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Extensive studies have been conducted regarding mother tongue (L1) interference and developing English writing skills. This study, however, aims to investigate the influence of the Spanish language on second language (L2) writing skills at several Ecuadorian senior high schools in Loja. To achieve this, 351 students and 42 teachers from second year senior high schools (public and private) were asked to participate in this study. The instruments for data collection were student and teacher questionnaires, as well as a written test in which students were asked to write a narrative passage. The information gathered from the instruments was then organized and tabulated to determine the various interference variables. Afterwards, the most representative samples from the narrative texts were analyzed based on their semantic, morphological and syntactical features. The results from this study indicate that English grammar and vocabulary were the linguistic areas that suffered the highest level of L1 language interference. The most common Spanish interference errors were misuse of verbs, omission of personal and object pronouns, misuse of prepositions, overuse of articles, and inappropriate/ unnatural word order. Finally, some suggestions are given to teachers in order to help students prevent further Spanish interference problems during writing/composition classes.

Electrification using renewable energy sources represents a clear path toward solving the current global energy crisis. In Colombia, this challenge also involves the diversification of the electrical energy sources to overcome the historical dependence on hydropower. In this context, green hydrogen represents a key energy carrier enabling the storage of renewable energy as well as directly powering industrial and transportation sectors. This work explores the realistic potential of the main renewable energy sources, including solar photovoltaics (8172 GW), hydropower (56 GW), wind (68 GW), and biomass (14 GW). In addition, a case study from abroad is presented, demonstrating the feasibility of using each type of renewable energy to generate green hydrogen in the country. At the end, an analysis of the most likely regions in the country and paths to deploy green hydrogen projects are presented, favoring hydropower in the short term and solar in the long run. By 2050, this energy potential will enable reaching a levelized cost of hydrogen (LCOH) of 1.7, 1.5, 3.1 and 1.4 USD/kg-H2 for solar photovoltaic, wind, hydropower and biomass, respectively. [ABSTRACT FROM AUTHOR]

Poly(dicyclopentadiene) (poly-DCPD) is a thermoset with potential for high-performance applications. In this research, epoxy resin was blended with different concentrations of fly ash class F particles at 0.0, 1.0, 10.0, and 50.0 wt.%, aiming to improve its use as a high-volume structural material by decreasing costs and reducing its negative environmental impact through using fly ash particles. A planetary Thinky mixer was used to initially mix the resin with the curing agent, followed by incorporating a Grubbs catalyst. The microstructures were analyzed using scanning electron microscopy (SEM), where particles were found to be homogeneously distributed over the polymer matrix. The thermomechanical behavior was evaluated via curing, compression, dynamic mechanical analysis (DMA), and thermo-gravimetric analysis (TGA). Nanoindentation tests were also conducted. Fly ash was found to decelerate the curing of the resin through the release of calcium ions that enhanced the exothermic reaction. [ABSTRACT FROM AUTHOR]

Large‐scale manufacturing of perovskite solar cells (PSCs) requires the deposition of homogeneous and defect‐free perovskite films on large‐area substrates. Up to now, the knowledge developed for industrial slot‐die processing has not been fully transferred to the perovskite photovoltaic community. Here, the deposition of uniform perovskite layers by slot‐die coating (SDC). Computer fluid dynamics (CFD) simulations, experimental validation, and calculation of industrial uniformity parameters are demonstrated, which enabled to establish processing conditions for SDC of perovskite ink. This approach allowed for obtaining stable cross‐web flow in the slot‐die head resulting in the formation of a stable coating bead yielding uniform perovskite films. The best processing parameters are used for the fabrication of slot‐die‐coated PSCs, which showed a more homogeneous spatial distribution of photovoltaic parameters compared to their spin‐coated counterparts. Better reproducibility observed in device performance is a step forward toward the commercialization of perovskite photovoltaic technology. For the first time, the industrial approach used for the optimization of slot‐die coating is applied for the processing of perovskite inks that have special conditions such as low viscosity and in situ crystallization on the substrate. [ABSTRACT FROM AUTHOR]

Perovskite solar technology stands on three different pillars: efficiency, stability, and processability. Focusing on processability, the field demands the achievement of optoelectronic grade active layers with high uniformity fabricated by industry‐compatible methods. Herein, the design and implementation of an air knife on a blade coating deposition system, which allows controlling the evaporation rate of the solvents improving the crystallization and uniformity of perovskite films in a p–i–n device are reported. The effect of doctor blade operational parameters is studied using image analysis combined with a machine learning method to identify the most relevant processing variables leading to a uniform perovskite layer with optimal thickness. After implementing the air knife system and finding the best processing conditions, a special perovskite solar minimodule enabling the evaluation of single inner subcells is fabricated. These perovskite subcells reach an average efficiency of 10.1% and remarkably all the subcells deviate less than 20% from this value over a large‐area substrate. These results demonstrate the promising potential of this fabrication method for low cost and high deposition rate photovoltaic devices, which is on the path to mass production. [ABSTRACT FROM AUTHOR]

