Preparation of Poly(Vinyl) Alcohol/Chitosan Hybrid Membranes Doped with Graphene Nanosheets

The development of ion exchange membrane technology has allowed its introduction in many industrial sectors, such as electrodialysis and electrolysis. Nowadays, membranes are the crucial element in electrochemical energy conversion and storage devices. This work is aimed at examining new eco-friendly membranes materials to improve structural, mechanical, electrical and barrier properties. A simple and ecological synthesis of alkaline anion exchange membranes based on a mixed matrix membrane of chitosan (CS) and poly(vinyl) alcohol (PVA) – CS:PVA polymeric matrix – was developed by using a 50:50 wt. % ratio. The CS:PVA matrix was modified with variable loadings of graphene pristine sheets (GPH) ranging between 0,5 and 4.0 wt. %. The physico-chemical characterization of each of the membranes prepared was carried out in order to examine the topology, structure, thermal stability, surface chemistry, and water content (WC), as well as the ionic conductivity by using electrochemical impedance spectroscopy (EIS). Results revealed that the incorporation of graphene (GPH) into the CS:PVA polymeric matrix leads to the improvement of the thermal stability, and the ionic conductivity of the pristine polymeric matrix. The loading of 1.0 wt. % of GPH into CS:PVA was optimal in terms of specific ionic conductivity that is related to surface chemistry of the membrane, WC, and slight roughness of the membrane topology. The presence of GPH only provided a slight loss of crystallinity of the memebrane compared to the unmodified CS:PVA membrane, which also resulted in the reduction of water content with moderately GPH loadings. With regard to the ionic conductivity, an almost twofold increase was obtained compared to the pure CS:PVA for an optimal loading of 1.0 wt. %.The authors thank the Ministerio de Economía y Competitividad for its financial support (CTQ2013-48280-C3-3-R). Also, Jesús Iniesta gives thanks to Relaciones Internacionales for the PPI grant suppoted by the University of Alicante, Spain

Desarrollo de semiconductores con estructuras tipo perovskitas para purificar el agua mediante oxidaciones avanzadas

En este trabajo se llevó a cabo la preparación a través del método sol-gel y la reacción en estado sólido de óxidos semiconductores pertenecientes a las familias del tipo perovskita simple, ABO3 y doble laminar, A2M2O7, como el NaTaO3, NaTaO3:A (A = La, Sm), y Sr2M2O7 (M = Ta, Nb), respectivamente. Éstos fueron probados en la reacción de degradación fotocatalítica de azul de metileno, cristal violeta y rojo alizarín S. En particular, la perovskita simple, NaTaO3:Sm, mostró la mejor eficiencia para la degradación de azul de metileno (t1/2 = 65 min), mientras que la perovskita doble laminar, Sr2Ta2O7, fue eficiente para degradar tanto el cristal violeta (t1/2 = 5 min), como el rojo alizarín S (t1/2 = 25 min). Para el caso del cristal violeta la eficiencia fue incluso mayor a la mostrada por la titania P25 Degussa. La eficiencia fotocatalítica mostrada por los óxidos tipo perovskita simple la hemos relacionado a la formación de su estructura cristalina y a los valores de área superficial específica, además del efecto favorable del dopante. Mientras que en el caso de los óxidos tipo perovskita laminar, la eficiencia se debió a la presencia de la fase cristalina y al pH del medio de reacción. Además, debido a que todos estos óxidos mostraron valores de Eg alrededor de 4.0 eV, su activida

