results show that the majority carrier's lifetime
τ is only slightly affected by the variations of sensitizer concentration. Mobility-lifetime product μhτh of holes, on its
turn decreases at the increasing sensitizer concentration, while μeτe of electrons keeps increasing. All this indicates that
the carrier's mobility is strongly influenced by the changes on sensitizer concentrations.
Organic semiconductors with bipolar (electron and hole) transport capability play a crucial role in electronic and
optoelectronic devices such as organic light-emitting diodes (OLEDs), bipolar transistors and photovoltaic cells.
Recently, a considerable amount of work has been devoted to the characterization of ambipolar transport in organic
materials, allowing for a better understanding of their properties as well as the physical processes, which take place in
materials and devices [1-4]. The experimental methods used to obtain information about charge transport in organic
semiconductors - time-of-flight (TOF) transient photoconductivity , charge extraction by linearly increasing voltage
(CELIV) , current-voltage measurements in space charge limited current regime , and field effect transistor (FET)
measurements [8, 9] are mostly focused on determination of charge carrier mobility. On the other hand, for many devices
(e.g. organic photovoltaic solar cells or light emitting diodes) the knowledge of the transport and recombination
characteristics of both carriers (electron and hole), and specifically their diffusion LD = the square root of Dτ (here D is the diffusion
coefficient and τ is the photocarriers lifetime) and drift lengths L0 = μτE0 (here μ is the carrier's mobility and E0 is
the electric dc field) is important.