In this work, we have synthesized and fabricated solar cells with the hybrid metal halide compounds with the general formula ABX3, where the A cation is methylammonium, the B cation is nickel, and the X anion is chlorine or a mixture of chlorine and iodine. We obtained experimental evidence that this material is a semiconductor with an orthorhombic crystalline structure which pertains to the space group Cmcm. The bandgap can be modulated from 1.4 eV to 1.0 eV by changing the chlorine anion to iodine. Therefore, we were able to obtain solar cells with efficiencies up to 0.16% with the CH3NH3NiCl2I composition. We have also studied by means of first-principles calculations, taking into account van der Waals dispersive forces, the ground state properties of these materials such as their crystal structure and formation and decomposition energies. We have found that these energies are lowered by the lighter mass anion, and the calculated decomposition energies show that only CH3NH3NiCl3 is stable with respect to the most probable decomposition pathway. The electronic band structure and band edge alignments have been calculated using quasiparticle effects through the GW0 approximation; these materials show an indirect bandgap with the valence band maxima at −6.93 and −5.49 eV with respect to vacuum and the conduction band minima at −5.62 and −4.60 eV with respect to vacuum for CH3NH3NiCl3 and CH3NH3NiI3, respectively. This work provides a pathway to explore new hybrid A + B 2 + X 3 − -type semiconductor materials. [ABSTRACT FROM AUTHOR]

Perovskite-based materials have been considered as the most promising materials in several solar-driven processes, especially photovoltaics. Some features such as high sunlight harvesting and improved carrier transport have been highlighted to have an impact on the efficiency of the above topics, but limited studies have pointed out their surface composition, which mainly influence the above abilities. As a starting point to recognize the surface environment and chemical states of these materials, x-ray photoelectron spectroscopy measurements were performed. Trication-mixed halide perovskite films based on Cs0.08MA0.18FA0.78PbBr0.42I2.58 were prepared by a one step process and deposited on an indium tin oxide substrate by spin-coating. Survey spectra, Pb 4f, I 3d, Br 3d, Cs 3d, C 1s, N 1s, Pb 4d, and Pb 5d core levels, and valence band spectra were measured for the semiconductor sample. Results exhibit symmetrical peaks, indicating that a homogenous solid solution was achieved. Main chemical states of this kind of perovskites such as Cs-Br and Pb-I species are also shown. We deduced that the later signals are associated with the [PbI6]4− octahedra existing in the perovskite lattice, while the former one is related to Cs+ bounded to [PbBr6]4− units on the perovskite surface. Interestingly, the NR4+ signal was also identified, associated with the presence of methylammonium and formamidinium cations. [ABSTRACT FROM AUTHOR]

The synergistic effects of different engineering strategies, especially interface engineering, band structure engineering, and micro/nano engineering, can be exploited for the development of efficient photoanodes for quantum dot-sensitized solar cells (QDSSCs). Herein, we investigate the energy transfer mechanism and the charge carrier transport capacity of a set of photoanodes developed for a CdSe QDSSC. Boron, nitrogen and fluorine-tridoped TiO2 nanotube (BNF-TNT) membranes were obtained by anodization of titanium to self-organized TiO2 nanotube (TNT) layers, followed by a lift-off process. Then BNF-TNT membranes were adhered onto indium–tin oxide (ITO) conductive glass and sensitized by varying the load of CdSe quantum dots (BNF-Y-CdSe) using the SILAR method. The as-prepared electrode materials were characterized by FESEM, HR-TEM, DRS, XPS and Raman spectroscopy. The photochemical, photoelectrochemical, and semiconducting properties of the electrode materials were investigated by photopotential, photovoltammetry, photocurrent transient measurements, and Mott–Schottky analyses in 1.0 M Na2S. CdSe quantum dots (QDs) were homogeneously and intimately coated on BNF-TNT, which favored electron transport to the ITO substrate, and promoted a red-shift in the light harvesting of the composite toward the visible region (1.65 eV) from UV (2.75 eV). The highest photoresponse was obtained for BNF-TNT grown in 0.06 wt% H3BO3, and sensitized with CdSe QDs after five SILAR cycles. Boron doping in BNF-5-CdSe increased the photoconversion efficiency with respect to the CdSe-sensitized nanotubes without B-doping (NF-5-CdSe) by around 176% under one sun illumination (AM 1.5 G, 100 mW cm−2). The results showed that B-doping/sensitization synergism occurs by a Ti3+ states-to-CdSe QD electron transfer, which increases electron flow toward back contact. This allowed the enhancement of the electron lifetime, charge-collection efficiency and incident-to-electron conversion efficiency. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) Ruddlesden–Popper perovskites have emerged as a new class of hybrid materials with high photoluminescence and improved stability compared to their three-dimensional (3D) counterparts. Studies of the photophysics of these new 2D perovskites are essential for the fast development of optoelectronic devices. Here, we study the power and temperature dependences of the photoluminescence properties of the (PA)2(MA)2Pb3Br10 hybrid perovskite. High electron–phonon coupling near room temperature was found to be dominated by longitudinal optical (LO) phonons via the Fröhlich interaction. However, we show that the presence of free carriers is also possible, with lower trapping states and higher and more stable emission compared to the 3D MAPbBr3. These characteristics make the studied 2D material very attractive for optoelectronic applications, including solar cells and light emitting diodes (LEDs). Our investigation provides new fundamental insights into the emission characteristics of 2D lead halide perovskites. [ABSTRACT FROM AUTHOR]