Shape-controlled metal nanoparticles for electrocatalytic applications

The application of shape-controlled metal nanoparticles is profoundly impacting the field of electrocatalysis. On the one hand, their use has remarkably enhanced the electrocatalytic activity of many different reactions of interest. On the other hand, their usage is deeply contributing to a correct understanding of the correlations between shape/surface structure and electrochemical reactivity at the nanoscale. However, from the point of view of an electrochemist, there are a number of questions that must be fully satisfied before the evaluation of the shaped metal nanoparticles as electrocatalysts including (i) surface cleaning, (ii) surface structure characterization, and (iii) correlations between particle shape and surface structure. In this chapter, we will cover all these aspects. Initially, we will collect and discuss about the different practical protocols and procedures for obtaining clean shaped metal nanoparticles. This is an indispensable requirement for the establishment of correct correlations between shape/surface structure and electrochemical reactivity. Next, we will also report how some easy-to-do electrochemical experiments including their subsequent analyses can enormously contribute to a detailed characterization of the surface structure of the shaped metal nanoparticles. At this point, we will remark that the key point determining the resulting electrocatalytic activity is the surface structure of the nanoparticles (obviously, the atomic composition is also extremely relevant) but not the particle shape. Finally, we will summarize some of the most significant advances/results on the use of these shaped metal nanoparticles in electrocatalysis covering a wide range of electrocatalytic reactions including fuel cell-related reactions (electrooxidation of formic acid, methanol and ethanol and oxygen reduction) and also CO2 electroreduction.The authors acknowledge financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) (project CTQ2016-76231-C2-2-R (AEI/FEDER, UE)). J.S-G. also acknowledges financial support from VITC (Vicerrectorado de Investigación y Transferencia de Conocimiento) of the University of Alicante (UATALENTO16-02)

Betalains and phenolic compounds profiling and antioxidant capacity of pitaya (Stenocereus spp.) fruit from two species (S. Pruinosus and S. stellatus)

[EN] Pitaya fruits (Stenocereus spp.) contain betalains and phenolic compounds that have not been completely characterized. Fruits of two ecotypes of S. pruinosus, red-fleshed (SpR) and orange-fleshed (SpO), and two of S. stellatus, red-fleshed (SsR) and white-fleshed (SsW), were characterized in their betalains and phenolic compounds. The chromatographic profile of betalains was similar in SpR, SpO, and SsR, where indicaxanthin, gomphrenin I, phyllocacthin, and their isomers predominated. Betaxanthins content was higher than betacyanins and ranged from 17,706.7 ± 1128.1 to 22,053.6 ± 328.1 mg/g dry sample. The identified phenolics mostly corresponded to hydroxycinnamoyl derivatives, flavonols and flavanones. The phenolics content was higher in S. stellatus than in S. pruinosus. The ecotype SsW, that had flesh without color, showed the highest concentration. The antioxidant capacity varied within 9.21 ± 0.84 and 2.41 ± 0.36 lmol Trolox/g fresh sample, as determined by the ABTS assay. By its phytochemical composition, the fruits of pitaya can be a good source of antioxidant compounds

Fabrication and Characterization of Anionic Exchange Membranes Based on Chitosan/Poly (Vinyl) Alcohol and Chitosan/Chondroitin Doped with an Amino Cumulene Derivative and Carbon Nanotubes

Anionic exchange membranes mainly based on mixed matrix membranes (MMM) via the crosslinking of either chitosan (CHT) with poly (vinyl alcohol) (CHT : PVA) or CHT with chondroitin sulfate (CHT : CS) in a 50 : 50 wt% were synthesized. The doping of CHT, CHT : PVA and CHT : CS membranes with either the dispersant agent aminocumulene derivative (named AC, coming from the polycondensation of hexamethylenetetramine in an anhydrous acid medium) or with the carbonaceous inch made of multi-walled carbon nanotubes (CNT) dispersed by using AC to perform (AC/CNT) were characterized by the exploration of the topology by scanning electron microscopy, the determination of water uptake, and the analysis of X-ray diffraction spectroscopy together with the measurement of the anionic conductivity by using electrochemical impedance spectroscopy. Results revealed that the modification of the MMMs with the above inorganic carbonaceous fillers, i.e. AC or AC/CNT, improved remarkably the OH– conductivity for all membranes. The modified CHT:CS blend membranes exhibited the highest ionic conductivities of the series. Water uptake increased for the modified CHT and CHT : PVA membranes, whereas a remarkable reduction of water uptake for the CHT : CS based membranes took place. The best membranes in terms of anionic conductivity were correlated with crystallinity and water uptake.The research was carried out at the expense of a grant from the Russian Science Foundation (project No. 15-13-10038). AG acknowledges the Presidential fellowship programme of the Ministry of Education and Science of the Russian Federation. Also LGC and JI are grateful to the Spanish MINECO through the project CTQ2016-76231-C2-2-R

On the performance of a polymer electrolyte membrane electrochemical reactor for electrosynthesis of carboxylic acids in alkaline media

A novel polymer electrolyte membrane electrochemical reactor (PEMER) configuration has been employed for the direct electrooxidation of propargyl alcohol (PGA), a model primary alcohol, towards its carboxylic acid derivatives in alkaline medium. The PEMER configuration comprised of an anode and cathode based on nanoparticulate Ni and Pt electrocatalysts, respectively, supported on carbonaceous substrates. The electrooxidation of PGA was performed in 1.0 M NaOH, where a cathode based on a gas diffusion electrode was manufactured for the reduction of oxygen in alkaline conditions. The performance of a novel alkaline anion-exchange membrane based on Chitosan (CS) and Poly(vinyl) alcohol (PVA) in a 50:50 composition ratio doped with a 5 wt.% of poly (4-vinylpyridine) organic ionomer cross-linked, methyl chloride quaternary salt resin (4VP) was assessed as solid polymer electrolyte. The influence of 4VP anionic ionomer loading of 7, 12 and 20 wt.% incorporated into the electrocatalytic layers was examined by SEM and cyclic voltammetry (CV) upon the optimisation of the electroactive area, the mechanical stability and cohesion of the catalytic ink onto the carbonaceous substrate for both electrodes. The performance of the 4VP/CS:PVA membrane was compared with the commercial alkaline anion-exchange membrane FAA -a membrane generally used in direct alcohol alkaline fuel cells- in terms of polarisation plots in alkaline conditions. Furthermore, preparative electrolyses of the electrooxidation of PGA was performed under alkaline conditions of 1 M NaOH at constant current density of 20 mA cm-2 using a PEMER configuration to provide proof of the principle of the feasibility of the electrooxidation of other alcohols in alkaline media. PGA conversion to Z isomers of 3-(2-propynoxy)-2-propenoic acid (Z-PPA) was circa 0.77, with average current efficiency of 0.32. Alkaline stability of the membranes within the PEMER configuration was finally evaluated after the electrooxidation of PGA.This work has been funded by the Spanish MINECO through grants CTQ2013-48280-C3-3-R, at the University of Alicante, and CTQ2012-31229 and RYC2011-08550, at the University of Cantabria. L.G.C. for her PhD fellowship BES-2011-045147 at the University of Alicante and the EEBB-14-09094 mobility grant for a research stay at the University of Cantabria. The authors gratefully thank Dr. José Solla Gullón for his advice on the synthesis of platinum nanoparticles, from the Institute of Electrochemistry at the University of Alicante

Facilidad y utilidad del uso de Internet: implicaciones para la innovación educativa

The use of the Internet, indicated by the degree of perception of usefulness and ease, has been observed as an antecedent of educational innovation. As it is a meaningful teaching-learning sequence, the adoption of technology, devices and networks imply accessibility and diversity of content that the perceptual dimensions determine. Consequently, a confirmatory, psychometric, and correlational study was carried out with a sample of 340 students, considering their participation in social networks and educational platforms. A structure was found that explained 29% of the total variance, suggesting the extension of the study to other scenarios and samples.El uso de Internet, indicado por el grado de percepción de utilidad y facilidad, se ha observado como un antecedente de innovación educativa. Al tratarse de una secuencia significativa de enseñanza-aprendizaje, la adopción de tecnología, dispositivos y redes implica accesibilidad y diversidad de contenidos que determinan las dimensiones perceptivas. En consecuencia, se realizó un estudio confirmatorio, psicométrico y correlacional con una muestra de 340 estudiantes, considerando su participación en redes sociales y plataformas educativas. Se encontró una estructura que explicaba el 29% de la varianza total, sugiriendo la extensión del estudio a otros escenarios y muestras