ABSTRACT: When making nanocomposites, there is a big challenge to obtain both functional and mechanical enhancement. In this study, a new in situ polymerization methodology for the incorporation of surface modified silver nanoparticles (AgNPs) in a thermoplastic polyurethane matrix was developed. AgNPs with contents ranging from 0 to 1.5 wt % were used. A double functionalization of the nanoparticles with oleic acid was performed, which lead to a reaction of carboxylic acid groups in the nanoparticle's surface with isocyanate groups of the 4,4′‐methylene diphenyl diisocyanate monomer as corroborated from the Raman results. The successful incorporation of the nanoparticles was verified with EDS, TGA, and Raman measurements. Thermal properties of nanocomposites were investigated by DSC. AgNPs made positive impact in two ways: first, increased more than twice the elastic modulus, as studied via nanoindentation measurements and second, based on the inhibition zone method, great bactericidal effectiveness for nanocomposites containing 1.5 wt % AgNPs was observed for Escherichia coli. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46180. [ABSTRACT FROM AUTHOR]

This work investigates the two-step polymerization between methylene diphenyl diisocyanate (MDI), two different poly(tetramethylene oxide) macrodiols, and 1,4-butanediol (BD) as chain extender. At the end of the prepolymerization, the reaction mixture contains MDI in excess and a prepolymer with isocyanate end group. Then, BD and a solvent (tetrahydrofuran) were added to start the finishing stage under nominal stoichiometric equilibrium. The reaction was analyzed by Fourier transform infrared spectroscopy, hydrogen nuclear magnetic resonance (1H-NMR), and size exclusion chromatography. 1H-NMR was employed to follow global concentrations of unreacted isocyanate end groups and internal urethane groups. This information enabled to estimate the following "effective" rate constants: k1 =1.07 x 10-3 L mol-1 s-1 for the prepolymerization; and k2=1.94 x 10-4 L mol-1 s-1 for the finishing stage. These values are subject to errors caused by biases introduced in the recipe, in the measurements, in the reaction conditions, in the quality of reagents, and in the reaction mechanism assumptions. Such errors also explain the dispersion of the published rate constants values. The ¹H-NMR measurements also enabled to estimate the evolution (with extent of reaction) of the numberaverage number of structural units along the prepolymerization and finishing stages; and such estimates reasonably verify Flory's classical expressions. [ABSTRACT FROM AUTHOR]

An investigation on the cooling-induced crystallization in three thermoplastic polyurethanes based on MDI, PTMG, and 1.4-BD as chain extender with different hard segment content is reported. Thermal transitions were determined using differential scanning calorimetry (DSC) measurements at different cooling rates, and thermal stability was studied by thermogravimetric analysis. Changes in Raman spectra were useful to correlate the thermal transitions with changes in the morphology of the polymers. The dissimilarity in the composition gave different rheological behavior in the molten state, indicated by the temperature dependence of the viscosity. The mechanical properties and the crystallinity was influenced not only by the cooling rate but also by the hard segment content. Thermoplastic polyurethanes with more hard segment content formed more crystalline hard domains as evidenced by the DSC and atomic force microscopy results. [ABSTRACT FROM AUTHOR]