Analysis of press around the frame rate sociopolitical hydric

El encuadre sociopolítico ha sido un instrumento de análisis en torno a la influencia de los medios de comunicación sobre la opinión pública. La difusión del tandeo y los subsidios asociados a la gestión desregulada del Estado, es analizada en el presente estudio para esclarecer la influencia de los medios impresos en la salud pública y el Desarrollo Local. Se realizó un estudio retrospectivo de corte cualitativo con la técnica de análisis de contenido en la que se llevó a cabo una selección no probabilística de 103 notas de prensa considerando el periodo que va de enero del año 2000 a diciembre del año 2012. Los resultados muestran que el encuadre socioeconómico es superior al encuadre sociopolítico identificado como preponderante en la literatura. En referencia a los estudios del estado del conocimiento, las implicaciones de ambos encuadres para la democratización de la administración de los servicios hídricos, la percepción de salud pública ambiental y el Desarrollo Local Sustentable fueron discutidas.The sociopolitical setting has been an instrument of analysis on the influence of media on public opinion. The spread of tandem and subsidies associated with deregulated state management is analyzed in the present study to clarify the influence of print media in public health and local development. A retrospective study with qualitative content analysis technique in which conducted a nonrandom selection of 103 press releases considering the period from January 2000 to December 2012 cut was made. Results show that socioeconomic and sociopolitical frame exceeds the frame identified as predominant in the literature. Referring to the studies of the state of knowledge, the implications of both frames for the democratization of the management of water services, the perception of environmental public health and Local Sustainable Development were discussed

A comparison of Clinical Risk Index for babies (CRIB-II), Score for Neonatal Acute Physiology (SNAP-II) and SNAPPE-II in predicting parenteral nutrition necessity in low birth weight preterm neonates.

Advances in perinatal care have made it possible to improve survival of low birth weight neonates. Clinical risk index for babies (CRIB-II), score for neonatal acute physiology (SNAP-II), and SNAP-perinatal extension-II (SNAPPE-II) have been used as mortality predictors for preterm infants. Feeding intolerance is very frequent in preterm neonates, and the development of an early effective biomarker for its prediction could be useful for carrying out a proper feeding strategy. Our aim was to compare the ability of CRIB-II, SNAP-II and SNAPPE-II in predict the feeding intolerance and parenteral nutrition necessity in preterm neonates. Methods: A retrospective cohort study on preterm neonates’ born at Jaen Hospital Complex with low birth weight and ≤ 36 weeks of gestation was done. Epidemiological, clinical and clinical scores CRIB II, SNAP-II and SNAPPE-II were recorded. Results: 255 low birth weight preterm neonates, 131 males (51.4%), aged ≤32 weeks of gestation (71%), were enrolled at our hospital. Parenteral nutrition needed were significantly higher in preterm neonates weighed 2500-1500 g (73.3%) and ≤ 1000g (87%). CRIB-II, SNAP-II and SNAPPE-II mean values were higher in neonates group subjected to parenteral nutrition compared with oral nutrition (p<0.05). CRIB-II and SNAPPE-II scores significantly correlated with parenteral nutrition days (p<0.05). Overall mortality rate was 11%. The 78.6% of all deceased infants needed parenteral nutrition. Conclusion: Clinical Risk Index for babies (CRIB-II) better than SNAPPE-II correlated with the feeding intolerance and thus the parenteral nutrition days in preterm neonates with low birth weight.Subvencionado: Ayuda del Plan Propio de Investigación de la UMA. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Self-discharge of AC/AC electrochemical capacitors in salt aqueous electrolyte

The self-discharge (SD) of electrochemical capacitors based on activated carbon electrodes (AC/AC capacitors) in aqueous lithium sulfate was examined after applying a three-hour cell potential hold at Ui values from 1.0 to 1.6 V. The leakage current measured during the potentiostatic period as well as the amplitude of self-discharge increased with Ui; the cell potential drop was approximately doubled by 10 °C increase of temperature. The potential decay of both negative and positive electrodes was explored separately, by introducing a reference electrode and it was found that the negative electrode contributes essentially to the capacitor self-discharge. A diffusion-controlled mechanism was found at Ui ≤ 1.4 V and Ui ≤ 1.2 V for the positive and negative electrodes, respectively. At higher Ui of 1.6 V, both electrodes display an activation-controlled mechanism due to water oxidation and subsequent carbon oxidation at the positive electrode and water or oxygen reduction at the negative electrode.The authors are grateful to the Foundation for Polish Science (FNP) for funding the ECOLCAP project within the WELCOME program, co-financed from European Union Regional Development Fund. LGC acknowledges the Spanish MINECO for funding her PhD mobility grant EEBB-1-13-06222 for the research stay at Poznan University of Technology